Environmental Dermatology

Lepidoptera is the second largest order of the class Insecta and comprises approximately 160,000 species of butterflies and moths classified among approximately 124 families and subfamilies. Venomous properties have been identified in 12 of these families, posing a serious threat to human health. ¹

The clinical manifestations from Lepidoptera envenomation can range from general systemic symptoms such as fever and abdominal distress; to more complex focal affections including hemorrhage, ophthalmologic lesions, and irritation of the respiratory tracts; to less severe reactions of the skin, which are the most common presentation.¹

Terminology

Lepidopterism is the term used to address a clinical spectrum of systemic manifestations from direct contact with venomous butterflies or moths and/or their products.² Conversely, erucism is a term used to describe localized cutaneous reactions after direct contact with toxins from caterpillars.

Lepidopterism is derived from the Greek roots lepis, meaning scale, and pteron, meaning wing. The term erucism stems from the Latin word eruca, which means larva.²

Ideally, lepidopterism should refer solely to reactions from butterflies and moths—adult forms of insects with scaly wings—while erucism should refer to reactions from contact with caterpillars—the larval form of butterflies and moths.

In common use, lepidopterism can describe any reaction from caterpillars, moths, or adult butterflies, as well as any case of Lepidoptera exposure with only systemic manifestations, regardless of cutaneous findings. Concurrently, erucism has been defined as either any reaction from caterpillars or any skin reaction from contact with caterpillars or moths.²

Because caterpillars are the larval form of butterflies and moths, caterpillar-associated skin reactions also have been conveniently denominated caterpillar dermatitis.¹ Henceforth in this article, both terms erucism and caterpillar dermatitis are used interchangeably.

Caterpillar Envenomation

Caterpillars cause the vast majority of adverse events from lepidopteran exposures.² Envenomation by caterpillars might stand as the world’s most common envenomation given the larvae proximity to humans.³ Although involvement of internal organs (eg, renal failure), cerebral hemorrhage, and joint lesions can occur, skin manifestations are more predominant with the majority of species. Initial localized pain, edema, and erythema usually are present at the site of direct contact and subsequently progress toward maculopapular to bullous lesions, erosions, petechiae, necrosis, and ulceration depending on the offending species.^1,4

Megalopyge opercularis

In the United States, more than 50 species of caterpillars have been identified as poisonous or venomous.⁵ Megalopyge opercularis (Figure 1), the larval form of the flannel moth, is an important cause of caterpillar-associated dermatitis in the southern United States.^6,7 Megalopyge opercularis also is commonly known as the puss caterpillar, opossum bug, wooly slug, el perrito, tree asp, or Italian asp.⁶ This lepidopteran insect is mainly found in the southeastern and southcentral United States, with noted particular abundance in Texas, Louisiana, and Florida.^6,8 The puss caterpillar has 2 generations per year; the first develops during the months of June to July, and the second develops from September to October, carrying seasonal health hazards.^6,8

Megalopyge opercularis is tapered at the ends and can measure 2.5 to 3.5×1 cm at maturity. It is covered by silky, long-streaked, wavy hairs that may appear single colored or as a mix of colors—from white to gray to brown—forming a mid-dorsal crest.⁶ Beneath this furry coat, rows of short sharp spines are hidden. Upon contact with the human skin, these spines will break and discharge venom.^1,6,8 Toxins contained within the hollow spines are thought to be produced by specialized basal cells, but there still is little knowledge about the dynamics and composition of the venom.¹

Clinical Manifestations

The severity of the reaction depends on the caterpillar’s size and the extent of contact.^1,4 Contact with M opercularis instantly presents with a throbbing or burning pain that may be followed by localized erythema and rash.^1,6 A characteristic gridlike pattern of erythematous macules develops, reflecting each site of puncture from the insect’s spines (Figure 2).^8,9 Skin lesions can progress from erythematous macules to hemorrhagic vesicles or pustules, usually self-resolving after a few days. The reaction also can present with radiating pain to regional lymph nodes and numbness of the affected area.^1,6,8 Moreover, some patients may report urticaria and pruritus.⁹

Envenomation by a puss caterpillar also can present with systemic manifestations including fever, headache, nausea, vomiting, shocklike symptoms, and seizures.^1,6,7 Anaphylactic reaction is rare but also can present.⁷ Uncommon cases have been reported with severe abdominal pain and muscle spasm mimicking acute appendicitis and latrodectism, respectively.^7,9

Diagnosis

The diagnosis of M opercularis envenomation is made clinically based on the morphology of the skin lesions and a history of probable exposure. Coexistent leukocytosis is likely, but laboratory testing is not warranted, as it is both nonspecific and insensitive.⁹

Management/Treatment

The most commonly reported immediate approaches to treatment involve attempts to remove the spines from the skin with tape (stripping), application of ice packs over the affected area, oral antihistamines, topical and intralesional anesthetics, regional nerve block, and oral analgesics.^6,9 There have been several cases detailing the successful use of parenteral calcium gluconate,^5,7 and diazepam has been used to treat severe muscle spasms. Anaphylactic reactions should be managed in a controlled monitored setting with subcutaneous epinephrine.⁷ Despite their common use, some data suggest that ice packs and mid- to high-potency topical steroids are ineffective.⁹

Incidence

From 2001 to 2005, a mean average of 94,552 annual cases of animal bites and stings were reported to poison control centers in the United States, of which 2094 were linked to caterpillars in this 5-year period.¹⁰ There were 3484 M opercularis caterpillar stings reported to the Texas Poison Center Network from 2000 to 2016.^5,6 Given their ability to sting throughout their life cycle, thousands of M opercularis caterpillar stings can occur each year.^1,6 Existing literature on M opercularis caterpillar stings mainly involves case reports with affections of the skin and oral mucosa, self-reported envenomation, and case studies.^5,6,8

Although multiple health concerns associated with caterpillar envenomation have been reported worldwide, the lack of official epidemiologic reports highly suggests that this problem remains underestimated. There also may be many unreported cases because certain reactions are mild or self-limited and can even go unnoticed.¹¹ Nonetheless, there is an evident rise of cases reported in the United States. According to the 2018 annual report of the American Association of Poison Control Centers, there were 2815 case mentions from caterpillar envenomation.¹²

In 1921 and 1952, some public schools in Texas were temporarily closed due to outbreaks of puss caterpillar–associated dermatitis.⁸ Similar outbreaks also have been reported in South Carolina, Virginia, and Oklahoma.⁹ Emerging data suggest that plant oil products and the pesticide cypermethrin may be helpful in controlling local infestations of the puss caterpillar.⁸

Lepidoptera is the second largest order of the class Insecta and comprises approximately 160,000 species of butterflies and moths classified among approximately 124 families and subfamilies. Venomous properties have been identified in 12 of these families, posing a serious threat to human health. ¹

The clinical manifestations from Lepidoptera envenomation can range from general systemic symptoms such as fever and abdominal distress; to more complex focal affections including hemorrhage, ophthalmologic lesions, and irritation of the respiratory tracts; to less severe reactions of the skin, which are the most common presentation.¹

Terminology

Lepidopterism is the term used to address a clinical spectrum of systemic manifestations from direct contact with venomous butterflies or moths and/or their products.² Conversely, erucism is a term used to describe localized cutaneous reactions after direct contact with toxins from caterpillars.

Lepidopterism is derived from the Greek roots lepis, meaning scale, and pteron, meaning wing. The term erucism stems from the Latin word eruca, which means larva.²

Ideally, lepidopterism should refer solely to reactions from butterflies and moths—adult forms of insects with scaly wings—while erucism should refer to reactions from contact with caterpillars—the larval form of butterflies and moths.

In common use, lepidopterism can describe any reaction from caterpillars, moths, or adult butterflies, as well as any case of Lepidoptera exposure with only systemic manifestations, regardless of cutaneous findings. Concurrently, erucism has been defined as either any reaction from caterpillars or any skin reaction from contact with caterpillars or moths.²

Because caterpillars are the larval form of butterflies and moths, caterpillar-associated skin reactions also have been conveniently denominated caterpillar dermatitis.¹ Henceforth in this article, both terms erucism and caterpillar dermatitis are used interchangeably.

Caterpillar Envenomation

Caterpillars cause the vast majority of adverse events from lepidopteran exposures.² Envenomation by caterpillars might stand as the world’s most common envenomation given the larvae proximity to humans.³ Although involvement of internal organs (eg, renal failure), cerebral hemorrhage, and joint lesions can occur, skin manifestations are more predominant with the majority of species. Initial localized pain, edema, and erythema usually are present at the site of direct contact and subsequently progress toward maculopapular to bullous lesions, erosions, petechiae, necrosis, and ulceration depending on the offending species.^1,4

Megalopyge opercularis

In the United States, more than 50 species of caterpillars have been identified as poisonous or venomous.⁵ Megalopyge opercularis (Figure 1), the larval form of the flannel moth, is an important cause of caterpillar-associated dermatitis in the southern United States.^6,7 Megalopyge opercularis also is commonly known as the puss caterpillar, opossum bug, wooly slug, el perrito, tree asp, or Italian asp.⁶ This lepidopteran insect is mainly found in the southeastern and southcentral United States, with noted particular abundance in Texas, Louisiana, and Florida.^6,8 The puss caterpillar has 2 generations per year; the first develops during the months of June to July, and the second develops from September to October, carrying seasonal health hazards.^6,8

Megalopyge opercularis is tapered at the ends and can measure 2.5 to 3.5×1 cm at maturity. It is covered by silky, long-streaked, wavy hairs that may appear single colored or as a mix of colors—from white to gray to brown—forming a mid-dorsal crest.⁶ Beneath this furry coat, rows of short sharp spines are hidden. Upon contact with the human skin, these spines will break and discharge venom.^1,6,8 Toxins contained within the hollow spines are thought to be produced by specialized basal cells, but there still is little knowledge about the dynamics and composition of the venom.¹

Clinical Manifestations

The severity of the reaction depends on the caterpillar’s size and the extent of contact.^1,4 Contact with M opercularis instantly presents with a throbbing or burning pain that may be followed by localized erythema and rash.^1,6 A characteristic gridlike pattern of erythematous macules develops, reflecting each site of puncture from the insect’s spines (Figure 2).^8,9 Skin lesions can progress from erythematous macules to hemorrhagic vesicles or pustules, usually self-resolving after a few days. The reaction also can present with radiating pain to regional lymph nodes and numbness of the affected area.^1,6,8 Moreover, some patients may report urticaria and pruritus.⁹

Envenomation by a puss caterpillar also can present with systemic manifestations including fever, headache, nausea, vomiting, shocklike symptoms, and seizures.^1,6,7 Anaphylactic reaction is rare but also can present.⁷ Uncommon cases have been reported with severe abdominal pain and muscle spasm mimicking acute appendicitis and latrodectism, respectively.^7,9

Diagnosis

The diagnosis of M opercularis envenomation is made clinically based on the morphology of the skin lesions and a history of probable exposure. Coexistent leukocytosis is likely, but laboratory testing is not warranted, as it is both nonspecific and insensitive.⁹

Management/Treatment

The most commonly reported immediate approaches to treatment involve attempts to remove the spines from the skin with tape (stripping), application of ice packs over the affected area, oral antihistamines, topical and intralesional anesthetics, regional nerve block, and oral analgesics.^6,9 There have been several cases detailing the successful use of parenteral calcium gluconate,^5,7 and diazepam has been used to treat severe muscle spasms. Anaphylactic reactions should be managed in a controlled monitored setting with subcutaneous epinephrine.⁷ Despite their common use, some data suggest that ice packs and mid- to high-potency topical steroids are ineffective.⁹

Incidence

From 2001 to 2005, a mean average of 94,552 annual cases of animal bites and stings were reported to poison control centers in the United States, of which 2094 were linked to caterpillars in this 5-year period.¹⁰ There were 3484 M opercularis caterpillar stings reported to the Texas Poison Center Network from 2000 to 2016.^5,6 Given their ability to sting throughout their life cycle, thousands of M opercularis caterpillar stings can occur each year.^1,6 Existing literature on M opercularis caterpillar stings mainly involves case reports with affections of the skin and oral mucosa, self-reported envenomation, and case studies.^5,6,8

Although multiple health concerns associated with caterpillar envenomation have been reported worldwide, the lack of official epidemiologic reports highly suggests that this problem remains underestimated. There also may be many unreported cases because certain reactions are mild or self-limited and can even go unnoticed.¹¹ Nonetheless, there is an evident rise of cases reported in the United States. According to the 2018 annual report of the American Association of Poison Control Centers, there were 2815 case mentions from caterpillar envenomation.¹²

In 1921 and 1952, some public schools in Texas were temporarily closed due to outbreaks of puss caterpillar–associated dermatitis.⁸ Similar outbreaks also have been reported in South Carolina, Virginia, and Oklahoma.⁹ Emerging data suggest that plant oil products and the pesticide cypermethrin may be helpful in controlling local infestations of the puss caterpillar.⁸

Lepidoptera is the second largest order of the class Insecta and comprises approximately 160,000 species of butterflies and moths classified among approximately 124 families and subfamilies. Venomous properties have been identified in 12 of these families, posing a serious threat to human health. ¹

The clinical manifestations from Lepidoptera envenomation can range from general systemic symptoms such as fever and abdominal distress; to more complex focal affections including hemorrhage, ophthalmologic lesions, and irritation of the respiratory tracts; to less severe reactions of the skin, which are the most common presentation.¹

Terminology

Lepidopterism is the term used to address a clinical spectrum of systemic manifestations from direct contact with venomous butterflies or moths and/or their products.² Conversely, erucism is a term used to describe localized cutaneous reactions after direct contact with toxins from caterpillars.

Lepidopterism is derived from the Greek roots lepis, meaning scale, and pteron, meaning wing. The term erucism stems from the Latin word eruca, which means larva.²

Ideally, lepidopterism should refer solely to reactions from butterflies and moths—adult forms of insects with scaly wings—while erucism should refer to reactions from contact with caterpillars—the larval form of butterflies and moths.

In common use, lepidopterism can describe any reaction from caterpillars, moths, or adult butterflies, as well as any case of Lepidoptera exposure with only systemic manifestations, regardless of cutaneous findings. Concurrently, erucism has been defined as either any reaction from caterpillars or any skin reaction from contact with caterpillars or moths.²

Because caterpillars are the larval form of butterflies and moths, caterpillar-associated skin reactions also have been conveniently denominated caterpillar dermatitis.¹ Henceforth in this article, both terms erucism and caterpillar dermatitis are used interchangeably.

Caterpillar Envenomation

Caterpillars cause the vast majority of adverse events from lepidopteran exposures.² Envenomation by caterpillars might stand as the world’s most common envenomation given the larvae proximity to humans.³ Although involvement of internal organs (eg, renal failure), cerebral hemorrhage, and joint lesions can occur, skin manifestations are more predominant with the majority of species. Initial localized pain, edema, and erythema usually are present at the site of direct contact and subsequently progress toward maculopapular to bullous lesions, erosions, petechiae, necrosis, and ulceration depending on the offending species.^1,4

Megalopyge opercularis

In the United States, more than 50 species of caterpillars have been identified as poisonous or venomous.⁵ Megalopyge opercularis (Figure 1), the larval form of the flannel moth, is an important cause of caterpillar-associated dermatitis in the southern United States.^6,7 Megalopyge opercularis also is commonly known as the puss caterpillar, opossum bug, wooly slug, el perrito, tree asp, or Italian asp.⁶ This lepidopteran insect is mainly found in the southeastern and southcentral United States, with noted particular abundance in Texas, Louisiana, and Florida.^6,8 The puss caterpillar has 2 generations per year; the first develops during the months of June to July, and the second develops from September to October, carrying seasonal health hazards.^6,8

Megalopyge opercularis is tapered at the ends and can measure 2.5 to 3.5×1 cm at maturity. It is covered by silky, long-streaked, wavy hairs that may appear single colored or as a mix of colors—from white to gray to brown—forming a mid-dorsal crest.⁶ Beneath this furry coat, rows of short sharp spines are hidden. Upon contact with the human skin, these spines will break and discharge venom.^1,6,8 Toxins contained within the hollow spines are thought to be produced by specialized basal cells, but there still is little knowledge about the dynamics and composition of the venom.¹

Clinical Manifestations

The severity of the reaction depends on the caterpillar’s size and the extent of contact.^1,4 Contact with M opercularis instantly presents with a throbbing or burning pain that may be followed by localized erythema and rash.^1,6 A characteristic gridlike pattern of erythematous macules develops, reflecting each site of puncture from the insect’s spines (Figure 2).^8,9 Skin lesions can progress from erythematous macules to hemorrhagic vesicles or pustules, usually self-resolving after a few days. The reaction also can present with radiating pain to regional lymph nodes and numbness of the affected area.^1,6,8 Moreover, some patients may report urticaria and pruritus.⁹

Envenomation by a puss caterpillar also can present with systemic manifestations including fever, headache, nausea, vomiting, shocklike symptoms, and seizures.^1,6,7 Anaphylactic reaction is rare but also can present.⁷ Uncommon cases have been reported with severe abdominal pain and muscle spasm mimicking acute appendicitis and latrodectism, respectively.^7,9

Diagnosis

The diagnosis of M opercularis envenomation is made clinically based on the morphology of the skin lesions and a history of probable exposure. Coexistent leukocytosis is likely, but laboratory testing is not warranted, as it is both nonspecific and insensitive.⁹

Management/Treatment

The most commonly reported immediate approaches to treatment involve attempts to remove the spines from the skin with tape (stripping), application of ice packs over the affected area, oral antihistamines, topical and intralesional anesthetics, regional nerve block, and oral analgesics.^6,9 There have been several cases detailing the successful use of parenteral calcium gluconate,^5,7 and diazepam has been used to treat severe muscle spasms. Anaphylactic reactions should be managed in a controlled monitored setting with subcutaneous epinephrine.⁷ Despite their common use, some data suggest that ice packs and mid- to high-potency topical steroids are ineffective.⁹

Incidence

From 2001 to 2005, a mean average of 94,552 annual cases of animal bites and stings were reported to poison control centers in the United States, of which 2094 were linked to caterpillars in this 5-year period.¹⁰ There were 3484 M opercularis caterpillar stings reported to the Texas Poison Center Network from 2000 to 2016.^5,6 Given their ability to sting throughout their life cycle, thousands of M opercularis caterpillar stings can occur each year.^1,6 Existing literature on M opercularis caterpillar stings mainly involves case reports with affections of the skin and oral mucosa, self-reported envenomation, and case studies.^5,6,8

Although multiple health concerns associated with caterpillar envenomation have been reported worldwide, the lack of official epidemiologic reports highly suggests that this problem remains underestimated. There also may be many unreported cases because certain reactions are mild or self-limited and can even go unnoticed.¹¹ Nonetheless, there is an evident rise of cases reported in the United States. According to the 2018 annual report of the American Association of Poison Control Centers, there were 2815 case mentions from caterpillar envenomation.¹²

In 1921 and 1952, some public schools in Texas were temporarily closed due to outbreaks of puss caterpillar–associated dermatitis.⁸ Similar outbreaks also have been reported in South Carolina, Virginia, and Oklahoma.⁹ Emerging data suggest that plant oil products and the pesticide cypermethrin may be helpful in controlling local infestations of the puss caterpillar.⁸

Epidemiology and Identification

Centruroides is a common genus of bark scorpions in the United States with at least 21 species considered to be medically important, including the closely related Centruroides exilicauda and Centruroides sculpturatus.¹ Scorpions can be recognized by a bulbous sac and pointed stinger at the end of a tail-like abdomen. They also have long lobsterlike pedipalps (pincers) for grasping their prey. Identifying characteristics for C exilicauda and C sculpturatus include a small, slender, yellow to light brown or tan body typically measuring 1.3 to 7.6 cm in length with a subaculear tooth or tubercle at the base of the stinger, a characteristic that is common to all Centruroides species (Figure).² Some variability in size has been shown, with smaller scorpions found in increased elevations and cooler temperatures.^1,3 Both C exilicauda and C sculpturatus are found in northern Mexico as well as the southwestern United States (eg, Arizona, New Mexico, Texas, California, Nevada).¹ They have a preference for residing in or around trees and often are found on the underside of bark, stones, or tables as well as inside shoes or small cracks and crevices. Scorpions typically sting in self-defense, and stings commonly occur when humans attempt to move tables, put on shoes, or walk barefoot in scorpion-infested areas. Most stings occur from the end of spring through the end summer, but many may go unreported.^1,4

The venom of the Centruroides genus includes peptides and proteins that play a fundamental role in toxic activity by impairing potassium, sodium, and calcium ion channels.^1,3 Toxins have been shown to be species specific, functioning either in capturing prey or deterring predators. Intraspecies variability in toxins has been demonstrated, which may complicate the production of adequate antivenin.³ Many have thought that C exilicauda Wood and C sculpturatus Ewing are the same species, and the names have been used synonymously in the past; however, genetic and biochemical studies of their venom components have shown that they are distinct species and that C sculpturatus is the more dangerous of the two.⁵ The median lethal dose 50% of C sculpturatus was found to be 22.7 μg in CD1 mice.⁶

Envenomation and Clinical Manifestations

Stings from C exilicauda and C sculpturatus have been shown to cause fatality in children more often than in adults.⁷ In the United States, Arizona has the highest frequency of serious symptoms of envenomation as well as the highest hospital and intensive care unit admission rates.⁶ Envenomation results in an immediate sharp burning pain followed by numbness.⁴ Wounds can produce some regional lymph node swelling, ecchymosis, paresthesia, and lymphangitis. More often than not, however, wounds have little to no inflammation and are characterized only by pain.⁴ The puncture wound is too small to be seen, and C exilicauda and C sculpturatus venom do not cause local tissue destruction, an important factor in distinguishing it from other scorpion envenomations.

More severe complications that may follow are caused by the neurotoxin released by Centruroides stings. The toxin components can increase the duration and amplitude of the neuronal action potential and enhance the release of neurotransmitters such as acetylcholine and norepinephrine.⁸ Stings can lead to cranial nerve dysfunction and somatic skeletal neuromuscular dysfunction as well as autonomic dysfunction, specifically salivation, fever, tongue and muscle fasciculations, opsoclonus, vomiting, bronchoconstriction, diaphoresis, nystagmus, blurred vision, slurred speech, hypertension, rhabdomyolysis, stridor, wheezing, aspiration, anaphylaxis, and tachycardia, leading to cardiac and respiratory compromise.^4,8 Some patients have experienced a decreased sense of smell or hearing and decreased fine motor movements.⁷ Although pancreatitis may occur with scorpion stings, it is not common for C exilicauda.⁹ Comorbidities such as cardiac disease and substance use disorders contribute to prolonged length of hospital stay and poor outcome.⁸

Treatment

Most Centruroides stings can be managed at home, but patients with more serious symptoms and children younger than 2 years should be taken to a hospital for treatment.⁷ If a patient reports only pain but shows no other signs of neurotoxicity, observation and pain relief with rest, ice, and elevation is appropriate management. Patients with severe manifestations have been treated with various combinations of lorazepam, glycopyrrolate, ipratropium bromide, and ondansetron, but the only treatment definitively shown to decrease time to symptom abatement is antivenin.⁷ It has been demonstrated that C exilicauda and C sculpturatus antivenin is relatively safe.⁷ Most patients, especially adults, do not die from C exilicauda and C sculpturatus stings; therefore, antivenin more commonly is symptom abating than it is lifesaving.¹⁰ In children, time to symptom resolution was decreased to fewer than 4 hours with antivenin, and there is a lower rate of inpatient admission when antivenin is administered.^4,10,11 There is a low incidence of anaphylactic reaction after antivenin, but there have been reported cases of self-limited serum sickness after antivenin use that generally can be managed with antihistamines and corticosteroids.^4,7

Epidemiology and Identification

Centruroides is a common genus of bark scorpions in the United States with at least 21 species considered to be medically important, including the closely related Centruroides exilicauda and Centruroides sculpturatus.¹ Scorpions can be recognized by a bulbous sac and pointed stinger at the end of a tail-like abdomen. They also have long lobsterlike pedipalps (pincers) for grasping their prey. Identifying characteristics for C exilicauda and C sculpturatus include a small, slender, yellow to light brown or tan body typically measuring 1.3 to 7.6 cm in length with a subaculear tooth or tubercle at the base of the stinger, a characteristic that is common to all Centruroides species (Figure).² Some variability in size has been shown, with smaller scorpions found in increased elevations and cooler temperatures.^1,3 Both C exilicauda and C sculpturatus are found in northern Mexico as well as the southwestern United States (eg, Arizona, New Mexico, Texas, California, Nevada).¹ They have a preference for residing in or around trees and often are found on the underside of bark, stones, or tables as well as inside shoes or small cracks and crevices. Scorpions typically sting in self-defense, and stings commonly occur when humans attempt to move tables, put on shoes, or walk barefoot in scorpion-infested areas. Most stings occur from the end of spring through the end summer, but many may go unreported.^1,4

The venom of the Centruroides genus includes peptides and proteins that play a fundamental role in toxic activity by impairing potassium, sodium, and calcium ion channels.^1,3 Toxins have been shown to be species specific, functioning either in capturing prey or deterring predators. Intraspecies variability in toxins has been demonstrated, which may complicate the production of adequate antivenin.³ Many have thought that C exilicauda Wood and C sculpturatus Ewing are the same species, and the names have been used synonymously in the past; however, genetic and biochemical studies of their venom components have shown that they are distinct species and that C sculpturatus is the more dangerous of the two.⁵ The median lethal dose 50% of C sculpturatus was found to be 22.7 μg in CD1 mice.⁶

Envenomation and Clinical Manifestations

Stings from C exilicauda and C sculpturatus have been shown to cause fatality in children more often than in adults.⁷ In the United States, Arizona has the highest frequency of serious symptoms of envenomation as well as the highest hospital and intensive care unit admission rates.⁶ Envenomation results in an immediate sharp burning pain followed by numbness.⁴ Wounds can produce some regional lymph node swelling, ecchymosis, paresthesia, and lymphangitis. More often than not, however, wounds have little to no inflammation and are characterized only by pain.⁴ The puncture wound is too small to be seen, and C exilicauda and C sculpturatus venom do not cause local tissue destruction, an important factor in distinguishing it from other scorpion envenomations.

More severe complications that may follow are caused by the neurotoxin released by Centruroides stings. The toxin components can increase the duration and amplitude of the neuronal action potential and enhance the release of neurotransmitters such as acetylcholine and norepinephrine.⁸ Stings can lead to cranial nerve dysfunction and somatic skeletal neuromuscular dysfunction as well as autonomic dysfunction, specifically salivation, fever, tongue and muscle fasciculations, opsoclonus, vomiting, bronchoconstriction, diaphoresis, nystagmus, blurred vision, slurred speech, hypertension, rhabdomyolysis, stridor, wheezing, aspiration, anaphylaxis, and tachycardia, leading to cardiac and respiratory compromise.^4,8 Some patients have experienced a decreased sense of smell or hearing and decreased fine motor movements.⁷ Although pancreatitis may occur with scorpion stings, it is not common for C exilicauda.⁹ Comorbidities such as cardiac disease and substance use disorders contribute to prolonged length of hospital stay and poor outcome.⁸

Treatment

Most Centruroides stings can be managed at home, but patients with more serious symptoms and children younger than 2 years should be taken to a hospital for treatment.⁷ If a patient reports only pain but shows no other signs of neurotoxicity, observation and pain relief with rest, ice, and elevation is appropriate management. Patients with severe manifestations have been treated with various combinations of lorazepam, glycopyrrolate, ipratropium bromide, and ondansetron, but the only treatment definitively shown to decrease time to symptom abatement is antivenin.⁷ It has been demonstrated that C exilicauda and C sculpturatus antivenin is relatively safe.⁷ Most patients, especially adults, do not die from C exilicauda and C sculpturatus stings; therefore, antivenin more commonly is symptom abating than it is lifesaving.¹⁰ In children, time to symptom resolution was decreased to fewer than 4 hours with antivenin, and there is a lower rate of inpatient admission when antivenin is administered.^4,10,11 There is a low incidence of anaphylactic reaction after antivenin, but there have been reported cases of self-limited serum sickness after antivenin use that generally can be managed with antihistamines and corticosteroids.^4,7

Epidemiology and Identification

Centruroides is a common genus of bark scorpions in the United States with at least 21 species considered to be medically important, including the closely related Centruroides exilicauda and Centruroides sculpturatus.¹ Scorpions can be recognized by a bulbous sac and pointed stinger at the end of a tail-like abdomen. They also have long lobsterlike pedipalps (pincers) for grasping their prey. Identifying characteristics for C exilicauda and C sculpturatus include a small, slender, yellow to light brown or tan body typically measuring 1.3 to 7.6 cm in length with a subaculear tooth or tubercle at the base of the stinger, a characteristic that is common to all Centruroides species (Figure).² Some variability in size has been shown, with smaller scorpions found in increased elevations and cooler temperatures.^1,3 Both C exilicauda and C sculpturatus are found in northern Mexico as well as the southwestern United States (eg, Arizona, New Mexico, Texas, California, Nevada).¹ They have a preference for residing in or around trees and often are found on the underside of bark, stones, or tables as well as inside shoes or small cracks and crevices. Scorpions typically sting in self-defense, and stings commonly occur when humans attempt to move tables, put on shoes, or walk barefoot in scorpion-infested areas. Most stings occur from the end of spring through the end summer, but many may go unreported.^1,4

The venom of the Centruroides genus includes peptides and proteins that play a fundamental role in toxic activity by impairing potassium, sodium, and calcium ion channels.^1,3 Toxins have been shown to be species specific, functioning either in capturing prey or deterring predators. Intraspecies variability in toxins has been demonstrated, which may complicate the production of adequate antivenin.³ Many have thought that C exilicauda Wood and C sculpturatus Ewing are the same species, and the names have been used synonymously in the past; however, genetic and biochemical studies of their venom components have shown that they are distinct species and that C sculpturatus is the more dangerous of the two.⁵ The median lethal dose 50% of C sculpturatus was found to be 22.7 μg in CD1 mice.⁶

Envenomation and Clinical Manifestations

Stings from C exilicauda and C sculpturatus have been shown to cause fatality in children more often than in adults.⁷ In the United States, Arizona has the highest frequency of serious symptoms of envenomation as well as the highest hospital and intensive care unit admission rates.⁶ Envenomation results in an immediate sharp burning pain followed by numbness.⁴ Wounds can produce some regional lymph node swelling, ecchymosis, paresthesia, and lymphangitis. More often than not, however, wounds have little to no inflammation and are characterized only by pain.⁴ The puncture wound is too small to be seen, and C exilicauda and C sculpturatus venom do not cause local tissue destruction, an important factor in distinguishing it from other scorpion envenomations.

More severe complications that may follow are caused by the neurotoxin released by Centruroides stings. The toxin components can increase the duration and amplitude of the neuronal action potential and enhance the release of neurotransmitters such as acetylcholine and norepinephrine.⁸ Stings can lead to cranial nerve dysfunction and somatic skeletal neuromuscular dysfunction as well as autonomic dysfunction, specifically salivation, fever, tongue and muscle fasciculations, opsoclonus, vomiting, bronchoconstriction, diaphoresis, nystagmus, blurred vision, slurred speech, hypertension, rhabdomyolysis, stridor, wheezing, aspiration, anaphylaxis, and tachycardia, leading to cardiac and respiratory compromise.^4,8 Some patients have experienced a decreased sense of smell or hearing and decreased fine motor movements.⁷ Although pancreatitis may occur with scorpion stings, it is not common for C exilicauda.⁹ Comorbidities such as cardiac disease and substance use disorders contribute to prolonged length of hospital stay and poor outcome.⁸

Treatment

Most Centruroides stings can be managed at home, but patients with more serious symptoms and children younger than 2 years should be taken to a hospital for treatment.⁷ If a patient reports only pain but shows no other signs of neurotoxicity, observation and pain relief with rest, ice, and elevation is appropriate management. Patients with severe manifestations have been treated with various combinations of lorazepam, glycopyrrolate, ipratropium bromide, and ondansetron, but the only treatment definitively shown to decrease time to symptom abatement is antivenin.⁷ It has been demonstrated that C exilicauda and C sculpturatus antivenin is relatively safe.⁷ Most patients, especially adults, do not die from C exilicauda and C sculpturatus stings; therefore, antivenin more commonly is symptom abating than it is lifesaving.¹⁰ In children, time to symptom resolution was decreased to fewer than 4 hours with antivenin, and there is a lower rate of inpatient admission when antivenin is administered.^4,10,11 There is a low incidence of anaphylactic reaction after antivenin, but there have been reported cases of self-limited serum sickness after antivenin use that generally can be managed with antihistamines and corticosteroids.^4,7

Epidemiology and Transmission

Pediculus humanus corporis, commonly known as the human body louse, is one in a family of 3 ectoparasites of the same suborder that also encompasses pubic lice (Phthirus pubis) and head lice (Pediculus humanus capitis). Adults are approximately 2 mm in size, with the same life cycle as head lice (Figure 1). They require blood meals roughly 5 times per day and cannot survive longer than 2 days without feeding.¹ Although similar in structure to head lice, body lice differ behaviorally in that they do not reside on their human host’s body; instead, they infest the host’s clothing, localizing to seams (Figure 2), and migrate to the host for blood meals. In fact, based on this behavior, genetic analysis of early human body lice has been used to postulate when clothing was first used by humans as well as to determine early human migration patterns.^2,3

Although clinicians in developed countries may be less familiar with body lice compared to their counterparts, body lice nevertheless remain a global health concern in impoverished, densely populated areas, as well as in homeless populations due to poor hygiene. Transmission frequently occurs via physical contact with an affected individual and his/her personal items (eg, linens) via fomites.^4,5 Body louse infestation is more prevalent in homeless individuals who sleep outside vs in shelters; a history of pubic lice and lack of regular bathing have been reported as additional risk factors.⁶ Outbreaks have been noted in the wake of natural disasters, in the setting of political upheavals, and in refugee camps, as well as in individuals seeking political asylum.⁷ Unlike head and pubic lice, body lice can serve as vectors for infectious diseases including Rickettsia prowazekii (epidemic typhus), Borrelia recurrentis (louse-borne relapsing fever), Bartonella quintana (trench fever), and Yersinia pestis (plague).^5,8,9 Several Acinetobacter species were isolated from nearly one-third of collected body louse specimens in a French study.¹⁰ Additionally, serology for B quintana was found to be positive in up to 30% of cases in one United States urban homeless population.⁴

Clinical Manifestations

Patients often present with generalized pruritus, usually considerably more severe than with P humanus capitis, with lesions concentrated on the trunk.¹¹ In addition to often impetiginized, self-inflicted excoriations, feeding sites may present as erythematous macules (Figure 3), papules, or papular urticaria with a central hemorrhagic punctum. Extensive infestation also can manifest as the colloquial vagabond disease, characterized by postinflammatory hyperpigmentation and thickening of the involved skin. Remarkably, patients also may present with considerable iron-deficiency anemia secondary to high parasite load and large volume blood feeding. Multiple case reports have demonstrated associated morbidity.^12-14 The differential diagnosis for pediculosis may include scabies, lichen simplex chronicus, and eczematous dermatitis, though the clinician should prudently consider whether both scabies and pediculosis may be present, as coexistence is possible.^4,15

Diagnosis

Diagnosis can be reached by visualizing adult lice, nymphs, or viable nits on the body or more commonly within inner clothing seams; nits also fluoresce under Wood light.¹⁵ Although dermoscopy has proven useful for increased sensitivity and differentiation between viable and hatched nits, the insects also can be viewed with the unaided eye.¹⁶

Treatment: New Concerns and Strategies

The mainstay of treatment for body lice has long consisted of thorough washing and drying of all clothing and linens in a hot dryer. Treatment can be augmented with the addition of pharmacotherapy, plus antibiotics as warranted for louse-borne disease. Pharmacologic intervention often is used in cases of mass infestation and is similar to head lice.

Options for head lice include topical permethrin, malathion, lindane, spinosad, benzyl alcohol, and ivermectin. Pyrethroids, derived from the chrysanthemum, generally are considered safe for human use with a side-effect profile limited to irritation and allergy¹⁷; however, neurotoxicity and leukemia are clinical concerns, with an association more recently shown between large-volume use of pyrethroids and acute lymphoblastic leukemia.^18,19 Use of lindane is not recommended due to a greater potential for central nervous system neurotoxicity, manifested by seizures, with repeated large surface application. Malathion is problematic due to the risk for mucosal irritation, flammability of some formulations, and theoretical organophosphate poisoning, as its mechanism of action involves inhibition of acetylcholinesterase.¹⁵ However, in the context of head lice treatment, a randomized controlled trial reported no incidence of acetylcholinesterase inhibition.²⁰ Spinosad, manufactured from the soil bacterium Saccharopolyspora spinosa, functions similarly by interfering with the nicotinic acetylcholine receptor and also carries a risk for skin irritation.²¹ Among all the treatment options, we prefer benzyl alcohol, particularly in the context of resistance, as it is effective via a physical mechanism of action and lacks notable neurotoxic effects to the host. Use of benzyl alcohol is approved for patients as young as 6 months; it functions by asphyxiating the lice via paralysis of the respiratory spiracle with occlusion by inert ingredients. Itching, episodic numbness, and scalp or mucosal irritation are possible complications of treatment.²²

Treatment resistance of body lice has increased in recent years, warranting exploration of additional management strategies. Moreover, developing resistance to lindane and malathion has been reported.²³ Resistance to pyrethroids has been attributed to mutations in a voltage-gated sodium channel, one of which was universally present in the sampling of a single population.²⁴ A randomized controlled trial showed that off-label oral ivermectin 400 μg/kg was superior to malathion lotion 0.5% in difficult-to-treat cases of head lice²⁵; utility of oral ivermectin also has been reported in body lice.²⁶ In vitro studies also have shown promise for pursuing synergistic treatment of body lice with both ivermectin and antibiotics.²⁷

A novel primary prophylaxis approach for at-risk homeless individuals recently utilized permethrin-impregnated underwear. Although the intervention provided short-term infestation improvement, longer-term use did not show improvement from placebo and also increased prevalence of permethrin-resistant haplotypes.²

Epidemiology and Transmission

Pediculus humanus corporis, commonly known as the human body louse, is one in a family of 3 ectoparasites of the same suborder that also encompasses pubic lice (Phthirus pubis) and head lice (Pediculus humanus capitis). Adults are approximately 2 mm in size, with the same life cycle as head lice (Figure 1). They require blood meals roughly 5 times per day and cannot survive longer than 2 days without feeding.¹ Although similar in structure to head lice, body lice differ behaviorally in that they do not reside on their human host’s body; instead, they infest the host’s clothing, localizing to seams (Figure 2), and migrate to the host for blood meals. In fact, based on this behavior, genetic analysis of early human body lice has been used to postulate when clothing was first used by humans as well as to determine early human migration patterns.^2,3

Although clinicians in developed countries may be less familiar with body lice compared to their counterparts, body lice nevertheless remain a global health concern in impoverished, densely populated areas, as well as in homeless populations due to poor hygiene. Transmission frequently occurs via physical contact with an affected individual and his/her personal items (eg, linens) via fomites.^4,5 Body louse infestation is more prevalent in homeless individuals who sleep outside vs in shelters; a history of pubic lice and lack of regular bathing have been reported as additional risk factors.⁶ Outbreaks have been noted in the wake of natural disasters, in the setting of political upheavals, and in refugee camps, as well as in individuals seeking political asylum.⁷ Unlike head and pubic lice, body lice can serve as vectors for infectious diseases including Rickettsia prowazekii (epidemic typhus), Borrelia recurrentis (louse-borne relapsing fever), Bartonella quintana (trench fever), and Yersinia pestis (plague).^5,8,9 Several Acinetobacter species were isolated from nearly one-third of collected body louse specimens in a French study.¹⁰ Additionally, serology for B quintana was found to be positive in up to 30% of cases in one United States urban homeless population.⁴

Clinical Manifestations

Patients often present with generalized pruritus, usually considerably more severe than with P humanus capitis, with lesions concentrated on the trunk.¹¹ In addition to often impetiginized, self-inflicted excoriations, feeding sites may present as erythematous macules (Figure 3), papules, or papular urticaria with a central hemorrhagic punctum. Extensive infestation also can manifest as the colloquial vagabond disease, characterized by postinflammatory hyperpigmentation and thickening of the involved skin. Remarkably, patients also may present with considerable iron-deficiency anemia secondary to high parasite load and large volume blood feeding. Multiple case reports have demonstrated associated morbidity.^12-14 The differential diagnosis for pediculosis may include scabies, lichen simplex chronicus, and eczematous dermatitis, though the clinician should prudently consider whether both scabies and pediculosis may be present, as coexistence is possible.^4,15

Diagnosis

Diagnosis can be reached by visualizing adult lice, nymphs, or viable nits on the body or more commonly within inner clothing seams; nits also fluoresce under Wood light.¹⁵ Although dermoscopy has proven useful for increased sensitivity and differentiation between viable and hatched nits, the insects also can be viewed with the unaided eye.¹⁶

Treatment: New Concerns and Strategies

The mainstay of treatment for body lice has long consisted of thorough washing and drying of all clothing and linens in a hot dryer. Treatment can be augmented with the addition of pharmacotherapy, plus antibiotics as warranted for louse-borne disease. Pharmacologic intervention often is used in cases of mass infestation and is similar to head lice.

Options for head lice include topical permethrin, malathion, lindane, spinosad, benzyl alcohol, and ivermectin. Pyrethroids, derived from the chrysanthemum, generally are considered safe for human use with a side-effect profile limited to irritation and allergy¹⁷; however, neurotoxicity and leukemia are clinical concerns, with an association more recently shown between large-volume use of pyrethroids and acute lymphoblastic leukemia.^18,19 Use of lindane is not recommended due to a greater potential for central nervous system neurotoxicity, manifested by seizures, with repeated large surface application. Malathion is problematic due to the risk for mucosal irritation, flammability of some formulations, and theoretical organophosphate poisoning, as its mechanism of action involves inhibition of acetylcholinesterase.¹⁵ However, in the context of head lice treatment, a randomized controlled trial reported no incidence of acetylcholinesterase inhibition.²⁰ Spinosad, manufactured from the soil bacterium Saccharopolyspora spinosa, functions similarly by interfering with the nicotinic acetylcholine receptor and also carries a risk for skin irritation.²¹ Among all the treatment options, we prefer benzyl alcohol, particularly in the context of resistance, as it is effective via a physical mechanism of action and lacks notable neurotoxic effects to the host. Use of benzyl alcohol is approved for patients as young as 6 months; it functions by asphyxiating the lice via paralysis of the respiratory spiracle with occlusion by inert ingredients. Itching, episodic numbness, and scalp or mucosal irritation are possible complications of treatment.²²

Treatment resistance of body lice has increased in recent years, warranting exploration of additional management strategies. Moreover, developing resistance to lindane and malathion has been reported.²³ Resistance to pyrethroids has been attributed to mutations in a voltage-gated sodium channel, one of which was universally present in the sampling of a single population.²⁴ A randomized controlled trial showed that off-label oral ivermectin 400 μg/kg was superior to malathion lotion 0.5% in difficult-to-treat cases of head lice²⁵; utility of oral ivermectin also has been reported in body lice.²⁶ In vitro studies also have shown promise for pursuing synergistic treatment of body lice with both ivermectin and antibiotics.²⁷

A novel primary prophylaxis approach for at-risk homeless individuals recently utilized permethrin-impregnated underwear. Although the intervention provided short-term infestation improvement, longer-term use did not show improvement from placebo and also increased prevalence of permethrin-resistant haplotypes.²

Epidemiology and Transmission

Pediculus humanus corporis, commonly known as the human body louse, is one in a family of 3 ectoparasites of the same suborder that also encompasses pubic lice (Phthirus pubis) and head lice (Pediculus humanus capitis). Adults are approximately 2 mm in size, with the same life cycle as head lice (Figure 1). They require blood meals roughly 5 times per day and cannot survive longer than 2 days without feeding.¹ Although similar in structure to head lice, body lice differ behaviorally in that they do not reside on their human host’s body; instead, they infest the host’s clothing, localizing to seams (Figure 2), and migrate to the host for blood meals. In fact, based on this behavior, genetic analysis of early human body lice has been used to postulate when clothing was first used by humans as well as to determine early human migration patterns.^2,3

Although clinicians in developed countries may be less familiar with body lice compared to their counterparts, body lice nevertheless remain a global health concern in impoverished, densely populated areas, as well as in homeless populations due to poor hygiene. Transmission frequently occurs via physical contact with an affected individual and his/her personal items (eg, linens) via fomites.^4,5 Body louse infestation is more prevalent in homeless individuals who sleep outside vs in shelters; a history of pubic lice and lack of regular bathing have been reported as additional risk factors.⁶ Outbreaks have been noted in the wake of natural disasters, in the setting of political upheavals, and in refugee camps, as well as in individuals seeking political asylum.⁷ Unlike head and pubic lice, body lice can serve as vectors for infectious diseases including Rickettsia prowazekii (epidemic typhus), Borrelia recurrentis (louse-borne relapsing fever), Bartonella quintana (trench fever), and Yersinia pestis (plague).^5,8,9 Several Acinetobacter species were isolated from nearly one-third of collected body louse specimens in a French study.¹⁰ Additionally, serology for B quintana was found to be positive in up to 30% of cases in one United States urban homeless population.⁴

Clinical Manifestations

Patients often present with generalized pruritus, usually considerably more severe than with P humanus capitis, with lesions concentrated on the trunk.¹¹ In addition to often impetiginized, self-inflicted excoriations, feeding sites may present as erythematous macules (Figure 3), papules, or papular urticaria with a central hemorrhagic punctum. Extensive infestation also can manifest as the colloquial vagabond disease, characterized by postinflammatory hyperpigmentation and thickening of the involved skin. Remarkably, patients also may present with considerable iron-deficiency anemia secondary to high parasite load and large volume blood feeding. Multiple case reports have demonstrated associated morbidity.^12-14 The differential diagnosis for pediculosis may include scabies, lichen simplex chronicus, and eczematous dermatitis, though the clinician should prudently consider whether both scabies and pediculosis may be present, as coexistence is possible.^4,15

Diagnosis

Diagnosis can be reached by visualizing adult lice, nymphs, or viable nits on the body or more commonly within inner clothing seams; nits also fluoresce under Wood light.¹⁵ Although dermoscopy has proven useful for increased sensitivity and differentiation between viable and hatched nits, the insects also can be viewed with the unaided eye.¹⁶

Treatment: New Concerns and Strategies

The mainstay of treatment for body lice has long consisted of thorough washing and drying of all clothing and linens in a hot dryer. Treatment can be augmented with the addition of pharmacotherapy, plus antibiotics as warranted for louse-borne disease. Pharmacologic intervention often is used in cases of mass infestation and is similar to head lice.

Options for head lice include topical permethrin, malathion, lindane, spinosad, benzyl alcohol, and ivermectin. Pyrethroids, derived from the chrysanthemum, generally are considered safe for human use with a side-effect profile limited to irritation and allergy¹⁷; however, neurotoxicity and leukemia are clinical concerns, with an association more recently shown between large-volume use of pyrethroids and acute lymphoblastic leukemia.^18,19 Use of lindane is not recommended due to a greater potential for central nervous system neurotoxicity, manifested by seizures, with repeated large surface application. Malathion is problematic due to the risk for mucosal irritation, flammability of some formulations, and theoretical organophosphate poisoning, as its mechanism of action involves inhibition of acetylcholinesterase.¹⁵ However, in the context of head lice treatment, a randomized controlled trial reported no incidence of acetylcholinesterase inhibition.²⁰ Spinosad, manufactured from the soil bacterium Saccharopolyspora spinosa, functions similarly by interfering with the nicotinic acetylcholine receptor and also carries a risk for skin irritation.²¹ Among all the treatment options, we prefer benzyl alcohol, particularly in the context of resistance, as it is effective via a physical mechanism of action and lacks notable neurotoxic effects to the host. Use of benzyl alcohol is approved for patients as young as 6 months; it functions by asphyxiating the lice via paralysis of the respiratory spiracle with occlusion by inert ingredients. Itching, episodic numbness, and scalp or mucosal irritation are possible complications of treatment.²²

Treatment resistance of body lice has increased in recent years, warranting exploration of additional management strategies. Moreover, developing resistance to lindane and malathion has been reported.²³ Resistance to pyrethroids has been attributed to mutations in a voltage-gated sodium channel, one of which was universally present in the sampling of a single population.²⁴ A randomized controlled trial showed that off-label oral ivermectin 400 μg/kg was superior to malathion lotion 0.5% in difficult-to-treat cases of head lice²⁵; utility of oral ivermectin also has been reported in body lice.²⁶ In vitro studies also have shown promise for pursuing synergistic treatment of body lice with both ivermectin and antibiotics.²⁷

A novel primary prophylaxis approach for at-risk homeless individuals recently utilized permethrin-impregnated underwear. Although the intervention provided short-term infestation improvement, longer-term use did not show improvement from placebo and also increased prevalence of permethrin-resistant haplotypes.²

Identification

The Hymenoptera order of insects includes Apidae (bees), Vespidae (wasps, yellow jackets, hornets), and Formicidae (fire ants). All 3 of these families of insects inject venom into their prey or as a defense mechanism via ovipositors in their abdomen. Vespids are the most aggressive and are found in each of the United States.¹ They have membranous wings, broad antennae, and a nonbarbed stinger (Figure 1).² The nonbarbed stinger of Vespidae differentiates them from Apidae and allows these insects to sting their prey multiple times. Vespids can build nests in the ground (yellow jackets), trees (hornets), or areas of cover such as window shutters (mud wasps). Because only the queens survive winter, larger populations do not develop until late summer when the most stings take place. Stings most often take place near the nest of the vespid or while the victim is eating outdoors.³

Envenomation

When vespids sting their prey they inject venom via their ovipositors.¹ The venom is composed of a mixture of low-molecular-weight proteins, kinins, proteolytic enzymes, lipids, carbohydrates, and high-molecular-weight proteins that act as allergens.^1,4,5 The proteolytic enzymes degrade the surrounding tissue, basophils become activated, and histamine is released secondary to mast cell degranulation, which results in vasodilation and an inflammatory response characterized by edema, erythema, warmth, and pain.¹ The pain of the sting is immediate and can be intense; almost all victims are acutely aware of the discomforting sensation.⁴

Management of Reactions

Three types of reactions can be seen after a vespid sting: uncomplicated local reactions, large local reactions, and systemic reactions (SRs). The most common reaction is the self-limiting uncomplicated local reaction that includes a focal area of warmth, edema, erythema, induration, and tenderness.¹ Treatment of this kind of reaction is supportive, with ice, nonsteroidal anti-inflammatory drugs, and H₁ and H₂ blockers being commonly used methods. Large local reactions (Figure 2) are similar to uncomplicated local reactions but are greater than 10 cm in diameter and last longer. The same symptomatic treatment may be used along with possible short (3–5 days) oral glucocorticoid (40–60 mg prednisone) or potent topical steroid administration if symptoms persist. Systemic reactions involve IgE-mediated generalized urticaria, angioedema, face swelling, stridor, bronchospasm, nausea, vomiting, flushing, and respiratory distress.¹ Emergency management includes maintenance of airway, breathing, and circulation. Epinephrine injection commonly is employed and should be given via intramuscular injection into the anterolateral thigh; a dose of 0.3 to 0.5 mg can be repeatedly injected every 5 to 15 minutes, as needed.¹

If an individual has an SR, it is recommended to go to an emergency department after stabilization for monitoring. Referral to an allergist for desensitization is appropriate. A radioallergosorbent test to measure allergen-specific IgE can be helpful to confirm an allergy.⁴ This test also should be done weeks after the incident because during the first few days IgE may be too low to measure. Once the allergy is confirmed, the desensitization with venom immunotherapy (VIT) can begin. Venom immunotherapy is effective and reduces a patient’s risk for recurrent SRs to less than 5% to 20%.⁶ A 2015 study recommended longer duration of VIT therapy due to risk for repeat SRs after discontinuing therapy. This study concluded that VIT is to be administered for 5 years, unless the patient is at high risk for SRs after VIT therapy—risk factors include older age, cardiopulmonary disease, SR during VIT treatment, mast cell disorders, and elevated serum tryptase—in which case VIT may have to be continued indefinitely. It is recommended that all patients with history of SR carry an epinephrine autoinjector in case of emergency.⁶

Epidemiologic data show a prevalence of 0.3% to 7.5% for self-reported SRs due to stings, with lower prevalence in children (0.15%–0.3%).^4,7 An additional study looking at data from an allergy practice determined 24% of all cases of anaphylaxis were due to insect stings.⁵

Conclusion

Although many vespid stings can be managed symptomatically, it is imperative for patients and providers to be aware of the possible severe reactions that can take place. It is essential for providers to be aware of how to care for and treat large local reactions and SRs, as symptom recognition and timely treatment can improve patient safety and result in better outcomes.

Identification

The Hymenoptera order of insects includes Apidae (bees), Vespidae (wasps, yellow jackets, hornets), and Formicidae (fire ants). All 3 of these families of insects inject venom into their prey or as a defense mechanism via ovipositors in their abdomen. Vespids are the most aggressive and are found in each of the United States.¹ They have membranous wings, broad antennae, and a nonbarbed stinger (Figure 1).² The nonbarbed stinger of Vespidae differentiates them from Apidae and allows these insects to sting their prey multiple times. Vespids can build nests in the ground (yellow jackets), trees (hornets), or areas of cover such as window shutters (mud wasps). Because only the queens survive winter, larger populations do not develop until late summer when the most stings take place. Stings most often take place near the nest of the vespid or while the victim is eating outdoors.³

Envenomation

When vespids sting their prey they inject venom via their ovipositors.¹ The venom is composed of a mixture of low-molecular-weight proteins, kinins, proteolytic enzymes, lipids, carbohydrates, and high-molecular-weight proteins that act as allergens.^1,4,5 The proteolytic enzymes degrade the surrounding tissue, basophils become activated, and histamine is released secondary to mast cell degranulation, which results in vasodilation and an inflammatory response characterized by edema, erythema, warmth, and pain.¹ The pain of the sting is immediate and can be intense; almost all victims are acutely aware of the discomforting sensation.⁴

Management of Reactions

Three types of reactions can be seen after a vespid sting: uncomplicated local reactions, large local reactions, and systemic reactions (SRs). The most common reaction is the self-limiting uncomplicated local reaction that includes a focal area of warmth, edema, erythema, induration, and tenderness.¹ Treatment of this kind of reaction is supportive, with ice, nonsteroidal anti-inflammatory drugs, and H₁ and H₂ blockers being commonly used methods. Large local reactions (Figure 2) are similar to uncomplicated local reactions but are greater than 10 cm in diameter and last longer. The same symptomatic treatment may be used along with possible short (3–5 days) oral glucocorticoid (40–60 mg prednisone) or potent topical steroid administration if symptoms persist. Systemic reactions involve IgE-mediated generalized urticaria, angioedema, face swelling, stridor, bronchospasm, nausea, vomiting, flushing, and respiratory distress.¹ Emergency management includes maintenance of airway, breathing, and circulation. Epinephrine injection commonly is employed and should be given via intramuscular injection into the anterolateral thigh; a dose of 0.3 to 0.5 mg can be repeatedly injected every 5 to 15 minutes, as needed.¹

If an individual has an SR, it is recommended to go to an emergency department after stabilization for monitoring. Referral to an allergist for desensitization is appropriate. A radioallergosorbent test to measure allergen-specific IgE can be helpful to confirm an allergy.⁴ This test also should be done weeks after the incident because during the first few days IgE may be too low to measure. Once the allergy is confirmed, the desensitization with venom immunotherapy (VIT) can begin. Venom immunotherapy is effective and reduces a patient’s risk for recurrent SRs to less than 5% to 20%.⁶ A 2015 study recommended longer duration of VIT therapy due to risk for repeat SRs after discontinuing therapy. This study concluded that VIT is to be administered for 5 years, unless the patient is at high risk for SRs after VIT therapy—risk factors include older age, cardiopulmonary disease, SR during VIT treatment, mast cell disorders, and elevated serum tryptase—in which case VIT may have to be continued indefinitely. It is recommended that all patients with history of SR carry an epinephrine autoinjector in case of emergency.⁶

Epidemiologic data show a prevalence of 0.3% to 7.5% for self-reported SRs due to stings, with lower prevalence in children (0.15%–0.3%).^4,7 An additional study looking at data from an allergy practice determined 24% of all cases of anaphylaxis were due to insect stings.⁵

Conclusion

Although many vespid stings can be managed symptomatically, it is imperative for patients and providers to be aware of the possible severe reactions that can take place. It is essential for providers to be aware of how to care for and treat large local reactions and SRs, as symptom recognition and timely treatment can improve patient safety and result in better outcomes.

Identification

The Hymenoptera order of insects includes Apidae (bees), Vespidae (wasps, yellow jackets, hornets), and Formicidae (fire ants). All 3 of these families of insects inject venom into their prey or as a defense mechanism via ovipositors in their abdomen. Vespids are the most aggressive and are found in each of the United States.¹ They have membranous wings, broad antennae, and a nonbarbed stinger (Figure 1).² The nonbarbed stinger of Vespidae differentiates them from Apidae and allows these insects to sting their prey multiple times. Vespids can build nests in the ground (yellow jackets), trees (hornets), or areas of cover such as window shutters (mud wasps). Because only the queens survive winter, larger populations do not develop until late summer when the most stings take place. Stings most often take place near the nest of the vespid or while the victim is eating outdoors.³

Envenomation

When vespids sting their prey they inject venom via their ovipositors.¹ The venom is composed of a mixture of low-molecular-weight proteins, kinins, proteolytic enzymes, lipids, carbohydrates, and high-molecular-weight proteins that act as allergens.^1,4,5 The proteolytic enzymes degrade the surrounding tissue, basophils become activated, and histamine is released secondary to mast cell degranulation, which results in vasodilation and an inflammatory response characterized by edema, erythema, warmth, and pain.¹ The pain of the sting is immediate and can be intense; almost all victims are acutely aware of the discomforting sensation.⁴

Management of Reactions

Three types of reactions can be seen after a vespid sting: uncomplicated local reactions, large local reactions, and systemic reactions (SRs). The most common reaction is the self-limiting uncomplicated local reaction that includes a focal area of warmth, edema, erythema, induration, and tenderness.¹ Treatment of this kind of reaction is supportive, with ice, nonsteroidal anti-inflammatory drugs, and H₁ and H₂ blockers being commonly used methods. Large local reactions (Figure 2) are similar to uncomplicated local reactions but are greater than 10 cm in diameter and last longer. The same symptomatic treatment may be used along with possible short (3–5 days) oral glucocorticoid (40–60 mg prednisone) or potent topical steroid administration if symptoms persist. Systemic reactions involve IgE-mediated generalized urticaria, angioedema, face swelling, stridor, bronchospasm, nausea, vomiting, flushing, and respiratory distress.¹ Emergency management includes maintenance of airway, breathing, and circulation. Epinephrine injection commonly is employed and should be given via intramuscular injection into the anterolateral thigh; a dose of 0.3 to 0.5 mg can be repeatedly injected every 5 to 15 minutes, as needed.¹

If an individual has an SR, it is recommended to go to an emergency department after stabilization for monitoring. Referral to an allergist for desensitization is appropriate. A radioallergosorbent test to measure allergen-specific IgE can be helpful to confirm an allergy.⁴ This test also should be done weeks after the incident because during the first few days IgE may be too low to measure. Once the allergy is confirmed, the desensitization with venom immunotherapy (VIT) can begin. Venom immunotherapy is effective and reduces a patient’s risk for recurrent SRs to less than 5% to 20%.⁶ A 2015 study recommended longer duration of VIT therapy due to risk for repeat SRs after discontinuing therapy. This study concluded that VIT is to be administered for 5 years, unless the patient is at high risk for SRs after VIT therapy—risk factors include older age, cardiopulmonary disease, SR during VIT treatment, mast cell disorders, and elevated serum tryptase—in which case VIT may have to be continued indefinitely. It is recommended that all patients with history of SR carry an epinephrine autoinjector in case of emergency.⁶

Epidemiologic data show a prevalence of 0.3% to 7.5% for self-reported SRs due to stings, with lower prevalence in children (0.15%–0.3%).^4,7 An additional study looking at data from an allergy practice determined 24% of all cases of anaphylaxis were due to insect stings.⁵

Conclusion

Although many vespid stings can be managed symptomatically, it is imperative for patients and providers to be aware of the possible severe reactions that can take place. It is essential for providers to be aware of how to care for and treat large local reactions and SRs, as symptom recognition and timely treatment can improve patient safety and result in better outcomes.

Classification

Blister beetles are both a scourge and the source of medical cantharidin (Figure 1). The term blister beetle refers to 3 families of the order Coleoptera: Meloidae, Oedemeridae, and Staphylinidae (Figure 2).

Meloidae is the most well-known family of blister beetles, with more than 200 species worldwide identified as a cause of blistering dermatitis.¹ The most notorious is Lytta vesicatoria, also known as the Spanish fly. Although some blister beetles are inconspicuous in appearance, most are brightly colored and easily spotted, making them attractive to small children.² They may be attracted to fluorescent lighting and commonly enter through open windows.³ Blister beetles do not bite or sting; rather, they release cantharidin via hemolymph, an oily yellow substance that is copiously expressed from the leg joints when disturbed by rubbing or pressing.^1,3-5 Blistering also is associated with exposure to the contents of crushed beetles, which is the source of pharmacologic cantharidin.^2,4,6

Oedemeridae are the smallest and least known beetles within the Coleoptera family. They often are called false blister beetles, which is a misnomer. Oedemeridae beetles also produce cantharidin, similar to Meloidae beetles; however, because Oedemeridae beetles are smaller, the vesiculobullous eruptions also are less pronounced.¹

A third well-known family of blister beetles is the Staphylinidae family. Rove beetles (genus Paederus) differ from the Meloidae and Oedemeridae families in that they produce the vesicant pederin rather than cantharidin. Pederin causes a more violent eruption called dermatitis linearis, which often is associated with intense urticaria prior to blistering.¹ Rove beetles are found in moist environments and tend to favor tropical and subtropical climates. They may emerge in large numbers after heavy rainfall.

Clinical Presentation

Blistering dermatitis—caused by exposure to cantharidin (families Meloidae and Oedemeridae) or pederin (genus Paederus)—begins as burning and tingling within minutes of exposure. Bullae later develop, often in a linear fashion, with subsequent bursting and crust formation.^1,3 Secondary infection can occur.⁵ Exposure occurring on the elbows, knees, or mirroring skin folds results in lesions on opposing surfaces that come into contact, otherwise known as kissing lesions.^1,3 Acantholysis of suprabasal keratinocytes can be seen on histologic sections of blisters (Figure 3)^1,7 due to cantharidin activation of the serine/threonine protein phosphatases that cause detachment of tonofilaments from desmosomes.^1,8 Washing of exposed sites with soap or alcohol can potentially prevent development of blistering dermatitis; however, lesions usually heal without complication when treated with topical antibiotics.³

If blister beetles are ingested, they can cause poisoning characterized by abdominal pain and hematuria.^1,3,9,10 In fact, blister beetle ingestion by animals consuming baled hay is an important agricultural and economical implication. Several cases of fatal farm animal ingestion resulting in gastrointestinal erosion have been reported.^4,6

Medicinal Properties

Medicinal use of cantharidin has been recorded as early as the 19th century and is believed to have been part of ancient medicinal practices in China, Spain, South Africa, and pre-Columbian America for its vesicant, abortifacient, and supposed aphrodisiac properties.^2,4,8

Toxicity from internal ingestion has been well documented.^1,3,9,10 The Mylabris and Epicauta genera of the family Meloidae, most commonly the Spanish fly, are used for modern extraction of cantharidin. Up to 5% of the dry weight of a blister beetle can be constituted by cantharidin.⁴

Although its use has diminished due to limited availability, cantharidin is still used for treatment of common warts, periungual warts, and molluscum contagiosum. It is a favorable choice for treating pediatric patients because of the tolerability and painlessness of application. Due to its acantholytic properties, warts generally slough with the cantharidin-induced blister.¹¹

In recent years, cantharidin has been studied for its anticancer properties. It has been shown to weaken cancer cell antioxidant properties by interfering with glutathione-related enzymes, thus inducing oxidative damage. Additionally, cantharidin is associated with decreased mitochondrial cytochrome C and increased cytosolic cytochrome C, an important signal for apoptosis.¹² Furthermore, cantharidin recently was shown to increase expression of proapoptotic proteins and decrease expression of antiapoptotic proteins causing cell death in nasopharyngeal carcinoma, making it a potential anticancer treatment.¹³

Conclusion

Blister beetles, long known for their production of vesicant agents, are both a cause of as well as a potential treatment of dermatologic disease. The blistering associated with exposure to a disturbed beetle generally is mild and heals without scarring if vital areas such as the eyelids are not affected.

Classification

Blister beetles are both a scourge and the source of medical cantharidin (Figure 1). The term blister beetle refers to 3 families of the order Coleoptera: Meloidae, Oedemeridae, and Staphylinidae (Figure 2).

Meloidae is the most well-known family of blister beetles, with more than 200 species worldwide identified as a cause of blistering dermatitis.¹ The most notorious is Lytta vesicatoria, also known as the Spanish fly. Although some blister beetles are inconspicuous in appearance, most are brightly colored and easily spotted, making them attractive to small children.² They may be attracted to fluorescent lighting and commonly enter through open windows.³ Blister beetles do not bite or sting; rather, they release cantharidin via hemolymph, an oily yellow substance that is copiously expressed from the leg joints when disturbed by rubbing or pressing.^1,3-5 Blistering also is associated with exposure to the contents of crushed beetles, which is the source of pharmacologic cantharidin.^2,4,6

Oedemeridae are the smallest and least known beetles within the Coleoptera family. They often are called false blister beetles, which is a misnomer. Oedemeridae beetles also produce cantharidin, similar to Meloidae beetles; however, because Oedemeridae beetles are smaller, the vesiculobullous eruptions also are less pronounced.¹

A third well-known family of blister beetles is the Staphylinidae family. Rove beetles (genus Paederus) differ from the Meloidae and Oedemeridae families in that they produce the vesicant pederin rather than cantharidin. Pederin causes a more violent eruption called dermatitis linearis, which often is associated with intense urticaria prior to blistering.¹ Rove beetles are found in moist environments and tend to favor tropical and subtropical climates. They may emerge in large numbers after heavy rainfall.

Clinical Presentation

Blistering dermatitis—caused by exposure to cantharidin (families Meloidae and Oedemeridae) or pederin (genus Paederus)—begins as burning and tingling within minutes of exposure. Bullae later develop, often in a linear fashion, with subsequent bursting and crust formation.^1,3 Secondary infection can occur.⁵ Exposure occurring on the elbows, knees, or mirroring skin folds results in lesions on opposing surfaces that come into contact, otherwise known as kissing lesions.^1,3 Acantholysis of suprabasal keratinocytes can be seen on histologic sections of blisters (Figure 3)^1,7 due to cantharidin activation of the serine/threonine protein phosphatases that cause detachment of tonofilaments from desmosomes.^1,8 Washing of exposed sites with soap or alcohol can potentially prevent development of blistering dermatitis; however, lesions usually heal without complication when treated with topical antibiotics.³

If blister beetles are ingested, they can cause poisoning characterized by abdominal pain and hematuria.^1,3,9,10 In fact, blister beetle ingestion by animals consuming baled hay is an important agricultural and economical implication. Several cases of fatal farm animal ingestion resulting in gastrointestinal erosion have been reported.^4,6

Medicinal Properties

Medicinal use of cantharidin has been recorded as early as the 19th century and is believed to have been part of ancient medicinal practices in China, Spain, South Africa, and pre-Columbian America for its vesicant, abortifacient, and supposed aphrodisiac properties.^2,4,8

Toxicity from internal ingestion has been well documented.^1,3,9,10 The Mylabris and Epicauta genera of the family Meloidae, most commonly the Spanish fly, are used for modern extraction of cantharidin. Up to 5% of the dry weight of a blister beetle can be constituted by cantharidin.⁴

Although its use has diminished due to limited availability, cantharidin is still used for treatment of common warts, periungual warts, and molluscum contagiosum. It is a favorable choice for treating pediatric patients because of the tolerability and painlessness of application. Due to its acantholytic properties, warts generally slough with the cantharidin-induced blister.¹¹

In recent years, cantharidin has been studied for its anticancer properties. It has been shown to weaken cancer cell antioxidant properties by interfering with glutathione-related enzymes, thus inducing oxidative damage. Additionally, cantharidin is associated with decreased mitochondrial cytochrome C and increased cytosolic cytochrome C, an important signal for apoptosis.¹² Furthermore, cantharidin recently was shown to increase expression of proapoptotic proteins and decrease expression of antiapoptotic proteins causing cell death in nasopharyngeal carcinoma, making it a potential anticancer treatment.¹³

Conclusion

Blister beetles, long known for their production of vesicant agents, are both a cause of as well as a potential treatment of dermatologic disease. The blistering associated with exposure to a disturbed beetle generally is mild and heals without scarring if vital areas such as the eyelids are not affected.

Classification

Blister beetles are both a scourge and the source of medical cantharidin (Figure 1). The term blister beetle refers to 3 families of the order Coleoptera: Meloidae, Oedemeridae, and Staphylinidae (Figure 2).

Meloidae is the most well-known family of blister beetles, with more than 200 species worldwide identified as a cause of blistering dermatitis.¹ The most notorious is Lytta vesicatoria, also known as the Spanish fly. Although some blister beetles are inconspicuous in appearance, most are brightly colored and easily spotted, making them attractive to small children.² They may be attracted to fluorescent lighting and commonly enter through open windows.³ Blister beetles do not bite or sting; rather, they release cantharidin via hemolymph, an oily yellow substance that is copiously expressed from the leg joints when disturbed by rubbing or pressing.^1,3-5 Blistering also is associated with exposure to the contents of crushed beetles, which is the source of pharmacologic cantharidin.^2,4,6

Oedemeridae are the smallest and least known beetles within the Coleoptera family. They often are called false blister beetles, which is a misnomer. Oedemeridae beetles also produce cantharidin, similar to Meloidae beetles; however, because Oedemeridae beetles are smaller, the vesiculobullous eruptions also are less pronounced.¹

A third well-known family of blister beetles is the Staphylinidae family. Rove beetles (genus Paederus) differ from the Meloidae and Oedemeridae families in that they produce the vesicant pederin rather than cantharidin. Pederin causes a more violent eruption called dermatitis linearis, which often is associated with intense urticaria prior to blistering.¹ Rove beetles are found in moist environments and tend to favor tropical and subtropical climates. They may emerge in large numbers after heavy rainfall.

Clinical Presentation

Blistering dermatitis—caused by exposure to cantharidin (families Meloidae and Oedemeridae) or pederin (genus Paederus)—begins as burning and tingling within minutes of exposure. Bullae later develop, often in a linear fashion, with subsequent bursting and crust formation.^1,3 Secondary infection can occur.⁵ Exposure occurring on the elbows, knees, or mirroring skin folds results in lesions on opposing surfaces that come into contact, otherwise known as kissing lesions.^1,3 Acantholysis of suprabasal keratinocytes can be seen on histologic sections of blisters (Figure 3)^1,7 due to cantharidin activation of the serine/threonine protein phosphatases that cause detachment of tonofilaments from desmosomes.^1,8 Washing of exposed sites with soap or alcohol can potentially prevent development of blistering dermatitis; however, lesions usually heal without complication when treated with topical antibiotics.³

If blister beetles are ingested, they can cause poisoning characterized by abdominal pain and hematuria.^1,3,9,10 In fact, blister beetle ingestion by animals consuming baled hay is an important agricultural and economical implication. Several cases of fatal farm animal ingestion resulting in gastrointestinal erosion have been reported.^4,6

Medicinal Properties

Medicinal use of cantharidin has been recorded as early as the 19th century and is believed to have been part of ancient medicinal practices in China, Spain, South Africa, and pre-Columbian America for its vesicant, abortifacient, and supposed aphrodisiac properties.^2,4,8

Toxicity from internal ingestion has been well documented.^1,3,9,10 The Mylabris and Epicauta genera of the family Meloidae, most commonly the Spanish fly, are used for modern extraction of cantharidin. Up to 5% of the dry weight of a blister beetle can be constituted by cantharidin.⁴

Although its use has diminished due to limited availability, cantharidin is still used for treatment of common warts, periungual warts, and molluscum contagiosum. It is a favorable choice for treating pediatric patients because of the tolerability and painlessness of application. Due to its acantholytic properties, warts generally slough with the cantharidin-induced blister.¹¹

In recent years, cantharidin has been studied for its anticancer properties. It has been shown to weaken cancer cell antioxidant properties by interfering with glutathione-related enzymes, thus inducing oxidative damage. Additionally, cantharidin is associated with decreased mitochondrial cytochrome C and increased cytosolic cytochrome C, an important signal for apoptosis.¹² Furthermore, cantharidin recently was shown to increase expression of proapoptotic proteins and decrease expression of antiapoptotic proteins causing cell death in nasopharyngeal carcinoma, making it a potential anticancer treatment.¹³

Conclusion

Blister beetles, long known for their production of vesicant agents, are both a cause of as well as a potential treatment of dermatologic disease. The blistering associated with exposure to a disturbed beetle generally is mild and heals without scarring if vital areas such as the eyelids are not affected.

Rattlesnakes are pit vipers with a rattle attached to the tip of the tail and facial pits located between the eyes and nose with a special organ that detects heat energy (infrared light) and is used for hunting prey. There are 2 genera of rattlesnakes, Sistrurus (3 species) and Crotalus (23 species). ¹ The pigmy rattlesnake belongs to the Sistrurus miliarius species that is subdivided into 3 subspecies: the Carolina pigmy rattlesnake (Sistrurus miliarius miliarius), the Western pigmy rattlesnake (Sistrurus miliarius streckeri ), and the dusky pigmy rattlesnake (Sistrurus miliarius barbouri ). ¹ The dusky pigmy rattlesnake is found in South Carolina, southern Georgia, southern Alabama, southeastern Mississippi, and Florida. ² It is the most abundant venomous snake in Florida. ³ Its rattle is barely audible, and it is an aggressive small snake ranging in length from 38 to 56 cm. ⁴ Its venom is hemorrhagic, causing tissue damage but not containing neurotoxins. ⁴ Although bites can be painful, resulting in localized necrosis and rare loss of digits, it is unlikely for bites to be fatal given the snake’s small fangs, small size, and amount of envenomation. However, bites on children may require hospitalization. The venom contains proteins, polypeptides, and enzymes. ⁵ One such peptide, barbourin, inhibits a transmembrane receptor that plays a role in platelet aggregation. ⁶

We report a case of a 54-year-old man who was bitten on the left index finger by a dusky pigmy rattlesnake. We describe the clinical course and successful treatment with crotalidae polyvalent immune fab (CPIF) antivenom.

Case Report

A 54-year-old man presented to the emergency department with a rapidly swelling and erythematous left hand following a snakebite to the left index fingertip while weeding in his yard (Figure 1). The patient was able to kill the snake with a shovel and photograph it, which helped identify it as a dusky pigmy rattlesnake (Figure 2). Vitals on presentation included a blood pressure of 161/98, pulse oximeter of 99%, temperature of 36.4°C, pulse of 84 beats per minute, and respiratory rate of 16 breaths per minute.

Given the poisonous snakebite, the patient was admitted to the intensive care unit. Laboratory test results at admission revealed the following values: platelet count, 235,000/µL (reference range, 150,000–450,000/µL); fibrinogen, 226.1 mg/dL (reference range, 185–410 mg/dL); fibrin degradation products, less than 10 µg/mL (reference range, <10 µg/mL); glucose, 145 mg/dL (reference range, 74–106 mg/dL). The remainder of the complete blood cell count and metabolic panel was unremarkable. His blood type was O Rh+. Radiography of the left second digit did not show any fractures, dislocations, or foreign object.

After consulting with the Tampa General Hospital Florida Poison Information Center, 6 vials of CPIF antivenom in 250 mL of sodium chloride initially were infused intravenously, followed by 2 additional vials each at 6, 12, and 18 hours. Serial laboratory test results revealed white blood cell counts of 13,600, 10,000, 6800, 6100, and 6800/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Platelet counts were 222,000, 159,000, 116,000, 99,000, and 129,000/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. The hemoglobin level was 14.8, 13.1, 13.8, 13.7, and 14.3 g/dL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Other laboratory test results including prothrombin time (10.0 s), fibrinogen (226.1 mg/dL), and fibrin degradation products (<10 µg/mL) at 4 hours postadmission remained within reference range during serial monitoring.

Comment

Envenomation
Snakebites and envenomation are a complex and broad subject beyond the scope of this article and further reading on this subject is highly encouraged. The clinical findings from snakebites range from mild local tissue reactions to severe systemic symptoms depending on the volume of venom injected, snake species, age and health of victim, and location of bite. Severe systemic symptoms include disseminated intravascular coagulation, acute renal failure, hypovolemic shock, and death.⁵ Venom can be hemotoxic and/or neurotoxic. Hemotoxic symptoms include pain, edema, swelling, ecchymoses, necrosis, and hemolysis. Neurotoxic symptoms may encompass diplopia, dysphagia, sweating, salivation, diaphoresis, respiratory depression, and paralysis.⁵ The pigmy rattlesnake venom is only hemotoxic, not neurotoxic.⁴ Eastern and western variety rattlesnakes account for most snake deaths due to their potent venom. Water moccasins (cottonmouths) have intermediate-potency venom, and copperhead snakes have the least-potent venom.⁵ Coral snakes are not pit vipers and require a different antivenom.

Management of Snakebites
Venomous snakes may bite a person without injecting venom. In fact, as many as 20% to 25% of all pit viper bites are dry.⁷ No attempts should be made to capture or kill the biting snake, but identifying it safely is helpful. Dead snakes should not be handled carelessly, as reflex biting after death has been reported.⁸ Cutting or suctioning the bite wound, nonsteroidal anti-inflammatory drugs, prophylactic antibiotics, tourniquets, prophylactic fasciotomy, and ice have not proven to be beneficial in the management of viper envenomation.^5,9-11 The best management involves immobilizing the affected extremity, seeking immediate medical attention, and initiating antivenom therapy as soon as possible.

Antivenom Therapy
Crotalidae polyvalent immune fab is an antivenom comprised of purified, sheep-derived fab IgG fragments and was approved by the US Food and Drug Administration in 2000 for the treatment of North American crotalid envenomation.^12,13 Its venom-specific fab fragments of IgG bind to and neutralize venom toxins and facilitate their elimination. Crotalidae polyvalent immune fab does not contain the Fc fragment of the IgG antibody, resulting in a low incidence of hypersensitivity reactions (8%) and serum sickness (13%).¹³ It is produced using 4 North American venoms: Crotalus atrox (western diamondback rattlesnake), Crotalus adamanteus (eastern diamondback rattlesnake), Crotalus scutulatus (Mojave rattlesnake), and Agkistrodon piscivorus (water moccasin).¹² It has become the standard-of-care antivenom for pit viper bites and has replaced its equine-derived predecessor antivenin crotalidae polyvalent, which is known for high rates of acute allergic reactions (23%–56%) including anaphylaxis and delayed serum sickness.^13,14 In postmarketing studies, CPIF has demonstrated control of envenomation regardless of severity. The most common adverse reactions reported include urticaria, rash, nausea, pruritus, and back pain.¹³ Anaphylaxis and anaphylactoid reactions may occur, and patients should be carefully observed during antivenom infusion. Appropriate management should be readily available including epinephrine, intravenous antihistamines, and/or albuterol. Contraindications include known hypersensitivity to papaya or papain, which is used to cleave the antibodies into fragments during the processing of CPIF. Patients also may react to it if allergic to other papaya extracts, chymopapain, or bromelain (pineapple enzyme), as well as some dust mite allergens and latex allergens that share antigenic structures with papain.¹⁵ Each vial of CPIF is reconstituted with 18 mL of 0.9% sodium chloride, as described in the package insert.¹³ The total dose (minimum of 4 to maximum of 12 vials initial dose) is then diluted in 250 mL of normal saline and infused over 1 hour starting for the first 10 minutes at a rate of 25 to 50 mL/h, and if tolerated, then increased to 250 mL/h until completion.

Treatment Algorithm
According to the envenomation consensus treatment algorithm, assess the site of the snakebite and mark leading edge of swelling every 15 to 30 minutes,¹⁶ as shown in our patient in Figure 6.Immobilize and elevate the affected extremity. Update tetanus vaccine and order initial laboratory tests to include prothrombin time, hemoglobin, platelets, and fibrinogen. If the patient does not exhibit local signs of envenomation such as redness, swelling, or ecchymosis, and the patient has no coagulation laboratory abnormalities and exhibits no systemic signs such as diarrhea, vomiting or angioedema, withhold CPIF and observe the patient for a minimum of 8 hours. Repeat laboratory tests prior to discharge. This clinical scenario most likely occurs in the setting of a dry bite or no bite at all. For minor envenomation, it also is possible to withhold CPIF and observe the patient for 12 to 24 hours if he/she remains stable and laboratory tests remain within reference range. If the patient has local or systemic signs of envenomation, start CPIF (4–6 vials and up to a maximum of 12 vials). The first dose of CPIF should be administered in the emergency department or intensive care unit. If after the first hour envenomation is worsening, an additional 4 to 6 vials may be infused. If after the first hour of observation the envenomation is controlled based on decreased swelling or lack of progression and there is improvement in laboratory values, then a maintenance regimen can be initiated. The maintenance dose consists of 2 vials every 6 hours for up to 18 hours (3 separate 2-vial doses). Patients can be discharged if stable and with no negative laboratory trends during the observation period.¹⁶ If CPIF was administered, follow-up laboratory tests results are dependent on prior findings of coagulation abnormalities, degree of envenomation, and signs and symptoms of coagulopathy postdischarge. Recurrent coagulopathy can occur in patients with coagulation abnormalities during initial envenomation, and patients should be monitored for possible re-treatment for at least 1 week or longer.¹⁷ Coagulopathy can present with decreased fibrinogen, decreased platelets, and elevated prothrombin time. Our patient experienced a drop in platelet count and hemoglobin level in addition to localized tissue effects, but he responded to the antivenom therapy. Lastly and importantly, no pediatric adjustments are necessary, and although mercury has been removed from the product’s manufacturing process, certain easily identifiable antivenom lots that have not expired contain ethyl mercury from thimerosal.^13,18,19 Some side effects of thimerosal include redness and swelling of the injection site, but scientific research does not show a connection with autism.²⁰

Conclusion

Dusky pigmy rattlesnake envenomations are clinically responsive to CPIF antivenom treatment.²¹ Although no clearly documented fatalities have been reported from dusky pigmy rattlesnake bites, coagulopathy and local tissue necrosis—as described in our patient—can result from such snakebites, requiring hospitalization. These snakes are common in the southeastern United States, and the treatment algorithm presented can be extrapolated to other more serious and deadly pit viper bites.

Rattlesnakes are pit vipers with a rattle attached to the tip of the tail and facial pits located between the eyes and nose with a special organ that detects heat energy (infrared light) and is used for hunting prey. There are 2 genera of rattlesnakes, Sistrurus (3 species) and Crotalus (23 species). ¹ The pigmy rattlesnake belongs to the Sistrurus miliarius species that is subdivided into 3 subspecies: the Carolina pigmy rattlesnake (Sistrurus miliarius miliarius), the Western pigmy rattlesnake (Sistrurus miliarius streckeri ), and the dusky pigmy rattlesnake (Sistrurus miliarius barbouri ). ¹ The dusky pigmy rattlesnake is found in South Carolina, southern Georgia, southern Alabama, southeastern Mississippi, and Florida. ² It is the most abundant venomous snake in Florida. ³ Its rattle is barely audible, and it is an aggressive small snake ranging in length from 38 to 56 cm. ⁴ Its venom is hemorrhagic, causing tissue damage but not containing neurotoxins. ⁴ Although bites can be painful, resulting in localized necrosis and rare loss of digits, it is unlikely for bites to be fatal given the snake’s small fangs, small size, and amount of envenomation. However, bites on children may require hospitalization. The venom contains proteins, polypeptides, and enzymes. ⁵ One such peptide, barbourin, inhibits a transmembrane receptor that plays a role in platelet aggregation. ⁶

We report a case of a 54-year-old man who was bitten on the left index finger by a dusky pigmy rattlesnake. We describe the clinical course and successful treatment with crotalidae polyvalent immune fab (CPIF) antivenom.

Case Report

A 54-year-old man presented to the emergency department with a rapidly swelling and erythematous left hand following a snakebite to the left index fingertip while weeding in his yard (Figure 1). The patient was able to kill the snake with a shovel and photograph it, which helped identify it as a dusky pigmy rattlesnake (Figure 2). Vitals on presentation included a blood pressure of 161/98, pulse oximeter of 99%, temperature of 36.4°C, pulse of 84 beats per minute, and respiratory rate of 16 breaths per minute.

Given the poisonous snakebite, the patient was admitted to the intensive care unit. Laboratory test results at admission revealed the following values: platelet count, 235,000/µL (reference range, 150,000–450,000/µL); fibrinogen, 226.1 mg/dL (reference range, 185–410 mg/dL); fibrin degradation products, less than 10 µg/mL (reference range, <10 µg/mL); glucose, 145 mg/dL (reference range, 74–106 mg/dL). The remainder of the complete blood cell count and metabolic panel was unremarkable. His blood type was O Rh+. Radiography of the left second digit did not show any fractures, dislocations, or foreign object.

After consulting with the Tampa General Hospital Florida Poison Information Center, 6 vials of CPIF antivenom in 250 mL of sodium chloride initially were infused intravenously, followed by 2 additional vials each at 6, 12, and 18 hours. Serial laboratory test results revealed white blood cell counts of 13,600, 10,000, 6800, 6100, and 6800/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Platelet counts were 222,000, 159,000, 116,000, 99,000, and 129,000/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. The hemoglobin level was 14.8, 13.1, 13.8, 13.7, and 14.3 g/dL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Other laboratory test results including prothrombin time (10.0 s), fibrinogen (226.1 mg/dL), and fibrin degradation products (<10 µg/mL) at 4 hours postadmission remained within reference range during serial monitoring.

Comment

Envenomation
Snakebites and envenomation are a complex and broad subject beyond the scope of this article and further reading on this subject is highly encouraged. The clinical findings from snakebites range from mild local tissue reactions to severe systemic symptoms depending on the volume of venom injected, snake species, age and health of victim, and location of bite. Severe systemic symptoms include disseminated intravascular coagulation, acute renal failure, hypovolemic shock, and death.⁵ Venom can be hemotoxic and/or neurotoxic. Hemotoxic symptoms include pain, edema, swelling, ecchymoses, necrosis, and hemolysis. Neurotoxic symptoms may encompass diplopia, dysphagia, sweating, salivation, diaphoresis, respiratory depression, and paralysis.⁵ The pigmy rattlesnake venom is only hemotoxic, not neurotoxic.⁴ Eastern and western variety rattlesnakes account for most snake deaths due to their potent venom. Water moccasins (cottonmouths) have intermediate-potency venom, and copperhead snakes have the least-potent venom.⁵ Coral snakes are not pit vipers and require a different antivenom.

Management of Snakebites
Venomous snakes may bite a person without injecting venom. In fact, as many as 20% to 25% of all pit viper bites are dry.⁷ No attempts should be made to capture or kill the biting snake, but identifying it safely is helpful. Dead snakes should not be handled carelessly, as reflex biting after death has been reported.⁸ Cutting or suctioning the bite wound, nonsteroidal anti-inflammatory drugs, prophylactic antibiotics, tourniquets, prophylactic fasciotomy, and ice have not proven to be beneficial in the management of viper envenomation.^5,9-11 The best management involves immobilizing the affected extremity, seeking immediate medical attention, and initiating antivenom therapy as soon as possible.

Antivenom Therapy
Crotalidae polyvalent immune fab is an antivenom comprised of purified, sheep-derived fab IgG fragments and was approved by the US Food and Drug Administration in 2000 for the treatment of North American crotalid envenomation.^12,13 Its venom-specific fab fragments of IgG bind to and neutralize venom toxins and facilitate their elimination. Crotalidae polyvalent immune fab does not contain the Fc fragment of the IgG antibody, resulting in a low incidence of hypersensitivity reactions (8%) and serum sickness (13%).¹³ It is produced using 4 North American venoms: Crotalus atrox (western diamondback rattlesnake), Crotalus adamanteus (eastern diamondback rattlesnake), Crotalus scutulatus (Mojave rattlesnake), and Agkistrodon piscivorus (water moccasin).¹² It has become the standard-of-care antivenom for pit viper bites and has replaced its equine-derived predecessor antivenin crotalidae polyvalent, which is known for high rates of acute allergic reactions (23%–56%) including anaphylaxis and delayed serum sickness.^13,14 In postmarketing studies, CPIF has demonstrated control of envenomation regardless of severity. The most common adverse reactions reported include urticaria, rash, nausea, pruritus, and back pain.¹³ Anaphylaxis and anaphylactoid reactions may occur, and patients should be carefully observed during antivenom infusion. Appropriate management should be readily available including epinephrine, intravenous antihistamines, and/or albuterol. Contraindications include known hypersensitivity to papaya or papain, which is used to cleave the antibodies into fragments during the processing of CPIF. Patients also may react to it if allergic to other papaya extracts, chymopapain, or bromelain (pineapple enzyme), as well as some dust mite allergens and latex allergens that share antigenic structures with papain.¹⁵ Each vial of CPIF is reconstituted with 18 mL of 0.9% sodium chloride, as described in the package insert.¹³ The total dose (minimum of 4 to maximum of 12 vials initial dose) is then diluted in 250 mL of normal saline and infused over 1 hour starting for the first 10 minutes at a rate of 25 to 50 mL/h, and if tolerated, then increased to 250 mL/h until completion.

Treatment Algorithm
According to the envenomation consensus treatment algorithm, assess the site of the snakebite and mark leading edge of swelling every 15 to 30 minutes,¹⁶ as shown in our patient in Figure 6.Immobilize and elevate the affected extremity. Update tetanus vaccine and order initial laboratory tests to include prothrombin time, hemoglobin, platelets, and fibrinogen. If the patient does not exhibit local signs of envenomation such as redness, swelling, or ecchymosis, and the patient has no coagulation laboratory abnormalities and exhibits no systemic signs such as diarrhea, vomiting or angioedema, withhold CPIF and observe the patient for a minimum of 8 hours. Repeat laboratory tests prior to discharge. This clinical scenario most likely occurs in the setting of a dry bite or no bite at all. For minor envenomation, it also is possible to withhold CPIF and observe the patient for 12 to 24 hours if he/she remains stable and laboratory tests remain within reference range. If the patient has local or systemic signs of envenomation, start CPIF (4–6 vials and up to a maximum of 12 vials). The first dose of CPIF should be administered in the emergency department or intensive care unit. If after the first hour envenomation is worsening, an additional 4 to 6 vials may be infused. If after the first hour of observation the envenomation is controlled based on decreased swelling or lack of progression and there is improvement in laboratory values, then a maintenance regimen can be initiated. The maintenance dose consists of 2 vials every 6 hours for up to 18 hours (3 separate 2-vial doses). Patients can be discharged if stable and with no negative laboratory trends during the observation period.¹⁶ If CPIF was administered, follow-up laboratory tests results are dependent on prior findings of coagulation abnormalities, degree of envenomation, and signs and symptoms of coagulopathy postdischarge. Recurrent coagulopathy can occur in patients with coagulation abnormalities during initial envenomation, and patients should be monitored for possible re-treatment for at least 1 week or longer.¹⁷ Coagulopathy can present with decreased fibrinogen, decreased platelets, and elevated prothrombin time. Our patient experienced a drop in platelet count and hemoglobin level in addition to localized tissue effects, but he responded to the antivenom therapy. Lastly and importantly, no pediatric adjustments are necessary, and although mercury has been removed from the product’s manufacturing process, certain easily identifiable antivenom lots that have not expired contain ethyl mercury from thimerosal.^13,18,19 Some side effects of thimerosal include redness and swelling of the injection site, but scientific research does not show a connection with autism.²⁰

Conclusion

Dusky pigmy rattlesnake envenomations are clinically responsive to CPIF antivenom treatment.²¹ Although no clearly documented fatalities have been reported from dusky pigmy rattlesnake bites, coagulopathy and local tissue necrosis—as described in our patient—can result from such snakebites, requiring hospitalization. These snakes are common in the southeastern United States, and the treatment algorithm presented can be extrapolated to other more serious and deadly pit viper bites.

Rattlesnakes are pit vipers with a rattle attached to the tip of the tail and facial pits located between the eyes and nose with a special organ that detects heat energy (infrared light) and is used for hunting prey. There are 2 genera of rattlesnakes, Sistrurus (3 species) and Crotalus (23 species). ¹ The pigmy rattlesnake belongs to the Sistrurus miliarius species that is subdivided into 3 subspecies: the Carolina pigmy rattlesnake (Sistrurus miliarius miliarius), the Western pigmy rattlesnake (Sistrurus miliarius streckeri ), and the dusky pigmy rattlesnake (Sistrurus miliarius barbouri ). ¹ The dusky pigmy rattlesnake is found in South Carolina, southern Georgia, southern Alabama, southeastern Mississippi, and Florida. ² It is the most abundant venomous snake in Florida. ³ Its rattle is barely audible, and it is an aggressive small snake ranging in length from 38 to 56 cm. ⁴ Its venom is hemorrhagic, causing tissue damage but not containing neurotoxins. ⁴ Although bites can be painful, resulting in localized necrosis and rare loss of digits, it is unlikely for bites to be fatal given the snake’s small fangs, small size, and amount of envenomation. However, bites on children may require hospitalization. The venom contains proteins, polypeptides, and enzymes. ⁵ One such peptide, barbourin, inhibits a transmembrane receptor that plays a role in platelet aggregation. ⁶

We report a case of a 54-year-old man who was bitten on the left index finger by a dusky pigmy rattlesnake. We describe the clinical course and successful treatment with crotalidae polyvalent immune fab (CPIF) antivenom.

Case Report

A 54-year-old man presented to the emergency department with a rapidly swelling and erythematous left hand following a snakebite to the left index fingertip while weeding in his yard (Figure 1). The patient was able to kill the snake with a shovel and photograph it, which helped identify it as a dusky pigmy rattlesnake (Figure 2). Vitals on presentation included a blood pressure of 161/98, pulse oximeter of 99%, temperature of 36.4°C, pulse of 84 beats per minute, and respiratory rate of 16 breaths per minute.

Given the poisonous snakebite, the patient was admitted to the intensive care unit. Laboratory test results at admission revealed the following values: platelet count, 235,000/µL (reference range, 150,000–450,000/µL); fibrinogen, 226.1 mg/dL (reference range, 185–410 mg/dL); fibrin degradation products, less than 10 µg/mL (reference range, <10 µg/mL); glucose, 145 mg/dL (reference range, 74–106 mg/dL). The remainder of the complete blood cell count and metabolic panel was unremarkable. His blood type was O Rh+. Radiography of the left second digit did not show any fractures, dislocations, or foreign object.

After consulting with the Tampa General Hospital Florida Poison Information Center, 6 vials of CPIF antivenom in 250 mL of sodium chloride initially were infused intravenously, followed by 2 additional vials each at 6, 12, and 18 hours. Serial laboratory test results revealed white blood cell counts of 13,600, 10,000, 6800, 6100, and 6800/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Platelet counts were 222,000, 159,000, 116,000, 99,000, and 129,000/µL at 4, 15, 43, 65, and 88 hours postadmission, respectively. The hemoglobin level was 14.8, 13.1, 13.8, 13.7, and 14.3 g/dL at 4, 15, 43, 65, and 88 hours postadmission, respectively. Other laboratory test results including prothrombin time (10.0 s), fibrinogen (226.1 mg/dL), and fibrin degradation products (<10 µg/mL) at 4 hours postadmission remained within reference range during serial monitoring.

Comment

Envenomation
Snakebites and envenomation are a complex and broad subject beyond the scope of this article and further reading on this subject is highly encouraged. The clinical findings from snakebites range from mild local tissue reactions to severe systemic symptoms depending on the volume of venom injected, snake species, age and health of victim, and location of bite. Severe systemic symptoms include disseminated intravascular coagulation, acute renal failure, hypovolemic shock, and death.⁵ Venom can be hemotoxic and/or neurotoxic. Hemotoxic symptoms include pain, edema, swelling, ecchymoses, necrosis, and hemolysis. Neurotoxic symptoms may encompass diplopia, dysphagia, sweating, salivation, diaphoresis, respiratory depression, and paralysis.⁵ The pigmy rattlesnake venom is only hemotoxic, not neurotoxic.⁴ Eastern and western variety rattlesnakes account for most snake deaths due to their potent venom. Water moccasins (cottonmouths) have intermediate-potency venom, and copperhead snakes have the least-potent venom.⁵ Coral snakes are not pit vipers and require a different antivenom.

Management of Snakebites
Venomous snakes may bite a person without injecting venom. In fact, as many as 20% to 25% of all pit viper bites are dry.⁷ No attempts should be made to capture or kill the biting snake, but identifying it safely is helpful. Dead snakes should not be handled carelessly, as reflex biting after death has been reported.⁸ Cutting or suctioning the bite wound, nonsteroidal anti-inflammatory drugs, prophylactic antibiotics, tourniquets, prophylactic fasciotomy, and ice have not proven to be beneficial in the management of viper envenomation.^5,9-11 The best management involves immobilizing the affected extremity, seeking immediate medical attention, and initiating antivenom therapy as soon as possible.

Antivenom Therapy
Crotalidae polyvalent immune fab is an antivenom comprised of purified, sheep-derived fab IgG fragments and was approved by the US Food and Drug Administration in 2000 for the treatment of North American crotalid envenomation.^12,13 Its venom-specific fab fragments of IgG bind to and neutralize venom toxins and facilitate their elimination. Crotalidae polyvalent immune fab does not contain the Fc fragment of the IgG antibody, resulting in a low incidence of hypersensitivity reactions (8%) and serum sickness (13%).¹³ It is produced using 4 North American venoms: Crotalus atrox (western diamondback rattlesnake), Crotalus adamanteus (eastern diamondback rattlesnake), Crotalus scutulatus (Mojave rattlesnake), and Agkistrodon piscivorus (water moccasin).¹² It has become the standard-of-care antivenom for pit viper bites and has replaced its equine-derived predecessor antivenin crotalidae polyvalent, which is known for high rates of acute allergic reactions (23%–56%) including anaphylaxis and delayed serum sickness.^13,14 In postmarketing studies, CPIF has demonstrated control of envenomation regardless of severity. The most common adverse reactions reported include urticaria, rash, nausea, pruritus, and back pain.¹³ Anaphylaxis and anaphylactoid reactions may occur, and patients should be carefully observed during antivenom infusion. Appropriate management should be readily available including epinephrine, intravenous antihistamines, and/or albuterol. Contraindications include known hypersensitivity to papaya or papain, which is used to cleave the antibodies into fragments during the processing of CPIF. Patients also may react to it if allergic to other papaya extracts, chymopapain, or bromelain (pineapple enzyme), as well as some dust mite allergens and latex allergens that share antigenic structures with papain.¹⁵ Each vial of CPIF is reconstituted with 18 mL of 0.9% sodium chloride, as described in the package insert.¹³ The total dose (minimum of 4 to maximum of 12 vials initial dose) is then diluted in 250 mL of normal saline and infused over 1 hour starting for the first 10 minutes at a rate of 25 to 50 mL/h, and if tolerated, then increased to 250 mL/h until completion.

Treatment Algorithm
According to the envenomation consensus treatment algorithm, assess the site of the snakebite and mark leading edge of swelling every 15 to 30 minutes,¹⁶ as shown in our patient in Figure 6.Immobilize and elevate the affected extremity. Update tetanus vaccine and order initial laboratory tests to include prothrombin time, hemoglobin, platelets, and fibrinogen. If the patient does not exhibit local signs of envenomation such as redness, swelling, or ecchymosis, and the patient has no coagulation laboratory abnormalities and exhibits no systemic signs such as diarrhea, vomiting or angioedema, withhold CPIF and observe the patient for a minimum of 8 hours. Repeat laboratory tests prior to discharge. This clinical scenario most likely occurs in the setting of a dry bite or no bite at all. For minor envenomation, it also is possible to withhold CPIF and observe the patient for 12 to 24 hours if he/she remains stable and laboratory tests remain within reference range. If the patient has local or systemic signs of envenomation, start CPIF (4–6 vials and up to a maximum of 12 vials). The first dose of CPIF should be administered in the emergency department or intensive care unit. If after the first hour envenomation is worsening, an additional 4 to 6 vials may be infused. If after the first hour of observation the envenomation is controlled based on decreased swelling or lack of progression and there is improvement in laboratory values, then a maintenance regimen can be initiated. The maintenance dose consists of 2 vials every 6 hours for up to 18 hours (3 separate 2-vial doses). Patients can be discharged if stable and with no negative laboratory trends during the observation period.¹⁶ If CPIF was administered, follow-up laboratory tests results are dependent on prior findings of coagulation abnormalities, degree of envenomation, and signs and symptoms of coagulopathy postdischarge. Recurrent coagulopathy can occur in patients with coagulation abnormalities during initial envenomation, and patients should be monitored for possible re-treatment for at least 1 week or longer.¹⁷ Coagulopathy can present with decreased fibrinogen, decreased platelets, and elevated prothrombin time. Our patient experienced a drop in platelet count and hemoglobin level in addition to localized tissue effects, but he responded to the antivenom therapy. Lastly and importantly, no pediatric adjustments are necessary, and although mercury has been removed from the product’s manufacturing process, certain easily identifiable antivenom lots that have not expired contain ethyl mercury from thimerosal.^13,18,19 Some side effects of thimerosal include redness and swelling of the injection site, but scientific research does not show a connection with autism.²⁰

Conclusion

Dusky pigmy rattlesnake envenomations are clinically responsive to CPIF antivenom treatment.²¹ Although no clearly documented fatalities have been reported from dusky pigmy rattlesnake bites, coagulopathy and local tissue necrosis—as described in our patient—can result from such snakebites, requiring hospitalization. These snakes are common in the southeastern United States, and the treatment algorithm presented can be extrapolated to other more serious and deadly pit viper bites.

Identification

The South African fattail scorpion (Parabuthus transvaalicus)(Figure) is one of the most poisonous scorpions in southern Africa.¹ A member of the Buthidae scorpion family, it can grow as long as 15 cm and is dark brown-black with lighter red-brown pincers. Similar to other fattail scorpions, it has slender pincers (pedipalps) and a thick square tail (the telson). Parabuthus transvaalicus inhabits hot dry deserts, scrublands, and semiarid regions.^1,2 It also is popular in exotic pet collections, the most common source of stings in the United States.

Stings and Envenomation

Scorpions with thicker tails generally have more potent venom than those with slender tails and thick pincers. Venom is injected by a stinger at the tip of the telson¹; P transvaalicus also can spray venom as far as 3 m.^1,2 Venom is not known to cause toxicity through skin contact but could represent a hazard if sprayed in the eye.

Scorpion toxins are a group of complex neurotoxins that act on sodium channels, either retarding inactivation (α toxin) or enhancing activation (β toxin), causing massive depolarization of excitable cells.^1,3 The toxin causes neurons to fire repetitively.⁴ Neurotransmitters—noradrenaline, adrenaline, and acetylcholine—cause the observed sympathetic, parasympathetic, and skeletal muscle effects.¹

Incidence
Worldwide, more than 1.2 million individuals are stung by a scorpion annually, causing more than 3250 deaths a year.⁵ Adults are stung more often, but children experience more severe envenomation, are more likely to develop severe illness requiring intensive supportive care, and have a higher mortality.⁴

As many as one-third of patients stung by a Parabuthus scorpion develop neuromuscular toxicity, which can be life-threatening.⁶ In a study of 277 envenomations by P transvaalicus, 10% of patients developed severe symptoms and 5 died. Children younger than 10 years and adults older than 50 years are at greatest risk for adverse outcomes.⁶ Children have a case fatality rate as high as 10 times the adult fatality rate.⁷

Clinical Presentation
The clinical presentation of scorpion envenomation varies with the species involved, the amount of venom injected, and the victim’s weight and baseline health.¹ Scorpion envenomation is divided into 4 grades based on the severity of a sting:

• Grade I: pain and paresthesia at the envenomation site; usually, no local inflammation

• Grade II: local symptoms as well as more remote pain and paresthesia; pain can radiate up the affected limb

• Grade III: cranial nerve or somatic skeletal neuromuscular dysfunction; either presentation can have associated autonomic dysfunction

• Grade IV: both cranial nerve and somatic skeletal neuromuscular dysfunction, with associated auto-nomic dysfunction

 

 

The initial symptom of a scorpion sting is intense burning pain. The sting site might be unimpressive, with only a mild local reaction. Symptoms usually progress to maximum severity within 5 hours.¹ Muscle pain, cramps, and weakness are prominent. The patient might have difficulty walking and swallowing, with increased salivation and drooling, and visual disturbance with abnormal eye movements. Pulse, blood pressure, and temperature often are elevated. The patient might be hyperreflexic with clonus.^1,6

Symptoms of increased sympathetic activity are hypertension, tachycardia, cardiac dysrhythmia, perspiration, hyperglycemia, and restlessness.^1,2 Parasympathetic effects are increased salivation, hypotension, bradycardia, and gastric distension. Skeletal muscle effects include tremors and involuntary muscle movement, which can be severe. Cranial nerve dysfunction may manifest as dysphagia, drooling, abnormal eye movements, blurred vision, slurred speech, and tongue fasciculations. Subsequent development of muscle weakness, bulbar paralysis, and difficulty breathing may be caused by depletion of neurotransmitters after prolonged excessive neuronal activity.¹

Distinctive Signs in Younger Patients
A child who is stung by a scorpion might have symptoms similar to those seen in an adult victim but can also experience an extreme form of restlessness that indicates severe envenomation characterized by inability to lay still, violent muscle twitching, and uncontrollable flailing of extremities. The child might have facial grimacing, with lip-smacking and chewing motions. In addition, bulbar paralysis and respiratory distress are more likely in children who have been stung than in adults.^1,2

Management

Treatment of a P transvaalicus sting is directed at “scorpionism,” envenomation that is associated with systemic symptoms that can be life-threatening. Treatment comprises support of vital functions, symptomatic measures, and injection of antivenin.⁸

Support of Vital Functions
In adults, systemic symptoms can be delayed as long as 8 hours after the sting. However, most severe cases usually are evident within 60 minutes; infants can reach grade IV as quickly as 15 to 30 minutes.^9,10 Loss of pharyngeal reflexes and development of respiratory distress are ominous warning signs requiring immediate respiratory support. Respiratory failure is the most common cause of death.¹ An asymptomatic child should be admitted to a hospital for observation for a minimum of 12 hours if the species of scorpion was not identified.²

Pain Relief
Most patients cannot tolerate an ice pack because of severe hyperesthesia. Infiltration of the local sting site with an anesthetic generally is safe and can provide some local pain relief. Intravenous fentanyl has been used in closely monitored patients because the drug is not associated with histamine release. Medications that cause release of histamine, such as morphine, can exacerbate or confuse the clinical picture.

Antivenin
Scorpion antivenin contains purified IgG fragments; allergic reactions are now rare. The sooner antivenin is administered, the greater the benefit. When administered early, it can prevent many of the most serious complications.⁷ In a randomized, double-blind study of critically ill children with clinically significant signs of scorpion envenomation, intravenous administration of scorpion-specific fragment antigen-binding 2 (F[(ab’]₂) antivenin resulted in resolution of clinical symptoms within 4 hours.¹¹

When managing grade III or IV scorpion envenomation, all patients should be admitted to a medical facility equipped to provide intensive supportive care; consider consultation with a regional poison control center. The World Health Organization maintains an international poison control center (at https://www.who.int/ipcs/poisons/centre/en/) with regional telephone numbers; alternatively, in the United States, call the nationwide telephone number of the Poison Control Center (800-222-1222).

The World Health Organization has identified declining production of antivenin as a crisis.¹²

Resolution
Symptoms of envenomation typically resolve 9 to 30 hours after a sting in a patient with grade III or IV envenomation not treated with antivenin.⁴ However, pain and paresthesia occasionally last as long as 2 weeks. In rare cases, more long-term sequelae of burning paresthesia persist for months.⁴

Conclusion

It is important for dermatologists to be aware of the potential for life-threatening envenomation by certain scorpion species native to southern Africa. In the United States, stings of these species most often are seen in patients with a pet collection, but late sequelae also can be seen in travelers returning from an endemic region. The site of a sting often appears unimpressive initially, but severe hyperesthesia is common. Patients with cardiac, neurologic, or respiratory symptoms require intensive supportive care. Proper care can be lifesaving.

Identification

The South African fattail scorpion (Parabuthus transvaalicus)(Figure) is one of the most poisonous scorpions in southern Africa.¹ A member of the Buthidae scorpion family, it can grow as long as 15 cm and is dark brown-black with lighter red-brown pincers. Similar to other fattail scorpions, it has slender pincers (pedipalps) and a thick square tail (the telson). Parabuthus transvaalicus inhabits hot dry deserts, scrublands, and semiarid regions.^1,2 It also is popular in exotic pet collections, the most common source of stings in the United States.

Stings and Envenomation

Scorpions with thicker tails generally have more potent venom than those with slender tails and thick pincers. Venom is injected by a stinger at the tip of the telson¹; P transvaalicus also can spray venom as far as 3 m.^1,2 Venom is not known to cause toxicity through skin contact but could represent a hazard if sprayed in the eye.

Scorpion toxins are a group of complex neurotoxins that act on sodium channels, either retarding inactivation (α toxin) or enhancing activation (β toxin), causing massive depolarization of excitable cells.^1,3 The toxin causes neurons to fire repetitively.⁴ Neurotransmitters—noradrenaline, adrenaline, and acetylcholine—cause the observed sympathetic, parasympathetic, and skeletal muscle effects.¹

Incidence
Worldwide, more than 1.2 million individuals are stung by a scorpion annually, causing more than 3250 deaths a year.⁵ Adults are stung more often, but children experience more severe envenomation, are more likely to develop severe illness requiring intensive supportive care, and have a higher mortality.⁴

As many as one-third of patients stung by a Parabuthus scorpion develop neuromuscular toxicity, which can be life-threatening.⁶ In a study of 277 envenomations by P transvaalicus, 10% of patients developed severe symptoms and 5 died. Children younger than 10 years and adults older than 50 years are at greatest risk for adverse outcomes.⁶ Children have a case fatality rate as high as 10 times the adult fatality rate.⁷

Clinical Presentation
The clinical presentation of scorpion envenomation varies with the species involved, the amount of venom injected, and the victim’s weight and baseline health.¹ Scorpion envenomation is divided into 4 grades based on the severity of a sting:

• Grade I: pain and paresthesia at the envenomation site; usually, no local inflammation

• Grade II: local symptoms as well as more remote pain and paresthesia; pain can radiate up the affected limb

• Grade III: cranial nerve or somatic skeletal neuromuscular dysfunction; either presentation can have associated autonomic dysfunction

• Grade IV: both cranial nerve and somatic skeletal neuromuscular dysfunction, with associated auto-nomic dysfunction

 

 

The initial symptom of a scorpion sting is intense burning pain. The sting site might be unimpressive, with only a mild local reaction. Symptoms usually progress to maximum severity within 5 hours.¹ Muscle pain, cramps, and weakness are prominent. The patient might have difficulty walking and swallowing, with increased salivation and drooling, and visual disturbance with abnormal eye movements. Pulse, blood pressure, and temperature often are elevated. The patient might be hyperreflexic with clonus.^1,6

Symptoms of increased sympathetic activity are hypertension, tachycardia, cardiac dysrhythmia, perspiration, hyperglycemia, and restlessness.^1,2 Parasympathetic effects are increased salivation, hypotension, bradycardia, and gastric distension. Skeletal muscle effects include tremors and involuntary muscle movement, which can be severe. Cranial nerve dysfunction may manifest as dysphagia, drooling, abnormal eye movements, blurred vision, slurred speech, and tongue fasciculations. Subsequent development of muscle weakness, bulbar paralysis, and difficulty breathing may be caused by depletion of neurotransmitters after prolonged excessive neuronal activity.¹

Distinctive Signs in Younger Patients
A child who is stung by a scorpion might have symptoms similar to those seen in an adult victim but can also experience an extreme form of restlessness that indicates severe envenomation characterized by inability to lay still, violent muscle twitching, and uncontrollable flailing of extremities. The child might have facial grimacing, with lip-smacking and chewing motions. In addition, bulbar paralysis and respiratory distress are more likely in children who have been stung than in adults.^1,2

Management

Treatment of a P transvaalicus sting is directed at “scorpionism,” envenomation that is associated with systemic symptoms that can be life-threatening. Treatment comprises support of vital functions, symptomatic measures, and injection of antivenin.⁸

Support of Vital Functions
In adults, systemic symptoms can be delayed as long as 8 hours after the sting. However, most severe cases usually are evident within 60 minutes; infants can reach grade IV as quickly as 15 to 30 minutes.^9,10 Loss of pharyngeal reflexes and development of respiratory distress are ominous warning signs requiring immediate respiratory support. Respiratory failure is the most common cause of death.¹ An asymptomatic child should be admitted to a hospital for observation for a minimum of 12 hours if the species of scorpion was not identified.²

Pain Relief
Most patients cannot tolerate an ice pack because of severe hyperesthesia. Infiltration of the local sting site with an anesthetic generally is safe and can provide some local pain relief. Intravenous fentanyl has been used in closely monitored patients because the drug is not associated with histamine release. Medications that cause release of histamine, such as morphine, can exacerbate or confuse the clinical picture.

Antivenin
Scorpion antivenin contains purified IgG fragments; allergic reactions are now rare. The sooner antivenin is administered, the greater the benefit. When administered early, it can prevent many of the most serious complications.⁷ In a randomized, double-blind study of critically ill children with clinically significant signs of scorpion envenomation, intravenous administration of scorpion-specific fragment antigen-binding 2 (F[(ab’]₂) antivenin resulted in resolution of clinical symptoms within 4 hours.¹¹

When managing grade III or IV scorpion envenomation, all patients should be admitted to a medical facility equipped to provide intensive supportive care; consider consultation with a regional poison control center. The World Health Organization maintains an international poison control center (at https://www.who.int/ipcs/poisons/centre/en/) with regional telephone numbers; alternatively, in the United States, call the nationwide telephone number of the Poison Control Center (800-222-1222).

The World Health Organization has identified declining production of antivenin as a crisis.¹²

Resolution
Symptoms of envenomation typically resolve 9 to 30 hours after a sting in a patient with grade III or IV envenomation not treated with antivenin.⁴ However, pain and paresthesia occasionally last as long as 2 weeks. In rare cases, more long-term sequelae of burning paresthesia persist for months.⁴

Conclusion

It is important for dermatologists to be aware of the potential for life-threatening envenomation by certain scorpion species native to southern Africa. In the United States, stings of these species most often are seen in patients with a pet collection, but late sequelae also can be seen in travelers returning from an endemic region. The site of a sting often appears unimpressive initially, but severe hyperesthesia is common. Patients with cardiac, neurologic, or respiratory symptoms require intensive supportive care. Proper care can be lifesaving.

Identification

The South African fattail scorpion (Parabuthus transvaalicus)(Figure) is one of the most poisonous scorpions in southern Africa.¹ A member of the Buthidae scorpion family, it can grow as long as 15 cm and is dark brown-black with lighter red-brown pincers. Similar to other fattail scorpions, it has slender pincers (pedipalps) and a thick square tail (the telson). Parabuthus transvaalicus inhabits hot dry deserts, scrublands, and semiarid regions.^1,2 It also is popular in exotic pet collections, the most common source of stings in the United States.

Stings and Envenomation

Scorpions with thicker tails generally have more potent venom than those with slender tails and thick pincers. Venom is injected by a stinger at the tip of the telson¹; P transvaalicus also can spray venom as far as 3 m.^1,2 Venom is not known to cause toxicity through skin contact but could represent a hazard if sprayed in the eye.

Scorpion toxins are a group of complex neurotoxins that act on sodium channels, either retarding inactivation (α toxin) or enhancing activation (β toxin), causing massive depolarization of excitable cells.^1,3 The toxin causes neurons to fire repetitively.⁴ Neurotransmitters—noradrenaline, adrenaline, and acetylcholine—cause the observed sympathetic, parasympathetic, and skeletal muscle effects.¹

Incidence
Worldwide, more than 1.2 million individuals are stung by a scorpion annually, causing more than 3250 deaths a year.⁵ Adults are stung more often, but children experience more severe envenomation, are more likely to develop severe illness requiring intensive supportive care, and have a higher mortality.⁴

As many as one-third of patients stung by a Parabuthus scorpion develop neuromuscular toxicity, which can be life-threatening.⁶ In a study of 277 envenomations by P transvaalicus, 10% of patients developed severe symptoms and 5 died. Children younger than 10 years and adults older than 50 years are at greatest risk for adverse outcomes.⁶ Children have a case fatality rate as high as 10 times the adult fatality rate.⁷

Clinical Presentation
The clinical presentation of scorpion envenomation varies with the species involved, the amount of venom injected, and the victim’s weight and baseline health.¹ Scorpion envenomation is divided into 4 grades based on the severity of a sting:

• Grade I: pain and paresthesia at the envenomation site; usually, no local inflammation

• Grade II: local symptoms as well as more remote pain and paresthesia; pain can radiate up the affected limb

• Grade III: cranial nerve or somatic skeletal neuromuscular dysfunction; either presentation can have associated autonomic dysfunction

• Grade IV: both cranial nerve and somatic skeletal neuromuscular dysfunction, with associated auto-nomic dysfunction

 

 

The initial symptom of a scorpion sting is intense burning pain. The sting site might be unimpressive, with only a mild local reaction. Symptoms usually progress to maximum severity within 5 hours.¹ Muscle pain, cramps, and weakness are prominent. The patient might have difficulty walking and swallowing, with increased salivation and drooling, and visual disturbance with abnormal eye movements. Pulse, blood pressure, and temperature often are elevated. The patient might be hyperreflexic with clonus.^1,6

Symptoms of increased sympathetic activity are hypertension, tachycardia, cardiac dysrhythmia, perspiration, hyperglycemia, and restlessness.^1,2 Parasympathetic effects are increased salivation, hypotension, bradycardia, and gastric distension. Skeletal muscle effects include tremors and involuntary muscle movement, which can be severe. Cranial nerve dysfunction may manifest as dysphagia, drooling, abnormal eye movements, blurred vision, slurred speech, and tongue fasciculations. Subsequent development of muscle weakness, bulbar paralysis, and difficulty breathing may be caused by depletion of neurotransmitters after prolonged excessive neuronal activity.¹

Distinctive Signs in Younger Patients
A child who is stung by a scorpion might have symptoms similar to those seen in an adult victim but can also experience an extreme form of restlessness that indicates severe envenomation characterized by inability to lay still, violent muscle twitching, and uncontrollable flailing of extremities. The child might have facial grimacing, with lip-smacking and chewing motions. In addition, bulbar paralysis and respiratory distress are more likely in children who have been stung than in adults.^1,2

Management

Treatment of a P transvaalicus sting is directed at “scorpionism,” envenomation that is associated with systemic symptoms that can be life-threatening. Treatment comprises support of vital functions, symptomatic measures, and injection of antivenin.⁸

Support of Vital Functions
In adults, systemic symptoms can be delayed as long as 8 hours after the sting. However, most severe cases usually are evident within 60 minutes; infants can reach grade IV as quickly as 15 to 30 minutes.^9,10 Loss of pharyngeal reflexes and development of respiratory distress are ominous warning signs requiring immediate respiratory support. Respiratory failure is the most common cause of death.¹ An asymptomatic child should be admitted to a hospital for observation for a minimum of 12 hours if the species of scorpion was not identified.²

Pain Relief
Most patients cannot tolerate an ice pack because of severe hyperesthesia. Infiltration of the local sting site with an anesthetic generally is safe and can provide some local pain relief. Intravenous fentanyl has been used in closely monitored patients because the drug is not associated with histamine release. Medications that cause release of histamine, such as morphine, can exacerbate or confuse the clinical picture.

Antivenin
Scorpion antivenin contains purified IgG fragments; allergic reactions are now rare. The sooner antivenin is administered, the greater the benefit. When administered early, it can prevent many of the most serious complications.⁷ In a randomized, double-blind study of critically ill children with clinically significant signs of scorpion envenomation, intravenous administration of scorpion-specific fragment antigen-binding 2 (F[(ab’]₂) antivenin resulted in resolution of clinical symptoms within 4 hours.¹¹

When managing grade III or IV scorpion envenomation, all patients should be admitted to a medical facility equipped to provide intensive supportive care; consider consultation with a regional poison control center. The World Health Organization maintains an international poison control center (at https://www.who.int/ipcs/poisons/centre/en/) with regional telephone numbers; alternatively, in the United States, call the nationwide telephone number of the Poison Control Center (800-222-1222).

The World Health Organization has identified declining production of antivenin as a crisis.¹²

Resolution
Symptoms of envenomation typically resolve 9 to 30 hours after a sting in a patient with grade III or IV envenomation not treated with antivenin.⁴ However, pain and paresthesia occasionally last as long as 2 weeks. In rare cases, more long-term sequelae of burning paresthesia persist for months.⁴

Conclusion

It is important for dermatologists to be aware of the potential for life-threatening envenomation by certain scorpion species native to southern Africa. In the United States, stings of these species most often are seen in patients with a pet collection, but late sequelae also can be seen in travelers returning from an endemic region. The site of a sting often appears unimpressive initially, but severe hyperesthesia is common. Patients with cardiac, neurologic, or respiratory symptoms require intensive supportive care. Proper care can be lifesaving.

Fleas of the order Siphonaptera are insects that feed on the blood of a mammalian host. They have no wings but jump to near 150 times their body lengths to reach potential hosts.¹ An epidemiologic survey performed in 2016 demonstrated that 96% of fleas in the United States are cat fleas (Ctenocephalides felis).² The bites often present as pruritic, nonfollicular-based, excoriated papules; papular urticaria; or vesiculobullous lesions distributed across the lower legs. Antihistamines and topical steroids may be helpful for symptomatic relief, but flea eradication is key.

Identification

Ctenocephalides fleas, including the common cat flea and the dog flea, have a characteristic pronotal comb that resembles a mane of hair (Figure 1) and genal comb that resembles a mustache. Compared to the dog flea (Ctenocephalides canis), cat fleas have a flatter head and fewer hair-bearing notches on the dorsal hind tibia (the dog flea has 8 notches and the cat flea has 6 notches)(Figure 2).

Flea Prevention and Eradication

Effective management of flea bites requires avoidance of infested areas and eradication of fleas from the home and pets. Home treatment should be performed by a qualified specialist and a veterinarian should treat the pet, but the dermatologist must be knowledgeable about treatment options. Flea pupae can lie dormant between floorboards for extended periods of time and hatch rapidly when new tenants enter a house or apartment. Insecticidal dusts and spray formulations frequently are used to treat infested homes. It also is important to reduce flea egg numbers by vacuuming carpets and areas where pets sleep.³ Rodents often introduce fleas to households and pets, so eliminating them from the area may play an important role in flea control. Consulting with a veterinarian is important, as treatment directed at pets is critical to control flea populations. Oral agents, including fluralaner, afoxolaner, sarolaner, and spinosad, can reduce flea populations on animals by as much as 99.3% after 7 days.^4,5 Fast-acting pulicidal agents, such as the combination of dinotefuran and fipronil, demonstrate curative activity as soon as 3 hours after treatment, which also may prevent reinfestation for as long as 6 weeks after treatment.⁶

Vector-Borne Disease

Fleas living on animals in close contact with humans, such as cats and dogs, can transmit zoonotic pathogens. Around 12,000 outpatients and 500 inpatients are diagnosed with cat scratch disease, a form of bartonellosis, annually. Ctenocephalides felis transmits Bartonella henselae from cat-to-cat and often cat-to-human through infected flea feces, causing a primary inoculation lesion and lymphadenitis. Of 3011 primary care providers surveyed from 2014 to 2015, 37.2% had treated at least 1 patient with cat scratch disease, yet knowledge gaps remain regarding the proper treatment and preventative measures for the disease.⁷ Current recommendations for the treatment of lymphadenitis caused by B henselae include a 5-day course of oral azithromycin.⁸ The preferred dosing regimen in adults is 500 mg on day 1 and 250 mg on days 2 through 5. Pediatric patients weighing less than 45.5 kg should receive 10 mg/kg on day 1 and 5 mg/kg on days 2 through 5.⁸ Additionally, less than one-third of the primary care providers surveyed from 2014 to 2015 said they would discuss the importance of pet flea control with immunocompromised patients who own cats, despite evidence implicating fleas in disease transmission.⁷ Pet-directed topical therapy with agents such as selamectin prescribed by a qualified veterinarian can prevent transmission of B henselae in cats exposed to fleas infected with the bacteria,⁹ which supports the importance of patient education and flea control, especially in pets owned by immunocompromised patients. Patients who are immunocompromised are at increased risk for persistent or disseminated bartonellosis, including endocarditis, in addition to cat scratch disease. Although arriving at a diagnosis may be difficult, one study found that bartonellosis in 13 renal transplant recipients was best diagnosed using both serology and polymerase chain reaction via DNA extraction of tissue specimens.¹⁰ These findings may enhance diagnostic yield for similar patients when bartonellosis is suspected.

Flea-borne typhus is endemic to Texas and Southern California.^11,12 Evidence suggests that the pathogenic bacteria, Rickettsia typhi and Rickettsia felis, also commonly infect fleas in the Great Plains area.¹³ Opossums carry R felis, and the fleas transmit murine or endemic typhus. A retrospective case series in Texas identified 11 cases of fatal flea-borne typhus from 1985 to 2015.¹¹ More than half of the patients reported contact with animals or fleas prior to the illness. Patients with typhus may present with fever, nausea, vomiting, rash (macular, maculopapular, papular, petechial, or morbilliform), respiratory or neurologic symptoms, thrombocytopenia, and elevated hepatic liver enzymes. Unfortunately, there often is a notable delay in initiation of treatment with the appropriate class of antibiotics—tetracyclines—and such delays can prove fatal.¹¹ The current recommendation for nonpregnant adults is oral doxycycline 100 mg twice daily continued 48 hours after the patient becomes afebrile or for 7 days, whichever therapy duration is longer.¹⁴ Because of the consequences of delayed treatment, it is important for clinicians to consider a diagnosis of vector-borne illness in a febrile patient with other associated gastrointestinal, cutaneous, respiratory, or neurologic symptoms, especially if they have animal or flea exposures. Flea control and exposure awareness remains paramount in preventing and treating this illness.

Yersinia pestis causes the plague, an important re-emerging disease that causes infection through flea bites, inhalation, or ingestion.¹⁵ From 2000 to 2009, 56 cases and 7 deaths in the United States—New Mexico, Arizona, Colorado, California, and Texas—and 21,725 cases and 1612 deaths worldwide were attributed to Y pestis. Most patients present with the bubonic form of the disease, with fever and an enlarging painful femoral or inguinal lymph node due to leg flea bites.¹⁶ Other forms of disease, including septicemic and pneumonic plague, are less common but relevant, as one-third of cases in the United States present with septicemia.^15,17,18 Although molecular diagnosis and immunohistochemistry play important roles, the diagnosis of Y pestis infection often is still accomplished with culture. A 2012 survey of 392 strains from 17 countries demonstrated that Y pestis remained susceptible to the antibiotics currently used to treat the disease, including doxycycline, streptomycin, gentamicin, tetracycline, trimethoprim-sulfamethoxazole, and ciprofloxacin.¹⁹

Human infection with Dipylidium caninum, a dog tapeworm, has been reported after suspected accidental ingestion of cat fleas carrying the parasite.²⁰ Children, who may present with diarrhea or white worms in their feces, are more susceptible to the infection, perhaps due to accidental flea consumption while being licked by the pet.^20,21

Conclusion

Cat fleas may act as a pruritic nuisance for pet owners and even deliver deadly pathogens to immunocompromised patients. Providers can minimize their impact by educating patients on flea prevention and eradication as well as astutely recognizing and treating flea-borne diseases.

Fleas of the order Siphonaptera are insects that feed on the blood of a mammalian host. They have no wings but jump to near 150 times their body lengths to reach potential hosts.¹ An epidemiologic survey performed in 2016 demonstrated that 96% of fleas in the United States are cat fleas (Ctenocephalides felis).² The bites often present as pruritic, nonfollicular-based, excoriated papules; papular urticaria; or vesiculobullous lesions distributed across the lower legs. Antihistamines and topical steroids may be helpful for symptomatic relief, but flea eradication is key.

Identification

Ctenocephalides fleas, including the common cat flea and the dog flea, have a characteristic pronotal comb that resembles a mane of hair (Figure 1) and genal comb that resembles a mustache. Compared to the dog flea (Ctenocephalides canis), cat fleas have a flatter head and fewer hair-bearing notches on the dorsal hind tibia (the dog flea has 8 notches and the cat flea has 6 notches)(Figure 2).

Flea Prevention and Eradication

Effective management of flea bites requires avoidance of infested areas and eradication of fleas from the home and pets. Home treatment should be performed by a qualified specialist and a veterinarian should treat the pet, but the dermatologist must be knowledgeable about treatment options. Flea pupae can lie dormant between floorboards for extended periods of time and hatch rapidly when new tenants enter a house or apartment. Insecticidal dusts and spray formulations frequently are used to treat infested homes. It also is important to reduce flea egg numbers by vacuuming carpets and areas where pets sleep.³ Rodents often introduce fleas to households and pets, so eliminating them from the area may play an important role in flea control. Consulting with a veterinarian is important, as treatment directed at pets is critical to control flea populations. Oral agents, including fluralaner, afoxolaner, sarolaner, and spinosad, can reduce flea populations on animals by as much as 99.3% after 7 days.^4,5 Fast-acting pulicidal agents, such as the combination of dinotefuran and fipronil, demonstrate curative activity as soon as 3 hours after treatment, which also may prevent reinfestation for as long as 6 weeks after treatment.⁶

Vector-Borne Disease

Fleas living on animals in close contact with humans, such as cats and dogs, can transmit zoonotic pathogens. Around 12,000 outpatients and 500 inpatients are diagnosed with cat scratch disease, a form of bartonellosis, annually. Ctenocephalides felis transmits Bartonella henselae from cat-to-cat and often cat-to-human through infected flea feces, causing a primary inoculation lesion and lymphadenitis. Of 3011 primary care providers surveyed from 2014 to 2015, 37.2% had treated at least 1 patient with cat scratch disease, yet knowledge gaps remain regarding the proper treatment and preventative measures for the disease.⁷ Current recommendations for the treatment of lymphadenitis caused by B henselae include a 5-day course of oral azithromycin.⁸ The preferred dosing regimen in adults is 500 mg on day 1 and 250 mg on days 2 through 5. Pediatric patients weighing less than 45.5 kg should receive 10 mg/kg on day 1 and 5 mg/kg on days 2 through 5.⁸ Additionally, less than one-third of the primary care providers surveyed from 2014 to 2015 said they would discuss the importance of pet flea control with immunocompromised patients who own cats, despite evidence implicating fleas in disease transmission.⁷ Pet-directed topical therapy with agents such as selamectin prescribed by a qualified veterinarian can prevent transmission of B henselae in cats exposed to fleas infected with the bacteria,⁹ which supports the importance of patient education and flea control, especially in pets owned by immunocompromised patients. Patients who are immunocompromised are at increased risk for persistent or disseminated bartonellosis, including endocarditis, in addition to cat scratch disease. Although arriving at a diagnosis may be difficult, one study found that bartonellosis in 13 renal transplant recipients was best diagnosed using both serology and polymerase chain reaction via DNA extraction of tissue specimens.¹⁰ These findings may enhance diagnostic yield for similar patients when bartonellosis is suspected.

Flea-borne typhus is endemic to Texas and Southern California.^11,12 Evidence suggests that the pathogenic bacteria, Rickettsia typhi and Rickettsia felis, also commonly infect fleas in the Great Plains area.¹³ Opossums carry R felis, and the fleas transmit murine or endemic typhus. A retrospective case series in Texas identified 11 cases of fatal flea-borne typhus from 1985 to 2015.¹¹ More than half of the patients reported contact with animals or fleas prior to the illness. Patients with typhus may present with fever, nausea, vomiting, rash (macular, maculopapular, papular, petechial, or morbilliform), respiratory or neurologic symptoms, thrombocytopenia, and elevated hepatic liver enzymes. Unfortunately, there often is a notable delay in initiation of treatment with the appropriate class of antibiotics—tetracyclines—and such delays can prove fatal.¹¹ The current recommendation for nonpregnant adults is oral doxycycline 100 mg twice daily continued 48 hours after the patient becomes afebrile or for 7 days, whichever therapy duration is longer.¹⁴ Because of the consequences of delayed treatment, it is important for clinicians to consider a diagnosis of vector-borne illness in a febrile patient with other associated gastrointestinal, cutaneous, respiratory, or neurologic symptoms, especially if they have animal or flea exposures. Flea control and exposure awareness remains paramount in preventing and treating this illness.

Yersinia pestis causes the plague, an important re-emerging disease that causes infection through flea bites, inhalation, or ingestion.¹⁵ From 2000 to 2009, 56 cases and 7 deaths in the United States—New Mexico, Arizona, Colorado, California, and Texas—and 21,725 cases and 1612 deaths worldwide were attributed to Y pestis. Most patients present with the bubonic form of the disease, with fever and an enlarging painful femoral or inguinal lymph node due to leg flea bites.¹⁶ Other forms of disease, including septicemic and pneumonic plague, are less common but relevant, as one-third of cases in the United States present with septicemia.^15,17,18 Although molecular diagnosis and immunohistochemistry play important roles, the diagnosis of Y pestis infection often is still accomplished with culture. A 2012 survey of 392 strains from 17 countries demonstrated that Y pestis remained susceptible to the antibiotics currently used to treat the disease, including doxycycline, streptomycin, gentamicin, tetracycline, trimethoprim-sulfamethoxazole, and ciprofloxacin.¹⁹

Human infection with Dipylidium caninum, a dog tapeworm, has been reported after suspected accidental ingestion of cat fleas carrying the parasite.²⁰ Children, who may present with diarrhea or white worms in their feces, are more susceptible to the infection, perhaps due to accidental flea consumption while being licked by the pet.^20,21

Conclusion

Cat fleas may act as a pruritic nuisance for pet owners and even deliver deadly pathogens to immunocompromised patients. Providers can minimize their impact by educating patients on flea prevention and eradication as well as astutely recognizing and treating flea-borne diseases.

Fleas of the order Siphonaptera are insects that feed on the blood of a mammalian host. They have no wings but jump to near 150 times their body lengths to reach potential hosts.¹ An epidemiologic survey performed in 2016 demonstrated that 96% of fleas in the United States are cat fleas (Ctenocephalides felis).² The bites often present as pruritic, nonfollicular-based, excoriated papules; papular urticaria; or vesiculobullous lesions distributed across the lower legs. Antihistamines and topical steroids may be helpful for symptomatic relief, but flea eradication is key.

Identification

Ctenocephalides fleas, including the common cat flea and the dog flea, have a characteristic pronotal comb that resembles a mane of hair (Figure 1) and genal comb that resembles a mustache. Compared to the dog flea (Ctenocephalides canis), cat fleas have a flatter head and fewer hair-bearing notches on the dorsal hind tibia (the dog flea has 8 notches and the cat flea has 6 notches)(Figure 2).

Flea Prevention and Eradication

Effective management of flea bites requires avoidance of infested areas and eradication of fleas from the home and pets. Home treatment should be performed by a qualified specialist and a veterinarian should treat the pet, but the dermatologist must be knowledgeable about treatment options. Flea pupae can lie dormant between floorboards for extended periods of time and hatch rapidly when new tenants enter a house or apartment. Insecticidal dusts and spray formulations frequently are used to treat infested homes. It also is important to reduce flea egg numbers by vacuuming carpets and areas where pets sleep.³ Rodents often introduce fleas to households and pets, so eliminating them from the area may play an important role in flea control. Consulting with a veterinarian is important, as treatment directed at pets is critical to control flea populations. Oral agents, including fluralaner, afoxolaner, sarolaner, and spinosad, can reduce flea populations on animals by as much as 99.3% after 7 days.^4,5 Fast-acting pulicidal agents, such as the combination of dinotefuran and fipronil, demonstrate curative activity as soon as 3 hours after treatment, which also may prevent reinfestation for as long as 6 weeks after treatment.⁶

Vector-Borne Disease

Fleas living on animals in close contact with humans, such as cats and dogs, can transmit zoonotic pathogens. Around 12,000 outpatients and 500 inpatients are diagnosed with cat scratch disease, a form of bartonellosis, annually. Ctenocephalides felis transmits Bartonella henselae from cat-to-cat and often cat-to-human through infected flea feces, causing a primary inoculation lesion and lymphadenitis. Of 3011 primary care providers surveyed from 2014 to 2015, 37.2% had treated at least 1 patient with cat scratch disease, yet knowledge gaps remain regarding the proper treatment and preventative measures for the disease.⁷ Current recommendations for the treatment of lymphadenitis caused by B henselae include a 5-day course of oral azithromycin.⁸ The preferred dosing regimen in adults is 500 mg on day 1 and 250 mg on days 2 through 5. Pediatric patients weighing less than 45.5 kg should receive 10 mg/kg on day 1 and 5 mg/kg on days 2 through 5.⁸ Additionally, less than one-third of the primary care providers surveyed from 2014 to 2015 said they would discuss the importance of pet flea control with immunocompromised patients who own cats, despite evidence implicating fleas in disease transmission.⁷ Pet-directed topical therapy with agents such as selamectin prescribed by a qualified veterinarian can prevent transmission of B henselae in cats exposed to fleas infected with the bacteria,⁹ which supports the importance of patient education and flea control, especially in pets owned by immunocompromised patients. Patients who are immunocompromised are at increased risk for persistent or disseminated bartonellosis, including endocarditis, in addition to cat scratch disease. Although arriving at a diagnosis may be difficult, one study found that bartonellosis in 13 renal transplant recipients was best diagnosed using both serology and polymerase chain reaction via DNA extraction of tissue specimens.¹⁰ These findings may enhance diagnostic yield for similar patients when bartonellosis is suspected.

Flea-borne typhus is endemic to Texas and Southern California.^11,12 Evidence suggests that the pathogenic bacteria, Rickettsia typhi and Rickettsia felis, also commonly infect fleas in the Great Plains area.¹³ Opossums carry R felis, and the fleas transmit murine or endemic typhus. A retrospective case series in Texas identified 11 cases of fatal flea-borne typhus from 1985 to 2015.¹¹ More than half of the patients reported contact with animals or fleas prior to the illness. Patients with typhus may present with fever, nausea, vomiting, rash (macular, maculopapular, papular, petechial, or morbilliform), respiratory or neurologic symptoms, thrombocytopenia, and elevated hepatic liver enzymes. Unfortunately, there often is a notable delay in initiation of treatment with the appropriate class of antibiotics—tetracyclines—and such delays can prove fatal.¹¹ The current recommendation for nonpregnant adults is oral doxycycline 100 mg twice daily continued 48 hours after the patient becomes afebrile or for 7 days, whichever therapy duration is longer.¹⁴ Because of the consequences of delayed treatment, it is important for clinicians to consider a diagnosis of vector-borne illness in a febrile patient with other associated gastrointestinal, cutaneous, respiratory, or neurologic symptoms, especially if they have animal or flea exposures. Flea control and exposure awareness remains paramount in preventing and treating this illness.

Yersinia pestis causes the plague, an important re-emerging disease that causes infection through flea bites, inhalation, or ingestion.¹⁵ From 2000 to 2009, 56 cases and 7 deaths in the United States—New Mexico, Arizona, Colorado, California, and Texas—and 21,725 cases and 1612 deaths worldwide were attributed to Y pestis. Most patients present with the bubonic form of the disease, with fever and an enlarging painful femoral or inguinal lymph node due to leg flea bites.¹⁶ Other forms of disease, including septicemic and pneumonic plague, are less common but relevant, as one-third of cases in the United States present with septicemia.^15,17,18 Although molecular diagnosis and immunohistochemistry play important roles, the diagnosis of Y pestis infection often is still accomplished with culture. A 2012 survey of 392 strains from 17 countries demonstrated that Y pestis remained susceptible to the antibiotics currently used to treat the disease, including doxycycline, streptomycin, gentamicin, tetracycline, trimethoprim-sulfamethoxazole, and ciprofloxacin.¹⁹

Human infection with Dipylidium caninum, a dog tapeworm, has been reported after suspected accidental ingestion of cat fleas carrying the parasite.²⁰ Children, who may present with diarrhea or white worms in their feces, are more susceptible to the infection, perhaps due to accidental flea consumption while being licked by the pet.^20,21

Conclusion

Cat fleas may act as a pruritic nuisance for pet owners and even deliver deadly pathogens to immunocompromised patients. Providers can minimize their impact by educating patients on flea prevention and eradication as well as astutely recognizing and treating flea-borne diseases.

Clinical Presentation

Millipedes secrete a noxious toxin implicated in millipede burns. The toxic substance is benzoquinone, a strong irritant secreted from the repugnatorial glands contained in each segment of the arthropod (Figure 1). This compound serves as a natural insect repellant, acting as the millipede’s defense mechanism from potential predators.¹ On human skin, benzoquinone causes localized pigmentary changes most commonly presenting on the feet and toes. Local lesions may be associated with pain or burning, but there are no known reports of adverse systemic effects.² Affected patients experience cutaneous pigmentary changes, which may be dark red, blue, or black, and spontaneously resolve over time.² The degree of pigment change may be associated with duration of skin contact with the toxin. The affected areas may resemble burns, dermatitis, or skin necrosis. More distal lesions may present similarly to blue toe syndrome or acute arterial occlusion but can be differentiated by the presence of intact peripheral pulses and lack of temperature discrepancy between the feet.^3,4 Histologic evaluation of the lesions generally reveals nonspecific full-thickness epidermal necrosis, making clinical suspicion and physical examination paramount to the diagnosis of millipede burns.⁵

Diagnostic Difficulties

Accurate diagnosis of millipede burns is more difficult when the burn involves an unusual site. The most common site of involvement is the foot (Figure 2), followed by other commonly exposed areas such as the arms, face, and eyes.^2,3,6,7 Covered parts of the body are much less commonly affected, requiring the arthropod to gain access via infiltration of clothing, often when hanging on a clothesline. In these cases, burns may be mistaken for child abuse, especially if certain areas of the body are involved, such as the groin and genitals.² The well-defined arcuate lesions of the burns may resemble injuries from a wire or belt to the unsuspecting observer.

Conclusion

Although millipedes often are regarded as harmless, they are capable of causing adverse reactions through the secretion of toxic chemicals. Millipede burns cause localized pigmentary changes that may be associated with pain or burning in some patients. Because these burns may resemble child abuse in pediatric patients, physicians should be aware of this diagnosis when unusual parts of the body are involved.

Clinical Presentation

Millipedes secrete a noxious toxin implicated in millipede burns. The toxic substance is benzoquinone, a strong irritant secreted from the repugnatorial glands contained in each segment of the arthropod (Figure 1). This compound serves as a natural insect repellant, acting as the millipede’s defense mechanism from potential predators.¹ On human skin, benzoquinone causes localized pigmentary changes most commonly presenting on the feet and toes. Local lesions may be associated with pain or burning, but there are no known reports of adverse systemic effects.² Affected patients experience cutaneous pigmentary changes, which may be dark red, blue, or black, and spontaneously resolve over time.² The degree of pigment change may be associated with duration of skin contact with the toxin. The affected areas may resemble burns, dermatitis, or skin necrosis. More distal lesions may present similarly to blue toe syndrome or acute arterial occlusion but can be differentiated by the presence of intact peripheral pulses and lack of temperature discrepancy between the feet.^3,4 Histologic evaluation of the lesions generally reveals nonspecific full-thickness epidermal necrosis, making clinical suspicion and physical examination paramount to the diagnosis of millipede burns.⁵

Diagnostic Difficulties

Accurate diagnosis of millipede burns is more difficult when the burn involves an unusual site. The most common site of involvement is the foot (Figure 2), followed by other commonly exposed areas such as the arms, face, and eyes.^2,3,6,7 Covered parts of the body are much less commonly affected, requiring the arthropod to gain access via infiltration of clothing, often when hanging on a clothesline. In these cases, burns may be mistaken for child abuse, especially if certain areas of the body are involved, such as the groin and genitals.² The well-defined arcuate lesions of the burns may resemble injuries from a wire or belt to the unsuspecting observer.

Conclusion

Although millipedes often are regarded as harmless, they are capable of causing adverse reactions through the secretion of toxic chemicals. Millipede burns cause localized pigmentary changes that may be associated with pain or burning in some patients. Because these burns may resemble child abuse in pediatric patients, physicians should be aware of this diagnosis when unusual parts of the body are involved.

Clinical Presentation

Millipedes secrete a noxious toxin implicated in millipede burns. The toxic substance is benzoquinone, a strong irritant secreted from the repugnatorial glands contained in each segment of the arthropod (Figure 1). This compound serves as a natural insect repellant, acting as the millipede’s defense mechanism from potential predators.¹ On human skin, benzoquinone causes localized pigmentary changes most commonly presenting on the feet and toes. Local lesions may be associated with pain or burning, but there are no known reports of adverse systemic effects.² Affected patients experience cutaneous pigmentary changes, which may be dark red, blue, or black, and spontaneously resolve over time.² The degree of pigment change may be associated with duration of skin contact with the toxin. The affected areas may resemble burns, dermatitis, or skin necrosis. More distal lesions may present similarly to blue toe syndrome or acute arterial occlusion but can be differentiated by the presence of intact peripheral pulses and lack of temperature discrepancy between the feet.^3,4 Histologic evaluation of the lesions generally reveals nonspecific full-thickness epidermal necrosis, making clinical suspicion and physical examination paramount to the diagnosis of millipede burns.⁵

Diagnostic Difficulties

Accurate diagnosis of millipede burns is more difficult when the burn involves an unusual site. The most common site of involvement is the foot (Figure 2), followed by other commonly exposed areas such as the arms, face, and eyes.^2,3,6,7 Covered parts of the body are much less commonly affected, requiring the arthropod to gain access via infiltration of clothing, often when hanging on a clothesline. In these cases, burns may be mistaken for child abuse, especially if certain areas of the body are involved, such as the groin and genitals.² The well-defined arcuate lesions of the burns may resemble injuries from a wire or belt to the unsuspecting observer.

Conclusion

Although millipedes often are regarded as harmless, they are capable of causing adverse reactions through the secretion of toxic chemicals. Millipede burns cause localized pigmentary changes that may be associated with pain or burning in some patients. Because these burns may resemble child abuse in pediatric patients, physicians should be aware of this diagnosis when unusual parts of the body are involved.

Incidence and Characteristics

Stingrays are the most common cause of fish-related stings worldwide.¹ The Urolophidae and Dasyatidae stingray families are responsible for most marine stingray injuries, including approximately 1500 reported injuries in the United States annually.^1,2 Saltwater stingrays from these families commonly are encountered in shallow temperate and tropical coastal waters across the globe and possess dorsally and distally located spines capable of injuring humans that step on them (Figure 1).^1,3 Freshwater stingrays (Potamotrygonidae family)(Figure 2) are not present in North America but rather inhabit lakes and river systems in South America, Africa, Laos, and Vietnam.⁴ Although recent incidence is unknown, Marinkelle⁵ estimated that thousands of stingray injuries occurred annually in the freshwater of Columbia during the 1960s. Unfortunately, the annual worldwide incidence of stingray injuries is generally unknown and is difficult to estimate, in part because injuries often go unreported.

Stingrays are dorsoventrally flattened, diamond-shaped fish with light-colored ventral and dark-colored dorsal surfaces. They have strong pectoral wings that allow them to swim forward and backward and even launch off waves.³ Stingrays range in size from the palm of a human hand to 6.5 ft in width. They possess 1 or more spines (2.5 to >30 cm in length) that are disguised by much longer tails.^6,7 They often are encountered accidentally because they bury themselves in the sand or mud of shallow coastal waters or rivers with only their eyes and tails exposed to fool prey and avoid predators.

Injury Clinical Presentation

Stingray injuries typically involve the lower legs, ankles, or feet after stepping on a stingray.⁸ Fishermen can present with injuries of the upper extremities after handling fish with their hands.⁹ Other rarer injuries occur when individuals are swimming alongside stingrays or when stingrays catapult off waves into moving boats.^10,11 Stingrays impale victims by using their tails to direct a retroserrate barb composed of a strong cartilaginous material called vasodentin. The barb releases venom by breaking through the venom-containing integumentary sheath that encapsulates it. Stingray venom contains phosphodiesterase, serotonin, and 5′-nucleotidase. It causes severe pain, vasoconstriction, ischemia, and poor wound healing, along with systemic effects such as disorientation, syncope, seizures, salivation, nausea, vomiting, abdominal pain, diarrhea, muscle cramps or fasciculations, pruritus, allergic reaction, hypotension, cardiac arrhythmias, dyspnea, paralysis, and possibly death.^1,8,12,13

Management

Pain Relief
As with many marine envenomations, immersion in hot but not scalding water can inactivate venom and reduce symptoms.^8,9 In one retrospective review, 52 of 75 (69%) patients reporting to a California poison center with stingray injuries had improvement in pain within 1 hour of hot water immersion before any analgesics were instituted.⁸ In another review, 65 of 74 (88%) patients presenting to a California emergency department within 24 hours of sustaining a stingray injury had complete relief of pain within 30 minutes of hot water immersion. Patients who received analgesics in addition to hot water immersion did not require a second dose.⁹ In concordance with these studies, we suggest immersing areas affected by stingray injuries in hot water (temperature, 43.3°C to 46.1°C [110°F–115°F]; or as close to this range as tolerated) until pain subsides.^8,9,14 Ice packs are an alternative to hot water immersion that may be more readily available to patients. If pain does not resolve following hot water immersion or application of an ice pack, additional analgesics and xylocaine without epinephrine may be helpful.^9,15

Infection
One major complication of stingray injuries is infection.^8,9 Many bacterial species reside in stingray mucus, the marine environment, or on human skin that may be introduced during a single injury. Marine envenomations can involve organisms such as Vibrio, Aeromonas, and Mycobacterium species, which often are resistant to antibiotic prophylaxis covering common causes of soft-tissue infection such as Staphylococcus and Streptococcus species.^8,9,16,17 Additionally, physicians should cover for Clostridium species and ensure patients are up-to-date on vaccinations because severe cases of tetanus following stingray injuries have been reported.¹⁸ Lastly, fungal infections including fusariosis have been reported following stingray injuries and should be considered if a patient develops an infection.¹⁹

Several authors support the use of prophylactic broad-spectrum antibiotics in all but mild stingray injuries.^8,9,20,21 Although no standardized definition exists, mild injuries generally represent patients with superficial lacerations or less, while deeper lacerations and puncture wounds require prophylaxis. Several authors agree on the use of fluoroquinolone antibiotics (eg, ciprofloxacin 500 mg twice daily) for 5 to 7 days following severe stingray injuries.^1,9,13,22 Other proposed antibiotic regimens include trimethoprim-sulfamethoxazole (160/800 mg twice daily) or tetracycline (500 mg 4 times daily) for 7 days.¹³ Failure of ciprofloxacin therapy after 7 days has been reported, with resolution of infection after treatment with an intravenous cephalosporin for 7 days.²⁰ Failure of trimethoprim-sulfamethoxazole therapy also has been reported, with one case requiring levofloxacin for a much longer course.²¹ Clinical follow-up remains essential after prescribing prophylactic antibiotics, as resistance is common.

Foreign Bodies
Stingray injuries also are often complicated by foreign bodies or retained spines.^3,8 Although these complications are less severe than infection, all wounds should be explored for material under local anesthesia. Furthermore, there has been support for thorough debridement of necrotic tissue with referral to a hand specialist for deeper injuries to the hands as well as referral to a foot and ankle specialist for deeper injuries of the lower extremities.^23,24 More serious injuries with penetration of vital structures, such as through the chest or abdomen, require immediate exploration in an operating room.^1,24

Imaging
Routine imaging of stingray injuries remains controversial. In a case series of 119 patients presenting to a California emergency department with stingray injuries, Clark et al⁹ found that radiographs were not helpful. This finding likely is due in part to an inability to detect hypodense material such as integumentary or glandular tissue via radiography.³ However, radiographs have been used to identify retained stingray barbs in select cases in which retained barbs are suspected.^2,25 Lastly, ultrasonography potentially may offer a better first choice when a barb is not readily apparent; magnetic resonance imaging may be indicated for more involved areas and for further visualization of suspected hypodense material, though at a higher expense.^2,9

Biopsy
Biopsies of stingray injuries are rarely performed, and the findings are not well characterized. One case biopsied 2 months after injury showed a large zone of paucicellular necrosis with superficial ulceration and granulomatous inflammation. The stingray venom was most likely responsible for the pattern of necrosis noted in the biopsy.²¹

Avoidance and Prevention

Patients traveling to areas of the world inhabited by stingrays should receive counseling on how to avoid injury. Prior to entry, individuals can throw stones or use a long stick to clear their walking or swimming areas of venomous fish.²⁶ Polarized sunglasses may help spot stingrays in shallow water. Furthermore, wading through water with a shuffling gait can help individuals avoid stepping directly on a stingray and also warns stingrays that someone is in the area. Individuals who spend more time in coastal waters or river systems inhabited by stingrays may invest in protective stingray gear such as leg guards or specialized wading boots.²⁶ Lastly, fishermen should be advised to avoid handling stingrays with their hands and instead cut their fishing line to release the fish.

Incidence and Characteristics

Stingrays are the most common cause of fish-related stings worldwide.¹ The Urolophidae and Dasyatidae stingray families are responsible for most marine stingray injuries, including approximately 1500 reported injuries in the United States annually.^1,2 Saltwater stingrays from these families commonly are encountered in shallow temperate and tropical coastal waters across the globe and possess dorsally and distally located spines capable of injuring humans that step on them (Figure 1).^1,3 Freshwater stingrays (Potamotrygonidae family)(Figure 2) are not present in North America but rather inhabit lakes and river systems in South America, Africa, Laos, and Vietnam.⁴ Although recent incidence is unknown, Marinkelle⁵ estimated that thousands of stingray injuries occurred annually in the freshwater of Columbia during the 1960s. Unfortunately, the annual worldwide incidence of stingray injuries is generally unknown and is difficult to estimate, in part because injuries often go unreported.

Stingrays are dorsoventrally flattened, diamond-shaped fish with light-colored ventral and dark-colored dorsal surfaces. They have strong pectoral wings that allow them to swim forward and backward and even launch off waves.³ Stingrays range in size from the palm of a human hand to 6.5 ft in width. They possess 1 or more spines (2.5 to >30 cm in length) that are disguised by much longer tails.^6,7 They often are encountered accidentally because they bury themselves in the sand or mud of shallow coastal waters or rivers with only their eyes and tails exposed to fool prey and avoid predators.

Injury Clinical Presentation

Stingray injuries typically involve the lower legs, ankles, or feet after stepping on a stingray.⁸ Fishermen can present with injuries of the upper extremities after handling fish with their hands.⁹ Other rarer injuries occur when individuals are swimming alongside stingrays or when stingrays catapult off waves into moving boats.^10,11 Stingrays impale victims by using their tails to direct a retroserrate barb composed of a strong cartilaginous material called vasodentin. The barb releases venom by breaking through the venom-containing integumentary sheath that encapsulates it. Stingray venom contains phosphodiesterase, serotonin, and 5′-nucleotidase. It causes severe pain, vasoconstriction, ischemia, and poor wound healing, along with systemic effects such as disorientation, syncope, seizures, salivation, nausea, vomiting, abdominal pain, diarrhea, muscle cramps or fasciculations, pruritus, allergic reaction, hypotension, cardiac arrhythmias, dyspnea, paralysis, and possibly death.^1,8,12,13

Management

Pain Relief
As with many marine envenomations, immersion in hot but not scalding water can inactivate venom and reduce symptoms.^8,9 In one retrospective review, 52 of 75 (69%) patients reporting to a California poison center with stingray injuries had improvement in pain within 1 hour of hot water immersion before any analgesics were instituted.⁸ In another review, 65 of 74 (88%) patients presenting to a California emergency department within 24 hours of sustaining a stingray injury had complete relief of pain within 30 minutes of hot water immersion. Patients who received analgesics in addition to hot water immersion did not require a second dose.⁹ In concordance with these studies, we suggest immersing areas affected by stingray injuries in hot water (temperature, 43.3°C to 46.1°C [110°F–115°F]; or as close to this range as tolerated) until pain subsides.^8,9,14 Ice packs are an alternative to hot water immersion that may be more readily available to patients. If pain does not resolve following hot water immersion or application of an ice pack, additional analgesics and xylocaine without epinephrine may be helpful.^9,15

Infection
One major complication of stingray injuries is infection.^8,9 Many bacterial species reside in stingray mucus, the marine environment, or on human skin that may be introduced during a single injury. Marine envenomations can involve organisms such as Vibrio, Aeromonas, and Mycobacterium species, which often are resistant to antibiotic prophylaxis covering common causes of soft-tissue infection such as Staphylococcus and Streptococcus species.^8,9,16,17 Additionally, physicians should cover for Clostridium species and ensure patients are up-to-date on vaccinations because severe cases of tetanus following stingray injuries have been reported.¹⁸ Lastly, fungal infections including fusariosis have been reported following stingray injuries and should be considered if a patient develops an infection.¹⁹

Several authors support the use of prophylactic broad-spectrum antibiotics in all but mild stingray injuries.^8,9,20,21 Although no standardized definition exists, mild injuries generally represent patients with superficial lacerations or less, while deeper lacerations and puncture wounds require prophylaxis. Several authors agree on the use of fluoroquinolone antibiotics (eg, ciprofloxacin 500 mg twice daily) for 5 to 7 days following severe stingray injuries.^1,9,13,22 Other proposed antibiotic regimens include trimethoprim-sulfamethoxazole (160/800 mg twice daily) or tetracycline (500 mg 4 times daily) for 7 days.¹³ Failure of ciprofloxacin therapy after 7 days has been reported, with resolution of infection after treatment with an intravenous cephalosporin for 7 days.²⁰ Failure of trimethoprim-sulfamethoxazole therapy also has been reported, with one case requiring levofloxacin for a much longer course.²¹ Clinical follow-up remains essential after prescribing prophylactic antibiotics, as resistance is common.

Foreign Bodies
Stingray injuries also are often complicated by foreign bodies or retained spines.^3,8 Although these complications are less severe than infection, all wounds should be explored for material under local anesthesia. Furthermore, there has been support for thorough debridement of necrotic tissue with referral to a hand specialist for deeper injuries to the hands as well as referral to a foot and ankle specialist for deeper injuries of the lower extremities.^23,24 More serious injuries with penetration of vital structures, such as through the chest or abdomen, require immediate exploration in an operating room.^1,24

Imaging
Routine imaging of stingray injuries remains controversial. In a case series of 119 patients presenting to a California emergency department with stingray injuries, Clark et al⁹ found that radiographs were not helpful. This finding likely is due in part to an inability to detect hypodense material such as integumentary or glandular tissue via radiography.³ However, radiographs have been used to identify retained stingray barbs in select cases in which retained barbs are suspected.^2,25 Lastly, ultrasonography potentially may offer a better first choice when a barb is not readily apparent; magnetic resonance imaging may be indicated for more involved areas and for further visualization of suspected hypodense material, though at a higher expense.^2,9

Biopsy
Biopsies of stingray injuries are rarely performed, and the findings are not well characterized. One case biopsied 2 months after injury showed a large zone of paucicellular necrosis with superficial ulceration and granulomatous inflammation. The stingray venom was most likely responsible for the pattern of necrosis noted in the biopsy.²¹

Avoidance and Prevention

Patients traveling to areas of the world inhabited by stingrays should receive counseling on how to avoid injury. Prior to entry, individuals can throw stones or use a long stick to clear their walking or swimming areas of venomous fish.²⁶ Polarized sunglasses may help spot stingrays in shallow water. Furthermore, wading through water with a shuffling gait can help individuals avoid stepping directly on a stingray and also warns stingrays that someone is in the area. Individuals who spend more time in coastal waters or river systems inhabited by stingrays may invest in protective stingray gear such as leg guards or specialized wading boots.²⁶ Lastly, fishermen should be advised to avoid handling stingrays with their hands and instead cut their fishing line to release the fish.

Incidence and Characteristics

Stingrays are the most common cause of fish-related stings worldwide.¹ The Urolophidae and Dasyatidae stingray families are responsible for most marine stingray injuries, including approximately 1500 reported injuries in the United States annually.^1,2 Saltwater stingrays from these families commonly are encountered in shallow temperate and tropical coastal waters across the globe and possess dorsally and distally located spines capable of injuring humans that step on them (Figure 1).^1,3 Freshwater stingrays (Potamotrygonidae family)(Figure 2) are not present in North America but rather inhabit lakes and river systems in South America, Africa, Laos, and Vietnam.⁴ Although recent incidence is unknown, Marinkelle⁵ estimated that thousands of stingray injuries occurred annually in the freshwater of Columbia during the 1960s. Unfortunately, the annual worldwide incidence of stingray injuries is generally unknown and is difficult to estimate, in part because injuries often go unreported.

Stingrays are dorsoventrally flattened, diamond-shaped fish with light-colored ventral and dark-colored dorsal surfaces. They have strong pectoral wings that allow them to swim forward and backward and even launch off waves.³ Stingrays range in size from the palm of a human hand to 6.5 ft in width. They possess 1 or more spines (2.5 to >30 cm in length) that are disguised by much longer tails.^6,7 They often are encountered accidentally because they bury themselves in the sand or mud of shallow coastal waters or rivers with only their eyes and tails exposed to fool prey and avoid predators.

Injury Clinical Presentation

Stingray injuries typically involve the lower legs, ankles, or feet after stepping on a stingray.⁸ Fishermen can present with injuries of the upper extremities after handling fish with their hands.⁹ Other rarer injuries occur when individuals are swimming alongside stingrays or when stingrays catapult off waves into moving boats.^10,11 Stingrays impale victims by using their tails to direct a retroserrate barb composed of a strong cartilaginous material called vasodentin. The barb releases venom by breaking through the venom-containing integumentary sheath that encapsulates it. Stingray venom contains phosphodiesterase, serotonin, and 5′-nucleotidase. It causes severe pain, vasoconstriction, ischemia, and poor wound healing, along with systemic effects such as disorientation, syncope, seizures, salivation, nausea, vomiting, abdominal pain, diarrhea, muscle cramps or fasciculations, pruritus, allergic reaction, hypotension, cardiac arrhythmias, dyspnea, paralysis, and possibly death.^1,8,12,13

Management

Pain Relief
As with many marine envenomations, immersion in hot but not scalding water can inactivate venom and reduce symptoms.^8,9 In one retrospective review, 52 of 75 (69%) patients reporting to a California poison center with stingray injuries had improvement in pain within 1 hour of hot water immersion before any analgesics were instituted.⁸ In another review, 65 of 74 (88%) patients presenting to a California emergency department within 24 hours of sustaining a stingray injury had complete relief of pain within 30 minutes of hot water immersion. Patients who received analgesics in addition to hot water immersion did not require a second dose.⁹ In concordance with these studies, we suggest immersing areas affected by stingray injuries in hot water (temperature, 43.3°C to 46.1°C [110°F–115°F]; or as close to this range as tolerated) until pain subsides.^8,9,14 Ice packs are an alternative to hot water immersion that may be more readily available to patients. If pain does not resolve following hot water immersion or application of an ice pack, additional analgesics and xylocaine without epinephrine may be helpful.^9,15

Infection
One major complication of stingray injuries is infection.^8,9 Many bacterial species reside in stingray mucus, the marine environment, or on human skin that may be introduced during a single injury. Marine envenomations can involve organisms such as Vibrio, Aeromonas, and Mycobacterium species, which often are resistant to antibiotic prophylaxis covering common causes of soft-tissue infection such as Staphylococcus and Streptococcus species.^8,9,16,17 Additionally, physicians should cover for Clostridium species and ensure patients are up-to-date on vaccinations because severe cases of tetanus following stingray injuries have been reported.¹⁸ Lastly, fungal infections including fusariosis have been reported following stingray injuries and should be considered if a patient develops an infection.¹⁹

Several authors support the use of prophylactic broad-spectrum antibiotics in all but mild stingray injuries.^8,9,20,21 Although no standardized definition exists, mild injuries generally represent patients with superficial lacerations or less, while deeper lacerations and puncture wounds require prophylaxis. Several authors agree on the use of fluoroquinolone antibiotics (eg, ciprofloxacin 500 mg twice daily) for 5 to 7 days following severe stingray injuries.^1,9,13,22 Other proposed antibiotic regimens include trimethoprim-sulfamethoxazole (160/800 mg twice daily) or tetracycline (500 mg 4 times daily) for 7 days.¹³ Failure of ciprofloxacin therapy after 7 days has been reported, with resolution of infection after treatment with an intravenous cephalosporin for 7 days.²⁰ Failure of trimethoprim-sulfamethoxazole therapy also has been reported, with one case requiring levofloxacin for a much longer course.²¹ Clinical follow-up remains essential after prescribing prophylactic antibiotics, as resistance is common.

Foreign Bodies
Stingray injuries also are often complicated by foreign bodies or retained spines.^3,8 Although these complications are less severe than infection, all wounds should be explored for material under local anesthesia. Furthermore, there has been support for thorough debridement of necrotic tissue with referral to a hand specialist for deeper injuries to the hands as well as referral to a foot and ankle specialist for deeper injuries of the lower extremities.^23,24 More serious injuries with penetration of vital structures, such as through the chest or abdomen, require immediate exploration in an operating room.^1,24

Imaging
Routine imaging of stingray injuries remains controversial. In a case series of 119 patients presenting to a California emergency department with stingray injuries, Clark et al⁹ found that radiographs were not helpful. This finding likely is due in part to an inability to detect hypodense material such as integumentary or glandular tissue via radiography.³ However, radiographs have been used to identify retained stingray barbs in select cases in which retained barbs are suspected.^2,25 Lastly, ultrasonography potentially may offer a better first choice when a barb is not readily apparent; magnetic resonance imaging may be indicated for more involved areas and for further visualization of suspected hypodense material, though at a higher expense.^2,9

Biopsy
Biopsies of stingray injuries are rarely performed, and the findings are not well characterized. One case biopsied 2 months after injury showed a large zone of paucicellular necrosis with superficial ulceration and granulomatous inflammation. The stingray venom was most likely responsible for the pattern of necrosis noted in the biopsy.²¹

Avoidance and Prevention

Patients traveling to areas of the world inhabited by stingrays should receive counseling on how to avoid injury. Prior to entry, individuals can throw stones or use a long stick to clear their walking or swimming areas of venomous fish.²⁶ Polarized sunglasses may help spot stingrays in shallow water. Furthermore, wading through water with a shuffling gait can help individuals avoid stepping directly on a stingray and also warns stingrays that someone is in the area. Individuals who spend more time in coastal waters or river systems inhabited by stingrays may invest in protective stingray gear such as leg guards or specialized wading boots.²⁶ Lastly, fishermen should be advised to avoid handling stingrays with their hands and instead cut their fishing line to release the fish.