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Parasitic infection emerging in the Southwestern U.S.




SAN DIEGO – Onchocerca lupi, a zoonotic parasite previously described as causing eye disease in cats and dogs, as well as in humans from Europe, Asia, and the Middle East, is emerging in the Southwestern United States.

“The life cycle of this organism is not yet clearly defined, but likely includes a canine and/or feline animal reservoir, as well as an insect vector,” Dr. Christiana Smith said in an interview at an annual scientific meeting on infectious diseases. “No specific risk factors for developing this disease have been identified, other than residing in or traveling through the Southwestern U.S.”

Onchocerca lupi, which causes eye infections in dogs and cats, is now affecting humans in an outbreak in the Southwestern U.S. Sally Koch Kubetin/Frontline Medical News

Onchocerca lupi, which causes eye infections in dogs and cats, is now affecting humans in an outbreak in the Southwestern U.S.

To date, six cases of humans infected by Onchocerca lupi have come to the attention of health officials, including those at the Centers for Disease Control and Prevention, due to symptoms from a nodule containing the parasite, according to Dr. Smith, a pediatrician with the University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora. The affected patients range in age from 22 months to 50 years of age; three of the six reside in Arizona, two in New Mexico, and one in Texas.

In three of the six cases, the nodule was located in the cervical spinal canal. In the remaining three cases, nodules were located on the scalp, the forearm, and the superior rectus muscle of the orbit. Two of the patients reported insect bites at the nodule site years prior to presentation, while another patient owned a dog with eye lesions.

“No previous Onchocerca parasites are known to have tropism for the central nervous system,” Dr. Smith said. “In addition, five of the six cases presented in children. It is not clear whether children are disproportionately affected by this disease, or whether they are diagnosed more frequently.”

Treatment included surgical excision and antiparasitic treatment for most cases. To date, all patients have remained asymptomatic following treatment. Dr. Smith said that more information about Onchocerca lupi will become available as additional cases are described. “Continued epidemiologic investigation will help define the life cycle of this organism, describe the spectrum of human disease, develop approaches to diagnosis and management, and design prevention strategies,” she said.

IDWeek marks the combined annual meetings of the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America, the HIV Medicine Association, and the Pediatric Infectious Diseases Society. The researchers reported having no financial disclosures.

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