The Emergence of Zoonotic Onchocerca lupi Infection in the United States – A Case-Series

The parasite, Onchocerca lupi , has caused unusually severe manifestations in patients identified in the United States. There is likely a transmission cycle in the southwestern United States. A treatment algorithm based on our understanding of Onchocerca volvulus is presented. This case-series describes the 6 human infections with Onchocerca lupi , a parasite known to infect cats and dogs, that have been identified in the United States since 2013. Unlike cases reported outside the country, the American patients have not had subconjunctival nodules but have manifested more invasive disease (eg, spinal, orbital, and subdermal nodules). Diagnosis remains challenging in the absence of a serologic test. Treatment should be guided by what is done for Onchocerca volvulus as there are no data for O. lupi . Available evidence suggests that there may be transmission in southwestern United States, but the risk of transmission to humans is not known. Research is needed to better define the burden of disease in the United States and develop appropriately-targeted prevention strategies.