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

Abstract

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.

Keywords: Onchocerca lupi; emerging infectious diseases; zoonotic infection.

Figure 1.

Image of the minimally tender, erythematous swollen area on the right posterior-parietal scalp of the patient described in case 2.

Figure 2.

Longitudinal section of the cuticle of O. lupi showing the characteristic transverse cuticular ridges, and the striae (arrows), that run between and below them. [Case 2, trichrome stain, 1000× magnification with oil].

Figure 3.

Cross-section of a female O. lupi, showing typical morphologic features of the genus, including reduced coelomyarian musculature (MU), short, yet conspicuous, lateral chords (LC), paired reproductive tubes (RT), and a small, simple intestine (IN). [Case 3, trichrome stain, 400×].

Figure 4.

Magnetic resonance imaging of the cervical spine with contrast performed prior to the first surgery demonstrating an intradural, extramedullary mass within the leftward aspect of the upper cervical canal at the C2-C3 level.