Zoonotic onchocerciasis is a rare human infection caused by Onchocerca species that normally parasitize non-human mammals. In Japan, all previously reported human cases have been attributed to Onchocerca japonica and have presented as localized, non-migratory subcutaneous nodules. Here, we report the first human infection caused by Onchocerca takaokai Uni et al., 2015. A 24-year-old male presented with linear migratory erythema on the forearm, clinically consistent with creeping eruption. Histopathological examination revealed an adult female filarial nematode with polymyarian-coelomyarian musculature, without internal cuticular ridges in the lateral cords, and lacking transverse ridges on the cuticle. Molecular analyses of the mitochondrial 12S rRNA and cytochrome c oxidase subunit I (cox1) genes confirmed that the parasite was O. takaokai, a parasite of wild boars in Japan. This case demonstrates a clinical presentation distinct from that of O. japonica and suggests that O. takaokai should be considered in the differential diagnosis of creeping eruption in endemic areas.
Ikenaga et al. (Fri,) studied this question.