Human dirofilariasis: raccoon heartworm causing a leg nodule.

Human dirofilariasis is a rare zoonotic infection caused by various filarial species of the genus Dirofilaria. Dirofilaria tenuis causes heartworm infection in raccoons and infrequently causes human disease. The Dirofilaria organism accidentally is transmitted to humans through the bite of a mosquito and subcutaneous nodules, coin lesions of the lungs, or ophthalmic lesions develop at the inoculation site. We report a rare case of D tenuis infection in a patient that manifested as a subcutaneous nodule.