Subcutaneous Dirofilariasis in the United States Literature Review and Case Report

Dirofilariasis is a filarial infection of domestic and sylvatic vertebrates such as canines, felines, raccoons, and bears (the definitive hosts) and is transmitted mostly by mosquitoes (the vector) with the exception being Dirofilaria ursi that is transmitted by the black fly. At least 60 cases of subcutaneous dirofilariasis in humans have been reported; however, the overall incidence of dirofilarial infection has increased, and dirofilariasis is considered an emerging zoonosis. Here, we present a case of subcutaneous Dirofilaria in an otherwise healthy woman in her sixth decade who presented with a painless, mobile, nonerythematous pea-sized nodule of the right upper extremity of 1 month's duration. Evaluation regarding possible disseminated infection, microfilaremia, filarial serology, pulmonary, and central nervous system involvement was negative. She reported no travel outside of South Carolina. Her only risk factor was exposure to mosquitoes 5 months prior in her backyard, composed primarily of wetlands, a common habitat in coastal southeastern United States. No antihelminthics were given. She had complete resolution of the lesion after surgical excision, with no sequelae. This is the second case reported in Charleston, South Carolina.