619Zoonotic filarial infections affecting humans have been reported worldwide, even in temperate countries. They might be caused by a variety of parasitic species, including Dirofilaria, Brugia, Onchocerca, Dipetalonema, Loaina, Meningonema, and certain Microfilariae. 1 While infection with Brugia is rather common in endemic areas of the world, it is a rare occurrence in the United States. In fact, less than 30 cases of locally acquired infection in human hosts have been described in the literature 2-7 since the first reported case in 1962. 8 Infection by Brugia species is considered a zoonotic disease transmitted by an insect vector, usually manifested by localized lymphadenitis or subcutaneous nodules in otherwise asymptomatic individuals when presenting in nonendemic geographic areas. The diagnosis is made by histopathologic demonstration of the parasite in the biopsied lesions. Since the majority of the reported cases showed localized disease, excisional biopsy was considered to be diagnostic and therapeutic simultaneously, making additional treatment unnecessary. We report the second case of zoonotic Brugia lymphadenitis acquired in Florida, and discuss the clinico-pathologic aspects of this unusual infectious disease.
Case PresentationA 32-year-old immunocompetent man presented with submandibular lymphadenopathy after an episode of upper respiratory tract infection. He was treated at that time with a course of an oral cephalosporin for several weeks, with subsequent resolution of the respiratory symptoms and mild improvement of the lymphadenopathy. Of interest, he worked as an aquatic environmentalist in several southern states, including Florida. He had no history of traveling outside the United States.A computerized tomography (CT) scan of the head and neck disclosed a distinctly enlarged submandibular lymph node, completely separate from a radiologically unremarkable submandibular salivary gland. He underwent surgical excision of the enlarged lymph node.
Clinical ProgressionHistopathological examination revealed reactive follicular lymphoid hyperplasia and a focus of granulomatous inflammation, elicited by a parasite located in the subcapsular sinus (Images 1 and 2). The tissue sections and paraffin block were forwarded to the Division of Infectious and Parasitic Diseases at the Armed Forces Institute of Pathology (AFIP) in Washington, DC, for further identification and speciation of the parasite. The organism was described by the consultant pathologists as an adult female nematode possessing a thin cuticle with thickened lateral ridges and paired uteri containing unfertilized eggs. The size and morphological features of the parasite were consistent with Brugia filarial species [a confirmatory polymerase chain reaction (PCR) test using ribosomal primers was not performed due to unavailability of this test at the time of consultation]. Laboratory findings including complete blood cell count with white cell differential and a basic metabolic profile showed values within normal reference ranges. There wa...