Work

The Brief Case: Dirofilaria species causing a subcutaneous nodule after a visit to the beach in Florida

Year: 2024

Type: article

Abstract: A 34-year-old woman with no significant past medical history presented to her primary care provider in the Midwest United States after returning from a trip to the state of Florida a few weeks prior.During her trip to Florida, she spent time outdoors and recalled receiving multiple bites from unknown insects on the beach.Since returning, she experienced painful, nodular swelling on her left foot which persisted without improvement.She denied systemic symptoms.On physical examination, there was a firm, 1-cm nodule on the dorsal aspect of her left foot with associated erythema.The remainder of the physical examination was unremarkable.The initial clinical suspicion was for a ganglion cyst.An excisional biopsy of the nodule was performed and sent for histopathologic evaluation.No microbiologic studies were otherwise performed.Microscopic examination of hematoxylin and eosin-stained slides (H&E) revealed a fibrotic subcutaneous nodule with associated acute inflammation.Within the nodule, multiple cross-sections of an adult filarial worm were identified.The helminth was characterized by a multilayered outer ridge with clearly defined longitudinal ridges, well-developed thick coelomyrian musculature (muscle surrounding the body cavity), internal ridges with adjacent lateral cords, paired reproductive tubes, and a central intestine (Fig. 1).The histopathology slides were sent to a commercial reference laboratory for further characterization.In addition, images of the organism were shared with the Centers for Disease Control Division of Parasitic Diseases and Malaria DPDx diagnostic assistance program.The organism was identified as a zoonotic filarial nematode of the genus Dirofilaria.A definitive species identification was not possible by microscopic appearance alone.However, the identification of Dirofilaria tenuis was favored based on the location of travel (State of Florida, United States of America) and the presence of cuticular ridges (not present in D. immitis).Ultimately the patient did well after the surgical excision and required no additional treatment. DISCUSSIONDirofilariasis is a vector-borne zoonotic infection caused by filarial nematodes of the genus Dirofilaria.The definitive hosts of Dirofilaria species include raccoons, bears, wild cats, and carnivorous domestic animals (i.e., cats and dogs); humans are incidental hosts.Dirofilaria species have a worldwide distribution, but within the United States, the Southeast has the highest prevalence of dirofilariasis (1).Transmission occurs via Culex, Aedes, and Anopheles mosquito species (2).Dirofilariasis in humans is characterized by two primary disease presentations: pulmonary disease and subcutaneous disease (2, 3).Pulmonary dirofilariasis occurs when

Source: Journal of Clinical Microbiology

DOI: 10.1128/jcm.00308-23

Authors: Jonathan Wilcock, Bobbi S. Pritt, Andrew P. Norgan

Institution: Mayo Clinic

Language: English

Topic: Parasitic Diseases Research and Treatment

Subfield: Infectious Diseases

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: green

OpenAlex ID: W4391811920