Dirofilariasis

(Dog Heartworm Infection)

ByChelsea Marie, PhD, University of Virginia;
William A. Petri, Jr, MD, PhD, University of Virginia School of Medicine
Reviewed/Revised Sep 2022
View Patient Education

    Dirofilariasis is a filarial nematode infection with Dirofilaria immitis, the dog heartworm, or other Dirofilaria species, which are transmitted to humans by infected mosquitoes.

    (See also Approach to Parasitic Infections and Overview of Filarial Nematode Infections.)

    Symptomatic human dirofilariasis is very rare, but larvae may become encapsulated in infarcted lung tissue and produce well-defined pulmonary nodules; rarely, larvae form nodules in the eyes, brain, and/or testes.

    Patients may have chest pain, cough, and occasionally hemoptysis. Many patients remain asymptomatic, and a pulmonary nodule, which may suggest a tumor, is discovered during routine chest x-ray.

    Dirofilariasis is diagnosed by histologic examination of a surgical specimen.

    No anthelmintic treatment is indicated in humans; infection is self-limited.

    quizzes_lightbulb_red
    Test your KnowledgeTake a Quiz!
    Download the free Merck Manual App iOS ANDROID
    Download the free Merck Manual App iOS ANDROID
    Download the free Merck Manual App iOS ANDROID