A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
Dirofilaria nematodes, a common cause of canine filarial disease, are increasingly recognized as emerging human pathogens. We report a case of human pulmonary dirofilariasis in the lung of a man from Northern Australia with pulmonary adenocarcinoma. This case highlights the risk for zoonotic transmission in regions with high canine heartworm prevalence.
Dirofilaria immitis is a mosquitoborne filarial nematode that causes canine filarial disease. Although this parasite primarily affects canids, human dirofilariasis caused by several canine Dirofilaria spp. nematodes are increasingly being reported, especially in Europe and Asia ( 1 - 4 ). Humans are accidental hosts for D. immitis nematodes and become infected after the bite of a mosquito carrying D. immitis larvae. Larvae migrate through the circulatory system and die within the pulmonary vasculature, where they infarct small vessels, leading to a surrounding pulmonary granuloma ( 5 ). Those granulomatous nodules are often diagnosed incidentally on routine chest radiography and appear as single or multiple 0.5–4.5 cm round, dense, and opaque coin lesions in the lungs, which can be mistaken for primary or metastatic pulmonary malignancy ( 1 , 5 ).
Human pulmonary dirofilariasis (HPD) caused by D. immitis infection is typically asymptomatic and self-limiting, and specific treatment is generally not necessary ( 1 ). Most cases of HPD are asymptomatic; wheezing, cough, hemoptysis, fever, chest pain, arthralgia and malaise can develop ( 1 ). HPD is rarely reported ( 2 , 3 ), possibly underdiagnosed ( 3 ), and commonly misdiagnosed ( 1 , 3 ). We describe a case of HPD caused by D. immitis infection, identified incidentally in conjunction with primary pulmonary adenocarcinoma.
The male patient was 75 years of age and living in the tropical city of Townsville, Queensland, Australia; he was seen at a trauma visit in 2023. He reported a 100 pack/year smoking history, an occupational exposure to asbestos and silica, and a chronic and nonproductive cough. During his visit, imaging revealed a spiculated mass lesion measuring 35 × 28 mm in the right upper lobe that obstructed the posterior segmental bronchus and was closely associated with a separate nodule.
Figure 1 . Dirofilaria organisms recovered from a patient with human pulmonary dirofilariasis in North Queensland, Australia, 2023. A) Degenerate D. immitis nematode (black arrow) within a necrotic human lung granuloma...
Figure 2 . Defining anatomic features of Dirofilaria immitis within a small blood vessel (arteriole) in a necrotic human lung granuloma, recovered from a patient with human pulmonary dirofilariasis in Queensland, Australia,...
The patient underwent a right upper lobectomy and mediastinal lymph node sampling for suspected primary pulmonary malignancy. Histopathologic and immunohistochemical evaluation of the pulmonary nodule confirmed a 34-mm solid-predominant primary adenocarcinoma. Gross dissection of the specimen revealed an additional nodule ( Figure 1 ). Initial findings suggested multifocal disease; microscopy of the sample revealed a helminthic co-infection. We sought consultation for he…