Iligan Dog and Cat Doctor - Sta. Felomina Clinic

30/04/2026

02/04/2026

Heartworm in Humans 😱

A 48-year-old man was found to have a well-circumscribed peripheral lung nodule on imaging, prompting surgical resection for definitive diagnosis. In clinically asymptomatic patients, such findings are approached with a high index of suspicion for malignancy.

Histopathological examination, however, revealed an unexpected and rare etiology — human pulmonary dirofilariasis.

This zoonotic condition, caused by Dirofilaria immitis, represents an aberrant infection in which the canine heartworm fails to complete its lifecycle in humans. Instead, the parasite becomes lodged within the pulmonary vasculature, where its eventual death incites a localized granulomatous and thromboembolic response. The resulting lesion manifests as a solitary “coin lesion,” often radiographically indistinguishable from primary lung neoplasia.

Such cases remain uncommon and diagnostically challenging, underscoring the importance of maintaining a broad differential when evaluating solitary pulmonary nodules, even in the absence of clinical signs.