Dirofilariasis

Dirofilariasis is a parasitic zoonotic infection caused by nematodes (roundworms) of the genus Dirofilaria, most commonly Dirofilaria immitis (heartworm) and Dirofilaria repens. Humans are accidental dead-end hosts, becoming infected through the bite of mosquitoes carrying infective larvae. Unlike in the natural animal hosts (dogs, cats, and other mammals), the parasites typically do not reach full maturity in humans. The disease can affect multiple body systems depending on the species involved. Dirofilaria immitis most commonly causes pulmonary dirofilariasis, where immature worms lodge in pulmonary arteries and create granulomatous nodules (coin lesions) in the lungs that may be mistaken for malignant tumors on imaging. Dirofilaria repens, more prevalent in Europe and Asia, typically causes subcutaneous or subconjunctival dirofilariasis, presenting as migratory subcutaneous nodules or periorbital swelling. Key symptoms vary by the site of infection. Pulmonary dirofilariasis may present with cough, chest pain, hemoptysis, or may be entirely asymptomatic, discovered incidentally on chest radiographs as solitary pulmonary nodules. Subcutaneous dirofilariasis manifests as painful or painless nodules under the skin, often in the face, trunk, or extremities. Ocular involvement can cause eye pain, redness, tearing, and the sensation of a foreign body. Rare cases of visceral involvement affecting the liver, peritoneal cavity, or other organs have been reported. Mild eosinophilia may be present in some patients. Treatment primarily involves surgical excision of the nodule or worm, which is both diagnostic and curative. Anthelmintic drug therapy (such as diethylcarbamazine or ivermectin) has been used in some cases but is generally not considered the primary treatment, as the worms are usually already dead or dying in the human host. Prognosis is generally excellent following surgical removal. Prevention focuses on mosquito bite avoidance in endemic areas. The disease is found worldwide but is more commonly reported in Mediterranean countries, parts of Asia, and the Americas.

Common questions about Dirofilariasis