Dirofilariasis

Definition

A mosquito-borne zoonotic disease caused by filarial nematodes of the genus Dirofilaria, primarily D. immitis (heartworm) and D. repens. Larvae are transmitted to definitive hosts—domestic and wild canids, occasionally felids or humans—through the bite of infected female mosquitoes (Culicidae). In dogs, D. immitis matures in the pulmonary arteries and right ventricle, causing cardiopulmonary pathology; in humans, worms typically fail to reach sexual maturity, instead forming benign but radiographically conspicuous pulmonary or subcutaneous nodules. The disease exemplifies biological vector transmission and parasite life-cycle complexity involving obligate arthropod intermediate hosts.

Etymology

From New Latin Dirofilaria (genus name, from Greek diros 'double' + Latin filum 'thread') + -iasis 'disease condition'

Example

In the southeastern United States, Dirofilaria immitis is maintained in a cycle involving domestic dogs as reservoirs and Aedes aegypti, Culex quinquefasciatus, and Anopheles quadrimaculatus as principal vectors; climate warming has expanded the suitable transmission zone northward.

Synonyms

• heartworm disease (when caused by D. immitis)

Related Terms

• Dirofilaria
• filarial nematode
• biological vector
• Zoonosis
• mosquito-borne disease
• definitive host
• pulmonary granuloma
• heartworm
• Culicidae

Usage Notes

In veterinary contexts, 'heartworm disease' specifically denotes D. immitis infection in canids and is often preferred; 'dirofilariasis' encompasses both D. immitis and D. repens infections and is standard in human medicine and epidemiological literature. The term should not be confused with dirofilariosis, which some parasitologists use for the condition in animal hosts specifically. Human pulmonary dirofilariasis is typically an incidental radiographic finding of a 'coin lesion' rather than a symptomatic infection, reflecting the dead-end host status of humans.