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Biology - Life Cycle of D. immitis

Life Cycle:

Life Cycle of D. immitis

During a blood meal, an infected mosquito (Aedes, Culex, Anopheles, Mansonia) introduces third-stage filarial larvae of Dirofilaria immitis into the skin of the definitive host, which is usually a domestic dog or coyote in the United States (although a wide variety of other animals can also be infected, including felids, mustelids, pinnipeds, beaver, horses, and humans), where they penetrate into the bite wound The number 1. In the definitive host, the L3 larvae undergo two more molts into L4 and adults. Adults reside in pulmonary arteries, and are occasionally found in the right ventricle of the heart The number 2. Adult females are usually 230-310 mm long by 350 µm wide; males are usually 120-190 mm long by 300 µm wide. Adults can live for 5 - 10 years. In the heart, the female worms are capable of producing microfilariae over their lifespan. The microfilariae are found in peripheral blood The number 3. A mosquito ingests the microfilariae during a blood meal The number 4. After ingestion, the microfilariae migrate from the mosquito’s midgut through the hemocoel to the Malpighian tubules in the abdomen The number 5. There the microfilariae develop into first-stage larvae The number 6 and subsequently into third-stage infective larvae The number 7. The third-stage infective larvae migrate to the mosquito's proboscis The number 8 and can infect another definitive host when it takes a blood meal The number 1. In humans The number 9, D. immitis larvae tend to follow the same migratory pathway as in the canine host, ending up in the lungs, where they often lodge in small-caliber vessels, causing infarcts and typical "coin lesions" visible on radiographs.

Life cycle image and information courtesy of DPDx.