Biology - Life Cycle of D. repens
During a blood meal, an infected mosquito (Aedes, Anopheles, Culex, Mansonia) introduces third-stage filarial larvae of Dirofilaria repens onto the skin of the canine definitive host (but also occasionally humans, especially in Europe), where they penetrate into the bite wound . In the definitive host, the L3 larvae undergo two more molts into L4 and adults, the latter of which resides in subcutaneous tissues . Adult females are usually 100-170 mm long by 460-650 µm wide; males are usually 50-70 mm long by 370-450 µm wide. Adults can live for 5 - 10 years. In subcutaneous tissue, the female worms are capable of producing microfilariae over their lifespan. The microfilariae are found in peripheral blood . A mosquito ingests the microfilariae during a blood meal . After ingestion, the microfilariae migrate from the mosquito’s midgut through the hemocoel to the Malpighian tubules in the abdomen . There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae . The third-stage infective larvae migrate to the mosquito's proboscis and can infect another definitive host when it takes a blood meal . In humans , D. repens usually manifests as either a wandering worm in the subcutaneous tissue or a granulomatous nodule, although there are reports of pulmonary dirofilariasis with this species .
Life cycle image and information courtesy of DPDx.