Life cycle of Mansonella perstans
During a blood meal, an infected Culicoides midge introduces third-stage filarial larvae of Mansonella perstans onto the skin of a human host, where they penetrate into the bite wound. They develop into adults that reside in body cavities, most commonly the peritoneal cavity or pleural cavity, but less frequently in the pericardium. The size range for female worms is 70 to 80 mm in length and 120 μm in diameter; males measure approximately 45 mm by 60 μm. Adults produce unsheathed and subperiodic microfilariae, measuring 200 by 4.5 μm, that reach the blood stream. A midge ingests microfilariae during a blood meal. After ingestion, the microfilariae migrate from the midge's midgut through the hemocoel to the thoracic muscles of the arthropod. There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae. The third-stage infective larvae migrate to the midge's proboscis and can infect another human when the midge takes a blood meal.
From Centers for Disease Control Parasites and Health website.