Lifecycle
During a blood meal, an infected midge (Culicoides grahami and C. austeni) introduces third-stage (L3) filarial larvae onto the skin of the human host, where they penetrate into the bite wound. Body heat likely activates the larvas and prompts them to leave the vector and actively penetrate the skin.
The third-stage larvae develop into adults that live in body cavities, most commonly the pleural and peritoneal cavities. They also can live in mesentery, perirenal spaces, retroperitoneal spaces, or the pericardium, and mature into adults.
Adults in the body cavities mate and produce unsheathed and subperiodic microfilariae that reach the bloodstream. The microfilariae can also be found in the cerebrospinal fluid. While the periodicity of these midges has been unclear, the most recent study suggests microfilariae indicate a weak but significant diurnal periodicity with a peak around 8 am.
A midge ingests microfilarae during a blood meal. After ingestion, the microfilariae migrate from the midge’s midgut through the hemocoel to the thoracic muscles of the midge. In the thoracic muscles, the microfilariae develop into second-stage larvae. They subsequently develop into third-stage larvae, which are infective.
The third-stage larvae migrate to the midge’s proboscis, where they can infect another human when the midge takes a blood meal.
Read more about this topic: Mansonella Perstans