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Mansonella streptocerca is one of the eight parasitic nematode (roundworm) species that account for most cases of filariasis in humans, although it is responsible for less morbidity than are many of the other seven species (notably, Wuchereria bancrofti and Brugia malayi, which cause lymphatic filariasis, and Onchocerca volvulus, which causes onchocerciasis (river blindness)). Mansonella streptocerca is found in Africa. (Centers for Disease Control Parasites and Health website) It is really endemic in just a few Central and West African countries (Hoerauf 2009).
During a blood meal, an infected Culicoides midge introduces third-stage filarial larvae onto the skin of a human host, where they penetrate into the bite wound. They develop into adults that reside in the dermis, most commonly less than 1 mm from the skin surface. The females measure approximately 27 mm in length. Their diameter is 50 μm at the level of the vulva (anteriorly) and ovaries (near the posterior end), and up to 85 μm at the mid-body. Males measure 50 μm in diameter. Adults produce unsheathed and non-periodic microfilariae, measuring 180 to 240 μm by 3 to 5 μm, which reside in the skin but can also reach the peripheral blood. A midge ingests the microfilariae during a blood meal. After ingestion, the microfilariae migrate from the midge's midgut through the hemocoel to the thoracic muscles. There the microfilariae develop into first-stage larvae and subsequently into third-stage larvae. The third-stage larvae migrate to the midge's proboscis and can infect another human when the midge takes another blood meal. (Centers for Disease Control Parasites and Health website)