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| Keywords: Onchocerca volvulus LifeCycle.gif Filariasis Life cycle of Onchocerca volvulus During a blood meal an infected blackfly genus Simulium introduces third-stage filarial larvae onto the skin of the human host where they penetrate into the bite wound In subcutaneous tissues the larvae develop into adult filariae which commonly reside in nodules in subcutaneous connective tissues Adults can live in the nodules for approximately 15 years Some nodules may contain numerous male and female worms Females measure 33 to 50 cm in length and 270 to 400 μm in diameter while males measure 19 to 42 mm by 130 to 210 μm In the subcutaneous nodules the female worms are capable of producing microfilariae for approximately 9 years The microfilariae measuring 220 to 360 µm by 5 to 9 µm and unsheathed have a life span that may reach 2 years They are occasionally found in peripheral blood urine and sputum but are typically found in the skin and in the lymphatics of connective tissues A blackfly ingests the microfilariae during a blood meal After ingestion the microfilariae migrate from the blackfly's midgut through the hemocoel to the thoracic muscles There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae The third-stage infective larvae migrate to the blackfly's proboscis and can infect another human when the fly takes a blood meal http //www dpd cdc gov/dpdx/images/ParasiteImages/A-F/Filariasis/O_volvulus_LifeCycle gif PD-USGov Onchocerca v life cycle CDC lifecycles | ||||
