The cause is Onchocerca volvulus. Life cycle The life of the parasite can be traced through the black fly and the human hosts in the following steps: # A Simulium female black fly takes a blood meal on an infected human host, and ingests microfilaria. # The microfilaria enter the gut and thoracic flight muscles of the black fly, progressing into the first larval stage (J1.). # The larvae mature into the second larval stage (J2.), and move to the proboscis and into the saliva in its third larval stage (J3.). Maturation takes about seven days. # The black fly takes another blood meal, passing the larvae into the next human host's blood. # The larvae migrate to the subcutaneous tissue and undergo two more molts. They form nodules as they mature into adult worms over six to 12 months. # After maturing, adult male worms mate with female worms in the subcutaneous tissue to produce between 700 and 1,500 microfilaria per day. # The microfilaria migrate to the skin during the day, and the black flies only feed in the day, so the parasite is in a prime position for the female fly to ingest it. Black flies take blood meals to ingest these microfilaria to restart the cycle.
Onchocerciasis
Pulicosis
Scarabiasis
Tungiasis
Leishmaniasis
Necatoriasis
Trichuriasis
Dracunculiasis