Onchocerca volvulus

Onchocerca volvulus

Onchocerca volvulus ( gr όγκος " barb ", κέρκος "tail"; Latin volvulus " small ball " ) is the name of a tropical, belonging to the filarial nematode. He is a human parasite and the causative agent of river blindness.

Dissemination

Onchocerca volvulus occurs in large areas of tropical Africa and in Central and northern South America in the front (Mexico, Guatemala, Venezuela and Ecuador). An insulated stove is located in Yemen. The distribution is restricted to humid regions along fast-flowing rivers.

Features

The adult worms are very small ( filamentous ) having a diameter of less than one millimeter. Females can be up to 70 centimeters long, the males reach a maximum length of 40 centimeters. The microfilariae ( larval form ) are 220 ​​to 280 microns long.

Life cycle

Onchocercarien as all parasitic filarial a life cycle with changing hosts. Humans are the only definitive host. In endemic areas, almost 100 % of the population are infected. As an intermediate host, the female blackfly ( Simulium damnosum ), which receives the microfilariae in the stitch used. In the mosquito, the larvae develop through molting to the infective stage L3, in which they are transferred when a new stitch to humans. You walk one to two years through the connective tissue and occasionally through the eyes. Full-grown (adult ) worms survive for years encapsulated in subcutaneous nodules ( Onchozerkom ). Often there are several filarial in such a knot. The females produce daily about a thousand microfilariae that migrate through the lymph spaces of the connective tissue and will eventually be washed into the bloodstream. The microfilariae infect the eye, so that the main harmful effects ( blindness ) is established.

Blackfly with the left sensor leaking filaria Onchocerca