Onchocerca volvulus

Male (3 - 5 cm long, 0.13 - 0.2 mm diameter) and female (3 - 5 cm long, 0.25 - 0.4 mm diameter) worms live in subcutaneous tissues, often forming tangle masses of threadlike worms in fibrous nodules.

Adult female can live for up to 17 years, the mean being about 10 years. Onchocerca volvulus can be found mainly in West Africa, and also in Central and South America. Most likely, this species was originally only in Africa, and was introduced to the Americas with African slaves.

This nematode worm transmitted through the feeding behavior of black flies (Simulium spp.), which also serve as intermediate hosts. In humans, microfilariae can be found in the skin, lymph vessels, lymph nodes, blood, urine, cerebrospinal fluid, and internal organs (especially the eyes).

The pathogenic, first-stage larvae or microfilariae live in human skin. Consequentially onchocerciasis is essentially a disease of skin and skin derivatives including the eyes.

Human onchocerciasis or river blindness is a serious neglected tropical disease caused by the filarial nematode parasite Onchocerca volvulus.
Onchocerca volvulus