Onchocerca volvulus

Name

Greek: onkos = nodule, kerkos = tail.

Synonyms

Nodule worm.

Geographic Distribution

Central Africa, Yemen, local in Central America.

Life Cycle

Figure 1 (page 1045); Filariidae, Fig. 1. Males 4 cm and females up to 70 cm live for 20 years and more in human skin. Often many females lay close together and form nodules (Figs. 2, 3, 4, and 5, pages 1046, 1047), within which they are fertilized by the small, wandering males. The females produce unsheathed microfilariae (310 × 6–9 μm), which occur all day long in the skin (Fig. 6, page 1047) and are driven with the lymph fluid to the eyes (Eye Parasites) leading to the so-called River-blindness due to immune reaction after their death. These larvae are taken up by bloodsucking simuliid ( Simulium spp.), where they develop into larvae 3 within 6–8 days. The L₃are transmitted during the next bites. The growing up until maturity needs about 9–14 months. However, symptoms of disease may occur earlier (after 3–4 months). The following...