Onchocerca volvulus
| Onchocerca volvulus | |
|---|---|
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| Onchocerca volvulus, the causative agent of river blindness. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Order: | Spirurida |
| Family: | Onchocercidae |
| Genus: | Onchocerca |
| Species: | O. volvulus |
| Binomial name | |
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Onchocerca volvulus Bickel, 1982 |
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Onchocerca volvulus is a nematode that causes onchocerciasis (river blindness), and is the second leading cause of blindness worldwide after trachoma. It is one of the seventeen neglected tropical diseases listed by the World Heath Organisation (WHO), with elimination from certain countries expected by 2020.
John O’Neill, an Irish surgeon, first described Onchocerca volvulus in 1874 where he found it to be the causative agent of ‘craw-craw’, a skin disease found in West Africa. A Guatemalan doctor Rodolfo Robles first linked it to visual impairment in 1917.
Onchocerca volvulus is primarily found in Sub-Saharan Africa and humans are the only known definitive host. It is spread from person to person via female biting blackflies of the genus Simulium.
Onchocerca volvulus obtain nutrients from the human host by ingesting blood or by diffusion through their cuticle. They may be able to trigger blood vessel formation because dense vascular networks are often found surrounding the worms. They are distinguished from other human infecting filarial nematodes by the presence of deep transverse striations.
It is a dioecious species, containing distinct males and females, which form nodules under the skin in humans. Mature female worms permanently reside in these fibrous nodules, while male worms are free to move around the subcutaneous tissue. The males are smaller than females, with male worms measuring 23mm in length compared to 230-700mm in females.
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Wikipedia