onchocerciasis / river blindness
- onchocerciasis is caused by the nematode (roundworm) parasite Onchocerca volvulus
- it is the world's second-leading infectious cause of blindness affecting some 270,000 of the 18 million people infected by it
- it is not the nematode, but its endosymbiont, Wolbachia pipientis, which is released once the nematode dies, that causes the severe inflammatory response that leaves many blind.
- the parasite is transmitted to humans through the bite of a black fly of the genus Simulium.
- the vast majority of infections occur in sub-Saharan Africa, although cases have also been reported in Yemen and isolated areas of Central and South America.
- humans are the hosts in the life cycle of this nematode and thus it is not a zoonosis.
- thus whole communities need to be treated to break the cycle.
- skin involvement typically consists of intense itching, swelling, and inflammation resulting in papules, hyperpigmentation, and later hypopigmentation (“leopard skin” especially on the shins), then elephant skin as it becomes thickened
- ocular involvement is initially a punctate keratitis which may resolve or become chronic sclerosing keratitis
- uveitis, retinitis and optic neuritis may also occur.
onchocerciasis.txt · Last modified: 2012/01/05 04:21 by 127.0.0.1