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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.

clinical features

  • 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

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