Skin-nontumor / Clinical dermatology
Infestations
Onchocerciasis

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc., FRCPC (see Authors page)

Revised: 2 June 2016, last major update July 2011

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Onchocerciasis [title] skin

Definition / General
  • Onchocerciasis is a parasitic disease caused by Onchocerca volvulus, a microfilaria
Terminology
  • Also called river blindness, Robles' disease
Clinical Features
  • #2 infectious cause of blindness worldwide (#1 is Trachoma), due to its endosymbiont, Wolbachia pipientis, a bacteria that causes the severe inflammatory response that leaves many blind (Wikipedia)
  • Worldwide affects 18 million people, and causes 270,000 cases of blindness
  • Transmitted to humans through the bite of blackfly of genus Simulium
  • Larva spread throughout the body, and when worms die, their Wolbachia symbionts are released, triggering a host immune system response that causes intense itching and can destroy nearby tissue, such as the eye
  • Adult worms live in nodules where the female worms produce high numbers of first-stage larvae known as microfilariae; they migrate from the nodules to the sub-epidermal layer of the skin, where they can be ingested by blackflies (WHO)
  • Most infections occur in sub-Saharan Africa, although global effort is reducing incidence (Disease and Mortality in Sub-Saharan Africa); also occurs in Yemen and isolated areas of Central and South America (Wikipedia)
Treatment
  • Ivermectin throughout entire affected community; single dose may kill first-stage larvae (microfilariae) in infected people and prevents transmission for many months in the remaining population (eMedicine)
  • Also doxycycline
Clinical Images

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Adult black fly

Micro Images

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36 year old Ethiopian man with no previous history, and a clinical diagnosis of inclusion cyst / pilomatrixoma of left thigh