Onchocerciasis: Symptoms & Signs

Medically Reviewed on 1/28/2022

Onchocerciasis is a parasitic disease caused by parasites known as Onchocerca volvulus. The disease has been referred to as river blindness because the vector, the blackfly, is usually found in the area of rapidly flowing streams and rivers and because a characteristic manifestation of the infection is blindness. Most cases occur in sub-Saharan Africa.

Signs and symptoms of onchocerciasis include

  • severe skin itching with raised bumps,
  • scarring,
  • saggy or drooping skin,
  • patchy loss of skin pigmentation, and
  • eye problems such as itching, swelling, or redness.

Visual problems are another associated symptom. The condition can lead to visual impairment, an inability to distinguish certain colors, and partial or complete blindness.

Cause of Onchocerciasis

The disease is transmitted to humans by the bite (blood meal) of the female blackfly (Simulium), which transfers the larvae of the parasite to the human.

Other onchocerciasis symptoms and signs

  • Eye Problems Such as Itching, Swelling, or Redness
  • Inability to Distinguish Certain Colors
  • Partial or Complete Blindness
  • Patchy Loss of Skin Pigmentation
  • Saggy or Drooping Skin
  • Scarring
  • Severe Skin Itching with Raised Bumps
  • Visual Impairment


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Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.