Symptoms of Onchocerciasis

Key points

  • Many people infected with onchocerciasis never develop symptoms.
  • Common symptoms include vision loss, skin rashes, and lumps under the skin.
  • Symptoms may take up to 18 months to appear.


It takes several bites from an infectious blackfly before people become infected. The larvae (immature worms) that cause the disease can take 12 – 18 months to develop into adults, when they start to reproduce inside a person's body. During that time, people infected with onchocerciasis may feel healthy.

Many people infected with the parasite that causes onchocerciasis never show any symptoms. They often feel well until after the adult worms start producing large numbers of microfilarie (immature worms). The most common symptoms are

  • Vision loss
  • Itchy skin rash
  • Lumps under the skin, known as nodes

Onchocerciasis can damage the cornea, the clear, protective layer around the eye. Without treatment, this causes the cornea to become cloudy and causes blindness. The body's response to infection can also result in damage to the optic nerves, which send signals from the eyes to the brain.

The inflammation in the skin, in addition to itching, can also cause long-term skin damage. The skin may become discolored, thin, and less elastic. On rare occasions, the infection can contribute to conditions such as "hanging groin".