Onchocerciasis (River Blindness Worm)

Onchocerciasis is an infection caused by the parasite onchocerca volvulus which can initially result in an itchy red rash, followed by firm nodules, eventually resulting in blindness and is spread through the bite of black flies.

It is called river blindness because the black flies that harbor the parasite breed along streams and rivers infecting millions in Africa causing blindness.

Where does it occur?

It occurs in Africa, Central and South America.

How is it transmitted?

Infection is transmitted through the bite of the infected female black fly.

Is it contagious from person to person?

It is not  contagious from person to person.

What is the risk for travelers?

The risk is generally low for short term visitors but is higher if visiting for longer periods (>3 months)

How soon after exposure will one develop symptoms?

Symptoms are usually seen a year after the initial bite.

What are the signs and symptoms?

After the bite of the black fly, larvae migrate deeper into tissue producing an itchy, red rash.  The larvae develop into adult worms in the tissues. The adult worms then produce microfilariae that migrate along the skin and die resulting in an intense itch that leads to scarring and discoloration referred to as ‘leopard skin’.

One can also see firm nodules throughout the skin which harbor adult worms. Skin can loose its elasticity and start hanging, especially in the groin area.

Microfilariae can reach the eye, where upon their death the tissue develops scars resulting in blindness.

Are there any lab tests to diagnose the illness?

Biopsy of the skin can reveal the microfilariae. Adult worms can be found in skin nodules. Slit lamp exam of the eye can show microfilariae as well.

Is there any treatment?

Ivermectin is the medication of choice.

What preventive measures can be taken?

Avoid bites of the black fly by following insect safety measures.

advice for your illness and travel
learn about an exotic disease