Onchocerciasis

Onchocerciasis, also known as river blindness, is a parasitic infection caused by the worm Onchocerca volvulus, transmitted through the bite of infected blackflies that breed near fast-flowing rivers. Long-term infection can damage the skin and eyes, potentially leading to blindness.

• Intense, persistent itching of the skin
• Skin changes over time, including thickened, discoloured patches, and in some cases loss of skin elasticity
• Firm, painless nodules under the skin, particularly over bony areas
• Eye involvement can cause visual disturbance and, if untreated over years, progressive and permanent vision loss

• Caused by the parasitic worm Onchocerca volvulus.
• Transmitted through repeated bites from infected blackflies, which breed in fast-flowing rivers and streams.
• Risk is highest for people living or working near rivers in known endemic areas, due to repeated blackfly exposure over time.

• Diagnosed clinically based on the characteristic itching, skin changes, and nodules in a person from a known endemic area.
• Skin snip examination under microscopy can identify the microscopic larvae (microfilariae) to confirm diagnosis where available.
• Eye examination is used to assess for any involvement affecting vision.

Ivermectin, given as a single oral dose based on body weight, is the treatment of choice and is repeated periodically (often annually) until the infection is controlled, since it kills the larvae but not the adult worms.

Community-based mass drug administration with ivermectin is conducted regularly in known endemic areas as the main public health control strategy.

Nodules may be surgically removed at specialist level in some settings to reduce the number of adult worms, though this is not always necessary.

Anyone with visual symptoms in an endemic area should be referred for eye assessment, as established eye damage may not be reversible even with treatment.

• Support community mass ivermectin distribution programmes in known endemic areas.
• Use insect repellent and protective clothing when near fast-flowing rivers in endemic regions.
• Support blackfly vector-control measures where implemented by local health authorities.
• Attend periodic treatment campaigns even without current symptoms, as ongoing treatment prevents disease progression and community transmission.