Adventure Doc Onchocercaisis

keeping you healthy for life's adventures

Erik McLaughlin MD, MPH

Also known as River Blindness. Filariae migrate through the tissues, leaving behind fibrous nodules. These nodules can also lead to blindness. Symptoms include characteristic subcutaneous nodules, “leopard” skin changes in lower limbs and “hanging groin” due to skin elasticity.

In the Americas: Southern Mexico, Guatemala and small pockets in Venezuela, Brazil, Colombia and Ecuador. In Africa: mostly localized to Central Africa.

Transmission/ Incubation:

Bites from an infected Black Fly (genus Simulium).

Bite prevention from flying insects, vector control, and avoidance of slow moving rivers or lakes.

Skin biopsy showing mcirofilariae.

Ivermectin 150 micrograms/kg once, yearly

Note the lack of a sheath and a bend in the tail.

This disease is similar to Loa Loa, as the filarial worms migrate through the body’s tissues. As the worms migrate, they leave fibrous (tought, hard) nodules or little bumps in the skin. The formation of these nodules in the eye is the cause of blindness. “Hanging groin” can occur as the skin literally loses it’s elastic properties. The lower limbs may also show “leopard skin” signs, caused by changes in skin pigmentation.

River blindness is the target of ivermectin donations to WHO, in an attempt to stop a large cause of preventable blindness.

Treatment is with a drug called Ivermectin. Use caution with this disease and treatment. A dose of DEC, the drug used to treat a similar illness (Loa Loa), may cause a Mazotti Reaction (severe itch after only 25 mg of DEC). If a treatment dose is given, the reaction will occur on a larger/worse scale. To avoid this disease, protect yourself from bites of the flies (DEET, long sleeves). Staying away from standing or slow moving water. The faster flowing rivers are too rough for the larvae. See the malaria section for tips on how to avoid being bitten and what clothes to wear.