Think of onchocerciasis (river blindness) as a worm infestation that is strongly connected to rivers and blackflies. It is particularly important in parts of Nigeria and other sub-Saharan African countries. The disease is caused by a filarial worm called Onchocerca volvulus. It is not spread directly from one person to another, but by an infected blackfly (Simulium), which bites a person and transmits the parasite.
These blackflies breed around fast-flowing rivers and streams. So, the connection between them is that onchocerciasis is caused by a filarial worm spread by the blackfly that breeds around rivers. That is why it is called “river blindness.” After an infected blackfly bites someone, it deposits infective larvae inside human skin where they mature into adult worms.
These adult worms live in nodules under the skin and can survive for many years. The female worms produce tiny larvae called microfilariae. These microfilariae move through the skin and eyes and cause most of the disease. The symptoms caused by this disease are mostly to be found in the skin, where the patient may develop severe itching, which is a key characteristic of the disease.
The other skin problem is the development of a rash, the scratching of which leads to thickened and often damaged skin. Loss of skin pigment occurs in the affected parts of the skin, leading to what is often described as a “leopard skin” appearance or “lizard skin” appearance.
