Onchocerciasis disease is more commonly known as river blindness. Onchocerciasis is the result of an infection by Onchocerca volvulus, which is a parasitic worm. The parasite is introduced into the human skin by the bite of the Simulium black fly, also known as buffalo gnat or biting black fly. These black flies breed in moving waters and rivers, hence the name river blindness. The disease is mostly concentrated in Africa and parts of South America, since the biting black fly is found there,
Significance
Onchocerca volvulus lives under the skin and in the muscles. It can reside there for up to 15 years. The adult worm produces millions of larvae over the years, which spread to other parts of the body, including muscle tissue and the eyes. According to the World Health Organization, about a quarter of a million of the 18 million people who are affected by onchocerciasis are blind or have severely limited vision.
Symptoms
The symptoms of onchocerciasis do not become apparent immediately after a bite by the blac kfly. It takes about 9 to 24 months for the larvae to mature and spread throughout the body. Initially, a rash appears wherever there is a collection of the adult worms under the skin. Over time, this rash can become severe and cause the skin to loose elasticity and start sagging. The infected areas of the skin also may undergo scarring and depigmentation, leading to a condition called leopard skin. An infection of the eyes results in itchiness, redness, sensitivity to light and eventually blindness.
Treatment
There is treatment available for the infection but the damage done to the eyes can not be reversed. The drug ivermectin,is used to paralyze the larvae and prevent the adult worms from producing more larvae. It does not kill the adult worm, but suppresses the symptoms and prevents them from worsening. It is recommended that ivermectin be administered every three to six months for 10 to 12 years. In severe cases of skin deformity, surgery can be helpful only if it completely removes all the worms.
Mortality
Onchocerciasis is the second most common infectious cause of blindness worldwide. Onchocerciasis is not fatal in itself, but the blindness it causes reduces life expectancy by 4 to 10 years. About 10 percent of all villagers in western Africa suffer from blindness because of onchocerciasis.
Prevention
There is no vaccine or medication that can prevent onchocerciasis. It is best to wear long sleeves and use insect repellent when traveling to areas where black flies are found.
Tags: adult worm, adult worms, biting black, black flies, Onchocerca volvulus