River Blindness

Onchocerciasis, also called River Blindness, is the world’s second leading blindness-causing infectious disease.

Symptoms

The symptoms of Onchocerciasis include:

Intense inflammatory responses, which are triggered by the microfilariae, especially upon their death. (They live up to 2 years in the human host). The extent of the inflammatory response depends on the number of microfilariae in the human host.

Blindness

Hyperpigmentation and/or depigmentation of the skin, causing “lizard skin” and/or “leopard skin” appearances

Inflammation

Itching Skin

Loss of skin elasticity, causing the skin to resemble tissue paper

Loss of vision

Skin plaques

Swelling

Vision loss occurs when the microfilariae migrate to the surface of the cornea, where they cause damage directly and are also attacked by the immune system. In severe infections, blindness results.

Causes

Onchocerciasis, also called River Blindness, is caused by parasitic worm, called Onchocerca volvulus.

Male and female O. volvus parasitic worms grow, mate, and reproduce in the skin of the human host. Adult female worms produce up to 3000 eggs per day, which mature inside the female work and are released individually (in a form known as microfilariae) into the human host where they remain under the skin (of the human host).

Following a bite by a female Black Fly, the larvae pass into the fly where they continue their life cycle, infecting the fly, and causing it to infect other humans when they, in turn, are bitten.

The parasitic worms can live for up to fifteen years in the human body, while the microfilariae can live for up to 2 years in the human body.

Transmission

Onchocerciasis, also called River Blindness, can only be transmitted to humans by the bite of an infected female Black Fly (genus Simulium).

Treatment

The treatment for Onchocerciasis, also called River Blindness, is a medication called Ivermectin (Mectizan), which does not kill the adult worms, but it has two beneficial effects:

-It paralyses the microfilariae and prevents them from causing itching and inflammation.
-Prevents the adult worms from producing additional offspring.

Therefore, treatment prevents the harmful symptoms of infection while also preventing the transmission of the disease. Treatment is only required once every twelve months.

The Ivermectin (Mectizan) medication is provided free of charge, to all people in areas where the disease occurs, by the World Health Organization (WHO) and supporting agencies, including Merck & Co, the World Bank, the United Nations Development Program, and the UN Food and Agriculture Organization.

More than 30 million people in 11 countries have benefited from this free medication.

The British medical journal, Lancet, has reported that the parasitic worm may be developing some resistance to Ivermectin. As a result, in the future, alternative medications may be required.

Prevention and Control

The following techniques are used to attempt to prevent and control Onchocerciasis (also called River Blindness):

Insect Control: the primary prevention measure is larvicide spraying of fast flowing rivers to control Black Fly populations.

Personal Protection: includes a range of measures, including covering exposed skin, using mosquito nets and screens on doors and windows, using insect repellents, and avoiding areas where female Black Fly are common.