River Blindness

Onchocerciasis, also known as river blindness, is an infectious disease that is caused by the parasitic worm Onchocerca volvulus. The infection is transmitted by Simulium blackflies through a bite. It is the second leading infectious disease that results in vision loss. Unlike other diseases, this disease requires repeated bites for an infection to happen. The disease is also called river blindness because the fly breeds in streams and rivers and leads to vision loss. Onchocerciasis is prevailing in remote rural areas which makes those who live or work in these areas more at risk.

In 2017, about 20.9 million people were affected by the disease globally, where 1.15 million experienced blindness and 14.6 million experienced skin issues. The prevalence of the disease mostly occurs in Africa - about 31 countries are impacted by it and more than 99% of people are infected. The disease is also common in South America and Yemen. Currently, 4 countries are no longer affected by onchocerciasis and these include Mexico, Ecuador, Colombia, and Guatemala.

After contracting, symptoms one may experience

Onchocerciasis affects the eyes and skin. Not everyone will display symptoms but some may experience symptoms. The common signs and symptoms include skin rash with severe itching, eye disease with the possibility of visual impairment and vision loss, and the appearance of nodules beneath the skin.

How is it diagnosed?

There are various methods to diagnose onchocerciasis and the most common way is to get a skin snip and observe under a microscope. Surgical excision is done for those who experience nodule formation under the skin. If a patient is experiencing eye manifestations, then a slit-lamp examination of the eye is performed. Sometimes, an antibody test can be helpful.

How is Onchocerciasis treated?

The current treatment is ivermectin which is given once every year for 10 to 15 years. Doxycycline is another medication that kills adult worms. The doctor may prescribe both medications depending on the case. The healthcare provider would give the best advice for treating the disease.

It is imperative to rule out Loa loa before any treatment begins because this parasite is found in the same area as Onchocerca volvulus. And Loa loa tends to produce serious consequences to the medications used for onchocerciasis.

Are there any preventive methods?

Yes, there are ways to prevent getting bitten by a blackfly. These preventive methods include using insect repellants and wearing clothes that cover the entire body such as long pants and sleeve shirts. Currently, there is no medication or vaccine to prevent onchocerciasis. Taking the necessary precautions is the only way to stay safe and avoid getting bitten.

Current situation

Due to successful disease control programs organized by the World Health Organization, Onchocerciasis cases have been reduced globally. The programs include mass administration of ivermectin drugs and controlling the population of blackfly. However, there are many lives still at risk but do not have accessible preventive methods and treatment. Therefore, educating on preventive measures is imperative to save the lives of people living in vulnerable areas.

Further Reading

Centers for Disease Control and Prevention. Parasites - Onchocerciasis (also known as River Blindness). 2019. Available from: https://www.cdc.gov/parasites/onchocerciasis/index.html

Neha Ramjuttun

About

Medical Advisor Audiopedia, Master in Public Health (MPH), MBBS