Onchocerciasis: What is it and what is being done to help those afflicted?

Onchocerciasis, or River Blindness, is a member of the Neglected Tropical Disease group. River Blindness is caused by the parasitic worm known as Onchocerca volvulus. Transmission occurs when someone is bitten by a blackfly that contains the parasite. The name River Blindness was given to the disease because the blackflies live and breed by rivers and streams, and once infected, blindness usually occurs. In addition to blindness, the disease can also cause a severe skin irritation, leading to extreme itching and the appearance of nodules under the skin (CDC, 2015).

The etiology of this disease is very interesting as the flies must bite the human host multiple times because the fly larvae must take time to grow. Larvae are introduced at different stages of development and they each contribute to another painful symptom. Early larvae cause skin irritation. As the larvae age and the fly bites again, more skin tissue is affected on the human host. At the latest stage of development, the fly will by the human again and infect with the larvae that will produce blindness. This life cycle can be clearly seen in Figure 1 (EyeWiki, 2015).

River Blindness occurs with the highest prevalence of the specific species of blackfly that breed by streams and rivers, which is in a predominantly tropic zone. Due to this specificity, 90% of the disease occurs in Africa. Other places such as Latin America and southern parts of the Arabian Peninsula have also had cases of River Blindness, most likely due to early trade with Africa (WHO, 2016). The areas affected by River Blindness can be seen in Figure 2. In Africa, hundreds of millions of people are at risk of contracting the disease. What makes this such a social issue is that many people live near fertile river areas, which help with easy access to crops and a water supply. Unfortunately, that is also the breeding spot for the blackfly. In some communities that live near a river, almost 50% of the adults are blind as a result of this disease. Due to this tragedy, many of these people are forced to leave their fertile land and go elsewhere to escape this debilitating disease (The End Fund, 2016).

Originally, the most effective method of prevention was vector control of the blackflies. Larvicides were used to get rid of the blackfly population, unfortunately, many infectious blackflies came in from different regions. They continued with this in West Africa and used the vector control method along a wide span of area, helping to control the population of infectious flies. The problem of migration of infectious flies is always the issue though. In addition to vector control, Ivermectin is a drug that can also be used to treat River Blindness. Ivermectin is a microfilaricide and therefore does not kill adult flies. The drug can help reduce transmission and can prevent ocular and dermal morbidity. The treatment is provided annually by manufacturers that donate the drugs. Without the help of outside support, the people affected by the disease can do very little to help prevent ar treat the disease, making this a major social and public health issue (Remme et al., 2006).

Figure 1: Life Cycle of Onchocerca volvulus

Figure 2: Prevalence of River Blindness

Works Cited:

“Parasites – Onchocerciasis (also Known as River Blindness).” Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 10 Aug. 2015. Web. 15 Oct. 2016.

“WHO | Onchocerciasis (river Blindness) – Disease Information.” WHO | Onchocerciasis (river Blindness) – Disease Information. World Health Organization, 2016. Web. 15 Oct. 2016.

Feldman, Brad, Hubert Pham, Maria Woodward, and Vinay Shah. “Onchocerciasis (African River Blindness).” – EyeWiki. N.p., 17 Feb. 2015. Web. 15 Oct. 2016.

“River Blindness.” River Blindness. The End Fund, 2016. Web. 15 Oct. 2016.
Remme, Jan H. F. “Tropical Diseases Targeted for Elimination: Chagas Disease, Lymphatic Filariasis, Onchocerciasis, and Leprosy.” Disease Control Priorities in Developing Countries. 2nd Edition. U.S. National Library of Medicine, 2006. Web. 15 Oct. 2016.