Onchocerciasis in Latin America

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  • Topic: Onchocerciasis, Ivermectin, Onchocerca volvulus
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  • Published : May 7, 2011
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Eliminating River Blindness in Ecuador
You notice a figure sitting on a porch in the North-Western region of Ecuador. As you approach it appears to be an elderly man but as you approach him you notice that he has features that you have never seen before. His skin looks as if it has been draped onto his skeletal frame causing him to lose all age indicators. Your eyes reach his and he does not make eye contact, a clear indication that he is blind. You approach the lizard man and ask his age, he replies “Cuarenta y tres.” You wonder to yourself how could a man who is 43 years old have lost his vision and aged so prematurely? The simple answer is Onchocerciasis or more commonly known as River Blindness.

Desowitz (1981) discusses the history, causes, and possible treatments of River Blindness in his book “New Guinea Tapeworms and Jewish Grandmothers. Tales of Parasites and People.” Desowitz mainly focuses on river blindness throughout Africa but discusses how this life-altering parasite was brought to Latin America and where it is prevalent.

Desowitz (1981, p. 92) states that river blindness was first introduced to America in two waves. The first wave was in 1590 when slaves from West Africa were brought to Columbia and Venezuela for gold mining. The second occurred when Napoleon III sent Sudanese troops to Oaxaca (a state in Southern Mexico) in 1862 to help French forces fighting in the region. Over four centuries later, according to the Carter Center’s website for the Onchocerciasis Elimination Program of the Americas (2008), “in the Americas, 500,000 people are at risk for river blindness, and 180,000 are infected in endemic nations.”

River Blindness is prevalent in six Latin American countries: Venezuela, Brazil, Columbia, Ecuador, Guatemala, and Mexico, and affects rural peasants who do not travel frequently. Foci, the center for main disease activity, exist in Mexico and Guatemalan highlands that are at an elevation between 1,600 and 5,000ft and areas on the banks of organically rich water sources. These areas are usually located on or near coffee plantations causing 30-75% of the workers to become infected with the disease and carry it back to their communities (Desowitz 1981, p.93). The disease affects Ecuadorians and Columbians living by rivers’ shores. In Brazil and Venezuela the nomadic Yanomami population (a group who hunts and travels throughout the Amazon Rainforest), is one of the most severely affected populations due to the fact that they are at continuous risk for exposure to the vector of the river blindness parasite (The Carter Center, 2008). The Pesky Filarial Worm Known as Onchocerca Volvulus

Onchocerca Volvulus is the first cousin to the parasite that causes Elephantiasis a disease that causes the thickening of the skin and underlying tissues of a human. The parasite (Onchocerca volvulus) is the cause of river blindness and is classified as a filarial nematode, shown in Figure 1. This type of parasite is an invertebrate animal more commonly known as a roundworm. The roundworms digestive tract makes it different than other invertebrates such as cnidarians or flatworms. Figure One: Onchocerca volvulus (adult worms)

Opperdoes (2002)
The adult worms are threadlike creatures that live within fibrous nodules beneath the human hosts skin on boney areas such as hip bones and knee caps. Female adult worms can produce over 2,000 microfilariae (eggs) everyday for its lifespan of 15-20 years. The eggs produced by the adult female worm hatch within its uterus and disperse throughout the hosts skin once released. This dispersal causes the devastating side affects of river blindness. But before the worm can begin to take its toll on the human body, it must mature within its vector the Simulium damnosum, the black fly (Desowitz 1981, p. 93). Simulium damnosum: The Vector

Desowitz (1981, p. 97) states that the black fly is highly selective in choosing where it will breed and lay its eggs. This...
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