Tropical Diseases: Onchocerciasis

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Introduction
Domain Animalia
Kingdom Nematoda
Phylum Rhabditea
Class Spirurida
Order Filariodea
Family Onchocercidae
Genus Onchocerca
Species Volvulus
Tropical Diseases are diseases that are found widely spread in tropical and subtropical regions all around the world. The most common disease carriers are mosquitos and flies as they may carry a parasite, bacterium or virus that is infectious to humans and animals. Onchocerciasis, found in Ethiopia, is transmitted by the Simulium blackfly (Figure 2) which is bred in fast flowing streams and rivers. It ranks as one of the world’s most formidable infectious diseases, yet is not widely known. The taxonomy of the small microfilariae can be seen in (Figure 3) as it shows the parasite’s classifications. This parasite is endemic in many African countries, including Ethiopia, as most of the country lack access to clean water and sanitation.

Life Cycle
The passing of the disease, Onchocerciasis, is in a cycle (Figure 4); as the disease is transmitted through the bites of a Simulium blackfly. The disease is not genetic with the blackfly, but once a female blackfly bites a person infected with Onchocerciasis, during a blood meal, the insect becomes infected with the disease as microfilariae are transferred from the human to the fly. Over one to three weeks, the microfilariae develop inside the blackfly to form infective first stage larvae, and then subsequently into third stage larvae, which then migrate to the blackflies proboscis. Once the larvae have migrated the fly can infect another human when it takes a blood meal.
During a blood meal the third stage larvae is transmitted from the blackflies’ proboscis to the skin of its new human host where they penetrate into the bite wounds. O...

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