The biology and control of human onchocerciasis

Published on October 26, 2010   49 min

Other Talks in the Series: Vector-Borne Diseases

0:00
Hello, and welcome to this presentation which will address the biology and control of human onchocerciasis. I'm Ed Cupp, and I'll present an in depth look at this important vector-borne disease.
0:16
Let's begin by looking at the life cycle of the ideological agent, Onchocerca volvulus. It's worth noting too, that human onchocerciasis is referred to as "river blindness" in Africa, and Robles disease in the Americas. Onchocerca volvulus is a filarial nematode, which means that it belongs to that group of parasitic worms that utilize a blood sucking arthropod as an intermediate host and vector. In this case, the vector intermediate host is a group of flies belonging to the genus, Simulium. Humans are the only natural host. This is a very important consideration from an epidemiological point of view, as well as when one addresses the issue of control, because it means that only Homo sapiens serves as the natural host. The adult female worms are sedentary, often growing to a length of a meter or more, and they usually occur in nodules. That is, in encapsulated areas in the human body, which can be seen externally and often palpated. Male worms are much smaller and move between nodules to inseminate the female worms, which then produce an embryonic stage referred to as the microfilarial stage. Microfilariae then spread through the skin, where they cause disease of the eye and of the skin. And also where they position themselves to be taken up in the blood meal by the vector. Development in the vector can be measured in days. Development of the parasite in the human body is measured in months, and often the prepatent period can range from 12 to 18 months in length.
Hide

The biology and control of human onchocerciasis

Embed in course/own notes