Landscape Epidemiology of Human Onchocerciasis in Southern Venezuela

Abstract

Human onchocerciasis is a chronic infection caused by the filarial parasitic nematode Onchocerca volvulus and transmitted through the bites of Simulium vectors (black flies). More than 80 million people are exposed to the risk of infection with 37 million persons infected (according to the latest results of rapid epidemiological mapping of onchocerciasis), and 1 million with severely impaired vision. Most of the cases are observed in tropical Africa (99%), with the remainder in smaller, more discrete foci in Yemen and Latin America. Its impact on human health is through the clinical repercussions of the infection for the skin (causing cutaneous disease) and for the eyes (causing loss of vision and even blindness). However, onchocerciasis can have more insidious and subtle systemic effects, rendering the people infected more susceptible to the same and other infections and impairing their ability to respond well to vaccination. Mortality of the blind and of those sighted individuals with heavy parasite burdens has been well documented, particularly in savannah areas of West Africa.