La oncocercosis humana en el foco amazónico

in this article we describe human onchocerciasis affecting yanomami people in the amazonian focus of southern venezuela and review recent knowledge about the disease and its control. the epidemiology of this parasitic infection (caused by onchocerca volvulus and transmitted by simulium vectors), is highly dependent on the environmental and entomological characteristics prevalent in the region, which are in turn determined by altitudinal, vegetational and geological gradients. similarly, sociocultural and demographic characteristics of the yanomami people play an important roll in the exposure to the vector and the transmission levels of the parasite. communities with higher infection intensity and transmission (hyperendemic) are located at higher altitudes, characterized by high parasite burden, ocular and dermatological lesions, and additionally a deep suppression of the immunological response to parasite antigens. the proportion of hyperendemic communities reaches 60% of communities stratified so far; however, risk maps using geographical information systems suggest that this proportion may be higher. the onchocerciasis elimination programme is based on mass ivermectin distribution twice a year to at least 85% of the eligible population. despite difficulties in achieving this goal, mainly caused by the remoteness of the communities, the impact of several rounds of treatment is an improvement on the parasitological and clinical indicators in the yanomami population included in the programme. finally, we discuss recent guidelines of epidemiological surveillances of the disease and describe new therapeutical approaches for onchocerciasis control.