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Landscape epidemiology of human onchocerciasis in southern venezuela

Abstract:

Human onchocerciasis is a chronic parasitic disease caused by Onchocerca volvulus and transmitted by Simulium black flies. Clinical manifestations include skin and eye disease, leading to loss of vision and blindness. The interaction between parasite, susceptible fly (vector), and human host highlights the relationship between environmental variables and infection risk. Environmental, cultural, entomological, and parasitological features influencing the heterogeneous geographical distribution of onchocerciasis in the Amazonian onchocerciasis focus of southern Venezuela are described and discussed. Unique features of the region where this focus is located include its ancient geological origin, highly structured and varied landscapes, large extensions of rainforest and mountainous areas crisscrossed by rivers where transmission occurs, mobile and rainforest-dwelling characteristics of the at-risk Yanomami population inhabiting the area, and multiplicity of Simulium vectors. Use of a landscape epidemiology approach and application of remote sensing and geographical information system technologies have permitted identification and mapping of environmental variables and landscape elements that collectively provide the niche in which the dynamics of parasite, human, and vector populations take place, both locally and connectedly. A thorough, yet holistic understanding of this host-parasite-vector system in intimate relationship with its special environment is essential for successful onchocerciasis control in the Amazonian focus.