REDUCED PREVALENCE OF ONCHOCERCIASIS IN UGANDA FOLLOWING EITHER DEFORESTATION OR VECTOR CONTROL WITH DDT

To determine the prevalence of onchocerciasis in western Uganda follow ing deforestation and vector control, three foci were re-examined 20 y ears after previous surveys. In the Ruteete focus Simulium neavei had apparently disappeared and the prevalence of onchocerciasis declined i n adults from about 70% in 1971 to a standardised prevalence of 12% in 1992, An increase of population density together with extended defore station was assumed as cause of this strong reduction, In Bugoye, a S. damnosum s.l. focus, the standardised prevalence of microfilaria carr iers declined from 62% in 1972 to 4.7% in 1992. Entomological data ind icated the absence of man biting blackflies in the nineties, It can be suggested that the vector control using DDT performed during the seve nties had lead to a change of the species composition from anthropophi lic so non-anthropophilic S. damnosum s.l. In the focus Kicheche envir onmental changes were insignificant, deforestation was not progressive and S. neavei was abundant, Here the standardised prevalence of micro filaria carriers was still high (61%).