Measures aimed at controlling the invasion ofSimulium damnosumTheobald s.l. (Diptera: Simuiiidae) into the Onchocerciasis Control Programme Area. II. Experimental aerial larviciding in the Sankarani and Fie Basins of Eastern Guinea in 1984 and 1985

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Abstract
Annually since the inception of the Onchocerciasis Control Programme in West Africa (OCP), the South‐east Mali portion of the Programme has been invaded by large numbers of onchocerciasis vectors, principally the savanna vector Simulium sirbanum coming from untreated breeding sites located outside the western boundary of the OCP. In an attempt to control these invasions, the Sankarani and Fié River Basins, the easternmost rivers in Guinea, were treated experimentally with the organophosphate larvicide temephos, for 7 weeks in 1984 and for 20 weeks in 1985. Despite the successful conduct of the treatment operations and dramatic falls in the adult vector populations in the Sankarani and Fié Basins, reductions at only the south‐easternmost capture point in the Mali invasion zone, Kankéla, could be attributed to vector control in Eastern Guinea. Here, man‐biting and transmission rates were reduced by over 80% when compared to averages of previous years. The Sankarani Basin was shown to be primarily a source of S. damnosum s.str., the principal species invading Kanketa. It was concluded that source breeding sites for the S. sirbanum which invade South‐eastern Mali must be located along other rivers in the Upper Niger Basin of Guinea.