Use of temephos larvicide in solid form for the control of onchocerciasis in Guatemala.

Three onchocerciasis vectors are recognized in Guatemala: Simulium ochraceum, Simulium metallicurn, and Simulium callidum (1); but the most important species is S. ochraceum. Its larvae generally breed in streams that carry a small volume of water and run under a canopy of dense vegetation, but that move swiftly because of the steep slopes of the foothills through which they fall. The larvae occur along finite stretches of these watercourses, never throughout their length (2,3). Large numbers of such larval habitats are scattered about the area endemic for onchocerciasis. Large-scale application of larvicides is extremely difficult under these circumstances, it being very hard to transport and apply appropriate materials. The rugged terrain precludes the use of motor vehicles, which are employed in Africa to combat S. damnosum (4). And since the elimination of simuliid larvae is a protracted process, it is imperative to find an effective application method that will also make