Ecological studies on aedes aegypti in East Africa preliminary to genetic control; annual research report, 1972/1973

This Yellow Fever Mosquito is one of the half-dozen most important insects affecting mankind. It has spread to almost all tropical and subtropical areas of the world, and it transmits many viruses, including yellow fever dengue, Asian hemmorrhagic fever, Chikungunya, and quite possibly elephantiasis. The mosquito is widespread and abundant in East Africa. It is dif- ficult and expensive to control chemically. Thus genetic means are being sought. Chromosome translocations, sex ratio distor- tion, genes for sterility, and other genetic devices have shown marked promise in the laboratory, but field research and trials are required to allow proper evaluation of these newer methods. Work conducted during the reporting period in East Africa was focused in several small villages in the Rabai area, west of Mombasa. The villages are satisfactory for experiments in genetic control. These villages have 10-25 buildings and a population of about 1,000 adult Aedes aegypti, with a natality rate of 500-100 per day. The selected villages are sufficiently distant from one another that each population can be considered a separate "ecological island." The mixture between the domestic, container-breeding, indoor form and the sylvan, tree-hole breed- ing, feral form is probably not a problem, and certainly not during the dry season. Facilities and plans have been developed for mass production and relase of mosquitoes bearing chromosome translocation. Genetic control experiments over the next two years of the project will involve translocation homozygotes in an attempt to replace the indigenous mosquitoes with a population of a genetic structure designed in the laboratory. This concept (the Serebrowski hypotheses) has yet to be field demonstrated. If replacement is feasible, years five and six of the project will be used to introduce conditional lethals that act seasonal- ly: otherwise those years will be used for releases of multiple translocation heterozygotes conferring sterility.