Mosquitoes of the Kano Plain, Kenya. I. Results of indoor collections in irrigated and nonirrigated areas using human bait and light traps

Abstract

The preliminary entomological results from a nonirrigated area of the Kano Plain and from the irrigated Pilot Rice Scheme at Ahero, Kenya, are used to demonstrate that irrigation has had a marked effect on the mosquito fauna. Catches inside houses using human bait and modified CDC light traps indicated that in the rice field environments numbers of the main malaria vectors of the area were higher than in nonirrigated areas, and that their breeding extended over some 6 months of the year. Abundance of these mosquitoes in dwellings was closely linked to the conditions in nearby rice fields, and the 2 main population peaks of A. gambiae were connected with hand transplanting of young rice from nurseries to the main fields. On the nonirrigated plain, prevalence of the major anopheline species followed a more classical pattern, being closely linked to local rainfall, and the predominant mosquito species were found to be those breeding in semipermanent swamps and water holes. The combined results of a series of human-bait catches gave a series of biting activity curves very similar to those found by other workers in Africa.