The transmission of Plasmodium falciparum was studied in relation to the incidence of severe malaria infections at nine sites in the Kilifi District in Kenya. Intensive mosquito sampling during a one-year period yielded Anopheles gambiae x.

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The larval habitats of Culicoides species were determined by examining a total of 1 476 samples collected from different ecological environments in various parts of Kenya. Immature stages were collected from suspected breeding habitats and adults were reared. Adults were also captured in emergence traps and then identified. To determine species preferences, if any, the materials yielding Culicoides were analysed for pH, organic matter and water content.Fifty-seven percent of the samples yielded a total of 26 species of Culicoides. Sites in which Culicoides occurred were classified into eleven habitats grouped into four major systems, namely, aquatic, transitional, terrestrial and general systems. Most species were found breeding over a wide pH range in sites which were wet at least part of the time. A few species appeared to select breeding habitats with a high organic content.

Abstract. A case-control study examined vector-related and environmental parameters associated with severe malaria in Kilifi District along the coast of Kenya. Over an 11-month period, 119 children identified with severe malaria infections at the Kilifi District Hospital were matched by age with control children who reported to the outpatient clinic with nonsevere infections. Intensive mosquito sampling was done in each of the case-control houses over a four-day period, beginning within a week of index case admission. A total of 109 environmental, demographic, behavioral, and animal husbandry variables were characterized for each household. Vector species (Anopheles gambiae s.l. and An. funestus) were detected in 40.1% and 36.1% of case and control houses, respectively. The relative abundance of vectors in individual houses was stable over the two-week resampling periods (r ϭ 0.9). Both the overall abundance of anopheline mosquitoes (odds ratio [OR] ϭ 1.5) and P. falciparum sporozoite rates (OR ϭ 1.5) were not significantly different between case and control houses. In a matched analysis, 11 of 109 house variables associated significantly with severe malaria were also associated with vector abundance, as determined by chi-square linear trend analysis. Under conditions of year-round, low-level transmission on the coast of Kenya, the risk of severe disease in children is multifactorial and not governed strictly by transmission intensity or environmental heterogeneity affecting vector abundance and distributions. This suggests that current interventions that appear to be achievable only in areas where transmission is already low to moderate should be appropriate. However, such interventions should be monitored so that inappropriate and possibly disastrous control activities can be avoided in Africa.In endemic areas of malaria transmission, most infections are asymptomatic. A major question is why only a small proportion of infected individuals develop severe, life-threatening malaria infections.

Chorionic sculpturing on eggs of Phlebotomus pedifer Lewis, Mutinga, and Ashford; the closely related Phlebotomus aculeatus Lewis, Minter, and Ashford (= P. elegonensis Ngoka, Madel, and Mutinga); and Phlebotomus martini Parrot was examined and compared by scanning electron microscopy. The eggs of P. pedifer had a general pattern of longitudinal ridges; those of P. aculeatus and P. martini exhibited intraspecific differences. Chorionic patterns of eggs were not reliable to differentiate these species. It is suggested that other methods of differentiation should be used on these species.