Anopheles Productivity of Aquatic Habitats Created Through Artisanal Capture Fishing on Mageta Island in Western Kenya

Abstract

The effect of physicochemical characteristics of mosquito larval habitats on Anopheles productivity is not well known. A cross-sectional survey was carried out on Mageta Island, western Kenya, to fill this knowledge gap. All stagnant water bodies were sampled once from 0900hrs to 1100hrs. Habitats were classified either as those created by or associated with artisanal capture fishing (ACF) activities on the Island (i.e. ACF-related) or as non-ACF. Mosquito larvae and pupae were sampled using sweep nets and physicochemical parameters of habitat water determined simultaneously. The parameters studied included physical habitat characteristics (perimeter, depth and habitat bottom surface), physical characteristics of habitat water (Temperature, turbidity and total suspended solids (TSS) and chemical aspects of water (Dissolved Oxygen or DO, pH, total dissolved solutes or TDS and conductivity). The effect of physicochemical factors on Anopheles larvae/pupae abundance was determined using Generalized Linear Models. A total of 40 habitats were sampled. Only 50% of these had Anopheles larvae while 25% had Anopheles pupae. From these habitats, 862 Anopheles larvae and 230 Anopheles pupae were collected. High numbers of Anopheles pupae were found in ACF (10.90±7.30) than in non-ACF habitats (1.11±0.72). There were significantly more Anopheles larvae in ACF (mean = 36.95±16.93) than non-ACF habitats (7.62±3.04), (P = 0.02). Habitats with wooden bottom surfaces (34.85±21.2) had more larvae than those with mud (21.35±9.09) and rock bottom surfaces (1.375±1.1). Of all factors studied, perimeter (p=0.023), TSS (p=0.001), temperature (p=0.08) and conductivity (p=0.052) influenced larval abundance significantly. Other factors interacted resulting in significant associations with Anopheles larval abundance. These were TDS with conductivity (P = 0.035), TSS with DO (P = 0.003) and TSS with temperature (P = 0.001). Even though individual physicochemical characteristics could be linked to density of Anopheles larvae and productivity of mosquito habitats, the results indicate that certain variables interact to regulate mosquito abundance. Malaria control measures tailored towards manipulating

physicochemical characteristics in mosquito breeding sites should be adopted in integrated mosquito programmes.