Pupal Prodictivity of Larval Habitats of Aedes Aegypti in Msambweni, Kwale County, Kenya

Abstract

Accurate identification of larval habitats of Ae. aegypti is considered an essential step in targeted control; of this important vector of several arboviruses including dengue and chikungunya viruses. This study determined Ae. aegyptiproductivity in selected larval habitats in Msambweni, Kwale County, Kenya. A total of 664 potential larval habitats were identified and classified based on their use and material into seven habitat types including: buckets, drums, jerrycans, pots, small domestic containers (SDC), tires and others during the habitat census survey. All Ae. aegypti immatures in 83 representative larval habitats were counted daily for 30 consecutive days during a wet and a dry season. All pupae were removed and allowed to emerge in the laboratory. Of 664 larval habitats examined at baseline, 144 larval habitats (21.7%) were found to be infested with Aedes aegypti larvae. 71% of the pupae were collected from tires and pots combined, which together accounted for 17% of the habitats. In contrast, buckets and SDC represented 55% of the total habitats, but only had an infestation rate of 11.8%, with just 13.5% of the pupae found in them. Multivariate analysis showed that only habitat type and the habitat to being movable were associated with pupal abundance. During the 30-day daily pupal production studies, only a few of the habitats harbored pupae persistently. In the wet season, pupae were collected from 28% (23/83) of the larval habitats. In the dry season, only 12% (10/83) of the habitats were ever found with pupae during the 30-day sampling period, with three habitats (all drums) accounting for 80% (293/365) of all the pupae collected. The results of the multivariate modelsfor the risk factors for pupal productivity showed that habitat type, placing of larval habitats in the backyard, larval habitats without purpose and rain water were significant predictors of larval habitat productivity during the wet season.Although the multivariate model for habitat type did converge, habitat type and large size larval habitats were the only significant predictors during the dry season. Drums, pots and tires were sources of more than 85% of Ae. aegypti pupae, reinforcing the ‘key containers concept’. Targeting these three types of habitats makes epidemiological sense, especially during the dry season.