Screening eaves of houses reduces indoor mosquito density in rural, western Kenya

Abstract

Background Despite the scale-up of insecticide-treated nets and indoor residual spraying, the bulk of malaria transmission in western Kenya still occurs indoors, late at night. House improvement is a potential long-term solution to further reduce malaria transmission in the region. Methods The impact of eave screening on mosquito densities was evaluated in two rural villages in western Kenya. One-hundred-and-twenty pairs of structurally similar, neighbouring houses were used in the study. In each pair, one house was randomly selected to receive eave screening at the beginning of the study while the other remained unscreened until the end of the sampling period. Mosquito sampling was performed monthly by motorized aspiration method for 4 months. The collected mosquitoes were analysed for species identification. Results Compared to unscreened houses, significantly fewer female Anopheles funestus (RR = 0.40, 95% CI 0.29–0.55), Anopheles gambiae Complex (RR = 0.46, 95% CI 0.34–0.62) and Culex species (RR = 0.53, 95% CI 0.45–0.61) were collected in screened houses. No significant differences in the densities of the mosquitoes were detected in outdoor collections. Significantly fewer Anopheles funestus were collected indoors from houses with painted walls (RR = 0.05, 95% CI 0.01–0.38) while cooking in the house was associated with significantly lower numbers of Anopheles gambiae Complex indoors (RR = 0.60, 95% CI 0.45–0.79). Nearly all house owners (99.6%) wanted their houses permanently screened, including 97.7% that indicated a willingness to use their own resources. However, 99.2% required training on house screening. The cost of screening a single house was estimated at KES6,162.38 (US$61.62). Conclusion Simple house modification by eave screening has the potential to reduce the indoor occurrence of both Anopheles and Culex mosquito species. Community acceptance was very high although education and mobilization may be needed for community uptake of house modification for vector control. Intersectoral collaboration and favourable government policies on housing are important links towards the adoption of house improvements for malaria control.

House Screening Reduces Exposure to Indoor Host-Seeking and Biting Malaria Vectors: Evidence from Rural South-East Zambia

“…House screening using non-insecticide-treated screens (wire mesh or mosquito netting) as physical barriers on windows and eaves have shown significant protection against malaria [ 7 , 14 , 15 , 16 , 17 ], dengue [ 18 , 19 ], and lymphatic filariasis [ 20 , 21 ]. Despite well-established benefits, house screening has not been encouraged on a large scale by national malaria programs and remains neglected by public health policy.…”

Treated eave screens in combination with screened doors and windows, are more effective than untreated eave screens in a similar combination in reducing indoor and outdoorAnophelespopulations under semi-filed conditions in western Kenya

“…House screening has demonstrated potential for control of disease transmitting vectors such as mosquitoes [26,28,[35][36][37]. Mosquitoes are adapted to enter and feed within human houses [18], hence transmitting malaria.…”

“…Eaves are the main avenues for indoor entry of mosquitoes [18,38], with doors and windows being additional routes. Blocking of eaves have been demonstrated to significantly reduce the numbers of mosquitoes indoors [28,39] while additional screening of doors and windows increase the success of reducing mosquitoes indoors [35,40]. In western Kenya, the major malaria vectors bite indoors, late and night [23][24][25] despite sustained use of ITNs.…”

“…Housing is a key contributor to health; it not only protects against the elements but also influences the physical and psychosocial well-being of its inhabitants. House modification has been reported in many settings to be an effective mosquito control strategy [26][27][28][29] including resulting in an epidemiological impact [27]. However, it has received little attention in much of Sub-Saharan Africa where malaria is endemic likely due to the lack of a standardized approach and perceived cost.…”

Indoor heat stress mitigation in low-income Kenyan homes with mosquito prevention intervention

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The impact of global warming on health is increasingly becoming profound, especially in low-and middle-income countries like Kenya. With rapid urbanization and massive low-income housing construction, Kenya is under severe risks of indoor and outdoor overheating, which is commonly seen as an accelerator of transmission and geographical expansion of vector-borne diseases, such as malaria [1]. Many mosquito prevention technologies have been implemented in residential houses, such as eave screening, window mesh, and bed nets.

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