Evaluating effectiveness of screening house eaves as an intervention for integrated vector management for malaria control in Nyabondo, Western Kenya
Mosquito-proofing of houses with appropriate screens fixed at potential mosquito entry points is gaining greater recognition as a practical intervention for reducing malaria transmission indoors. The study aimed at evaluating the effectiveness of house eaves screening in preventing mosquito entry and malaria prevalence in Nyabondo, western Kenya. Methods 160 houses were selected for the study, with half of them randomly chosen for screening at the eaves with fibre-glass coated wire mesh
... d wire mesh (experimental group) and the other half left without screening (control group). Randomization was carried out by use of computer-generated list, in permuted blocks of ten houses and 16 village blocks in the study site, with treatments in the ratio of 1:1. Crosssectional baseline entomological and malaria parasitological data were collected before house eave screening. After the baseline period, series of sampling of indoor adult mosquitoes were conducted once a month in each village using CDC light traps. Three cross-sectional malaria parasitological surveys were also conducted at three month intervals after installation of the screens. The primary outcome measures were indoor Anopheles mosquito density and malaria parasite prevalence. Results A total of 15,286 mosquitoes were collected over the two years period using CDC light trap in 160 houses distributed over 16 study villages (mean = 4.35, SD = 11.48). Of all mosquitoes collected, 2,872 were anophelines (2,869 An. gambiae s.l., 1 An. funestus and 2 other anopheles). Overall, among An. gambiae collected, 92.6% were non-blood fed, 3.57% were blood fed and the remaining 0.47% were composed of gravid and half gravid females. Overall more mosquitoes were collected in the control than experimental arms of the study. Results from four cross-sectional prevalence surveys showed that screened houses recorded relatively low malaria prevalence rates compared to the control houses. Overall, malaria prevalence was 5.6% (95%CI: 4.2-7.5) N=1,918, with baseline survey recording 6.1% prevalence (95%CI: 3.9-9.4), n=481 and third follow-up survey recording 3.6% prevalence (95%CI: 2.0-6.8) n=494. At all the three follow-up survey points, house screening 3 significantly reduced the malaria prevalence by 100% (p<0.001), 63.6% (p=0.026), and 100% (p<0.001) for first, second and third follow-ups surveys respectively. The house screening significantly reduced malaria prevalence by 54% (OR = 0.46, 95%CI: 0.24-0.87, p = 0.017). Conclusions The study demonstrated that house eave screening has potential to reduce indoor vector densities and malaria transmission in high transmission areas in Kenya.