Evaluating effectiveness of screening house eaves as a potential intervention for reducing indoor vector densities and malaria prevalence in Nyabondo, western Kenya.

BACKGROUND: Mosquito-proofing of houses using wire mesh screens is gaining greater recognition as a practical intervention for reducing exposure to malaria transmitting mosquitoes. Screening potentially protects all persons sleeping inside the house against transmission of mosquito-borne diseases indoors. The study assessed the effectiveness of house eaves screening in reducing indoor vector densities and malaria prevalence in Nyabondo, western Kenya. METHODS: 160 houses were selected for the study, with half of them randomly chosen for eaves screening with fibre-glass coated 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, with half of them allocated treatment in a ratio of 1:1. Cross-sectional baseline entomological and parasitological data were collected before eave screening. After baseline data collection, 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 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 year period using CDC light traps in 160 houses distributed over 16 study villages (mean mosquitoes = 4.35, SD = 11.48). Of all mosquitoes collected, 2,872 (18.8%) were anophelines (2,869 Anopheles gambiae sensu lato, 1 Anopheles funestus and 2 other Anopheles spp). 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. More indoor adult mosquitoes were collected in the control than experimental arms of the study. Results from cross-sectional parasitological surveys showed that screened houses recorded relatively low malaria parasite prevalence rates compared to the control houses. Overall, malaria prevalence was 5.6% (95% CI: 4.2-7.5) n = 1,918, with baseline prevalence rate of 6.1% (95% CI: 3.9-9.4), n = 481 and 3rd follow-up survey prevalence of 3.6% (95% CI: 2.0-6.8) n = 494. At all the three parasitological follow-up survey points, house screening significantly reduced the malaria prevalence by 100% (p < 0.001), 63.6% (p = 0.026), and 100% (p < 0.001) in the 1st, 2nd and 3rd follow-up surveys respectively. CONCLUSIONS: The study demonstrated that house eave screening has potential to reduce indoor vector densities and malaria prevalence in high transmission areas.

Community knowledge and perceptions on malaria prevention and house screening in Nyabondo, Western Kenya.

BACKGROUND: Screening of houses to prevent mosquito entry is increasingly being recommended as an effective and practical method against malaria transmission through reduced human-mosquito contact. The objective of the study was to assess community knowledge and perceptions on malaria prevention and house screening in a malaria endemic area of Western Kenya. METHODS: A cross-sectional household survey was conducted in 2017 in Nyabondo area of western Kenya. A total of 80 households were randomly selected to participate in the study within 16 villages. Structured questionnaires, focus group discussions and key informant interviews were used to collect data. RESULTS: A total of 80 respondents participated in the survey and more than half (53.8%) reported to have attained primary education. About 91% of the respondents had previously seen or heard malaria messages and this was associated with the respondents level of education (χ2 = 10.163; df 4; P = 0.038, 95% CI). However, other variables like gender, marital status, religion and occupation were not significantly associated with knowledge in malaria. Insecticide treated mosquito nets was by far the most reported known (97.4%) and applied (97.6%) personal protective while only 15.6% respondents were aware of house screening. The major reason given for screening doors, windows and eaves was to prevent entry of mosquito and other insects (> 85%). Lack of awareness was the major reason given for not screening houses. Grey colour was the most preferred choice for screen material (48%), and the main reason given was that grey matched the colour of the walls (21%) and did not 'gather' dust quickly. CONCLUSION: House screening was not a common intervention for self-protection against malaria vectors in the study area. There is need to advocate and promote house screening to increase community knowledge on this as an additional integrated vector management strategy for malaria control.