Small islands serve as potential malaria reservoirs through which new infections might come to the mainland and may be important targets in malaria elimination efforts. This study investigated malaria vector species diversity, blood-meal hosts, Plasmodium infection rates, and long-lasting insecticidal net (LLIN) coverage on Mageta, Magare and Ngodhe Islands of Lake Victoria in western Kenya, a region where extensive vector control is implemented on the mainland. From trapping for six consecutive nights per month (November 2012 to March 2015) using CDC light traps, pyrethrum spray catches and backpack aspiration, 1868 Anopheles mosquitoes were collected. Based on their cytochrome oxidase I (COI) and intergenic spacer region PCR and sequencing, Anopheles gambiae s.l. (68.52%), Anopheles coustani (19.81%) and Anopheles funestus s.l. (11.67%) mosquitoes were differentiated. The mean abundance of Anopheles mosquitoes per building per trap was significantly higher (p < 0.001) in Mageta than in Magare and Ngodhe. Mageta was also the most populated island (n = 6487) with low LLIN coverage of 62.35% compared to Ngodhe (n = 484; 88.31%) and Magare (n = 250; 98.59%). Overall, 416 (22.27%) engorged Anopheles mosquitoes were analysed, of which 41 tested positive for Plasmodium falciparum infection by high-resolution melting (HRM) analysis of 18S rRNA and cytochrome b PCR products. Plasmodium falciparum infection rates were 10.00, 11.76, 0, and 18.75% among blood-fed An. gambiae s.s. (n = 320), Anopheles arabiensis (n = 51), An. funestus s.s. (n = 29), and An. coustani (n = 16), respectively. Based on HRM analysis of vertebrate cytochrome b, 16S rRNA and COI PCR products, humans (72.36%) were the prominent blood-meal hosts of malaria vectors, but 20.91% of blood-meals were from non-human vertebrate hosts. These findings demonstrate high Plasmodium infection rates among the primary malaria vectors An. gambiae s.s. and An. arabiensis, as well as in An. coustani for the first time in the region, and that non-human blood-meal sources play an important role in their ecology. Further, the higher Anopheles mosquito abundances on the only low LLIN coverage island of Mageta suggests that high LLIN coverage has been effective in reducing malaria vector populations on Magare and Ngodhe Islands.

Malaria is highly sensitive to climatic variables and is strongly influenced by the presence of vectors in a region that further contribute to parasite development and sustained disease transmission. Mathematical analysis of malaria transmission through the use and application of the value of the basic reproduction number (R0) threshold is an important and useful tool for the understanding of disease patterns. Temperature dependence aspect of R0 obtained from dynamical mathematical network model was used to derive the spatial distribution maps for malaria transmission under different climatic and intervention scenarios. Model validation was conducted using MARA map and the Annual Plasmodium falciparum Entomological Inoculation Rates for Africa. The inclusion of the coupling between patches in dynamical model seems to have no effects on the estimate of the optimal temperature (about 25 °C) for malaria transmission. In patches environment, we were able to establish a threshold value (about α = 5) representing the ratio between the migration rates from one patch to another that has no effect on the magnitude of R0. Such findings allow us to limit the production of the spatial distribution map of R0 to a single patch model. Future projections using temperature changes indicated a shift in malaria transmission areas towards the southern and northern areas of Africa and the application of the interventions scenario yielded a considerable reduction in transmission within malaria endemic areas of the continent. The approach employed here is a sole study that defined the limits of contemporary malaria transmission, using R0 derived from a dynamical mathematical model. It has offered a unique prospect for measuring the impacts of interventions through simple manipulation of model parameters. Projections at scale provide options to visualize and query the results, when linked to the human population could potentially deliver adequate highlight on the number of individuals at risk of malaria infection across Africa. The findings provide a reasonable basis for understanding the fundamental effects of malaria control and could contribute towards disease elimination, which is considered as a challenge especially in the context of climate change.

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. 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. 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. 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.