A combination of accelerated population growth and severe droughts have created pressure on food security and driven the development of irrigation schemes across sub-Saharan Africa. Irrigation has been associated with increased malaria risk, but it remains difficult to understand the underlying mechanism and develop countermeasures to mitigate its impact. While investigating transmission dynamics is helpful, malaria models cannot be applied directly in irrigated regions as they typically rely only on rainfall as a source of water to quantify larval habitats. By coupling a hydrologic model with an agent-based malaria model for a sugarcane plantation site in Arjo, Ethiopia, we demonstrated how incorporating hydrologic processes to estimate larval habitats can affect malaria transmission. Using the coupled model, we then examined the impact of an existing irrigation scheme on malaria transmission dynamics. The inclusion of hydrologic processes increased the variability of larval habitat area by around two-fold and resulted in reduction in malaria transmission by 60%. In addition, irrigation increased all habitat types in the dry season by up to 7.4 times. It converted temporary and semi-permanent habitats to permanent habitats during the rainy season, which grew by about 24%. Consequently, malaria transmission was sustained all-year round and intensified during the main transmission season, with the peak shifted forward by around one month. Lastly, we demonstrated how habitat heterogeneity could affect the spatiotemporal dynamics of malaria transmission. These findings could help larval source management by identifying transmission hotspots and prioritizing resources for malaria elimination planning.

Long-lasting insecticidal nets are an effective tool in reducing malaria transmission. However, with increasing insecticide resistance little is known about how physiologically resistant malaria vectors behave around a human-occupied bed net, despite their importance in malaria transmission. This study assessed the host-seeking behavior of the major malaria vector Anopheles gambiae s.s, when an intact human-occupied treated bed net is in place, with respect to their insecticide resistance status under semi-field conditions. Pyrethroid resistant and susceptible females of Anopheles gambiae s.s were released inside a semi-field environment housing a hut which was occupied by a human host sleeping under treated or untreated bed net trap. Mosquitoes resting inside the hut or exiting and resting outside were collected using a prokopack aspirator, window exit trap and clay pots. The proportion of resistant females caught in the treated bed net trap was higher compared to the susceptible females (OR=1.445; P<0.00019). Resistant mosquitoes were less likely to exit the house when a treated bed net was present compared to the susceptible mosquitoes. The susceptible females were 2.3 times more likely to stay outdoors away from the treated bed net (OR=2.25; P<0.0001).The resistant mosquitoes showed significantly reduced avoidance behavior compared to the susceptible mosquitoes that were observed to exit the house and remained outdoors when a treated bed net was used. However, further investigations of the behavior of resistant mosquitoes under natural conditions should be undertaken to confirm these observations and improve the current intervention which are threatened by insecticide resistance and altered vector behavior.