Biting time of day in malaria mosquitoes is modulated by nutritional status
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Background and objectives
Vector-borne disease transmission follows daily rhythms because the transmission of pathogens occur at the time of day vectors forage for blood. Insecticide-treated bed nets significantly reduce malaria transmission by interrupting the host seeking behaviour of Anopheles spp. mosquitoes, yet residual transmission is an increasing problem. Biting when humans are unprotected by bed nets is thought to be a driver of residual transmission, but why mosquitoes are shifting their biting rhythms is poorly understood. We test whether food availability, which mediates activity and foraging rhythms across diverse animal taxa, influences the time of day that mosquitoes bite.
Methodology
We varied the amount of blood and sucrose that female Anopheles gambiae s.l. received, and used human-mimic traps in a semi-field system to test the hypothesis that low resources cause host seeking to occur at earlier and later times of day.
Results
Nutritional resources determine both the likelihood and time of day that host seeking occurs. Specifically, low-resourced mosquitoes were 2-3 fold more likely to host seek overall, and 5-10 fold more likely to host seek at an earlier time of day than well-resourced mosquitoes, which predominantly sought a host in the second half of the night time.
Conclusions and Implications
By driving plasticity in biting time of day, mosquito nutritional condition is an underappreciated contributor to residual malaria transmission. Understanding the drivers of biting time of day variation, and their impacts on parasite development, is crucial for the future success of vector control tools and controlling malaria transmission.
Lay summary
We reveal that the nutritional status of mosquitoes influences the time of day that they seek a human to bite. Specifically, poorly-fed mosquitoes attempt to bite humans in the early evening when they are unlikely to be protected by bed nets, which could lead to increased malaria transmission.
