The Malaria Reservoir: Micro-scale studies of human to mosquito malaria transmission

Biting heterogeneity and infectiousness

Although anyone is theoretically at risk of contracting malaria where the parasite and the vector are present, research shows that infection and disease burden are unevenly distributed in the population. As few as 20% of individuals suffer 80% of malaria episodes. This highly over-dispersed burden of malaria may enhance persistence and also suggests that onward transmission may originate from a small subpopulation of infected humans. It should be possible to identify and characterize this group of individuals responsible for the majority of onward transmission. Targeting this group of transmitters – also called the malaria ‘reservoir’ – would have the largest impact on transmission in a population.

The objective of our work is to investigate, under natural conditions, which humans are bitten by mosquito vectors, and which humans transmit malaria infections to mosquitoes. To do this, we have established a longitudinal cohort in western Kenya where we collect mosquitoes each week and monitor individuals for malaria infection. By matching mosquito bloodmeals to individual household members, we can learn about mosquito behavior and whether mosquitoes bite randomly or prefer certain individuals. Biting preference could have a substantial impact on malaria persistence. Going further, by matching malaria infections in mosquitoes to those in the human hosts, we can understand who is infecting mosquitoes and directly characterize the reservoir of infection.

Matching infections between mosquitoes and people requires advanced parasite genotyping methods that are being developed and refined in collaboration with Dr. Steve Taylor’s lab. By combining intensive human and entomological sampling with sequence-based, high-resolution parasite genotyping techniques, we can directly track individual parasite infections between mosquitoes and humans and identify which human hosts are most infectious.

Collaborators: Steve Taylor, Andrew Obala (Moi University), Judith Mangeni (Moi University)

Publications