Experiments to help understand what makes an infectious mosquito have been performed using cultured malaria parasites and blood donated by naturally infected parasite carriers. With a newly developed pipeline, we measured malaria parasites during their development in mosquitoes, up to the point they are injected by the mosquito inartificial skin tissue. We uncovered that there is a previously unappreciated bottleneck for malaria parasites in mosquitoes and found evidence that i) a non-negligible proportion of infected mosquitoes does not inject parasites during probing; ii) mosquitoes with a high infection burden expell more parasites upon probing without the need to take a bloodmeal.
In Ethiopia, Uganda and The Gambia, we examined how malaria spreads through communities. We were able to detect transmission chains and uncovered that a novel mosquito vector plays an important role in spreading malaria in Ethiopia. This work has helped define a regional containment strategy for this invasive mosquito. In Uganda, we demonstrated in several cohorts that school age children are an important source of onward transmission of malaria parasites to mosquitoes. This work has supported a policy guideline to extend malaria interventions, including chemoprevention strategies, to this age group. This is expected to reduce the clinical burden in this age group and also have a beneficial community effect by reducing community-wide transmission.
In settings across Africa, we examined naturally acquired immunity to the transmission stages of malaria parasites. We uncovered that strong functional immunity that can prevent transmission to mosquitoes can be naturally acquired, is associated to recent exposure to malaria parasites and can be long-lived in a minority of individuals. This work identified a number of potent monoclonal antibodies that may be used as intervention or help improve vaccination strategies.
