Transmission strategies of vector-borne parasites: genetic variation, phenotypic plasticity, and consequences for control measures – STORM

Despite ongoing control efforts, mosquito-borne diseases have recently shown an increasing ability to spread to new geographic areas. Evaluating the risk of emergence and transmission of these diseases requires a good knowledge of the genetic and environmental contributions to pathogen transmission traits. Despite medical importance, the causes of variability of a key transmission traits of malaria, namely the parasite development duration within the vector remain largely unknown. This important gap in our knowledge needs to be bridged in order to obtain an integrative view of the ecology and evolution of parasite transmission strategies. This project will assess the relative importance of environmental and genetic determinants in shaping parasite transmission traits within their mosquito vectors using Plasmodium falciparum, responsible for the most severe form of human malaria, and its major mosquito vectors Anopheles coluzzii and An. gambiae. Mosquitoes will be experimentally infected in controlled conditions with natural field isolates of the parasite. This project will determine for the first time whether parasite's development duration depends on:
(i) Parasite genetic (do some parasite isolates grow faster than others?)
(ii) Mosquito genetic (do some mosquito genetic species/lines slow down or speed up parasite development?)
(iii) Genetic interactions between the mosquito and the parasite (do some parasite isolates grow faster only in some specific mosquito species/lines?)
(iv) Mosquito age (do parasite speed up their development when in an old vector?)
(v) Mosquito exposure to sub-lethal doses of insecticides (do parasite speed up their development when in a mosquito with reduced life expectancy?)
(vi) Presence of other parasites (do parasites speed up their development when the vector is already infected with P. falciparum?).
Associations to vector longevity and other mosquito/parasite fitness-related traits (e.g. mosquito fecundity, parasite load) will also be identified (are fast developing parasites also those that are the most virulent i.e. those that induce greatest longevity reduction? Are fast developing parasites also those that produce the least transmissible stages? etc). These correlations often reveal trade-offs and constraints and have important implications for understanding the evolution of parasite transmission strategies. Finally, computational models will be built to evaluate (i) how genetic and environmental influences on parasite’s transmission strategies can shape disease dynamic and (ii) how disease control programs can influence the evolution of parasite’s transmission strategies. Beyond its fundamental interest, this project will provide important insights into the control of malaria and other important vector-borne diseases which remain leading causes of morbidity and mortality worldwide. The ground-breaking nature of the project holds in the highly original questions asked and in the opportunity to transfer knowledge from ecology and evolutionary biology to infectious diseases. We will conduct the research at the MIVEGEC Lab in Montpellier and at the IRSS in Bobo Dioulasso, Burkina Faso.