Effects of the environment on host-parasite coevolutionary conflicts: parasitic manipulation and self-medication in mosquito-human malaria associations. – EMMA

(1) Infected and uninfected mosquitoes were fed with nectars from several plant species and we measured host and parasite fitness.
(2) In the lab, we fed infected and uninfected mosquitoes with blood from a range of vertebrate host species and we measured host and parasite fitness as well as blood chemistry (lipids, sugars, proteins).

(1) We found that plant diversity affect both parasite fitness (prevalence intensity) and host fitness (survival, fecundity) (see scientific summary).
(2) We found that vertebrate host diversity affect both parasite fitness (prevalence intensity) and host fitness (survival, fecundity) and that the nutritive quality of blood-meal types differ.

(1) Do uninfected and infected mosquities have similar preference among the studied plants? parasite manipulation versus host self-medication.
(2) Do uninfected and infected mosquities have similar preference among the studied vertebrate hosts? parasite manipulation versus host self-medication.

- de Roode J, Lefevre T, & Hunter MD (2013) Self-medication in animals. Science. 340, 150-151.

- Lefevre T, Vantaux A, Dabiré KR, Mouline K & Cohuet A. Non-genetic determinants of mosquito competence to malaria parasites (2013) PLoS Pathogens. 9, e1003365.

- Sawadogo SP, Diabaté A, Toé HK, Sanon A, Lefevre T, Baldet T, Gilles J, Simard F, Gibson G, Sinkins S & Dabiré KR (2013) Effects of age and size on Anopheles gambiae s.s. male mosquito mating success. Journal of Medical Entomology. 50, 285-293.

- de Roode JC & Lefevre T. Behavioral immunity in insects (2012) Insects. 3, 789-820
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All organisms serve as hosts for one or more parasite species. While parasites evolve to optimise their host exploitation and between-host transmission, hosts evolve to prevent infection and minimise the parasite-induced fitness loss. Until now most studies on these conflicting evolutionary processes have focused on direct and genetic interactions between parasites and their hosts, and have largely ignored the role of environment in which hosts and parasites interact. This approach is proving to be inadequate, as several recent studies show that environmental conditions experienced by hosts and parasites can strongly affect the outcome of infection. The aim of the proposed research is to investigate (1) how environmental conditions modulate the interactions between the mosquito vector Anopheles gambiae and its protozoan parasite Plasmodium falciparum responsible for human malaria, and (2) whether the host and the parasite can exploit their environment to their own benefit. This host-parasite interaction provides an ideal system to conduct this research for two main reasons. First, there is an increasing realisation that P. falciparum has strong detrimental effects on its mosquito host. Second, recent evidence suggest that environmental conditions including mosquito sugar sources, mosquito blood meal and temperature can differentially affect host and parasite fitness. Therefore, natural selection could have favoured conflicting diet and temperature adaptations in An. gambiae and P. falciparum. Here, we will study these adaptations by determining how a range of plant nectars, vertebrate host species, and temperatures influence the fitness of both mosquito hosts and parasites, and whether hosts are able to self-medicate, or whether parasites can manipulate host behaviour to increase their own fitness. These objectives will be addressed both in the laboratory in Montpellier and in the field in south-western Burkina Faso, a malaria endemic area of West Africa. This project will elucidate how the ecological dimension influences the host-parasite interactions and will produce crucial information relevant to other fields such as parasite manipulation of host behaviours, animal self-medication and chemical ecology. Beyond its fundamental interest, this project will also provide important insights into the control of malaria, which remains a leading cause of morbidity and mortality worldwide. I will conduct the research within the unit MIVEGEC, headed by Dr Didier Fontenille, at the Institut de Recherche pour le Dévelopement (IRD) in Montpellier. Other researchers will also be actively involved in this project, including Dr Anna Cohuet (IRD/IRSS, Bobo-Dioulasso, Burkina Faso), Dr Karine Mouline (IRD/IRSS, Bobo-Dioulasso, Burkina Faso), Drs Roch Dabiré and Abdoulaye Diabaté (Laboratoire d'Entomologie, IRSS/Centre Muraz, Bobo-Dioulasso, Burkina Faso) and Prof. Rickard Ignell (Vector Chemical Ecology group, Swedish University of Agricultural Sciences, Alnarp, Sweden).