Evolution of host preferences and mechanisms of parasite resistance in birds and mosquitoes infected with avian malaria

Avian malaria parasites are emerging as a model system for understanding the ecology and evolution of malaria parasites in the wild. Their high diversity and spatial variability make them a versatile system for the study of coevolutionary dynamics and the epidemiology of wildlife diseases. Despite recent advances in the field, large gaps still exist in the knowledge of the interplay among the three players of this bird-mosquito-Plasmodium interaction. For example, the costs of parasite resistance in both vertebrate hosts and vectors, along with the mechanisms by which hosts are chosen by vectors, have implications for host–vector-parasite coevolution and disease epidemiology.

In a current research project funded by the SNF, substantial spatial variation has been found in malaria parasite lineages infecting great tits (Parus major), as well as temporal variation in lineages infecting the mosquito Culex pipiens. The first experimental test for coevolution among Plasmodium parasites and their hosts has also been conducted. A link between the ability to resist parasite infection and host oxidative stress is suggested by these studies, and a series of experiments is planned to further test this hypothesis.

The present application is a continuation of the research program on avian malaria in the wild and in captive canaries (Serinus canaria), focusing on the role of the vector Culex pipiens in parasite epidemiology. Specifically, a series of field and lab experiments will be performed in order to:

• a) Evaluate the long-term consequences of infection with Plasmodium lineages on life-history traits in the great tit population.

• b) Experimentally investigate how host oxidative stress levels and parasitaemia are affected by antioxidant supplementation, and how parasite transmission could be influenced.

• c) Test if metabolic rate is modified by malarial infection and how oxidative stress levels are affected as a result.

Secondly, different aspects of the interactions between Plasmodium and mosquitoes will be focused upon. Through lab experiments and field data:

• d) The driving of temporal variation in Plasmodium lineage prevalence by mosquito-feeding preference will be tested.

• e) Whether a vector preference for juvenile male birds exists will be investigated under laboratory conditions.

• f) The cost of resistance in mosquitoes will be investigated by comparing life-history parameters and immune defense gene expression between individuals exposed to Plasmodium and those that were not.

Overall, it is expected that these experiments will disentangle the complex interactions and constraints affecting the relationship between hosts, vectors, and parasites. Through these future studies, light will be shed on the coevolutionary interactions and epidemiology of avian malaria parasites.

Project Details

Basic Science

Apr 2015 — Oct 2018

$536,509

France
Switzerland