Determinants of variation in host-parasite interactions

Principal researcher: Francisco Valera Hernández:

Period: 2015-2018

Disease occurs non-randomly in space and factors such as climate, physical habitat characteristics, community context, host species identity and parasite species identity may account for such variation. Yet, our understanding on how biotic and abiotic factors determine host-parasite interactions is still limited and we ignore much about the general rules and mechanisms explaining the above-mentioned relationships. Another important gap in our knowledge about emerging infectious diseases is that, while the host specificity between specific hosts and parasites has been frequently revealed, the specificity between parasites and their vectors remains largely neglected even for major host-vector-parasite systems. This shortcoming has been suggested as the major obstacle to dealing with the current emerging infectious diseases crisis.

The main goal of this project is to disentangle the context dependency of local host-parasite interactions and the relative importance of the processes influencing parasitism intensity by following a community ecology-oriented approach encompasing various study systems and spatio-temporal scales. We also aim at uncovering some mechanisms underlying the links between habitat and disease, both between hosts and parasites and between hosts, vectors and haematozoan parasites. The general hypothesis of the project is that environmental conditions strongly influence, either directly and/or indirectly, the occurrence of epidemics and host-parasite interactions. Specifically the project focuses on:

- the effect of spatial and temporal variation in climatic conditions on the ecto and endoparasitic community of several study systems,

- the effect of physical features of the habitat on the ectoparasitic community of an avian guild and on parasite dispersal via its influence on local host density and host community structure,

- the evaluation of the variability and context dependency of local host-parasite interactions,

- the identification of the host-vector-parasite associations in our study systems.

The strength of this project relies on its broad framework that jointly considers the interactions among biotic drivers (e.g. host density), and abiotic/physical drivers of epidemics. This approach is necessary for a complete understanding of disease ecology once the study of hostparasite interactions in isolation has proved insufficient. Moreover, by studying patterns of variation of parasitisation across a range of scales, we can gain insight into the relative importance of different processes involved in the dynamics of diseases. This project will improve the understanding of links between climate, microclimate, habitat structure, species interactions, and parasitism. Highlighting these links and the underlying mechanisms is necessary to predict accurately the likelihood of epidemics in particular locations, what is of major interest fin the current scenario of climate warming. Finally, if the vectorial role of some of our study species is confirmed, this project will have a norteworthy impact because vector and host ecology are studied simultaneously and comprehensively to reveal their effects on the spread of avian haemoparasites