Are emerging Infectious Disease determinant of socially structured Population evolution? The case of Ebola-Gorilla system. – IDiPop

The novelty of this project is the demo-genetic approach .
We study the dynamics of loci undergoing selection(Major Histocompatibility Complex) before and after the outbreak in wild populations using a non-invasive sampling.
The analysis of individual life histories, using multi-state capture-recapture and integrated population modeling, allow us to estimate the recruitment of individuals after Ebola outbreaks.

Six months after the start of the project, we develop the protocol for studying variability of MHC loci. Anlayses of the results are in progress.
The study of social dynamics and immigration rate in a population affected by Ebola, allow us to determine that the disease pertubed the transfer of individuals between social units and that immigration is crucial to the viability of the population.

The long-term prospects of this project are to determine the fate of the evolutionary potential of the species and to integrate spatial scale in the models.

in progress

The current global changes related to human activities favor the development of emerging infectious diseases because of pathogen adaptation to new environmental conditions, or introduction of pathogens into naive populations. These diseases can have serious consequences on the functioning of host populations by reducing their size, by changing their genetic composition, especially when acting on genes involved in immunity response, and by changing life history traits of the populations. These changes have major impacts on the evolutionary dynamics of biodiversity. Moreover, emerging diseases increase the risk of population extinction if the affected population is small, if the pathogen transmission is frequency-dependent - as in the socially structured populations, or if there is a reservoir host. These three disease-induced extinction mechanisms are likely to occur in the case of the Ebola disease affecting humans and great apes. The hemorrhagic fevers caused by Ebola virus have caused up to 95% mortality in affected great ape populations. Understanding the impact of diseases on the evolutionary potential of wild populations is a major challenge to human health and biodiversity conservation.

This fundamental research project aims to understand the impacts of Ebola outbreaks on the dynamics of Western lowland gorilla (Gorilla gorilla gorilla) populations thanks to long-term monitoring of two pre-and post-epidemic populations in the Republic the Congo and one unaffected population located in the same area. The first issue of the project concerns the study of the selective pressure of the disease by examining the dynamics of loci undergoing selection, such as genes of the Major Histocompatibility Complex (MHC) involved in the defense against pathogens. The MHC genes have a high allelic variability that is believed to be an adaptive strategy for accommodating rapidly evolving infectious agents that periodically afflict natural populations. Comparison of the MHC loci variability before and after Ebola and variability of neutral markers will permit to understand the roles of genetic and demographic processes induced by the disease on the evolutionary potential of the populations. This project involves developing new methods of analysis of MHC loci from non-invasive samples, with many implications for studying selection in wild endangered populations.
The second issue of the project aims to examine the demographic changes related to Ebola perturbations, in particular the recruitment of new individuals through immigration and reproduction. This study needs gathering of all information on the presence of identified individuals (direct observation and genetic monitoring) and completion of monitoring on the field. Analysis of individual presence-absence histories using multi-state capture-recapture models will allow determining classes of disease susceptibility in regards to social and genetic structure. Using an integrated model of population dynamics, integrating a complex social structure, we will estimate and compare the immigration and breeding success rates in the populations before and after Ebola. The development of models of socially structured population dynamics offers perspectives for analyzing the responses of such populations to anthropic and environmental stresses.

Given that Ebola affects both the viability of primate populations and human health, understanding Ebola consequences on the demo-genetic dynamics of wild primate populations is crucial for the biological, evolution and conservation sciences.