MHC diversity and emerging infectious disease in parakeet populations on Mauritius

Male Echo Parakeet

Principal Investigator: Dr. Jim Groombridge
Project Dates 2008 – 2011
Funding: Leverhulme Trust
Collaborators: IMSAS, University of Kent; Queen Mary University of London; International Zoo Veterinary Group, UK; Mauritian Wildlife Foundation, Mauritius
Given the global biodiversity crisis, estimating the effect of non-native wildlife on endemics is crucial, and shifting patterns in the climate may serve to increase the pressure on endangered species. Islands are a particularly significant source of biodiversity and have become a particular focus of concern for conservation biologists.

Two important ways that non-native species can adversely affect endemic wildlife is through competition for resources and transmission of pathogens. The latter is especially devastating as endemic species are often immunologically naïve with respect to newly introduced pathogens. This is problematic for species already teetering on the edge of extinction as their limited population size will often bring with it low genetic diversity, including the genes of the immune system. In particular, Major Histocompatibility Complex (MHC) genes, whose products are crucial in immunity, tend to be highly variable allowing the individual to recognise a wide array of pathogens. Arguably, diminution of this variability leaves a greater proportion of a population at risk to non-endemic strains of pathogen.

Understanding the epidemiology of infection with a view to controlling possible outbreaks requires extensive data on host and pathogen population history and on individual host life-histories. This is rarely available for natural populations, even for endangered species. However, the endangered Mauritius parakeet (Psittacula echo) has been carefully monitored for over 20 years. This bird is endemic to the island of Mauritius where by 1987, following a century of habitat loss and competition from the ringneck parakeet (a highly successful and globally distributed feral species), the population crashed to just a handful of individuals. The establishment of one of the most successful avian restoration programmes by the Mauritian Wildlife Foundation and the Durrell Wildlife Conservation Trust has seen the population recover to more than 300 individuals. Recently however, the species has experienced an outbreak of Psittacine Beak and Feather Disease (PBFD), a contagious and potentially fatal parrot-specific virus (see at right and below).

The combination of long-term island population data, an introduced species and a well-characterised pathogen presence makes the Mauritius parakeet ideal to study the effects of disease and non-endemic competition on endangered island species.

Principal Investigator – Dr. Jim Groombridge
Co-Investigator – Dr. Owen Lyne (IMSAS, University of Kent)
Co-Investigator – Dr. Chris Faulkes (Queen Mary University of London)
Postdoctoral Researcher – Dr. Samit Kundu
Project Partner – International Zoo Veterinary Group, UK
Project Partner – Mauritian Wildlife Foundation, Mauritius

This 3 year project aims to:

  1. Survey the parakeet populations on Mauritius for several important pathogens, including PBFD virus,  to determine prevalence and route of transmission.
  2. Create epidemiological models based on the pathogen data that will allow prediction of possible future outbreaks. We will make use of a number of genetic and environmental variables, such as the number of MHC alleles per individual and dispersal rate.
  3. Investigate if MHC diversity is indeed low in the endangered species and to look for specific associations between MHC alleles and pathogens, i.e., are individuals that carry fewer alleles or lack a particular allele more likely to be infected or killed by a given pathogen?

The project benefits from a close collaboration with the Mauritius Wildlife Foundation on Mauritius, and aims to integrate modern epidemiological modelling and immunogenetics with detailed population data to help manage populations of endangered species. Furthermore, Psittacula parakeets are a global bird species, popular in the pet trade and are highly conspicuous. Given these factors, this project has the potential to provide important benefits beyond the conservation community. For example, the large population of feral ringneck parakeets in the U.K. may pose an uncharacterised risk to livestock, native wildlife and, occasionally, humans, due to the pathogens they may harbour. We anticipate that inferences drawn from this project could be applicable to other avian populations around the world.

Publications:

Kundu, S., C. G. Faulkes, A. G. Greenwood, C. G. Jones, P. Kaiser, O. D. Lyne, S. A. Black, A. Chowrimootoo & J. J. Groombridge (2012). Tracking viral evolution during a disease outbreak: the rapid and complete selective sweep of a circovirus in the endangered echo parakeet. Journal of Virology In Press.

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