Sex-Related Heterogeneity in the Life-History Correlates of Mycobacterium bovis Infection in European Badgers (Meles meles)

Heterogeneity in the progression of disease amongst individual wild animals may impact on both pathogen and host dynamics at the population level, through differential effects on transmission, mortality and reproductive output. The role of the European badger (Meles meles) as a reservoir host for Mycobacterium bovis infection in the UK and Ireland has been the focus of intense research for many years. Here, we investigate life-history correlates of infection in a high-density undisturbed badger population naturally infected with M.bovis. We found no evidence of a significant impact of M.bovis infection on female reproductive activity or success, with evidence of reproduction continuing successfully for several years in the face of M.bovis excretion. We also found evidence to support the hypothesis that female badgers are more resilient to established M.bovis infection than male badgers, with longer survival times following the detection of bacterial excretion. We discuss the importance of infectious breeding females in the persistence of M.bovis in badger populations, and how our findings in male badgers are consistent with testosterone-induced immunosuppression. In addition, we found significant weight loss in badgers with evidence of disseminated infection, based on the culture of M.bovis from body systems other than the respiratory tract. For females, there was a gradual loss of weight as infection progressed, whereas males only experienced substantial weight loss when infection had progressed to the point of dissemination. We discuss how these differences may be explained in terms of resource allocation and physiological trade-offs.