Sex-Related Heterogeneity in the Life-History Correlates ofMycobacterium bovisInfection in European Badgers (Meles meles)

Abstract

SummaryHeterogeneity 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.

Inbreeding intensifies sex‐ and age‐dependent disease in a wild mammal

“…Male badgers have an intrinsically higher mortality than females, regardless of their bTB infection status (Graham et al., ). Male badgers are known to experience faster progression of bTB once infected show weaker immune responses (Beirne et al., ; Tomlinson, Chambers, Carter, et al., ; Tomlinson, Chambers, Wilson, et al., ) and experience a higher rate of disease‐induced mortality compared to females (Graham et al., ; McDonald et al., ). It is possible that investment in intrasexual competition diverts resource away from investment in immunity among males, lowering their tolerance of bTB infection (Beirne et al., ).…”

“…All exposed badgers contributed their entire set of capture data and diagnostic test results to the analysis. Although all the diagnostic tests have their limitations, the combination of test results provide biologically meaningful information on the incidence and subsequent progression of infection within individuals (Tomlinson, Chambers, Carter, et al., ; Tomlinson, Chambers, Wilson, McDonald, & Delahay, ). TB progression in badgers is assumed to be one way (i.e., infected individuals do not recover) (Gallagher, Monies, Gavier‐Widen, & Rule, ; Graham et al., ).…”

Social and environmental factors affect tuberculosis related mortality in wild meerkats

“…() and Tomlinson et al . () found evidence that infected female badgers have longer survival times than males, and Jackson () reported a greater infection risk in male possums ( Trichosurus vulpecula ) with TB.…”

“…Alternatively, infected males may be more likely to be lost to follow-up before they develop signs. Both Wilkinson et al (2000) and Tomlinson et al (2013b) found evidence that infected female badgers have longer survival times than males, and Jackson (1995) reported a greater infection risk in male possums (Trichosurus vulpecula) with TB.…”

Demographic buffering and compensatory recruitment promotes the persistence of disease in a wildlife population

“…Badgers with advanced tuberculosis, determined by positive culture of M. bovis and hence indicative of an infectious state, experience significant weight loss (Tomlinson et al . ) and high mortality (Graham et al . ).…”