Tuberculosis, genetic diversity and fitness in the red deer, Cervus elaphus

• Determinants of the presence and severity of TB were identified in red deer.
• TB presence was correlated with Ceh45 locus, body size and wild boar TB prevalence.
• TB severity was associated with population genetic diversity (AR and FIS).
• An indirect genetic effect on deer TB, mediated by body size, was suggested.
• This study highlights the complexity of host-TB interactions in wild populations.

Understanding how genetic diversity, infections and fitness interact in wild populations is a major challenge in ecology and management. These interactions were addressed through heterozygosity-fitness correlation analyses, by assessing the genetic diversity, tuberculosis (TB) and body size in adult red deer. Heterozygosity-fitness correlation models provided a better understanding of the link between genetic diversity and TB at individual and population levels. A single local effect was found for Ceh45 locus at individual level, enhancing the importance of its close functional genes in determining TB presence. At population level, the ability of the red deer to control TB progression correlated positively with population genetic diversity, indicating that inbred populations might represent more risk of deer TB severity. Statistical models also gained insights into the dynamics of multi-host interaction in natural environments. TB prevalence in neighbouring wild boar populations was positively associated with deer TB at both individual and population levels. Additionally, TB presence correlated positively with red deer body size, for which “general and local effect” hypotheses were found. Although body size might be correlated with age, an indirect genetic effect on TB presence could be implied. This study provides new insights towards understanding host-pathogen interactions in wild populations and their relation to fitness traits.