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

1. The mutation accumulation theory of senescence predicts that age-related deterioration of fitness can be exaggerated when inbreeding causes homozygosity for deleterious alleles. A vital component of fitness, in natural populations, is the incidence and progression of disease. 2. Evidence is growing for natural links between inbreeding and ageing; between inbreeding and disease; between sex and ageing; and between sex and disease. However, there is scant evidence, to date, for links among age, disease, inbreeding and sex in a single natural population. 3. Using ecological and epidemiological data from a long-term longitudinal field study, we show that in wild European badgers (Meles meles) exposed naturally to bovine tuberculosis (bTB), inbreeding (measured as multi-locus homozygosity) intensifies a positive correlation between age and evidence of progressed infection (measured as an antibody response to bTB), but only among females. Male badgers suffer a steeper relationship between ...