Who's at risk: heterogeneities in individuals' risk of tuberculosis in wild meerkat groups

Tuberculosis (TB) is an important disease of wildlife, livestock, and humans worldwide, but long-term datasets describing this condition are rare. A population of meerkats (Suricata suricatta) in South Africa’s Kalahari... [ view full abstract ]

Tuberculosis (TB) is an important disease of wildlife, livestock, and humans worldwide, but long-term datasets describing this condition are rare. A population of meerkats (Suricata suricatta) in South Africa’s Kalahari Desert are infected with Mycobacterium suricattae, a novel strain of TB causing fatal disease in this group-living species. Our objective was to identify characteristics of individuals and groups at highest risk of developing TB. We conducted a retrospective cohort study based on a unique, long-term life history dataset that included over 2000 individually-identified animals and spanned 14 years, following on from the population’s first TB diagnosis in 2001. Time-dependent Cox regression was used to examine the potential influence of risk factors on development of terminal disease due to TB.
Results: Disease affected 144 individuals in 27 of 73 social groups, in 12 of the 14 study years (incidence rate 3.78 cases/100 study years). Age had the greatest effect on individual-level disease outcome, a hazard ratio of 4.7 (95%CI: 1.92-11.53, p<0.01) for meerkats aged 24-48 months compared to animals aged <24 months, and a hazard ratio of 9.36 (3.34-26.25, p<0.001) for animals >48 months. A history of TB in the group increased the hazard by a factor of 4.29 (2.00-9.17, p<0.01). Immigrations of new group members in the previous year increased the group-level hazard by a factor of 3.00 (1.23-7.34, p=0.016). There was weaker evidence of an environmental effect with a hazard ratio for low rainfall (<200 mm) years of 2.28 (0.91-5.72, p=0.079). This analysis of this unusually detailed long-term dataset from a wildlife population has advanced our knowledge of individual- and group-level risk factors for TB. Our findings corroborate and build upon knowledge of TB in other species such as European badgers (Meles meles) and brushtail possums (Trichosurus vulpecula), and hence may assist management of this currently intractable disease.