Social and environmental factors affect tuberculosis related mortality in wild meerkats

'Tuberculosis (TB) is animportant and widespread disease of wildlife, livestock and humans world-wide,but long-term empirical datasets describing this condition are rare. Apopulation of meerkats (Suricata suricatta) in South Africa's Kalahari Deserthave been diagnosed with Mycobacterium suricattae, a novel strain of TB,causing fatal disease in this group-living species. This study aimed to findcharacteristics associated with clinical TB in meerkats. These characteristicscould subsequently be used to identify ‘at-risk’ animals within a population,and target these individuals for control measures. We conducted a retrospectivestudy based on a unique, long-term life-history dataset of over 2000individually identified animals covering a 14-year period after the firstconfirmatory diagnosis of TB in this population in 2001. Individual- andgroup-level risk factors were analysed using time-dependent Cox regression toexamine their potential influence on the time to development of end-stage TB.Cases of disease involved 144 individuals in 27 of 73 social groups, across 12of 14 years (an incidence rate of 3·78 cases/100 study years). At theindividual level, increasing age had the greatest effect on risk of diseasewith a hazard ratio of 4·70 (95% CI: 1·92–11·53, P < 0·01) formeerkats aged 24–48 months, and a hazard ratio of 9·36 (3·34–26·25,P < 0·001) for animals aged over 48 months (both agecategories compared with animals aged below 24 months). Previous grouphistory of TB increased the hazard by a factor of 4·29 (2·00–9·17,P < 0·01), and an interaction was found between this variable andage. At a group level, immigrations of new group members in the previous yearincreased hazard by a factor of 3·00 (1·23–7·34, P = 0·016). Therewas weaker evidence of an environmental effect with a hazard ratio for a lowrainfall (<200 mm) year of 2·28 (0·91–5·72, P = 0·079). Ourfindings identify potential individual characteristics on which to basetargeted control measures such as vaccination. Additional data on the dynamicsof the infection status of individuals and how this changes over time wouldcomplement these findings by enhancing understanding of disease progression andtransmission, and thus the implications of potential management measures.