Two decades of tuberculosis surveillance reveal disease spread, high
levels of exposure and mortality, and marked variation in disease
progression in wild meerkats
Abstract
Infections with Tuberculosis (TB)-causing agents of the
Mycobacterium tuberculosis complex threaten human, livestock, and
wildlife health globally due to the high capacity to cross trans-species
boundaries. Tuberculosis is a cryptic disease characterized by
prolonged, sometimes lifelong subclinical infections, complicating
disease monitoring. Consequently, our understanding of infection risk,
disease progression, and mortality across species affected by TB remains
limited. The TB agent Mycobacterium suricattae was first recorded
in the late 1990s in a wild population of meerkats inhabiting the
Kalahari in South Africa and has since spread considerably, becoming a
common cause of meerkat mortality. This offers an opportunity to
document the epidemiology of naturally spreading TB in a wild
population. Here, we synthesize more than 25 years-worth of TB reporting
and social interaction data across 3,420 individuals to track disease
spread, and quantify rates of TB social exposure, progression, and
mortality. We found that most meerkats had been exposed to the pathogen
within eight years of first detection in the study area, with exposure
reaching up to 95% of the population. Approximately one quarter of
exposed individuals progressed to clinical TB stages, followed by
physical deterioration and death within a few months. Since emergence,
11.6% of deaths were attributed to TB, although the true toll of
TB-related mortality is likely higher. Lastly, we observed marked
variation in disease progression among individuals, suggesting
inter-individual differences in both TB susceptibility and resistance.
Our results highlight that TB prevalence and mortality could be higher
than previously reported, particularly in species or populations with
complex social group dynamics. Long-term studies, such as the present
one, allow us to assess temporal variation in disease prevalence and
progression and quantify exposure, which is rarely measured in wildlife.
Long-term studies are highly valuable tools to explore disease emergence
and ecology, and study host-pathogen co-evolutionary dynamics in
general, and its impact on social mammals.