Print PageBovine tuberculosis (BTB), an exotic invasive disease in Kruger National Park, was detected in Kruger’s lions during 1995. While BTB may impact individual animals, observational studies did not find population effects of BTB on lion abundance and demographics once the effects of prey biomass had been accounted for. These studies, however, were constrained by limiting experimental designs and assumptions about stable age distributions of lions. Lions in Kruger contract BTB both from prey (through consumption of infected tissues and through aerosol transmission during suffocation) and from other lions (through aerosol transmission and through percutaneous transmission from bite wounds during fighting). Measuring these transmission rates is difficult. We merged a stochastic, spatial, individual-based simulation model with a disease dynamics model to investigate the relative importance of different modes of BTB transmission in Kruger's lion population. Based on expert opinion, we varied BTB transmission rates from prey to lion, from mother to cub, from lion to lion within a pride, and from lion to lion between prides. We then allowed the simulated host-disease dynamics to evolve and measured population size, disease prevalence, and disease spread over time. By matching our simulation results against observed data of Kruger's lions, we defined the likely statistical distribution of transmission rates and used these to forecast lion population size and disease prevalence.
Results/Conclusions
Transmission of BTB from prey to lions dominates the spread of bovine tuberculosis in lions across the park. Transmission from mother to cub is the least important mode, while high transmission rates from lion to lion within or between prides result in substantially different lion population outcomes than actually observed. These results suggest that lions are a spill-over species for BTB infection and that the prevalence and spread of BTB in prey is the biggest predictor of prevalence and spread of BTB in the lion population. Implications of model results for management of BTB in lions carries large uncertainty associated with assumptions and input parameters. The range of reasonable outcomes is wide enough such that management recommendations are unwarranted at this time. However, the robust definition of lion vital rates, disease transmission rates, and disease dynamics could improve certainty of host-disease modeling outcomes.
