Integrating multi-host modelling with empirical wildlife-livestock contacts reveals an essential population in a pathogen reservoir

Infections at the animal-human or wildlife-livestock interfaces have severe health and socio-economic consequences. Combined with empirical data, mathematical models can contribute to a better understanding of the reservoirs of these infections, which is a priority for mitigating their impact by using appropriate management interventions. Taking brucellosis in the Bargy massif (French Alps) as an example of a zoonosis at the wildlife-livestock interface, we developed and calibrated a multi-host model integrating data on direct and environment-mediated cross-species contacts from field observations. Estimates of the basic reproduction number ( R ₀ ) allowed to identify the population of Alpine ibex ( Capra ibex ) and its environment as an essential host in the reservoir, driving both pathogen maintenance (within-species R ₀ ≥1: 1.66, 95% credible interval: 1.42-2.03) and its transmission to livestock (between-species R ₀ >0: 0.035, 0.01-0.05). Our approach can be adapted to other multi-host pathogens, which will contribute to improve the understanding and management of these complex systems.