When can predation control vector-borne pathogens?

Pathogens transmitted by arthropod vectors are common in human populations, agricultural systems, and natural communities. Transmission of these vector-borne pathogens depends on the population dynamics of the vector species as well as its interactions with other species within the community. In particular, predation may be sufficient to control pathogen prevalence indirectly via the vector. To examine the indirect effect of predators on pathogen dynamics we developed a theoretical model that integrates predator-prey and host-pathogen theory. We use this model to determine whether predation can prevent pathogen persistence or alter the stability of host-pathogen dynamics. We used a susceptible-infected (SI) model with explicit vector and predator populations to determine the persistence threshold for the pathogen in the presence or absence of a predator. We found that in the absence of predation, increases in vector fecundity led to increased infection prevalence in the host population. Predation can reverse this relationship, and at high predation rates on the vector the pathogen may be unable to persist. We also found that predation on a vector may drastically slow the initial spread of a pathogen. These results highlight the importance of considering the entire community when studying disease dynamics and also suggest situations where an introduced predator or the natural enemies of a vector may slow the rate of spread of an emerging vector-borne pathogen.