Effects of Diseased Top Predators in Food Chains

Ecoepidemiology studies spreading diseases among interacting populations. Food webs occur everywhere in nature. In this paper we investigate a dynamical system for an epidemic affecting the top predators in a three-trophic level food chain. The feasible model equilibria are identified and their stability is assessed, showing transcritical bifurcations relating some of them, and analytically establishing the impossibility of Hopf bifurcations, with the exception for the coexistence equilibrium. Simulations reveal indeed that all subpopulations can thrive together by sustained periodic oscillations. This investigation supplements other parallel studies on other tri-trophic ecoepidemic food chains. The general conclusions support earlier findings that purely demographic models are not an adequate description of real environments, if possible disease effects are not suitably accounted for in the model formulation.