Modeling control methods to manage the sylvatic plague in black-tailed prairie dog towns

Abstract

Black-tailed prairie dogs (Cynomys ludovicianus) are a keystone species of shortgrass and midgrass prairies, and they are essential for successful reintroduction efforts of endangered black-footed ferrets (Mustela nigripes). Sylvatic plague extirpates black-tailed prairie dog colonies. We present a model to determine optimal control methods to sustain a black-tailed prairie dog colony against the plague, including a recently developed vaccine. Our host submodel is a susceptible, exposed, infectious, vaccinated model, and our vector submodel is a susceptible, exposed, early-stage and late-stage infectious model with questing and on-host vectors. Both submodels are hybrid ordinary differential and difference equation models to reflect the phenology of black-tailed prairie dogs. Our model suggests vaccination efforts can substantially outperform previous control methods (e.g. reactive insecticidal dusting). Our model suggests that a vaccine that provides 18 months of immunity, administered annually, starting one year before an outbreak, can efficiently sustain a black-tailed prairie dog colony against the plague. Recommendations for resource managers The current sylvatic plague vaccine, administered annually, is insufficient to protect a black-tailed prairie dog colony against the sylvatic plague. Developing a vaccine with an immunity period of 18 months is critical for the persistence of a colony against the plague. While insecticidal dusting appears unable to assist in helping a black-tailed prairie dog colony recover from a plague outbreak, insecticidal dusting is still a critical prevention tool as plague transmission from the prairie dog flea is capable of causing a plague outbreak by itself. Black-tailed prairie dog colony recovery efforts appear sensitive to regularly administered culling. We recommend that colonies that are designated as part of the black-footed ferret recovery program be protected from population losses from recreational hunting and poisoning.