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

Abstract

Black-tailed prairie dogs (Cynomys ludovicianus) are keystone species of short-grass prairie ecosystems and are essential to the success of efforts to re-introduce endangered black-footed ferrets (Mustela nigripes). The bacterium Yersinia pestis is the foundation of the sylvatic plague, an infectious disease that causes epizootics in black-tailed prairie dogs. These epizootics prove dangerous for black-tailed prairie dogs as well as for the survival of species that depend upon them. Previous research has sought to understand and compare transmission routes of the plague, in particular the common vector, the prairie dog flea (Oropsylla hirsuta). We present a model to determine optimal control methods to sustain a black-tailed prairie dog town against the plague, including the implementation of a recently developed and tested vaccine. For our host submodel we create a Susceptible, Exposed, Infectious, Vaccinated model, and for our vector submodel we create a Susceptible, Exposed, Early-Stage Infectious, and Late-Stage Infectious model with questing and on-host vectors. Both submodels operate using a hybrid ordinary differential equation and difference equation model with respect to the phenology of black-tailed prairie dogs. Our model suggests the optimal control method combination includes a vaccination plan of vaccinating multiple times per year and must be started at least one year before the arrival of plague.