Modeling and analysis of a temperature-driven outbreak of waterfowl disease in the Upper Mississippi River

Bithynia tentaculata is an invasive snail that was discovered in the Upper Mississippi River (UMR) in 2002. In addition to being a threat to native benthos, the snail also harbors parasite associated with annual outbreaks of waterfowl mortality in the UMR. Trophic transmission of parasites between snails and birds occurs during seasonal waterfowl migrations, which can depend intimately on temperature. We developed an annual model for waterfowl disease in the UMR where transmission depends on water temperatures gleaned from empirical studies. By running simulations from annual temperature profiles selected randomly from a normal distribution, we quantified the association between the number of infected hosts and annual average temperatures. Model output demonstrated that as annual average temperatures rise, infected host populations initially increase and then decay after temperatures exceed a certain threshold. Results from this work suggest that increasing temperatures in the region may have a negative effect on parasites, decreasing their transmission and reducing infected host populations.