Outbreak of waterfowl disease in the Upper Mississippi River with temperature dependent transmission rates

Background/Question/Methods

Bithynia tentaculata is an invasive snail that was discovered in the upper Mississippi River in 2002. In addition to being a threat to native benthos, the snail harbors two parasite species that kill thousands of migrating waterfowl when infected snails are consumed.  Both parasite species exhibit temperature-dependent transmission patterns with no transmission occurring when temperatures either fall below or exceed certain thresholds.  The transmission window overlaps the waterfowl's seasonal migrations. The inclusion of temperature into disease models has been very important for better predicting infection outcomes across a number of host-parasite systems including trematode parasites such as human schistosomes. Using data collected from our empirical work, we developed an annual model for the host-parasite system in which transmission depends on water temperatures.  

Results/Conclusions

The size of the infected host populations display a sensitivity on the range of the transmission window.  We quantify the dependence of the number of infected hosts to the annual average temperature with three variance scenarios (low, medium, and high variance).  As the annual average temperature increases, the prediction intervals for infected populations initially increase, reaching a threshold, after which they decay.  Results suggest that warming trends in water temperature may have a positive effect on future uninfected populations.