RAPID: Do extreme climatic events and predator diversity interact to shape the biogeography of disease?

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This research will provide critical information on the Sin Nombre Virus (SNV) that can help improve the safety of hundreds of thousands of National Park visitors each year, as well as involve two graduate students and a postdoctoral scientist. Many diseases that affect humans (e.g. Lyme disease, hantaviruses, West Nile disease, rabies, toxoplasmosis) are zoonotic diseases, i.e. diseases where an animal is the primary host for the disease. As a result, understanding the ecological forces that govern the prevalence of disease in animals is very important for understanding human disease risk. However, predicting disease prevalence can be difficult because the size of animal populations is likely affected by both predators and by resource availability (e.g. the amount of food available for animals). Understanding how predators and resource availability interact to affect host populations may be further complicated by extreme climatic events that may become more common under future climate scenarios, since climate (e.g. the amount of annual precipitation) often determines resource availability. In addition, human activities are changing the worldwide distribution of top predators, likely affecting the nature of predator effects on animal populations. Despite the importance of understanding how predators and climate shape disease, such research is challenging because predators are rarely known with certainty, and because extreme climatic events may occur so rapidly that it is difficult to study them. This research project will use multiple island ecosystems where predator diversity is known, providing an unprecedented opportunity to understand how extreme climatic events and predator diversity affect the prevalence of Sin Nombre Virus (SNV), which causes hantavirus pulmonary syndrome, a severe disease in humans. Specifically, this research entails measuring SNV prevalence in deer mice on the California Channel Islands during and after a drought more severe than any drought in the last 500 years. These data, especially when coupled with existing pre-drought data, provide a rare opportunity to understand the interplay between extreme climatic events and predators in affecting large-scale prevalence of disease, and also provides an opportunity to evaluate the novel hypothesis that predator diversity reduces the rate at which disease prevalence rebounds in animal populations.