EAGER: Disentangling how community composition differentially acts on multiple determinants of transmission in a directly-transmitted zoonotic pathogen

University Of Montana, Missoula MT

Investigators

Abstract

Biodiversity is disappearing at an alarming rate, and at the same time, infectious diseases increasingly spill over from wildlife to humans. Therefore, it is urgent to understand how biodiversity affects infectious diseases in wildlife. In some ecosystems, a more diverse community decreases disease risk, termed the 'dilution' effect because biodiversity dilutes out infection. However, in other systems, a more diverse community increases disease risk, termed the 'amplification' effect. When to expect dilution or amplification is a topic of debate among disease ecologists. This project aims to reconcile the competing effects of biodiversity on disease risk using Sin Nombre hantavirus (SNV) in deer mice as a model, which displays aspects of both dilution and amplification in the same system at the same time. Researchers will examine how biodiversity can have competing effects by examining the underlying mechanisms, especially how competition between deer mice and other species in the community affects disease dynamics. This research will help unify the theories of dilution vs. amplification. It will also benefit society by advancing prevention efforts for hantavirus pulmonary syndrome (HPS), which has infected more than 700 people (and killed more than 250) since its discovery in 1993. HPS has disproportionately affected Native Americans, who will be involved in this research on tribal lands. This project will test the hypothesis that competition between deer mice and other small mammal competitors affects host density, contact rates among hosts, and the probability of transmission from an infected to an uninfected host given contact between them. Based on previous observational studies, SNV displays an overall dilution effect through a decrease in deer mouse density with increased small mammal diversity, but also a component amplification effect through an increase in the transmission rate (a product of the contact rate for a given host density and the probability of transmission given contact). Here, researchers will test whether competition between deer mice and other small mammals drives both of these observed patterns. Aim 1 will determine if the decrease in deer mouse density is a result of competition or some other aspect of diversity, habitat type, or environmental conditions, using Bayesian analysis of long-term population data. Aim 2 will determine experimentally if an increase in competition leads to stress and depressed immunity and/or changes in behavior and contact rates (which affect the transmission rate). Deer mouse and competitor density will be manipulated in enclosures and contacts, stress, and immunity measured. Additionally, dynamics in an unmanipulated natural population will be monitored to expand interpretation of the experimental study. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.