Spatial virulence dynamics: Pathogen evolution during epidemics in highly mobile hosts
Mathematical Biosciences Institute & Aquatic Ecology Laboratory, The Ohio State University
(February 6, 2014 10:20 AM - 11:15 AM)
Infectious diseases are a major public and environmental health concern, and are ubiquitous in nature. The evolutionary dynamics of pathogen virulence is driven by fitness differences among strains, and the selective forces that shape those fitness differences. A major contributing factor in these virulence dynamics is the well known transmission-virulence tradeoff, in which individuals infected with highly virulent strains (i.e., strains that induce high mortality) also on average yield fewer new infections due to a shorter window of infectiousness. This work is motivated by empirical observation of a second (and seemingly novel) tradeoff, between host movement and virulence, observed during the empirical study of the pathogenic bacterium Mycoplasma gallisepticum in North American House Finch populations.
In this talk, I will first discuss the motivating biological system, and introduce a partial differential equations (PDE) model of pathogen spread throughout a susceptible host population. I will then discuss an extension of that model which includes a novel movement-virulence tradeoff between pathogen strains, whereby sickness behaviour reduces the mobility of this otherwise highly mobile host. This second tradeoff can significantly alter the spatiotemporal virulence dynamics that arise in the classical case that only includes transmission-virulence tradeoff. I'll also present a Price Equation reformulation of this model to clarify how different ecological and evolutionary forces shape the overall dynamics. These results have important implications for the observation and interpretation of spatio-temporal epidemic data from a number of emerging wildlife and human diseases, and may help explain transient virulence dynamics in spatially spreading emerging infectious diseases.