With the recent emergence of many severe human diseases (e.g., West Nile, SARS, Hantavirus), it has become increasingly important to understand the factors that determine whether pathogens evolve to become virulent or benign. The conventional wisdom states that a pathogen should always evolve towards a benign coexistence with its host. However, there is substantial evidence that pathogens sometimes evolve to cause severe disease, suggesting that high virulence may be advantageous in some cases. This is referred to as virulence trade-offs. In this project the fish virus IHNV and its rainbow trout host will be used to explore the evolution of virulence. Virus strains that differ in virulence will be tested in a novel system for quantifying viral fitness during infection in living juvenile trout. Results will be used to develop a population-scale model that will identify factors predicted to lead to increased virulence. Finally, the model predictions will be tested by comparing virulence of virus field strains that occur in different environments.
The evolution of pathogen virulence has become a major field of investigation and numerous theoretical models have been developed invoking virulence trade-offs. Progress in this field is hampered by a general lack of experimental data, particularly in vertebrate host-pathogen systems. In this project a combination of experimental and theoretical approaches will provide novel information on the existence and nature of virulence tradeoffs, enhancing our understanding of how important veterinary and human diseases emerge. The project will also train graduate and undergraduate students, including individuals from groups under-represented in the sciences.
