Prophylactic host behaviour discourages pathogen exploitation

Abstract

1Much work has considered the evolution of pathogens, but little is known about 2 how they respond to changes in host behaviour. We build a model where hosts are 3 able to choose to engage in prophylactic measures that reduce the likelihood of disease 4 transmission. This choice is mediated by costs and benefits associated with prophylaxis, 5 but the fraction of hosts engaged in prophylaxis is also affected by population dynamics. 6 We identify a critical cost threshold above which hosts do not engage in prophylaxis. 7Below the threshold, prophylactic host behaviour does occur and pathogen virulence, 8 measured by the extent to which it exploits its host, is reduced by the action of selection 9 relative to the level that would otherwise be predicted in the absence of prophylaxis. 10 Our work emphasizes the significance of the dual nature of the trade-off faced by the 11 pathogen between balancing transmission and recovery, and creating new infections in 12 hosts engaging or not engaging in prophylaxis.13