title: Multiple infections, kin selection and the evolutionary epidemiology of parasite traits.
abstract: The coinfection of a host by several parasite strains is known to affect selective pressures on parasite strategies of host exploitation. I present a general model of coinfections that ties together kin selection models of virulence evolution and epidemiological models of multiple infections. I derive an analytical expression for the invasion fitness of a rare mutant in a population with an arbitrary distribution of the multiplicity of infection (MOI) across hosts. When a single mutation affects parasite strategies in all MOI classes, I show that the evolutionarily stable level of virulence depends on a demographic average of within-host relatedness across all host classes. This generalization of previous kin selection results requires that within-host parasite densities do not vary between hosts. When host exploitation strategies are allowed to vary across classes, I show that the strategy of host exploitation in a focal MOI class depends on the relative magnitudes of parasite reproductive values in the focal class and in the next. Thus, in contrast to previous findings, lower within-host relatedness in competitive parasite interactions can potentially correspond to either higher or lower levels of virulence.
authors.affiliation: CEFE UMR 5175-1919, Montpellier Cedex 5, France.
authors.forename: S
authors.initials: S
authors.lastname: Lion
mesh_terms: D000818:Animals; D005075:Biological Evolution; D060085:Coinfection / Q000469:parasitology*; D006790:Host-Parasite Interactions; D008954:Models, Biological; D010271:Parasites / Q000472:pathogenicity* / Q000502:physiology; D014774:Virulence
keywords: coinfection; epidemiology; relatedness; reproductive value; virulence