Data from: Pharmaceutical pollution alters the cost of bacterial infection and its relationship to pathogen load

The relationship between pathogen proliferation and the cost of infection
experienced by a host drives the ecology and evolution of host-pathogen
dynamics. While environmental factors can shape this relationship, there
is currently limited knowledge on the consequences of emerging
contaminants, such as pharmaceutical pollutants, for the commonly observed
trade-off between a pathogen’s growth within the host and the damage it
causes, termed its virulence. Here, we investigated how exposure to
fluoxetine (Prozac), a commonly detected psychoactive pollutant, could
alter this key relationship using the water flea Daphnia magna and its
bacterial pathogen Pasteuria ramosa as a model system. Across a variety of
fluoxetine concentrations, we found that fluoxetine shaped the damage a
pathogen caused, such as the reduction in fecundity or intrinsic growth
experienced by infected individuals, but with minimal change in average
pathogen spore loads. Instead, fluoxetine modified the relationship
between the degree of pathogen proliferation and its virulence, with both
the strength of this trade-off and the component of host fitness most
affected varying by fluoxetine concentration and host genotype. Our study
underscores the potential for pharmaceutical pollution to modify the
virulence of an invading pathogen, as well as the fundamental trade-off
between host and pathogen fitness, even at the trace amounts increasingly
found in natural waterways.