Data from: A nutrient mediates intraspecific competition between rodent malaria parasites in vivo

Hosts are often infected with multiple strains of a single parasite
species. Within-host competition between parasite strains can be intense
and has implications for the evolution of traits that impact patient
health, such as drug resistance and virulence. Yet the mechanistic basis
of within-host competition is poorly understood. Here, we demonstrate that
a parasite nutrient, para-aminobenzoic acid (pABA), mediates competition
between a drug resistant and drug susceptible strain of the malaria
parasite, Plasmodium chabaudi. We further show that increasing pABA supply
to hosts infected with the resistant strain worsens disease and changes
the relationship between parasite burden and pathology. Our experiments
demonstrate that, even when there is profound top-down regulation
(immunity), bottom-up regulation of pathogen populations can occur and
that its importance may vary during an infection. The identification of
resources that can be experimentally controlled opens up the opportunity
to manipulate competitive interactions between parasites and hence their
evolution.