One of the more recent studies examining host resources and parasitism comes from a group out of France led by Sophie Labaude and published in Parasites & Vectors. Here the authors tested for an effect of nutritional deprivation on the prevalence and intensity of a helminth (Pomphorhynchus laevis) in a crustacean host (the lagoon sand shrimp, Gammarus insensibilis). Authors provided the hosts with an experimental food treatment that, quite nicely, both varied the quantity and quality of resources. Individuals in the standard treatment were fed weekly and with a diet high in protein, while the experimental group were fed only every two weeks and with a diet lacking in protein (i.e., leaves only, no larvae). Hosts were monitored for parasite infection and had intensity recorded, and the authors also recorded when parasite-induced death occurred. Other outcomes of the experiment that the authors recorded were metabolic rate as a measure of host condition and the host behavioral response to infection (refugia usage).
The authors used standard GLMM approaches to examine how food treatment, host size, and parasite population influenced parasitism. The decision to include parasite population in these models wasn't quite clear to me, as the paper doesn't detail why the parasites from two populations within the studied river system would differ. Perhaps there are virulence differences? Regardless, authors identified a strong food treatment by parasite population interaction, with parasitism being more severe in one of the two populations and in which the nutritional deprivation had no effect. Among the other parasite population, however, reduced feeding frequency and protein content did result in lower infection intensity.
The most interesting result here used a Cox regression to ask if host survival differed between food treatments and infected and non-infected hosts. Given the above intensity results, we might think food-deprived and infected hosts might counterintuitively have a higher survival probability, given that these individuals also had lower infection. Food treatment alone (i.e., on uninfected hosts) actually had no effect on survival, which to me is surprising since enhancement of survival would be one of the more expected consequences of improved feeding success and nutrition. As we would traditionally expect though, the authors did find that parasitism did impose a survival cost (i.e., virulence) and that for at least one of the parasite populations this cost was greatest in the food deprived treatment group (below).
The full link of the paper, which is open access, is here. And the citation if interested is below.
Labaude S, Cézilly F, Tercier X, Rigaud T. Influence of host nutritional condition on post-infection traits in the association between the manipulative acanthocephalan Pomphorhynchus laevis and the amphipod Gammarus pulex. Parasites Vectors. 2015 Jul 30;8(1):1–12.