I got 99 problems but a bee ain't one: how does host condition affect parasite development?

Over the course of the past few weeks I've been fascinated by extreme life cycles and had planned on writing about the development of organisms that possessed some of those life cycles. I stumbled upon a few examples of parasites that had complex multi-host lifecycles which perked my interest and also was something we hadn't dwelled on in class. We've touched briefly on in utero development which I suppose is somewhat like a parasite developing in a host, but parasite development hasn't been covered. Furthermore, is parasite development subject to similar environmental stressors as the ones we've discussed?  In a paper (cited below) by Logan A. et al., the authors want to know if pollen starvation (low food abundance) in hosts can alter parasite abundance in hosts. 

The researchers did an experiment involving Crithidia bombi (gut parasite) in bumble bees. In this experiment, the researchers were curious about how pollen starvation effects parasite abundance in host systems. Essentially, they exposed 40 bees to 2 treatments (20 apiece); one treatment being "no pollen" and the other being "pollen". Immediately before trials began, bees were given a dose of  approximately 25,000 parasite cells in inoculum. The bees were all given sugar water during the experiments. Over the course of 15 days, feces were collected and analyzed for parasite loads. 

Generally speaking, low food abundance and host malnutrition can lead to increased susceptibility in hosts (Sprunt and Flanigan 1956). However, how does low food abundance affect already established parasites? The authors came up with three mechanisms by which they expected to see a change in parasite abundance: (i) nutritionally mediated changes in host defenses, (ii) malnutrition of the parasite, and (iii) nutritionally mediated changes in the environment of the parasite. The results of the study show that in the pollen starved treatments, parasite abundance was lower and developmental stage demography was different in comparison with the reference population (figure 2); the authors believe that this decreased abundance and altered developmental stage demography was an adaptive response to changing conditions in the gut. In this study, the authors do not seek to determine exactly which mechanism is responsible for their results, although they do believe that some mechanisms may be acting synergistically. Rather, they sought to quantify what effect pollen starvation had on parasite development. 

When thinking about host environment effects on parasites, I think about bioaccumulation and maternal environment effects on offspring. In the case of bioaccumulation, exposure of prey to a given contaminant has a cumulatively larger effect on the consumer a trophic level above. The effects of this accumulation can trickle down to offspring development. With maternal environment effects, exposure to a pollutant or stress can cause alteration of development in offspring. How do macro-level environmental effects trickle down to smaller systems of development, especially host-parasite systems? Are the effects felt "to scale" in a sort of Russian nesting doll framework? For instance, how would malnutrition of a deer affect the development of Babesia (protozoa) that lives inside of a tick, which is then parasitizing said deer? These are some of the things I thought about after reading this paper. What comparisons can be made between what we've learned so far concerning development and the results of this study? 

Sources:

Logan A. et al., 2004. The impact of host starvation on parasite development and population dynamics in an intestinal trypanosome parasite of bumble bees. Parasitology (2005), 130, 637–642.

Sprunt D.H., and C.C. Flanigan. 1956. The effect of malnutrition on the susceptibility of the host to viral infection. University of Tennessee, 1956.