Costs of co-infection

(and how hosts mitigate them)

How do costs of infection and host defense strategies change when hosts are co-infected with multiple parasites? Can they use supplemental or selective foraging to mitigate the costs of infection and immunity? In collaboration with Andrea Graham, Courtney Thomason and many undergraduate researchers, I am studying wild Peromyscus maniculatus and P. leucopus populations that are co-infected with multiple helminths (e.g. gastrointestinal nematodes), ecotparasites (e.g. fleas, ticks), viruses (e.g. Sin nombre virus), and protozoa (e.g. Babesia, coccidia). As part of this long-term mark-recapture project, I am assessing mouse body condition, diet selection by metabarcoding, and protein and fat reserves to see how they are affected by co-infection. We are also removing nematodes from a subset of mice to experimentally assess costs of nematode infection and study how nematodes interact with other parasites to affect mouse survival.

Resources and within-host disease dynamics

What are the consequences of within-host resource distribution for individual health and parasite loads? How should host defense strategies vary with resource availability?  To address such questions, I utilize laboratory experiments, outdoor mesocoms, and field studies. Mentored undergraduate researchers have developed complementary projects examining physiological and immunological responses to infection. Additionally, in collaboration with Andrea Graham, Anieke van Leeuwen, and Clay Cressler, we have developed a dynamic energy budget model of within-host resource dynamics.

Resources and co-infection

The effects of environmental and within-host resources on co-infected individuals and interactions among parasites is largely unknown. I study these interactions, and their implications for individual health and disease transmission in laboratory, field, and human studies. I collaborate with researchers at the University of Georgia, Princeton University, Leiden University Medical Center, Stanford University, and Virginia Tech for these projects.

Host responses and fitness costs of infection

Host defense strategies (both behavioral and immunological) can mediate the individual and population-level consequences of infection. In collaboration with Vanessa Ezenwa and Anna Jolles, I combined the power of a removal experiment with a longitudinal, species-level infection study to quantify the costs of worm infection and the contributions of differential host responses to those costs in a wild population of African buffalo. I was also able to verify the accuracy of a sublethal, combined molecular-morphological approach to assess parasite communities in the wild. Additionally, multiple undergraduates have helped with field work in South Africa, developed independent research projects, and published their findings on assessing nematode fecundity.

Experimental parasite community ecology

Extending community assembly theory to communities of co-infecting parasites, I used a gastrointestinal nematode removal experiment in free-ranging African buffalo to examine the community assembly patterns and processes.

Macroecology of Infectious Diseases

Macroecology image.png
Stephens et al. 2016. Ecology Letters, 19:1159-1171. 

In collaboration with Macroecology of Infectious Diseases RCN, I study large-scale patterns of host-parasite interactions. My work investigates global patterns of helminth infection and reverse zoonoses, the spillover of disease from humans to non-human animals.

Pesticides and infection

I investigated the effects of pesticide exposure on growth, development, survival, and susceptibility to parasite infection in larval amphibians in collaboration with Bill Hopkins and Lisa Belden,