We study the ecology of infectious diseases with a specific focus on linking processes across scales. We investigate how behavioral, physiological, and ecological processes at the individual level shape interactions between hosts and their parasites, and the consequences for population and community-wide patterns of disease. Our work combines field studies with laboratory approaches (e.g. molecular, immunological) and theory to address key questions about the ecology of infectious diseases in wild animal populations. Below are some ongoing projects our lab is focused on.
ANIMAL BEHAVIOR AND PARASITE INFECTION
Animal behavior plays a key role in parasite transmission and parasites are crucial drivers of animal behavior. Behavior can affect how often individuals come into contact with parasites, how susceptible they are once contact is made, and how likely they are to disseminate parasites once infected. Likewise, parasites can influence animal behavior both directly and indirectly with interesting ecological and evolutionary consequences. We use wild ungulates as a model to study relationships between animal behavior and parasitism. Our current study on Grant’s gazelle based at the Mpala Research Centre, Kenya is addressing questions about how and why parasites generate variability in animal behavior. In male gazelle, we are exploring how feedbacks between parasitic worm infection and mating behavior underlie variation in male mating tactics. In female gazelle, we are examining whether parasite infection can induce trade-offs in behavioral time allocation and investigating the consequences of social relationships for the transmission of pathogenic versus beneficial gut microbes.
Most animals are infected with multiple parasites simultaneously, and co-infection has interesting consequences for both host and parasite fitness. Helminth (i.e. parasitic worm) co-infection is particularly fascinating because these parasites can influence the mammalian immune system in ways that alter how hosts interact with intracellular parasites like viruses and many bacteria. Focusing free-ranging African buffalo in Kruger National Park South Africa, we are exploring the immunological and ecological consequences of helminth co-infection in the wild. Do helminths suppress the host immune response to intracellular pathogens? What are the consequences for the spread of pathogens like bovine tuberculosis? What’s the relative contribution of different members of the buffalo helminth community to these effects? Do co-infection outcomes depend on the environmental context? This work is in collaboration with Anna Jolles (Oregon State University). As an extension of our within-species studies, we are also interested in whether immune-mediated interactions among parasites that occur within a host have the potential to explain cross-species or cross-population patters on infectious diseases. In collaboration with Charlie Nunn (Duke University), we recently tested this idea in primates using the Global Mammal Parasite Database.
A female African buffalo in Kruger photographed during the wet season when resources are abundant and a lab mouse. Since we cannot manipulate resource availability in the field, PhD student Sarah Budischak extended the field study by test ing the effects of resources on the outcome of co-infection in a mouse model. The mouse work was a collaboration between the Ezenwa lab and the Sakamoto lab in UGA College of Veterinary Medicine.
IMMUNE TRADE-OFFS AND TISSUE REGENERATION IN MAMMALS
We recently launched a new project in collaboration with Ashley Seifert (University of Kentucky) on the relationship between immune function and regeneration in wild mammals. Understanding the mechanisms that favor tissue regeneration in lieu of tissue repair remains one of the great unanswered questions in biology. A particularly intriguing hypothesis, though poorly investigated, is that the loss of regenerative capacity in higher vertebrates coincides with the presence of a strong adaptive immune response. Now, the recent discovery of complete tissue regeneration in wild African spiny mice by the Seifert lab allows us to comprehensively examine the links between immunity and regeneration in wild, pathogen-exposed, and fully immunocompetent adult mammals. Specifically, we are testing the hypothesis that tradeoffs in immunity along (1) innate vs. adaptive and (2) pro vs. anti-inflammatory axes underlie variation in the ability and rate of regeneration in sympatric wild rodents.
Read about our recent findings from this project: Gawriluk et al 2016
Spiny Mice (Acomys percivali)