The long-term objective of my research program is to understand host-parasite population dynamics using experimental and field epidemiology and theoretical studies. Through my research, I explore factors relevant to, and consequences of, parasite control methods applied at the level of the host population or community.
Much of my research over the past 15 years has focussed on the nutrition-parasite-immunity complex. In collaboration with Dr. Kris Koski of the School of Dietetics and Human Nutrition, McGill University, students, and other collaborators, we have undertaken experimental studies on the consequences of restriction of zinc, protein, vitamin A and energy deficiency, and components of fiber, in isolation and in combination, using the Heligmosomoides bakeri (Nematoda) mouse model. Our current studies consider the effects of protein re-feeding as a means to improve the ability of the host to manage parasitic infections, the energetic trade-offs that occur when energy restricted hosts face competing demands of growth or reproduction, infection, tissue repair and immune defenses, and the effects of Vitamin A supplementation on re-infection rates in Panamanian children (in collaboration with Dr. Eduardo Ortega, University of Panama). We have written three major review articles that provide an overview of our accomplishments in this field, and we presented our work at the FASEB Summer Research Conference "The Impact of Nutritional Status on Immune Function and Health" in 2002. Our students receive in depth training both in nutrition and in parasitology, and find that this unique combination offers them a breadth of possibilities as their careers develop.
My lab is also investigating the effect of waterborne zinc on Gyrodactylus turnbulli, an ectoparasite of guppies. We have shown that infection substantially increases zinc toxicity to isolated fish, and plan to investigate the consequences of waterborne zinc on the rate of epidemic spread of the parasites through a host populations.
A third active area of research concerns the genetics of host susceptibility or resistance to infection. I have shown that genetically susceptible strains of mice loose their susceptible phenotype when placed in large indoor arenas where they live with other mice as a population, and where they are exposed continuously to parasite larvae in their environment. I have also shown that this phenotype can be restored if rates of parasite transmission are elevated. Experiments are planned to better understand the mechanisms underlying how transmission rate can shift a susceptible phenotype into a resistant phenotype.
I also have a current PhD student whose research is designed to identify the principal vectors of malaria in Panama, to consider their biogeography and ecology with a goal of defining rationale approaches to vector control.
In the past, I have studied the population dynamics of H. bakeri in free-running mouse populations, the transmission dynamics of infection, the role of parasites in regulating host population abundance, the factors that "predispose" certain individuals to heavy infection, and the role of infection in determining mate choice in mice.
My lab has also been involved in a series of studies on the ecological changes associated with evolution of drug resistance in gastrointestinal nematodes, both in the mouse-model system, and also in sheep parasites.
We have also been involved in a number of community-based projects in developing countries including a study to evaluate the relative effectiveness of various control strategies in managing intestinal nematode infections in humans in Dominica and in sheep and goats in Kenya, a health education program in Guatemala, and a study of parasite transmission patterns in the Republic of Congo (previously Zaire) and in Mexico.