Marilyn Scott

Image by Alex Tran.


T: 514-398-7996  |  marilyn.scott [at] (Email)  |  Parasitology Building P214


BSc (New Brunswick)
PhD (McGill)

Short Bio

After receiving her PhD from the Institute of Parasitology at Macdonald Campus of McGill University, Marilyn spent two years at Imperial College, London, UK doing postdoctoral research in experimental parasite epidemiology. She returned to the Institute of Parasitology as an Assistant Professor in 1982 and is currently a Professor. She was Director of the Institute of Parasitology from 1990-2000, Director of the McGill School of Environment from 2008-2013, and Associate Dean (Academic) for the Faculty of Agricultural and Environmental Sciences from 2014-2022.

Through her career, she has trained 49 graduate students and 8 post-doctoral fellows, and has published 2 books, 16 review articles and book chapters, and over 130 original articles. She was the 1991 recipient of the Henry Baldwin Ward Medal from the American Society of Parasitologists for her contributions to the field by a researcher under the age of 40. In 2006, she received the Robert Wardle Award from the Canadian Society of Zoologists (Parasitology Section) for outstanding contributions by a Canadian to parasitology. She was the recipient of both the Macdonald Campus and the Principal’s Prize for Teaching Excellence in 2011.

Awards and Recognitions

2011: Principal’s Teaching Award (Associate Professor Category)
2011: Macdonald Campus Award for Teaching Excellence
2006: Robert A. Wardle Award from Canadian Society of Zoologists (award for outstanding contributions to Canadian Parasitology and/or by a Canadian to Parasitology)
2000: Outstanding Conference Participant Award, 6th International Interdisciplinary Conference on the Environment
1994-1995: Robert and Virginia Rausch Visiting Professorship, Western College of Veterinary Medicine, University of Saskatchewan
1991: Henry Baldwin Ward Medal, American Society of Parasitologists (award for outstanding research contributions by parasitologist under the age of 40)

Research Interests

Animals are host to a wide variety of parasites. As people used to think that successful parasites did no harm to their hosts, only those parasites that obviously caused disease or death were considered of relevance to the ecology of their host. Now, however, we understand that parasites lead to subtle, but important, changes that make a difference for the life of the infected individual, the infected host population and the community and ecosystem in which that host-parasite system is embedded. Our research explores the ways in which parasites influence their hosts, and the implications for their host populations. Furthermore, evidence is emerging that, in certain circumstances, some infections may actually be beneficial to the host.

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.

No longer taking new students effective September 2022

Highlights of Previous Research

Nematodes in Mice:  An active area of research concerns the genetics of host susceptibility or resistance to infection. I have shown that genetically susceptible strains of mice lose 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.

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.

Much of my research over the past 20 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. We have considered 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. 

Ectoparasites of Guppies:  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 that it reduces survival and reproduction of the parasite.  We have also explored the temporal dynamics of skin mucous production to waterborne zinc and infection, both alone and when combined.

Veterinary Research:  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 explored the impacts of strategic treatment strategies for health of mixed sheep and goats herds in Kenya. 

Human Studies:  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, a health education program in Guatemala, and a study of parasite transmission patterns in the Republic of Congo (previously Zaire) and in Mexico.

Current Research

Host-parasite population dynamics in mice, guppies and human populations

Nematodes in Mice: Our previous research demonstrated that maternal infection and protein deficiency independently influenced fetus and neonatal growth, and that the impaired growth was associated with shifts in cytokine and hormone concentrations in maternal serum, amniotic fluid and fetal serum. More recently, we have demonstrated that a nematode infection restricted to the maternal intestine exerted dramatic impacts on gene expression in the brain of uninfected neonates, including upregulated expression of genes and pathways associated with long-term potentiation that is important for cognition and spatial learning. We are now studying whether the altered gene expression might improve spatial learning of neonates. We have also shown that this maternal infection alters the on microbiomes in regions of the intestine, and in breast milk of the infected lactating dam, and in the stomach of the neonate.

Ectoparasites of Guppies: Our recent work has revealed context dependency in the epidemic dynamics of the directly transmitted Gyrodactylus skin ectoparasite of guppies. Mesocosm studies showed that the presence of competitors limited parasite-induced reduction of female growth, and that evolutionary history (river drainage) had a stronger impact on host-parasite dynamics than ecological history (predation regime). Male and female guppies respond differently to both evolutionary and ecological factors. Male resistance to Gyrodactylus remained stable for eight generations after the parasite was removed from a Trinidadian river whereas females evolved to be more resistant. Compared with being isolated, living in single sex groups benefitted females who had lower parasite numbers, but had benefit for males. In metapopulations, focal parasite introduction lowered infection to the advantage of the host but dispersed introduction prolonged persistence to the parasite’s advantage. We are currently exploring whether tolerance to infection-induced damage and resistance to infection influence the infected guppy’s competence at promoting transmission.

Human Studies: Over the past decade, our epidemiological studies have focussed on preschool children and on maternal and infant health. In Panama, we have used an ecosystem health approach to explore the impact of intensification of subsistence agriculture balance on the balance between improvements of agricultural production, food security, child diversity and child growth versus the risks of increased infection with soil-transmitted nematode parasites in preschool children. We have also explored the health implications of multiple infections, nutrient deficiencies and inflammation (MINDI) in pregnant women and in the mother-infant dyad in an extremely impoverished rural indigenous population, including their impact on neonatal growth and maternal anemia and blood pressure.

In Guatemala, we have explored the complex network of maternal stresses (infection, nutrition, psychosocial) and their association with salivary cortisol and infant growth in a rural indigenous community. We have focussed on subclinical mastitis, its association with cultural practices and beliefs, and its consequences on infant growth. We have also linked maternal characteristics with the microbiome of breast milk samples.


PARA 410 Environment and Infection 3 Credits
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View a list of current publications.

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