Dr. Tosha RUTH Kelly
REARCH INTERESTS & RELEVANCE
I am interested in host-parasite interactions of wildlife at
ecological, microbial, and physiological scales:
How do parasites affect host physiology and microbial communities?
What physiological and microbial traits determine
host resistance and tolerance to infection?
How does a host's ecology affects parasite exposure?
To what extent do parasites affect large-scale movements of hosts?
What are the effects of ectoparasitism on survival and development of juvenile hosts?
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Parasite ranges are expanding and are being altered by climate change.
The answers to my research questions are important in order to understand/anticipate
how wildlife populations respond to changes in parasitic pressure
& zoonotic disease spillover to human populations.

CURRENT RESEARCH
Plasmodium (malaria; red arrows) infection in red blood cells of a song sparrow. The white arrow identifies an uninfected red blood cell.
I use avian malaria (Plasmodium; left image) as a model to test whether the hypothalamic-pituitary-adrenal (HPA) axis mediates resistance (the ability to prevent/limit parasite loads) and tolerance (the ability to maintain condition during infection) to disease. Via the release of glucocorticoids, the HPA axis can modulate immunity of vertebrates with repurcussions for parasite dynamics in the host.
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Wildlife are exposed to an increasing number of severe storms, novel predators/ competitors, due to climate change as well as anthropogenic disturbances (habitat loss, fragmentation, and urbanization), all of which activate the HPA axis (= release of glucocorticoids). If resistance and tolerance are mediated by the HPA axis, then the ability of wildlife to adapt to the changes in parasite pressure may be constrained by the additional HPA axis activation that results from climate change.
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Resistance and tolerance are traits most relevant to population-level disease dynamics. Understanding the mechanism(s) that regulate these traits are critical to predict the spread of disease.

COLLABORATIONS
LEUCOCYTOZOON & WILD TURKEY DECLINE
I collaborate with Dr. Lane Foil and the Louisiana Department of Wildlife and Fisheries to evaluate whether Leucocytozoon (parasitic protozoa, similar to malaria) is a cause for decline of wild turkey (Meleagris gallopavo) populations in Louisiana. To date, over 80% of the sampled individuals have tested positive for Leucocytozoon. Additionally, we recieved a blood smear from a turkey whose cause of death was attributed to Leucocytozoon. This individual had the highest Leucocytozoon load I have ever observed and they were co-infected with Plasmodium (image below). Black flies (definitive host; vector to avian hosts) have tested positive for Leucocytozoon (PCR conducted by Ben Aker). I supervise Miss Kenedi Lynch, an undergraduate student, in diagnosing malaria infections via PCR.
A turkey heavily infected with Leucocytozoon. Dark blue flagellate parasites are female Leucocytozoon and light/translucent are male. Pink white blood cells are eosinophils and they represented 75% of the white blood cells I observed.
ECTOPARASITISM OF NESTLINGS
I study ectoparasites, too! I have experience evaluating how ectoparasites impact growth, immune development, and survival. Immunologically-naive nestlings are unable to escape parasitized nests and siblings are not parasitized equally. How do these differences in parasitism within a nest affect variation in immune responses and growth rates of European starling (Sturnus vulgaris) nestlings? These traits affect long-term survival and, therefore, recruitment to the population.
Additionally, I helped supervise Miss Kaitlin Couvillon in mite collection and quantification for her honour's thesis to test for a relationship between ectoparasite load and the microbial community of nestling skin.
Northern fowl mites (Ornithonyssus sylviarum) obtained from nestling house sparrows (Passer domesticus) in a previous field season.
The mites range in size from 0.6 - 1 mm in size.
Yours truly with a 12 day old European starling nestling, "Birdie Sanders".
RESEARCH DURING EDUCATION
Doctorate - Western University (2018)
Physiological and behavioural responses of songbirds to pathogens during migration
​Supervisor: Dr. Beth MacDougall-Shakleton
Co-supervisor: Dr. Scott MacDougall-Shackleton
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Our ability to predict the contribution of migratory animals to the spread of disease depends inherently upon behavioural and physiological responses of the animals while in migratory condition. To determine the extent that sparrows may contribute to the spread of avian malaria (projected to benefit from warmer temperatures), I conducted a series of controlled experiments in migratory white-throated sparrows (Zonotrichia albicollis) and song sparrows (Melospiza melodia).
After exposure to avian malaria, I found that resistant song sparrows had reduced lean mass and infected birds tended to have later departure dates from the breeding grounds (Publication 5). Captive white-throated sparrows did not exhibit reductions in physiology, but both infected and resistant birds exhibited reductions in migration intensity (Publication 11). After exposure to a non-infectious antigen, I found increases in body mass and migratory activity of white-throated sparrows (Publication in prep), suggesting that mounting an acute-phase immune response during migration does not incur behavioural or physiological costs.
Altogether, my PhD research suggests (1) birds may make migratory movements before incurring costs of malaria infection and (2) incurred costs of infection are primarily due to the harmful effects of the pathogen on host traits. These findings are important considerations when predicting how migratory animals may contribute to the spread of disease.
Master's - Western University (2014)
Stable hydrogen isotope analysis of migration distance and its relationship with immune function
and parasitism in Song sparrows
​Supervisor: Dr. Beth MacDougall-Shakleton
Co-supervisor: Dr. Scott MacDougall-Shackleton
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Migratory birds are exposed to multiple parasite communities, and long-distance migrants encounter a larger set of parasite fauna than short-distance migrants. For my Masters I examined how long-distance migrants allocate resources to immune defense while feuling their long migration. Using stable hydrogen isotope analysis as a proxy for latitude and a variety of immune techniques, I assessed the relationship between immune function, malaria infection, and migration distance in song sparrows. Birds that migrated further had a greater likelihood of infection with a blood-borne parasite at their breeding grounds. Despite this, there was no relationship between different aspects of immune function and migration distance. These results indicate that the distance a bird migrates may directly affect its parasitism upon arrival to breeding grounds, but there is no noticeable effects on immunity. As birds are blamed for long-distance transport of pathogens and disease, such information is critically important in the face of a changing climate.
Honour's Thesis - Trent University (2012)
Experimental manipulation of prenatal environment in Japanese quail affects offspring phenotype to maturity
Supervisor: Dr. Gary Burness
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Experiencing adverse conditions during early ontogeny may result in costs to the individual in terms of growth, immune function, and development of sexually-selected traits, with ultimate consequences for long-term survival and reproductive output. Yolk is composed of lipids, proteins, and antibodies but little is known about how individuals deprived of such components are affected later in life. For my honour's thesis I examined how maternal effects mediated by egg quality affect offspring phenotype to maturity. Specifically, I removed small amounts of yolk from eggs before initiating incubation. In brief, I found negative impacts on hatchling mass and tarsus length, the latter lasting to maturity, and differential effects on male and female growth rates and immune function. This work highlights the importance of maternal resource allocation via the egg to her offspring until maturity.