Department of Chemistry & Biology, Toronto Metropolitan (formerly Ryerson) University
Research
Emerging and re-emerging infectious diseases are a major concern for the health of humans, domestic animals, and wildlife. Effective disease management requires an intimate understanding of how hosts resist and tolerate parasitism, including how these abilities are affected by their environment. Work in the Koprivnikar lab takes an integrative approach to such questions, incorporating behaviour, habitat, molecular analyses, and physiology that has applied value for disease ecology.
Environmental influences on parasitism
Abiotic and biotic factors may affect host susceptibility to parasitism, resulting pathology, and parasite prevalence and diversity. This is critical in understanding how environmental features, and any subsequent changes, may be expected to impact both disease and host populations. Various environmental perturbations can influence parasite reproduction, activity, longevity, and infectivity, altering host encounter rate and parasite prevalence/load. These same factors will also affect host resistance and tolerance to parasites. We tackle such questions with a combination of fieldwork, laboratory, and mesocosm approaches. Current areas of focus include biodiversity, contaminants, and landscape influences. For instance, road and forest density differ around agricultural vs. non-agricultural ponds, affecting the presence of generalist and specialist parasites (Koprivnikar & Redfern, 2012), and exposure to road salt can increase the susceptibility of larval amphibians to infection by trematode parasites (Milotic et al., 2017).
Understanding the effects of parasitism
It is now widely recognized that multiple stressors can affect organisms in unexpected ways through interactive effects. This means that separate examinations do not accurately reflect most natural processes and can generate misleading conclusions. Because host-parasite interactions can also be strongly context-dependent, naturally-occurring infections may become harmful in the presence of additional stressors that are becoming more common owing to environmental changes and fewer available habitats. For example, we have found that parasitized larval amphibians were not able to speed up their development in response to habitat drying (Koprivnikar et al. 2014). Consequently, we assess host susceptibility and tolerance, as well as effects on parasites themselves, under a number of environmental conditions, incorporating a variety of host and parasite taxa to examine the general occurrence and importance of such synergisms for disease dynamics. In addition, we study parasite influences on host interactions within ecosystems as these may play a significant role in the structure of natural communities. Conservation and management efforts will be enhanced by the integration of parasites into individual, population, community, and ecosystem-level processes.
Host defences against parasitism
Past studies of host resistance to parasites have largely focused on immunology, yet growing evidence suggests that behavioural defences often play an important complementary role. Notably, avoiding infections might be simpler and less costly than fighting invading parasites. Our lab continues to explore the extent and effectiveness of host anti-parasite behaviour, a relatively unknown area of study. If such behaviours are common and effective, environmentally-induced alterations of host behaviour may have important implications for disease dynamics. While many studies have examined the effects of predators on host behavioural choices, parasites likely represent an even greater universal natural enemy and their influences require far more study to truly understand the ecological forces shaping animal behaviours. As an example, we have found that larval amphibians prefer to forage in the presence of cues indicating a risk of parasitism rather than a threat of predation (Koprivnikar & Penalva, 2015). Recently, we discovered that quinones, which are effective anti-microbial chemicals secreted by many arthropods, can also negatively affect entomopathogenic nematodes (Smith et al., 2023).
Parasites don’t just eat, they are also consumed!
Many parasites have life cycles that involve at least one free-living stage that is present in the environment, and a surprising number of aquatic organisms may consume these stages (Koprivnikar et al., 2023). We’ve used various tools to track such consumption of parasite infectious stages (Schultz & Koprivnikar, 2021), and found that these can be a source of energy and nutrition which can sustain a variety of aquatic animals (McKee et al., 2020; Babaran et al., 2021), as well as affect zooplankton populations by reducing predation pressure (Schultz & Koprivnikar, 2019).
Emerging and re-emerging infectious diseases are a major concern for the health of humans, domestic animals, and wildlife. Effective disease management requires an intimate understanding of how hosts resist and tolerate parasitism, including how these abilities are affected by their environment. Work in the Koprivnikar lab takes an integrative approach to such questions, incorporating behaviour, habitat, molecular analyses, and physiology that has applied value for disease ecology.
Abiotic and biotic factors may affect host susceptibility to parasitism, resulting pathology, and parasite prevalence and diversity. This is critical in understanding how environmental features, and any subsequent changes, may be expected to impact both disease and host populations. Various environmental perturbations can influence parasite reproduction, activity, longevity, and infectivity, altering host encounter rate and parasite prevalence/load. These same factors will also affect host resistance and tolerance to parasites. We tackle such questions with a combination of fieldwork, laboratory, and mesocosm approaches. Current areas of focus include biodiversity, contaminants, and landscape influences. For instance, road and forest density differ around agricultural vs. non-agricultural ponds, affecting the presence of generalist and specialist parasites (Koprivnikar & Redfern, 2012), and exposure to road salt can increase the susceptibility of larval amphibians to infection by trematode parasites (Milotic et al., 2017).
It is now widely recognized that multiple stressors can affect organisms in unexpected ways through interactive effects. This means that separate examinations do not accurately reflect most natural processes and can generate misleading conclusions. Because host-parasite interactions can also be strongly context-dependent, naturally-occurring infections may become harmful in the presence of additional stressors that are becoming more common owing to environmental changes and fewer available habitats. For example, we have found that parasitized larval amphibians were not able to speed up their development in response to habitat drying (Koprivnikar et al. 2014). Consequently, we assess host susceptibility and tolerance, as well as effects on parasites themselves, under a number of environmental conditions, incorporating a variety of host and parasite taxa to examine the general occurrence and importance of such synergisms for disease dynamics. In addition, we study parasite influences on host interactions within ecosystems as these may play a significant role in the structure of natural communities. Conservation and management efforts will be enhanced by the integration of parasites into individual, population, community, and ecosystem-level processes.
Past studies of host resistance to parasites have largely focused on immunology, yet growing evidence suggests that behavioural defences often play an important complementary role. Notably, avoiding infections might be simpler and less costly than fighting invading parasites. Our lab continues to explore the extent and effectiveness of host anti-parasite behaviour, a relatively unknown area of study. If such behaviours are common and effective, environmentally-induced alterations of host behaviour may have important implications for disease dynamics. While many studies have examined the effects of predators on host behavioural choices, parasites likely represent an even greater universal natural enemy and their influences require far more study to truly understand the ecological forces shaping animal behaviours. As an example, we have found that larval amphibians prefer to forage in the presence of cues indicating a risk of parasitism rather than a threat of predation (Koprivnikar & Penalva, 2015). Recently, we discovered that quinones, which are effective anti-microbial chemicals secreted by many arthropods, can also negatively affect entomopathogenic nematodes (Smith et al., 2023).
Many parasites have life cycles that involve at least one free-living stage that is present in the environment, and a surprising number of aquatic organisms may consume these stages (Koprivnikar et al., 2023). We’ve used various tools to track such consumption of parasite infectious stages (Schultz & Koprivnikar, 2021), and found that these can be a source of energy and nutrition which can sustain a variety of aquatic animals (McKee et al., 2020; Babaran et al., 2021), as well as affect zooplankton populations by reducing predation pressure (Schultz & Koprivnikar, 2019).