Grant: Discovery Grants Program - Individual

My research focuses on the interactions between blood parasites and their vertebrate and invertebrate hosts to investigate the processes that result in the complex life cycles, host specificity and virulence of these parasites.  One of the most important groups of one-celled animals, or protozoa, is the phylum Apicomplexa.  Parasites in this phylum cause many devastating diseases, including malaria and toxoplasmosis of humans, and coccidiosis and neosporosis of domesticated animals.  Additionally, nearly every species of wildlife is parasitised with a number of apicomplexan parasites in their blood, tissues or intestinal tracts.  The aim of my proposal is to identify the functional, immunological, ecological and phylogenetic features associated with the interaction between blood-dwelling apicomplexan parasites and vertebrate and invertebrate host cells.  I propose a diverse research approach using two well-defined model systems that will discern mechanisms forming the basis of interactions between apicomplexan parasites and hosts. The first system involves two blood parasites of the genus Hepatozoon, namely Hepatozoon clamatae and Hepatozoon catesbianae, which are transmitted among green frogs and bullfrogs by blood-feeding mosquitoes.  The second system features another species, Hepatozoon sipedon, which is passed to mosquitoes that feed on snake blood, and then to frogs that feed on infected mosquitoes. Snakes that feed on infected frogs complete the cycle.   My students and I are interested in how Hepatozoon parasites, which are related to human malaria parasites, are influenced by temperatures in freeze-tolerant and freeze-sensitive frog species, and how they modulate their development in frogs and snakes so that they maximise transmission to mosquitoes, while at the same time ensuring that they do not kill any of their hosts.  However, heavy infections are frequently observed in the blood of frogs and snakes, and although these hosts appear not to be adversely affected, such infections will kill mosquitoes.  We propose to determine the cause of this pathology by investigating the immune response, or lack thereof, in such mosquitoes. We also plan to investigate which species of mosquitoes, frogs and snakes are suitable hosts for these Hepatozoon parasites, and how resistant hosts eliminate these protozoa at different stages of the parasite life cycle.  Such studies will be useful for determining the ecological role of these parasites, and for developing novel control measures against species of mosquitoes that transmit West Nile Virus and other pathogens in Canada and elsewhere.  This research will also assess if these parasites cause disease in vulnerable frog populations in Canada, and ascertain the relationship between these parasites and more virulent pathogens, such as Ranavirus and chytrid fungi, that have devastated frog populations in Canada and other parts of the world.