Abstract
Toxoplasma gondii, a zoonotic parasite that infects a wide variety of warm-blooded hosts, has been documented causing significant mortality in marine mammals in the Pacific Northwest.3 Seroprevalence in marine mammals can range from 7–52%,4,5 however the true extent of T. gondii infection in arctic populations of marine mammals, many of which are threatened or endangered, is unknown. Many native and first nation peoples of North America rely on these marine mammals as a source of nutrition, further highlighting the importance of this zoonotic parasite in these populations. Understanding the distribution and transmission dynamics of T. gondii, a parasite shed in the feces of any felid species, within the arctic marine ecosystem is critical for both marine mammal and human health. To address such questions of distribution and transmission in marine mammals in the Arctic, healthy, hunter-harvested Beluga (23 individuals) sampled over 3 years were assessed for T. gondii and other protozoan infection(s) using multi-locus PCR-DNA sequencing directly from host tissues. Surprisingly, genetic analyses uncovered a prevalence rate of 13% (3/23) infection with T. gondii and 87% (20/23) infection with a novel species of Sarcocystis previously documented in a single sperm whale.3 T. gondii genotype was determined as previously described3 and compared against reference sequences from known archetypal strains, Types I, II, III, and X. Multilocus typing at the unlinked genetic markers B1, NTS2, and GRA7 identified two novel, genetically recombinant strains that possessed different inheritance patterns of the archetypal alleles. This is the first study to genetically characterize T. gondii infections in healthy, free-ranging Beluga with no histopathologic indication of a T. gondii infection. This is also the first study to document non-pathogenic chronic infections with a novel Sarcocystis species in healthy Beluga. Given the importance of Beluga as a food-source, people inhabiting northern communities who practice subsistence hunting may be at increased risk of exposure to and infection with T. gondii due to traditional food preparation techniques.2 The identification of two novel, recombinant strains of T. gondii infecting Beluga may indicate that the definitive felid host is expanding this parasite in the Arctic. This is further highlighted by the fact that Beluga are primarily piscivorous and do not ingest warm-blooded prey, suggesting the route of exposure in these animals to be direct ingestion of T. gondii oocysts, products of this parasite's sexual cycle. The evidence of recombinant T. gondii strains in the Arctic is important for both marine mammal and human health and further research is needed to elucidate the mechanisms of land-to-sea transfer of this highly pathogenic, zoonotic parasite.
Acknowledgements
The authors would like to thank Dr. N Sundar of the National Institutes of Health for initial sample preparation and processing. We would also like to thank Fisheries and Oceans Canada, the International Polar Year (IPY) Global Warming and Marine Mammals and the IPY Circumpolar Flaw Lead projects, ArcticNet, the Northern Contaminants Program, and the Fisheries Joint Management Committee. We are grateful for the partnerships and support of Hunters and Trappers Committees of Inuvik, Aklavik, Tuktoyaktuk, and Paulatuk for the Beluga sample collection program, and F. Pokiak and B. Wolki for Beluga tissue collections.
* Presenting author
+ Student presenter
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