Abstract
Terrestrial-sourced protozoan parasites are increasingly identified as infecting marine mammals and causing mortality along the western seaboard of the United States and Canada.1,2 Toxoplasma gondii and Sarcocystis neurona parasites are established pathogens capable of causing severe protozoal encephalitis among stranded marine mammals in the Pacific Northwest.1 In this study we describe a novel Sarcocystis spp. which causes a necrotizing hepatitis in a wide range of pinniped species. It was first identified causing fulminant disease in grey seals (Halichoerus grypus) during a mortality event in the northwest Atlantic3 and has since been found associated with mortality in endangered Hawaiian monk seals (Monachus schauinslandi), and a California sea lion (Zalophus californianus). All ringed seals (Pusa hispida) identified as infected with this pathogen were asymptomatic. PCR-DNA sequencing and phylogenetic analysis at the conserved (18S) and variable (ITS1) portions of nuclear ribosomal DNA gene array from DNA extracted from schizont-laden tissue(s) from grey seals, ringed seals, a California sea lion, and Hawaiian monk seals identified a unique genetic signature that we hypothesize is a new Sarcocystis species, which we have tentatively proposed as Sarcocystis pinnipedi. Disease-related pathology observed in S. pinnipedi infections is similar to that seen during fulminant S. canis infections in dogs, polar bears, and black bears.4 Phylogenetic reconstruction of S. pinnipedi supports a close evolutionary relationship to S. canis. These findings document the importance of S. canis-like infections, such as S. pinnipedi, in marine mammals along the North Atlantic and Pacific coasts, and further highlight the need to identify the S. pinnipedi life cycle, its definitive host and susceptible intermediate hosts to determine at risk populations of recovering threatened or endangered pinniped species.
Acknowledgements
The authors wish to thank Dr. Natarajan Sundar and Jered Wendte of the National Institutes of Health for sample preparation, processing, and initial analysis. We also thank Dr. Helen Schwantje with the British Columbia Ministry of Environment and Drs. Chelsea Himsworth and Ann Britton with the Animal Health Centre (Abbotsford, British Columbia) for providing tissues from S. canis infected black bears.
* Presenting author
+ Student presenter
Literature Cited
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