Abstract
Zoonotic parasites of seals that are harvested for food may pose a health risk when seal meat or organ tissues of infected animals are eaten raw or undercooked. In this study, 124 tissue samples from 81 seals, comprising four species, were collected from northern and eastern Canada. Tissues from 23 ringed seals (Pusa hispida), 8 hooded seals (Cystophora cristata), 21 harp seals (Pagophilus groenlandicus), and 29 grey seals (Halichoerus grypus) were tested for parasites of the Sarcocystidae family including Toxoplasma gondii, Sarcocystis spp., and Neospora spp. using nested PCR followed by Sanger sequencing. Toxoplasma gondii DNA was present in 26% of ringed seals, 63% of hooded seals, 57% of harp seals, and 31% of grey seals. Sarcocystis sp. DNA was found in 9% of ringed seals, 13% of hooded seals, 14% of harp seals, and 4% of grey seals, while N. caninum-like DNA was present in 26% of ringed seals. While it is unclear how pinnipeds may become infected with these protozoans, horizontal transmission is most likely. However, one harp seal pup (4 days old) was PCR-positive for T. gondii, suggesting vertical transmission may also occur. Phylogenetic analysis of the 18S gene region indicates that Sarcocystis sp. in these seals belongs to a unique genotype. Furthermore, this study represents a new host report for T. gondii in harp seals, a new host and geographic report for N. caninum-like parasites in ringed seals, and four new hosts and geographic reports for Sarcocystis sp. These results demonstrate that parasites of the Sarcocystidae family are prevalent in northern and eastern Canadian seals. While the zoonotic potential of Sarcocystis sp. and the N. caninum-like parasite are unclear, consumption of raw or undercooked seal meat or organ tissues pose a risk of T. gondii infection to consumers.
Highlights
Seal meat and organs are important country foods of Inuit in Arctic and subarctic Canada and Greenland
The objective of this study was to determine the prevalence of Toxoplasma, Sarcocystis, and Neospora infections in four species of seals that are harvested for food in northern and eastern Canada
PCR was performed on all tissues using 18S and B1 primers as described in Table 1. 18S Sarcocystidae primers were used to detect all parasites of the Sarcocystidae family
Summary
S.J. Reiling et al / Food and Waterborne Parasitology 17 (2019) e00067 eastern Canada (Hammill and Stenson, 2007; DFO, 2016), and seal meat is available at retail in this region. Seven pinniped species are hunted in Canada, including: walrus (Odobenus rosmarus), bearded seals (Erignathus barbutus), ringed seals (Pusa hispida), harbour seals (Phoca vitulina), hooded seals (Cystophora cristata), harp seals (Pagophilus groenlandicus), and grey seals (Halichoerus grypus). Most of these species are hunted for subsistence purposes by Inuit and others, but the latter three species are commercially hunted, with meat and by-products being sold to restaurants and exported. They have different diets which affect their exposure to parasites and pose differential zoonotic risks to human consumers
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