Fatal Hepatic Sarcocystosis in Three Captive and One Free-ranging Pinniped

Fatal hepatic sarcocystosis was diagnosed as the cause of death in four pinnipeds: two captive Hawaiian monk seals (), a captive, and a free-ranging California sea lion (). Based on necropsy, histopathology, electron microscopy and DNA sequencing, intralesional protozoal schizonts were determined to have caused the necrotizing hepatitis observed. Transmission Electron Microscopy (TEM) revealed schizonts similar to in hepatocytes. PCR-DNA sequencing and phylogenetic analysis at the conserved and variable gene markers within the nuclear rRNA gene array from schizont-laden tissue established that the parasites were indistinguishable from at the locus. However, six distinct single nucleotide polymorphisms (SNPs) were resolved at suggesting that the parasites infecting pinnipeds were distinct from which commonly infects bears and dogs. We hypothesize that the parasite represents a novel variant that we refer to as . like that infects pinnipeds. The definitive host of is enigmatic and its life cycle incomplete. These findings document a critical need to identify the life cycle(s), definitive host(s), and all susceptible marine and terrestrial intermediate hosts of and the like variant infecting pinnipeds.