Clinicopathologic, molecular, and ultrastructural features of <i>Sarcocystis pinnipedi</i> infection in 2 California sea lions with fatal necrotizing hepatitis

<i>Sarcocystis pinnipedi</i> is an apicomplexan protozoal parasite that was first recognized during a mass mortality event in juvenile grey seals (<i>Halichoerus grypus</i>) in the northwest Atlantic Ocean. Since its identification, this parasite has been reported in various pinniped species and has been associated with fatal necrotizing hepatitis. Little is known of the host range of <i>S. pinnipedi</i>. Here we report 2 cases of California sea lions (<i>Zalophus californianus</i>) in managed care that died following an 8-d history of inappetence, vomiting, diarrhea, and progressive lethargy with elevated hepatic enzyme activities. Postmortem examination identified hepatitis and icterus. <i>Sarcocystis</i> schizonts and zoites were identified in regions of necrosis. Molecular and ultrastructural findings demonstrated the close relatedness of this <i>Sarcocystis</i> to <i>S. canis</i>, which produces a similar lesion in bears.