title: Detection and characterization of diverse coccidian protozoa shed by California sea lions.
abstract: Tissue-cyst forming coccidia in the family Sarcocystidae are etiologic agents of protozoal encephalitis in marine mammals including the federally listed Southern sea otter (Enhydra lutris). California sea lions (Zalophus californianus), whose coastal habitat overlaps with sea otters, are definitive hosts for coccidian protozoa provisionally named Coccidia A, B and C. While Coccidia A and B have unknown clinical effects on aquatic wildlife hosts, Coccidia C is associated with severe protozoal disease in harbor seals (Phoca vitulina). In this study, we conducted surveillance for protozoal infection and fecal shedding in hospitalized and free-ranging California sea lions on the Pacific Coast and examined oocyst morphology and phenotypic characteristics of isolates via mouse bioassay and cell culture. Coccidia A and B were shed in similar frequency, particularly by yearlings. Oocysts shed by one free-ranging sea lion sampled at Año Nuevo State Park in California were previously unidentified in sea lions and were most similar to coccidia infecting Guadalupe fur seals (Arctocephalus townsendi) diagnosed with protozoal disease in Oregon (USA). Sporulated Coccidia A and B oocysts did not replicate in three strains of mice or in African green monkey kidney cells. However, cultivation experiments revealed that the inoculum of fecally-derived Coccidia A and B oocysts additionally contained organisms with genetic and antigenic similarity to Sarcocystis neurona; despite the absence of detectable free sporocysts in fecal samples by microscopic examination. In addition to the further characterization of Coccidia A and B in free-ranging and hospitalized sea lions, these results provide evidence of a new role for sea lions as putative mechanical vectors of S. neurona, or S. neurona-like species. Future work is needed to clarify the distribution, taxonomical status, and pathogenesis of these parasites in sea lions and other marine mammals that share their the near-shore marine environment.
authors.affiliation: Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Yvette A
authors.initials: YA
authors.lastname: Girard
authors.affiliation: Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Christine K
authors.initials: CK
authors.lastname: Johnson
authors.affiliation: Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA; Department of Veterinary Pathology and Microbiology, College of Veterinary Medicine, Washington State University, Pullman, WA, USA.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Fritz
authors.affiliation: Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Shapiro
authors.affiliation: Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Packham
authors.affiliation: Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Ann C
authors.initials: AC
authors.lastname: Melli
authors.affiliation: Vanderbilt Institute for Global Health, Vanderbilt University, Nashville, TN, USA.
authors.forename: Daphne
authors.initials: D
authors.lastname: Carlson-Bremer
authors.affiliation: The Marine Mammal Center, Sausalito, CA, USA.
authors.forename: Frances M
authors.initials: FM
authors.lastname: Gulland
authors.affiliation: California Animal Health and Food Safety, Davis, CA, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rejmanek
authors.affiliation: Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA; Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Conrad
keywords: California sea lions; Marine mammals; Neospora sp.; Sarcocystidae; Sarcocystis neurona; Tissue cyst-forming coccidia