Abstract

Protozoal infections in stranded southern sea otters (Enhydra lutris nereis; SSO) present significant diagnostic and treatment challenges. Over a 15-year period (1998–2012), Toxoplasma and/or Sarcocystis exposure was documented in 78% of sampled otters (421/541) and was a primary or contributory cause of death for at least 20% (108/547).¹ Antemortem diagnosis of protozoal infection is primarily through serology (IFAT).² While a positive result indicates current or previous infection, serologic findings frequently do not directly correlate with reported clinical and/or histopathologic disease.¹ Between May 2017 and October 2022, 19 of 26 (73%) of live-stranded sea otters admitted for rehabilitation at The Marine Mammal Center (Sausalito, CA, USA) were serologically positive for Toxoplasma, Sarcocystis, or both. Ten of 26 seropositive otters died or were euthanized within 6 days, before a diagnosis was established. Five of 26 were seropositive but were not treated with antiprotozoal medication as they did not exhibit neurologic signs; four of these five were released and one remains in care. Four of the 26 seropositive otters displayed neurologic signs consistent with protozoal disease (tremors, ataxia, and/or generalized weakness). These four were treated with antiprotozoal medication (ponazuril and/or trimethoprim-sulfamethoxazole) in a food item for an average of four weeks with varying patient compliance. Neurologic disease resolved in each case and these four were released. Inconsistencies among clinical presentation, serologic results, and patient outcome highlight the need for improved, rapid, and accurate antemortem diagnostic capabilities for this threatened species.

Acknowledgements

We thank the dedicated volunteers and staff of The Marine Mammal Center, the Monterey Bay Aquarium, and the California Department of Fish and Wildlife for their excellent animal response and care. Sea otter response and rehabilitation activities are conducted under U.S. Fish and Wildlife Permit #MA101713-1. This work is greatly supported by the U.S. Fish and Wildlife Service Prescott Marine Mammal Rescue Assistance Grant #F20AP12044-00.

*Presenting author

Literature Cited

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