Abstract
In utero exposure to domoic acid (DA) in California sea lions (Zalophus californianus; CSL) has been implicated in disturbances to fetal neurodevelopment.1-4 DA exposure at any point throughout the gestational period can affect seizure susceptibility later in life due to the large degree of brain development occurring throughout this time.1 Between 2000 and 2016, 15% of CSLs placed in managed care facilities developed neurologic signs after placement.3 Of those, almost half (44%) stranded as neonates, suggesting further investigations are needed into the role of in utero exposure to DA on the development of chronic DA symptomatology in non-releasable CSLs.2,3 Here, we describe a case of adult-onset epilepsy and progressive hippocampal neuropathology in a male CSL placed with the U.S. Navy Marine Mammal Program in 2009 as an asymptomatic yearling. Unilateral, right-sided hippocampal atrophy was diagnosed via 3T magnetic resonance imaging and volumetric analyses of hippocampuses relative to brain size were conducted.5-7 Diffusion tensor imaging was also performed to quantify white matter pathology and hippocampal structural connectivity.8 While other causes of unilateral hippocampal atrophy cannot be completely excluded, this case may represent in vivo evidence of the adult-onset epileptiform condition of chronic DA caused by in utero exposure, in a CSL placed at a managed facility. This finding may have significant implications on wildlife managers and rehabilitation recommendations, as well as animal care management implications on non-releasable CSLs placed in managed facilities. Further investigations, including behavioral assessments and advanced imaging studies, on both facility-born and non-releasable CSLs, may aid in better characterizing development of neuropathology in chronic DA animals.
Acknowledgements
The authors thank the trainers, veterinary technicians, and veterinarians of the National Marine Mammal Foundation and the U.S. Navy Marine Mammal Program for their assistance with the treatment and care of this animal. A special thanks to the vets and staff of The Marine Mammal Center, the Neuroradiology Service at Balboa Hospital, Sophie Dennison, Spencer Fire, and Frances Gulland for their assistance and expertise.
* Presenting author
Literature Cited
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