Development of Hippocampal Neuropathology in an Adult California Sea Lion (Zalophus californianus): Considerations for Animal Care Managers
IAAAM 2018
Carolina Le-Bert1*; Peter Cook2; Jenny Meegan1; Forrest Gomez1; Betsy Lutmerding1; Marina Ivančić1,3; Eric Jensen4
1National Marine Mammal Foundation, San Diego, CA, USA; 2New College of Florida, Sarasota, FL, USA; 3Chicago Zoological Society, Brookfield, IL, USA; 4U.S. Navy Marine Mammal Program, San Diego, CA, USA

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

1.  Ramsdell JS, Zabka TS. 2008. In utero domoic acid toxicity: a fetal basis to adult disease in the California sea lion (Zalophus californianus). Mar Drugs. 6:262–290.

2.  Goldstein T, Mazet JAK, Zabka TS, Langlois G, et al. 2008. Novel symptomatology and changing epidemiology of domoic acid toxicosis in California sea lions (Zalophus californianus): an increasing risk to marine mammal health. Proc Royal Soc B: Biol Sci. 275(1632):267–276.

3.  Simeone CA, Fauquier D, Skidmore J, Rowles TK, Gulland FMD. 2017. Assessment of neurologic signs in non-releasable California sea lions (Zalophus californianus) in the United States, 2000–2016. IAAAM 48th Annual Conference Proceedings, Cancun, Mexico.

4.  Buckmaster PS, Wen X, Toyoda I, Gulland FMD, Van Bonn W. 2014. Hippocampal neuropathology of domoic acid-induced epilepsy in California sea lions (Zalophus californianus). J Comp Neurol. 522(7):1691–1706.

5.  Cook PF, Reichmuth C, Rouse AA, Libby LA, Dennison SE, Carmichael OT, Kruse-Elliott KT, Bloom J, Singh B, Fravel VA, Barbosa L, Stuppino JJ, Van Bonn WG, Gulland FMD, Ranganath C. 2015. Algal toxin impairs sea lion memory and hippocampal connectivity, with implications for strandings. Science. 350(6267):1545–1547.

6.  Cook PF, Reichmuth C, Rouse A, Dennison S, Van Bonn B, Gulland F. 2016. Natural exposure to domoic acid causes behavioral perseveration in wild sea lions: neural underpinnings and diagnostic application. Neurotoxicol Teratol. 57:95–105.

7.  Montie E, Wheeler E, Pussini N, Battey TWK, et al. 2010. Magnetic resonance imaging quality and volumes of brain structures from live and postmortem imaging of California sea lions with clinical signs of domoic acid toxicosis. Dis Aquat Org. 91:243–256.

8.  Cook PF, Berns GS, Colegrove K, Johnson S, Gulland F. 2017. Postmortem DTI reveals altered hippocampal connectivity in wild sea lions diagnosed with chronic toxicosis from algal exposure. J Comp Neurol. 1–13.

 

Speaker Information
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Carolina Le-Bert
National Marine Mammal Foundation
San Diego, CA, USA


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