Abstract
Exposure to the marine biotoxin domoic acid (DA) is common among wild stranded California sea lions along the California coast, and has been linked to hippocampal atrophy, neuronal necrosis, and disruption of the limbic system.1 Although many sea lions suffering from domoic acid toxicity succumb to neurologic disease, not all deaths are a direct result of brain disease. Domoic acid is an excitatory neurotoxin that causes cell death by binding to neurons via glutamate receptors, and is thought to act not only on the brain but also in other areas including the cardiac nervous system. A degenerative cardiomyopathy has been identified histopathologically in sea lions exposed to DA and may be an important contributor to morbidity and mortality.2 Echocardiograms were performed on 95 California sea lions; measurements including left ventricular internal dimension, interventricular septal wall thickness, left ventricular posterior wall thickness, ejection fraction, and fractional shortening were obtained. Echocardiographic parameters from 14 California sea lions that died or were euthanized with histopathologically confirmed domoic acid toxicity affecting the brain were compared to those from six healthy animals with no previous suspected exposure to the toxin. Significant differences in fractional shortening and ejection fraction between the two groups suggest that domoic acid plays an important role in cardiac function via alterations in the conduction pathway. Among DA-exposed individuals, echocardiographic changes were also compared with histopathologic cardiac abnormalities. We present echocardiography as a valuable antemortem cardiac function test for evaluating DA-exposed California sea lions being considered for release back into the wild.
Acknowledgements
The authors would like to thank the staff and volunteers at The Marine Mammal Center for their help with animal care and with necropsy during this study.
* Presenting author
Literature Cited
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2. Zabka TS, Goldstein T, Cross C, Meuller RW, Kreuder-Johnson C, Gill S, Gulland FMD. Characterization of a degenerative cardiomyopathy associated with domoic acid toxicity in California sea lions (Zalophus californianus). Vet Pathol. 2009;46:105–119.