Clinical Signs and Pathology Associated With Domoic Acid Toxicosis in Southern Sea Otters (Enhydra lutris nereis)

The marine biotoxin domoic acid (DA) is an analog of the neurotransmitter glutamate that exerts potent excitatory activity in brain, heart, and other tissues. Produced by diatom Pseudo-nitzschia spp., DA accumulates invertebrates, fish, sediment. Southern sea otters ( Enhydra lutris nereis ) feed primarily on including crabs bivalves, concentrate slowly depurate DA. Due to their high prey consumption (25% body weight/day), are commonly exposed A total 823 necropsied southern were examined complete this study; first we assessed 560 subadult, adult, aged adult sampled from 1998 through 2012 for DA-associated pathology, focusing mainly central nervous system (CNS) cardiovascular system. We applied what was learned additional cohort all demographics (including fetuses, pups, juveniles, after 2012: n = 263 animals). Key findings derived our initial efforts consistently observed more demographically diverse cohort. Finally, chronicity pathology CNS heart independently 54 otters. Our goals compare temporal consistency lesions determine whether multiple episodes toxicosis could be detected histopathology. Sea with acute, fatal typically presented neurological signs severe, diffuse congestion multifocal microscopic hemorrhages (microhemorrhages) spinal cord, system, eyes. microhemorrhages associated detection concentrations postmortem urine or gastrointestinal content preceded histological cellular necrosis apoptosis. Cases chronic often severe than pathology; however, at both sites relatively quiescent, reflecting previous damage. subacute exhibited concurrent characterized progressive lesion expansion host response tissue Acute, subacute, cases had same distribution heart. common hippocampus, olfactory, entorhinal parahippocampal cortex, periventricular neuropil, ventricles. circumventricular organs identified as important targets; examination pituitary gland, area postrema, organs, eyes facilitated confirmation acute histopathology also cardiomyocytes coronary arterioles, especially left ventricular free wall, papillary muscles, cardiac apex, atrial walls. Progressive cardiomyocyte loss arteriosclerosis occurred areas, suggesting a underlying mechanism. stage matched 87% 47/54) chronicity, process (e.g., toxicosis) cause these lesions. This temporally pattern indicative single episode toxicosis. 13% 7/54) overlapping suggestive recurrent rigorous case definition facilitate diagnosis Diagnosing but occult condition improving clinical care assessing population-level impacts exposure federally listed threatened subspecies. Because most likely source toxin consumption, because humans, otters, animals consume foods, characterize health effects can provide strong collateral benefits.