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Evaluation of cardiac lesions and risk factors associated with myocarditis and dilated cardiomyopathy in southern sea otters (Enhydra lutris nereis)

Christine Kreuder VMD, MPVM, PhD1, Melissa A. Miller DVM, PhD2,3, Linda J. Lowenstine DVM, PHD4, Patricia A. Conrad DVM, PhD5, Tim E. Carpenter PhD6, David A. Jessup DVM, MPVM7, and Jonna A.K. Mazet DVM, MPVM, PhD8
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  • 1 Wildlife Heath Center, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 2 Wildlife Heath Center, School of Veterinary Medicine, University of California, Davis, CA 95616
  • | 3 Marine Wildlife Veterinary Care and Research Center, California Department of Fish and Game, 1451 Shaffer Rd, Santa Cruz, CA 95060.
  • | 4 Departments of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 5 Wildlife Heath Center and the Departments of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 6 Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.
  • | 7 Marine Wildlife Veterinary Care and Research Center, California Department of Fish and Game, 1451 Shaffer Rd, Santa Cruz, CA 95060.
  • | 8 Wildlife Heath Center and the Departments of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

Abstract

Objective—To describe cardiac lesions and identify risk factors associated with myocarditis and dilated cardiomyopathy (DCM) in beach-cast southern sea otters.

Animals—Free-ranging southern sea otters.

Procedure—Sea otters were necropsied at the Marine Wildlife Veterinary Care and Research Center from 1998 through 2001. Microscopic and gross necropsy findings were used to classify sea otters as myocarditis or DCM case otters or control otters. Univariate, multivariate, and spatial analytical techniques were used to evaluate associations among myocarditis; DCM; common sea otter pathogens; and potential infectious, toxic, and nutritional causes.

Results—Clusters of sea otters with myocarditis and DCM were identified in the southern aspect of the sea otter range from May to November 2000. Risk factors for myocarditis included age, good body condition, and exposure to domoic acid and Sarcocystis neurona. Myocarditis associated with domoic acid occurred predominantly in the southern part of the range, whereas myocarditis associated with S neurona occurred in the northern part of the range. Age and suspected previous exposure to domoic acid were identified as major risk factors for DCM. A sample of otters with DCM had significantly lower concentrations of myocardial L-carnitine than control and myocarditis case otters.

Conclusions and Clinical Relevance—Cardiac disease is an important cause of death in southern sea otters. Domoic acid toxicosis and infection with S neurona are likely to be 2 important causes of myocarditis in sea otters. Domoic acid–induced myocarditis appears to progress to DCM, and depletion of myocardial L-carnitine may play a key role in this pathogenesis. (Am J Vet Res 2005;66:289–299)

Abstract

Objective—To describe cardiac lesions and identify risk factors associated with myocarditis and dilated cardiomyopathy (DCM) in beach-cast southern sea otters.

Animals—Free-ranging southern sea otters.

Procedure—Sea otters were necropsied at the Marine Wildlife Veterinary Care and Research Center from 1998 through 2001. Microscopic and gross necropsy findings were used to classify sea otters as myocarditis or DCM case otters or control otters. Univariate, multivariate, and spatial analytical techniques were used to evaluate associations among myocarditis; DCM; common sea otter pathogens; and potential infectious, toxic, and nutritional causes.

Results—Clusters of sea otters with myocarditis and DCM were identified in the southern aspect of the sea otter range from May to November 2000. Risk factors for myocarditis included age, good body condition, and exposure to domoic acid and Sarcocystis neurona. Myocarditis associated with domoic acid occurred predominantly in the southern part of the range, whereas myocarditis associated with S neurona occurred in the northern part of the range. Age and suspected previous exposure to domoic acid were identified as major risk factors for DCM. A sample of otters with DCM had significantly lower concentrations of myocardial L-carnitine than control and myocarditis case otters.

Conclusions and Clinical Relevance—Cardiac disease is an important cause of death in southern sea otters. Domoic acid toxicosis and infection with S neurona are likely to be 2 important causes of myocarditis in sea otters. Domoic acid–induced myocarditis appears to progress to DCM, and depletion of myocardial L-carnitine may play a key role in this pathogenesis. (Am J Vet Res 2005;66:289–299)