Abstract
An adolescent, male, North American river otter (Lontra canadensis) was submitted for necropsy after being treated at a wildlife sanctuary for prolonged lethargy, incoordination and one episode of hematemesis. No bloodwork or other diagnostics were performed antemortem. This animal was born at the facility and was the only survivor from a litter of five. Lontra sp. are known for their playful nature and inhabit freshwater riverbanks and costal marine estuaries.1 The IUCN has listed this species as stable and permittable for harvest in selected areas. The most common causes of mortality are trauma, followed by idiopathic, infectious, nutritional, metabolic, and neoplasia.2 At necropsy, this male otter was in good body condition with ample adipose and no evidence of trauma. The lungs were diffusely red, wet, and heavy. The heart was large and round with a thin right ventricle (0.2 cm) and left ventricle (1 cm) wall. Microscopically, multifocal to coalescing hemorrhage with congestion in the lungs with alveolar histiocytosis and numerous pigment laden macrophages. There was no gross or microscopic evidence of systemic infectious disease or inflammation and PCRs for Toxoplasma gondii and Sarcocystis neurona, IHC for leptospirosis, a DFA for distemper virus, lung cultures and fecal float were negative.3 Findings are most consistent with dilated cardiomyopathy and pulmonary changes due to heart failure. Dilated cardiomyopathy (DCM) can be an acquired heart disease in which the ventricular myocardium weakens and loses its ability to contract normally. Over time, this ineffective pumping results in congestive heart failure. DCM can be inherited, but it is also linked to nutritional deficiencies, including taurine, L-carnitine, and thiamine, in sea lions and various species of terrestrial mammals including sea lions, hamsters, and humans.4,5,6 Within mustelids, DCM death is reported in ferrets (Mustela putorius furo) and southern sea otters (Enhydra lutris nereis).7,8 The diet of this otter consisted largely of frozen and thawed fish, which is true for many river otters under human care. The process of freezing and thawing, however, results in rapid loss of nutrients like water-soluble vitamins, including thiamine.9,10 Thus, for all primarily piscivorous species under human care, daily thiamine supplementation is recommended at 25–30 mg/kg fish “as fed”.7,8 This otter was being administered ½ cc of thiamine paste once a week; a dose that could not have provided enough of the vitamin to replace the inherent dietary deficiency. It is possible that this thiamine deficiency led to the development of cardiomyopathy, previously undocumented within the North American river otter.
*Presenting author
+Student presenter
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