Camelidae and Cervidae Selenium-Responsive Myopathy Study Guide

Overview and Clinical Importance

Selenium-responsive myopathy, also known as white muscle disease (WMD) or nutritional myodegeneration (NMD), is a degenerative muscle disease caused by deficiency of selenium and/or vitamin E. This condition affects both skeletal and cardiac muscle and is clinically significant in camelids (llamas, alpacas, dromedary and Bactrian camels) and cervids (deer, elk, moose). Understanding this disease is critical for the NAVLE as it tests knowledge of pathophysiology, clinical recognition, species-specific considerations, and management in exotic and production animal species.

Although overt myopathy is rare in South American camelids compared to other livestock, selenium deficiency remains a disease of concern in many regions of North America, Europe, Australia, and New Zealand. Cervids, particularly farmed deer and elk, are susceptible to WMD, especially in selenium-deficient geographic regions.

Etiology and Pathophysiology

Role of Selenium and Vitamin E

Selenium is an essential trace element that functions as an integral component of the enzyme glutathione peroxidase (GPx). This selenoenzyme catalyzes the reduction of hydrogen peroxide and lipid hydroperoxides to water and alcohols, respectively, using glutathione (GSH) as a cofactor. The main reaction is: 2GSH + H?O? → GSSG + 2H?O.