RESUMO
Over a period of 5 mo, seven out of eight American white pelicans (Pelecanus erythrorhynchos) housed on a spring-fed pond at a zoo died or were euthanized. Clinical signs included inability to stand, anorexia, and weight loss. Clinicopathologic findings included heterophilic leukocytosis and elevated creatine kinase and aspartate aminotransferase. Histopathologic findings on all pelicans demonstrated severe, chronic, diffuse rhabdomyofiber degeneration and necrosis, making vitamin E deficiency a differential diagnosis despite routine supplementation. Based on tissue and pond water assays for the cyanobacterial toxin, microcystin, toxicosis is suspected as the inciting cause of death in these cases. We hypothesize that vitamin E exhaustion and resultant rhabdomyodegeneration and cardiomyopathy were sequelae to this toxicosis.