ACUTE ARSENIC TOXICOSIS IN 5 HORSES

Five adult horses presented with acute clinical signs of watery diarrh ea, excessive salivation, muscle tremors, ataxia, and depression. Four died within 24 hours and the fifth was euthanatized approximately 48 hours after onset of clinical signs. Necropsy findings in two of the h orses included hyperemia of gastric mucosa, intestines filled with gre en to black watery fluid, and multifocal to coalescing, hemorrhagic 1. 0-2.0-cm-diameter ulcers of the mucosa of the cecum and large colon. H istopathologic changes in the cecum and large colon consisted of mucos al necrosis and ulceration, vascular thrombosis, necrosis of submucosa l blood vessels, and infiltration by mixed mononuclear inflammatory ce lls and neutrophils. Arsenic toxicosis was suspected. The owner had no t been feeding the horses any grain; however a mixture of grain and pi nk powder was found in the pasture. Liver arsenic concentrations in th e two horses were 14.0 and 11.0 ppm, a sample of renal cortex containe d 108 ppm arsenic, and the grain/powder mixture found in the pasture w as positive for arsenic at >3,000 ppm. Kidney lead concentrations were 6.5 and 4.2 ppm. Results were consistent with lead arsenate or lead a rsenite poisoning.