Treatment of chronic chlorpyrifos poisoning in a Limousin bull

A purebred three-year-old Limousin bull developed diarrhea, anorexia, and weight loss a few days following topical application of chlorpyrifos Dow Chemical Co., Midland, Michigan 48640. Approximately one month following exposure, the bull was referred to the Oklahoma State University, College of Veterinary Medicine Teaching Hospital for evaluation and treatment. The clinical syndrome was very similar to chlorpyrifos poisoning previously described in dairy bulls. Chlorpyrifos [0, 0-dimethyl-0-) 3, 5, 6-trichloro -2-pyridyl) phosphorothioate], insecticide is used for the control of lice and horn flies on beef-breed cattle by pouring on the skin at the withers as a one-time seasonal treatment.