Blister beetle poisoning in horses.

Case records of 21 horses with acute illness following ingestion of hay containing dead striped blister beetles (Epicauta spp) were selected for review. Abdominal pain, fever, depression, frequent urination, shock, and, occasionally, synchronous diaphragmatic flutter characterized clinical illness. Hematologic findings included hemoconcentration, neutrophilic leukocytosis, and hypocalcemia. Hematuria and low urine specific gravity were abnormal urinalysis results. Sloughing of the epithelium of the esophageal part of the stomach, hemorrhagic and ulcerative cystitis, enterocolitis, and myocardial necrosis were important post-mortem findings. Signs and lesions in 5 horses experimentally poisoned were similar to those of the natural disease. The findings were regarded as sufficiently characteristic of blister beetle poisoning to be useful in differential diagnosis but were not constant in all cases. Therefore, when blister beetle poisoning is suspected, access of affected horses to hay containing striped blister beetles should be demonstrated.