Three horses recently died of blister beetle poisoning in Clay County, Fla., and two have returned after treatment at the University of Florida following ingestion of alfalfa hay contaminated with blister beetles. The hay was delivered from a supplier in Oklahoma.

Blister beetles, any of six species of the genus Epicauta, can inhabit alfalfa and clover fields from the central through the southern United States. They cause inflammation and blistering of the skin within hours of contact. If ingested, cantharidin, a toxic substance in the beetle, is absorbed and rapidly excreted in the animal’s urine, causing inflammation of the digestive and urinary tracts. Horses can suffer severe poisoning from even a few beetles, alive or dead (hay processing can kill the beetles and release the toxin). Decreased feed intake, frequent drinking and urination, colic, and depression are signs of blister beetle poisoning. At its worst, blister beetle poisoning can cause horses to suffer severe pain, shock, and death within a few hours.
 
Bill Jeter, DVM, diagnostic veterinary manager for Florida’s Division of Animal Industry, said that the affected hay was sent from Oklahoma to a Florida feed distributor to feed stores or personal owners. He said, “I would assume that the distributor had tracked down the hay within 24-48 hours and removed it–we have had no other reports of horses with (toxicity) or other hay being contaminated