Blister beetle poisoning is a rare but deadly threat. Blister beetles carry cantharidin, a toxic defense chemical that is a blistering agent. They are found in alfalfa hay with blooms or that contains other insects, especially grasshoppers, since blister beetles are attracted to both. There are several varieties, so the appearance of the beetles depends on the species, which vary by geographic region.
Source: Western Horseman, August 2016, page 24. (link unavailable)
When a blister beetle is consumed, it burns the mucosal membranes inside the horse from the mouth all the way through the digestive system. It affects kidney and bladder tissue, as well as the heart. There is no antidote and most horses poisoned by a blister beetle die painfully.
INSIGHTS: The article features hay buying strategies which veterinary teams, sales reps and retail associates can provide to horse owners to help them avoid a blister beetle problem.