Horse Health Care - Blister Beetle Threat

I received the following question a few days ago: “My friend was telling me that she read an article in a Horse Newspaper about beetles being poisonous to horses and that sometimes these beetles get into the hay where if the horses eat them, they will die. My friend couldn’t find the newspaper, so can you write about this?”

What your friend was referring to was a type of beetle called Blister Beetles. They are hard to identify as there are over 7,500 species. They are not so common in the Northern parts of the United States. There is an old wife’s tale about only spotted beetles can be blister beetles and this is not true. They can be red with black spots, or plain black or really any color. Do not rely on markings or color to identify Blister Beetles. They are pretty damn odd looking bugs, with a separate head, shoulders and body – although I doubt the technical body terms are correct. They do have three pairs of legs (6 legs total). Look at the pictures below and you’ll see what I mean.

I have only seen Beetles present in alfalfa maybe three times in the past 12-15 years. I threw out that bale, and was careful to pull apart and go through the other bales from that load, which came from the Dallas , Texas area. It did not keep me from contracting hay loads from the same transport or farm, but I always check my alfalfa, flake by flake when I feed, not only for Beetles but for mold and foreign contaminants. Heck, I have found turtles, rabbits, old shoes, paper bags, string, newspapers, beer and soda cans and a lot of other objects as well. So it just pays to check your hay.

What is dangerous to horses is that these Blister Beetles secrete a blister agent type of chemical called Cantharidin. Alive or dead these beetles can poison a horse with this chemical. It will blister the gut and cause pain and colic type symptoms, and there may be ulcer type sores in the mouth as the horses chew their hay, crush the beetles and release the toxin.

I am told the Blister Beetles feed off of the alfalfa flowers, which appear usually after the first cut. It only takes a horse to eat three or four of these beetles to kill it. So you can see that a very small amount of Cantharidin to be toxic and lethal.

I looked up the other symptoms and they may include frequent urination and dehydration. Treatment includes treating for colic; Some treatments include treating for colic; use of mineral oil to help move the poison through the gut more quickly and maybe to absorb some of the toxin and coat the lining of the gut; some people advise Charcoal may also be used to help absorb some of the toxin.

Consumption of Blister Beetles is life threatening for a horse you must take quick and effective action to save the horse, but it starts with checking your alfalfa and knowing what to look for. Safe Journey.