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Horse owners should check hay for toxic blister beetles

News Release Distributed 09/05/14

BATON ROUGE, La. – Louisiana horse owners need to inspect alfalfa hay bales for blister beetles, which are tiny, toxic and potentially fatal, said LSU AgCenter equine specialist Neely Walker.

The LSU School of Veterinary Medicine recently treated a case of blister beetle toxicity, Walker said. As few as 25 ingested beetles can be toxic to an average-sized horse, and poisoned animals can die within 72 hours, she said.

Blister beetles are members of a family of plant-feeding insects that contain cantharidin, a toxic chemical that protects the beetles from predators. They have narrow bodies that are 3/4 to 1 1/4 inches long, broad heads and antennae that are about one-third of their body length.

Color of blister beetles ranges from solid ash gray and black to black with light margins and striped. Walker said striped blister beetles have the highest cantharidin content and tend to congregate in large clusters along field margins, which can result in a greater number of beetles in a section of hay.

Hay crimpers, which crush hay so it dries faster and evenly, kill the beetles, but they are still toxic after they die, Walker said. Dead beetles remain in hay once it is baled.

The severity of the reaction ranges from temporary poisoning to reduced digestive ability to death, but depends on the overall health of the horse and how much cantharidin was ingested. Still, if horse owners suspect blister beetle poisoning, they should contact a veterinarian immediately.

“Symptoms typically appear within hours of ingestion and include inflammation of the digestive and urinary tract, colic and straining during increased urination,” Walker said. “Secondary infection may occur, causing kidney failure, increased heart rate and respiration, dehydration, sweating, diarrhea and decreased calcium levels, which can damage the heart.”

Animals that recover from poisoning may develop laminitis or other systemic infections, Walker said.

Buying hay from local producers is one way to reduce chances of getting hay that contains blister beetles.

“Develop a relationship with your hay producer and be aware of their production practices,” Walker said. “Also look for first-cutting hay, when blister beetles are not active, and hay that is harvested at the late bud stage or when the first flowers open.”

Even if hay is purchased from a reputable local producer, Walker said, it is still important to check hay for blister beetles before feeding it to horses.

Olivia McClure

Last Updated: 9/5/2014 12:49:29 PM

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