Are False Blister Beetles Poisonous to Horses?

Livestock die each year from the toxin created by false blister beetles, according to Justin Schmidt of Colorado State University. Although referred to as "false blister beetles," the insects in the Oedemeridae family create the exact same toxin as regular blister beetles. Cantharidin is produced by several different beetle families, all of which present potential danger to horses. False blister beetles can kill a horse when ingested. Understanding the risks associated with false blister beetles helps horse owners take preventative measures.

  1. Description

    • Adult false blister beetles range from 5 to 12 mm in length, depending on the species of beetle. They are almost indistinguishable from the true blister beetle of the family Meloidae. The only difference lies in the pronotum. Located between the head and the elytra, the pronotum of the false blister beetle is larger in front and narrows towards the elytra. True blister beetles feature a pronotum that is narrow in the front and widens at the elytra. Approximately 1,500 species of false blister beetles exist worldwide, according to the Armed Forces Pest Management Board. They range from gray to black with colorful stripes, depending on the species. Also known as "pollen feeding beetles," they are often seen on flowers.

    Cantharidin Production

    • The Armed Forces Pest Management board notes that although few references to false blister beetles exist in medical literature, their ability to produce cantharidin makes them a potential problem for humans and animals. False blister beetles protect themselves when threatened by bleeding a mix of hemolymph and cantharidin from their joints and various body parts. All stages of false blister beetle life exhibit levels of cantharidin. Only male false blister beetles produce cantharidin, but they transfer it to females during mating. The female then transfers the cantharidin to the eggs she produces in order to protect them from potential predators.

    Equine Cantharidiasis

    • The consumption of any type of blister beetle, including the false blister beetle, has the potential of causing cantharidiasis in horses. Beetles feeding on alfalfa become trapped when farmers cut and wrap their fields into hay, especially alfalfa. Although primarily found in the western United States, horses in all states are at risk due to the widespread transportation of hay. Cantharidin exhibits extreme stability and does not easily lose toxicity, even when heated and dried, according to Kansas State University.

    Cantharidiasis Symptoms

    • Penn State College of Agricultural Sciences warns that sudden death is possible when a horse ingests large doses of cantharidin. In most cases, the ingestion of cantharidin irritates the lining of the stomach and intestines, resulting in colic. The elimination of the toxin through urinary system results in blood in the urine and difficulty in urinating. The toxin may also affect the neurological condition of the horse, cause heart problems or result in oral lesions. Symptoms may appear within four to six hours of ingestion and last four hours to days before death or recovery. Veterinarians use a variety of treatments to reduce irritation and eliminate the toxin from the animal.

    Precautions

    • Hay without beetles may still be contaminated, because cantharidin may be transferred to the hay when beetles are crushed during harvesting. North Dakota State University recommends avoiding alfalfa hay cut during the bloom stage, as blister beetles are attracted to flowering plants. Horse owners should inspect hay pastures prior to cutting for false blister beetle infestations. Insecticides may reduce infestations, but the beetles may move back in once the residual chemicals wear off. While it is impossible to guarantee the elimination of false blister beetles from a pasture, proper management practices reduce the risk.