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Blister Beetle Toxicity

Other Names: Cantharidin Poisoning

Blister beetles are insects from the Meloidae family that contain cantharidin, a toxic chemical that protects them from predators. Cantharidin is highly toxic when ingested by chickens and can be fatal. Since the toxin is very stable it remains toxic even in the dried remains of these beetles. Blister beetle toxicity are a common problem for horses who are fed alfalfa hay, as the beetles usually congregate on the plant and crushed up during harvesting.

The characteristic features of blister beetles include long (19 to 25 mm) narrow bodies and broad heads. There are over 7,500 different species which come in a variety of colors, body shapes and sizes. A feature that helps distinguish them from other beetles is that the front wings of blister beetles are soft and flexible, as opposed to stiff and hard like most other beetles.

Blister beetles are found worldwide. They are especially common in the southern and eastern areas of the United States. It's best to consult with your local extension or agricultural agent on which species are found local to your specific area.

Blister beetle larvae consume grasshopper eggs.
Adult blister beetles feed on the flowers and leaves of a variety of plants, especially those in the families Amaranthaceae, Asteraceae, Fabaceae and Solanaceae. Some commonly cultivated crops from these plant families include potato, tomato, alfalfa, beet, peas, beans, peanuts, soybean, and chickpeas. Some other popular plants amongst blister beetles include pigweed, goldenrod, goathead, puncturevine and mesquite. Adult blister beetles are usually seen eating plants during the day and are attracted to outdoor lights at night. Some species will swarm in large numbers, especially during the flowering stages of plants.

Clinical Signs of Blister Beetle Poisoning in Chickens

Cantharidin is a potent vesicant and acantholytic agent which causes irritation through direct contact. Once ingested, it damages the bird’s gastrointestinal tract, kidneys, and heart. Endotoxemia can develop secondary to damage to the gastrointestinal mucosa. Clinical signs of blister beetle poisoning in chickens vary considerably and depend on the amount consumed, body size of the bird and health status. However, in many cases the birds are found dead.

Treatment of Blister Beetle Poisoning in Chickens

There is no specific antidote for cantharidin poisoning. Treatment is supportive and aimed at reducing further absorption of the toxin, preventing dehydration, correcting electrolyte and blood gas abnormalities and reduction of pain.

Clinical Signs

Loss of appetite
Tachycardia (accelerated heart rate)
Tachypnea (increased respiratory rate)
Sudden death
Vomiting beetles


  • History
  • Clinical Signs
  • Laboratory testing - toxicology
  • Necropsy - look for erosive lesions in the gastrointestinal tract and identification of beetles in the crop.

Reported Cases

  • Case 1: Cantharidin poisoning in a Bustard A great bustard died by a traumatism, but also presented diarrhoea, congestion of the gastrointestinal tract and kidneys. They had ingested several blister beetles of the species Berberomeloe majalis. The analysis of the stomach content by GC–MS revealed the presence of cantharidin at a concentration of 1.37 g/g of wet weight, a similar level than in other birds poisoned in captivity. Ref

  • Case 2: Cantharidin poisoning in a Chickens Mortality in young chickens was associated with blister beetle consumption. Two species of these insects, Cyaneolytta sp. and Cylindrothorax sp., were found in the chickens' crops, and erosive lesions in the gastrointestinal tract were compatible with blister beetle poisoning (cantharidiasis). Ref

  • Case 3: Cantharidin poisoning in a Emus In 1992, the Texas Veterinary Medical Diagnostic Laboratory received for necropsy several frozen 1-3 month old emu chicks from 1 ranching operation. Insects had swarmed to blooms on mesquite trees (Prosopis glandulosa) near the chick barn, and when a cool front arrived, lights were left on inside to encourage the chicks to seek shelter. As dusk fell, the insects were attracted to the lighted area, and could be seem covering the floor of the barn. Following consumption of the insects, some chicks became ataxic, vomited beetles, became prostate, and died. Others survived following vigorous treatment with oral fluids. At necropsy, the esophagus of each bird was congested and edematous, and the proventricular serosa was hemorrhagic. The gizzard linings were sloughed, the intestinal contents were pink and the livers pale. Ref


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Activated charcoalTo absorb the toxin in the GI tract.
Intravenous fluid therapyTo help correct hypovolemia, provide calcium and magnesium, and to induce diuresis.
Pain medication



  • Be aware of the species of blister beetles that are found in your local area. Keep on the lookout for them in any plants your chickens have access to.
  • Don't allow your chickens access to plants known for attracting blister beetles.
  • Don't feed random insects that you can't identify to your birds.



Scientific References

Risk Factors

  • Growing plants known for attracting blister beetles.
  • Feeding unidentified insects to your birds.