Blister beetles (family Meloidae) produce cantharidin, a potent toxin that protects them from predators. This compound is highly toxic to chickens if ingested and can be fatal. Notably, cantharidin remains active even in dead or dried beetles.
Blister beetle poisoning is well recognized in horses consuming contaminated alfalfa hay, as beetles often cluster on plants and may be crushed during harvesting.
Identification and Habitat
Blister beetles typically have long, narrow bodies (19–25 mm) and broad heads. Unlike most beetles, their front wings are soft and flexible rather than rigid. There are over 7,500 species, varying widely in color and appearance.
They are found worldwide and are especially common in the southern and eastern United States. Local extension or agricultural agencies can provide information on species in your area.
Larvae feed on grasshopper eggs, while adults consume leaves and flowers from a variety of plants, particularly:
- Amaranthaceae (amaranth family)
- Asteraceae (daisy family)
- Fabaceae (legume family)
- Solanaceae (nightshade family)
Common host plants include alfalfa, tomato, potato, beans, peas, soybeans, pigweed, goldenrod, and puncturevine. Adult beetles are active during the day and may be attracted to lights at night. Some species gather in large numbers, especially during plant flowering.
Clinical Signs
Cantharidin is a powerful irritant that damages tissues on contact. After ingestion, it can cause severe injury to the gastrointestinal tract, kidneys, and heart. Secondary endotoxemia may occur due to intestinal damage. Clinical signs vary depending on the dose consumed but may include:
- Sudden death
- Loss of appetite
- Depression/lethargy
- Increased heart and respiratory rate
- Ataxia (incoordination)
- Regurgitation or presence of beetles in vomitus
In many cases, affected birds are found dead without prior signs.
Treatment
There is no specific antidote for cantharidin poisoning. Treatment is supportive and should be initiated by a veterinarian as soon as possible.Management may include:
- Activated charcoal to limit toxin absorption
- Fluid therapy to correct dehydration and electrolyte imbalances
- Pain control
- Supportive care and monitoring
