🪲 Vet Warning 2025: Blister Beetles in Alfalfa Can Be Deadly for Horses 🐴⚠️

Author: Dr Duncan Houston, BVSc

Feeding your horse alfalfa hay is usually a smart nutritional choice—unless it's contaminated with blister beetles. These tiny but deadly insects contain cantharidin, a potent toxin that can lead to severe gastrointestinal issues, colic, and even death. In this 2025 vet guide, Dr Duncan Houston breaks down how to protect your horse from blister beetle poisoning. 🐎💀

🔍 What Are Blister Beetles?

Blister beetles are a group of over 200 beetle species in the U.S., but the striped blister beetle—common in the southwestern states—is the most dangerous to horses. These beetles often swarm alfalfa fields in bloom, feeding on the flowers before harvest. 🌼🪲

Even dried beetles remain toxic. According to the Texas Veterinary Medical Diagnostic Lab, just four grams of dried beetles can be fatal to an average-sized horse. 🚨

⚠️ What Is Cantharidin and Why Is It Dangerous?

Cantharidin is a toxic chemical stored within blister beetles. It causes severe irritation and ulceration to mucous membranes and the gastrointestinal tract. Once ingested, symptoms can develop rapidly. 🧪

🩺 Clinical Signs of Cantharidin Poisoning

• 🥵 Colic and severe abdominal pain
• 🍽️ Loss of appetite and depression
• 💦 Sweating and elevated heart/respiratory rates
• ⚫ Blood in urine and dark gums
• 💧 Dehydration
• 👅 Oral ulcers and excessive salivation

Immediate veterinary intervention is required to have any chance of survival. ⏱️

🧪 Diagnosis and Lab Testing

Definitive diagnosis may include:

• 🧫 Identifying beetles in hay
• 🧬 Detecting cantharidin in stomach contents or feces

Testing is crucial if a horse dies suddenly after eating alfalfa or shows unusual colic symptoms. 🧠

💉 Treatment Protocol in 2025

Treatment for cantharidin poisoning is supportive and aggressive:

• 💊 Pain management with NSAIDs and anti-spasmodics
• 💧 IV fluids to combat dehydration
• 🪣 Mineral oil and activated charcoal to bind toxins
• 🧴 Omeprazole and sucralfate to reduce gastric damage

⚠️ Unfortunately, survival rates are low, especially if treatment is delayed. Prevention is your best defense. 🛡️

🌿 How to Prevent Blister Beetle Poisoning

• 🚫 Avoid feeding alfalfa in bloom harvested from high-risk beetle regions
• 🧑‍🌾 Purchase hay from trusted suppliers who use beetle-safe practices (e.g., cutting before bloom)
• 🔍 Visually inspect alfalfa flakes for beetle remains
• 📝 Ask hay suppliers about their region, harvest date, and pest control methods

🧠 Dr Duncan Houston’s Advice

"Blister beetles are a hidden threat. Always source alfalfa wisely—especially during bloom season—and never ignore suspicious colic symptoms." 🐴🧬

🆘 When to Call Your Vet Immediately

Seek veterinary help right away if your horse shows:

• 🔁 Colic that doesn’t respond to walking or mild treatment
• 💧 Signs of dehydration or sweating
• 🩸 Blood in urine or severe oral pain

Fast action may save your horse’s life. Time is critical. ⏱️

🔚 Final Word: Safe Hay, Safe Horse

Alfalfa hay can be nutritious—but only if it’s free of blister beetles. By understanding the risks and working with your veterinarian and hay supplier, you can keep your horses well-fed and safe from this deadly threat. 🐎🌿

Need help sourcing safe hay or identifying beetle risks? Visit AskAVet.com or download the Ask A Vet app for real-time veterinary support. 📱🪲