Botulism suspected in deaths of four horses

Early last month, four horses became sick and died in Kittitas Valley, a scenic region of the U.S. state of Washington. Equine botulism is the suspect in all four deaths.

The horses, which came from the same farm, began experiencing symptoms — including weakness, difficulty swallowing and tongue paralysis — around the same time. Two were kept in pens, while two were kept in stalls, but they shared the same kind of feed: compressed alfalfa hay.

Equine botulism, which comes from the bacteria Clostridium botulinum, is usually deadly. It’s a progressive neuromuscular disease that quickly leads to weakness and flaccid paralysis (lack of muscle tone with reduced ability to move).

“They go down and can’t get up again,” veterinarian Michael Fuller told Daily Record News. “Once they get down, the survival rate is pretty much zero.”

Respiratory failure is typically the end result in infected horses.

Where does the botulism bacteria come from?

In the Kittitas Valley case, Fuller suspects that botulism was transferred to the horses through their feed, which in turn may have been contaminated when the hay was first baled.

“Those cases were probably from the ground,” Fuller said. “The damp ground gets a layer of hay and stuff on top of it and it gets sealed up, then bacteria grow in the absence of oxygen. Spores develop, and the horses eat the spores.”

Warm, wet winters can make for easy growing conditions for Clostridium botulinum. Because of this, Fuller advises horse owners to be on the lookout for water damage or discoloration in feed, and to avoid giving their horses any feed that causes doubt.

Can I vaccinate my horse for botulism?

Yes. Neogen offers the vaccine BotVax B, which inoculates against botulism in three doses, each one month apart. BotVax B is the only U.S. Department of Agriculture-approved Clostridium botulinum type B toxoid licensed for preventing equine botulism in healthy horses.