The deaths in April of a dozen horses on one pasture in Natrona County, WY were due to botulism. Over last weekend, KCWY-13, Wyoming’s NBC affiliate reported that:
Dr. George Marble says 3 horses were already dead on April 10th and when he went to the ranch he found two more that weren’t able to walk. Within two days, all twelve the of the rancher’s horses were dead or euthanized. Almost all the horses suffered paralysis of the legs and tongue which are both classic signs of botulism. The vet says no other pastures were affected by the toxin.
The veterinarian told KCWY-13, "the animals that were upstream so to speak from this particular pasture cause there was a little creek that ran through and those downstream from those horses and those that bordered on a fence line are all unaffected."
An equine health site associated with Horse Magazine says: "Horses usually become infected with botulism by ingesting the neurotoxin produced by the anaerobic bacterium Clostridium botulinum in contaminated feed or water. Feed contamination can occur when the decomposing carcass of a rodent or bird is baled in hay. This is seen more often in round bales. Feed can also be contaminated through improper storage or poor fermentation. Rarely, horses can get botulism when C. botulinum from the soil gets into an open wound."
KCWY-13 said it is extremely important for ranchers to check the hay before feeding, especially in the summer.