Four horses outside of Hebbronville, Texas, died after they showed clinical signs of an unknown illness in February; one horse is recovering. The horses’ owner suspects the animals’ problems might have been caused by a dewormer, and she is awaiting necropsy and other test results. The company that manufactured the dewormer found nothing unusual about the product lot in question, and it has notified the Food and Drug Administration (FDA) of the owner’s complaint.

On the morning of Feb. 16, the horses’ owner, Kerry (who asked that her last name be withheld), noticed five of her horses were acting lethargic, developing fevers, and in some cases were drooling. She immediately contacted her veterinarian.

“They couldn’t eat or drink, though they would try to,” Kerry said. The horse’s symptoms progressed over the next 24 hours to include head pressing, staggering, muscle trembling, sweating, disorientation (they were bumping into things), and finally lateral recumbency (they were unable to rise).

“They would then go down and paddle their feet, and their eyes were glassy looking,” she said. “Once they went down like that, they couldn’t get up. They were like that until they died.” Four days after the first clinical signs, four horses had died, but the fifth showed signs of improvement