Four Horses Dead, One Ill; Dewormer Questioned

Four horses on a South Texas farm died from unknown causes in February; one horse is recovering. The horses' owner suspects the problems might have been caused by a dewormer; she has necropsy and other test results, but she has not released them. The dewormer's manufacturer found nothing unusual about the product lot in question, and it has notified the FDA of the complaint.

On Feb. 16, Kerry (who wanted her last name withheld), noticed five of her horses were lethargic, feverish, drooling, and unable to eat and drink. She called her veterinarian.

The horse's signs progressed in 24 hours to include head pressing, ataxia (incoordination), muscle trembling, sweating, disorientation, drooling, and lateral recumbency (inability to rise).

Four days after the first clinical signs, four horses had died, but the fifth was improving.

Kerry worried her other horses might be in danger, so she began examining her farm for the source of the illness. "We tested the grain, the water, the weeds in the field," Kerry said. All tests came back normal.

"The only difference in the horses (those alive and dead) is the dewormer," she said. The day before the horses became ill, she dewormed them with a generic ivermectin brand (Bimectin). Kerry notified Bimeda, the manufacturer, of her suspicion.

Bimeda tested samples from the lot and released a state-ment that said the company "conducted potency testing on retention samples of Lot 5J019, and the results were found to be normal and within the original lot release potency specifications."

According to Bimedia, around 58,000 doses from Lot 5J019 have been distributed throughout the United States, with no other reports of safety or efficacy issues. However, Bimedia has offered to replace products from Lot 5J019 with those from another lot.

Two retailers that offered Bimectin--Country Supply and Jeffers--temporarily suspended sale of the product until Bimeda could test the product. Both companies resumed sales (with the exception of Lot 5J019) after Bimeda released its test results. For more information see

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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