Horses and dogs get many of the same worms. Although horse dewormers are cheaper on a per-pound treatment basis, they are not designed for nor recommended to use on your dog.
The most common horse wormer used for dogs is ivermectin. It is also given to dogs for mange and in dog heartworm medications.
One of the main issues of using horse dewormers on dogs is dosage. Ivermectin for horses is usually in paste form at 8.7 mg/ml. For dogs the medicine is in oral pill form at 0.003 to 0.006 mg/kg.
Using horse wormer on your dog is dangerous. Collies and collie mixes are the most sensitive to poisoning. Ivermectin toxicosis is caused by giving a dog too much ivermectin or using wormer for other species on your dog. The symptoms include blindness, coma, depression, stupor, tremors, drooling and death.
Do not use wormers for horses on your dog. Do not allow your dog to be around horses or cattle that have recently been wormed and make sure all used tubes are safely disposed of. Juli Torson, editor/associate publisher of Horse and Rider, says that even one-fourth teaspoon dropped from the animal’s mouth or in a discarded tube is enough to hurt your dog.
If your dog is poisoned there is no antidote for ivermectin toxicosis. Your dog can be hospitalized, given fluids, medications and other treatment to help decrease reaction.