Fenbendazole for Deworming a Horse

Internal parasites can cause colic as well as respiratory digestive problems in a horse. Deworming programs are necessary to ensure the health of your horse. Most horses should be dewormed every six to eight weeks, with the exception of foals under one year of age or older horses. Parasites, especially small strongyles, can develop resistance to dewormers, making it important to rotate the dewormer you use on a regular basis. Whether your program includes rotation or not, fenbendazole is an important part of the deworming process.

  1. Fenbendazole

    • Fenbendazole is one of the safest dewormers for horses on the market. Fenbendazole belongs to the benzimidazole class of dewormers. Benzimidazoles work by disturbing the energy metabolism of the worm on a cellular level. This is a much more basic mode of attack than other dewormers on the market, allowing fenbendazole to kill nematode eggs that other dewormers can’t. Benzimidazoles are most effective when given several days in a row.

    Uses

    • Fenbendazole is effective against redworms, pinworms, roundworms, stomach hair worms and large-mouthed stomach worms. Used against small strongyles, a fenbendazole purge can be more effective than other dewormers. Fenbendazole has an extremely high safety margin. You would have to give 100 times more than the recommended dosage to cause toxicity in a horse.

    Directions

    • Fenbendazole can be given as a one-time paste or a daily pellet. One syringe of paste will typically deworm a 2,500 pound horse. Standard dosage is 2.3 milligrams per pound. To use the one-time paste, set the provided syringe to the appropriate weight-based dose, insert it into your horse’s mouth and push the plunger all the way down. Try to make sure the horse swallows all of the paste. To use the daily pellet, mix the appropriate dose for your horse’s weight into his grain. To complete a fenbendazole purge, give the dewormer every day for five days in a row or as directed by your veterinarian.

    Pregnant Mares and Foals

    • Not all dewormers are safe for pregnant mares and foals, but fenbendazole can be used. Fenbendazole has been proven safe for both foals and pregnant mares at doses up to 11.4 milligrams per pound, almost five times the standard dose. However, you should always give the recommended dose to your pregnant mare or foal, or check with your veterinarian if you feel more is needed.

    Side Effects

    • Fenbendazole typically only becomes toxic at doses 100 times greater than the standard dose. However, a high level of parasite die-off can cause an inflammatory reaction. Multitudes of dead parasites release toxins in your horse’s body, leading to possible colic, laminitis or body-wide inflamation. If you suspect your horse is heavily invested with parasites, consult your veterinarian before treating your horse with dewormer. You may want to ask your vet about keeping banamine, a non-steroidal anti-inflammatory, on hand in case your horse does have a reaction.