Resistance to equine deworming medication has been a concern for the last few decades; the newest dewormer was invented in the 1960s and no new deworming medication is on the horizon. With many horse owners sticking to scheduled deworming protocol instead of performing fecal tests to determine the worm burden in each horse as an individual, the threat of parasite resistance is very real.
The United States Food and Drug Administration (FDA) has requested that animal drug companies revise product labels on equine and other livestock antiparasitics in the next 12 months to include information about parasite resistance. While susceptible worms die with the administration of dewormers, the parasites that survive pass on the resistant genes to their offspring.
As horse are grazing animals, they are continually exposed to worm eggs while turned out on pasture. Horses with heavy worm loads may have weight loss, anemia and diarrhea; some may die from the parasites.
Dewormers are over-the-counter medications; as such they are required to have labels that are easily understood by non-veterinarians. The FDA is requesting that the new labels include these points:
- Dewormers are only one part of a comprehensive internal parasite control program
- Proper dosing is critical
- Any use of a dewormer can result in resistance
- Horse owners should work in conjunction with their veterinarian to monitor antiparasitic resistance
It is hoped that the new labels will assist horse owners in the proper use of dewormers to monitor and slow parasitic resistance. The labels are not intended to replace the involvement of a veterinarian to help determine the most effective combination of parasite control.
Read more at BloodHorse.
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