How to Deworm Your Horse
Deworming your horse should be based on fecal egg count (FEC) results. This applies to all ages and breeds of horses. Our goal is to MINIMIZE how often we are using a deworming product for most horses.
Recent research into the current status of the effectiveness of our equine deworming products has revealed increased RESISTANCE to ALL of our available drugs. For instance:
- Benzimidazoles (this includes Panacur and Anthelcide): All studies show resistance amongst strongyle parasites and 3 out of 13 studies show reduced efficacy against ascarids. *Also the PowerPac shows resistance at all larval stages meaning a 5 day Panacur treatment no longer is effective against encysted strongyles.
- Pyrimidines (Pyrantel, Strongid): 34 out of 37 studies showed NO EFFICACY of this type of drug against strongyles. Resistance of ascarids was observed in 4 out of 16 studies.
- Macrocyclic lactones (Ivermectin, Moxidectin-which is Quest): 13 out of 57 studies showed resistance amongst strongyles. NO EFFICACY against ascarids or pinworms in 29 different studies.
- Praziquantel- Typically this is our only drug that has had any effectiveness against tapeworms. Now in highly concentrated areas (like Kentucky) NO EFFICACY is observed in horse populations. They are seeing HIGHER egg counts after treatment than before treatment.
ADDITIONALLY egg reappearance periods are decreasing. Meaning the amount of time that the horse is shedding low parasite counts after a deworming is becoming SHORTER. The parasites are reaching mature and reproductive stages faster than in the past.
NEEDLESS TO SAY this is all incredibly concerning. Experts state that "heavy intensity of deworming over the past decade has selected not only for drug resistance but also for strains of parasites with shorter life cycles that give them a survival advantage by increased egg production in a shorter time frame" (source EquiManagement Spring 2024)
WHAT CAN YOU DO?
Here is a short list of important steps you can take to help decrease your contribution to resistance and to protect your horse.....
1. STOP BUYING DEWORMER AT RANDOM FROM THE STORE AND GIVING IT WITH NO MEDICAL GUIDANCE. Deworming every other month or 4 times per year is no longer appropriate.
2. GET A FECAL EGG COUNT PERFORMED or even better, a fecal egg count reduction test. These tests help us classify your horse into a high, moderate or low shedder category. A reduction test allows us to actually see if the dewormer you used was effective. And please remember that susceptibility to parasites is INDIVIDUAL. We need to test every member of the herd. One animal is not representative of a herd.
3. ENVIRONMENTAL MANAGEMENT: Parasites are primarily transmitted via ingestion of feces. If you clean up manure regularly, drag and rest pastures, avoid overcrowding, and keep feed sources away from manure, you can reduce exposure.
It is important to note that ZERO PARASITES IS NOT THE GOAL. Reducing high shedders and limiting exposure of vulnerable populations (young, old and ill) is the most important. Again, we emphasize that it is imperative that a veterinarian be involved in the deworming plan of your horse or herd of horses. We are able to take into account your horse's individual risk factors as well as the environment that they are in to help you use dewormers effectively and appropriately. Please call us for help.
Deworming Recommendations (Based on FEC result)
Low Shedder (FEC Less than 200)
Fall: Ivermectin or Moxidectin plus Praziquantel (Equimax or Quest PLUS)
- Perform FEC at least once per year
Moderate Shedder (FEC 200-500)
Spring: Panacur
Fall: Ivermectin or Moxidectin plus Praziquantel (Equimax or Quest PLUS)
- Perform FEC twice per year (spring and fall)
High Shedder (FEC greater than 500)
Deworm according to your veterinarian’s recommendations
- Perform FEC 2-3 times per year (spring, summer and fall)