Deworming

Recommendations for Equine Deworming & Fecal Egg Counts

A fecal egg count (FEC) is used to estimate a horse’s parasite burden and therefore helps us to make recommendations on how often that horse should be dewormed in a year. A FEC consists of collecting 2-3 fresh fecal balls and examining the sample under a microscope at the clinic. This test can be performed preferably on fresh manure or fresh samples that have been stored in a air-tight container in the refrigerator for up to 3 days. A deworming program utilizing fecal egg counts can save you money and allow the use of less dewormer.

When to perform a FEC:

• Twice yearly for every horse on the farm prior to deworming
• Testing new horses before introducing to the farm
• Testing the efficacy of a deworming product in a high shedding horse

Horses are placed into 3 main categories based on their FEC results:

1. A “low shedder” has 200 eggs per gram (epg or less)
   • Typically needs to be dewormed twice a year (spring & fall)
     • Spring – Ivermectin (Equell, Zimecterin, Bimectin) or Moxidectin (Quest)
     • Fall – (after first frost) – Ivermectin with Praziquantel (Equimax, Zimecterin Gold) or Moxidectin with Praziquantel (Quest Plus)
2. A “moderate shedder” has 200-500 epg
   • Typically needs to be dewormed 3-4 times per year
     • Spring – Ivermectin (Equell, Zimecterin, Bimectin) or Moxidectin (Quest)
     • Late Summer – Pyrantel Pamoate (Strongid), Fenbendazole (Panacur), or Oxibendazole (Anthelcide)
     • Fall – (after first frost) – Ivermectin with Praziquantel (Equimax, Zimecterin Gold) or Moxidectin with Praziquantel (Quest Plus)
3. A “high shedder” has >500 epg
   • Typically needs to be dewormed 4-6 times a year (potentially every 2 months)
     • Spring – Ivermectin (Equell, Zimecterin, Bimectin) or Moxidectin (Quest)
     • Late Summer – Pyrantel Pamoate (Strongid) or Fenbendazole (Panacur) or Oxibendazole (Anthelcide)
     • Fall – (after first frost) – Ivermectin with Praziquantel (Equimax, Zimecterin Gold) or Moxidectin with Praziquantel (Quest Plus)
     • Winter – Pyrantel Pamoate (Strongid) or Fenbendazole (Panacur) or Oxibendazole (Anthelcide)
     • Recommended to perform a fecal egg count reduction test (FECRT) 14 days after deworming for horses with a FEC > 1000 epg

Deworming Protocol Guidelines:

1. Performing a fecal egg count (FEC)
   • To provide the greatest information about an individual horse’s parasite burden, it is important to know when the horse was last dewormed and what product was used.
   • For Moxidectin (Quest products) – it should be 16 weeks or more since the horse was last dewormed to perform a FEC
   • For Ivermectin (Zimecterin or Equimax products) – it should be 12 weeks or more since the horse was last dewormed to perform a FEC
   • For Fenbendazole (Panacur) or Pyrantel (Strongid) – it should be 9 weeks or more since the horse was last dewormed to perform a FEC
2. Testing the efficacy of a deworming product
   • Performing a fecal egg count reduction test (FECRT) is recommended for horses with a FEC > 1000 epg. The worm count should decrease by 90% when a FEC is repeated 14 days after a deworming product is administered
3. Pasture management
   • Remove manure frequently
   • Rotate pastures
   • Harrow/drag pastures in hot weather and keep horses off pasture for 2 months
   • Avoid overstocking pastures

Additional Recommendations:

• All horses should be dewormed for tapeworms at least once per year with a Praziquantel containing product. This is ideally done in late fall after a frost.
• It is important to deworm horses on an accurate weight estimate with a weight tape. This is especially important for very large or small horses/foals to avoid under or over dosing; bigger horses may need more than one tube.
• All horses should be treated for encysted strongyles once per year. We recommend a Panacur PowerPac or Quest/Quest Plus.
• To deworm for bots, an Ivermectin or Moxidectin product given in the fall is effective.
• Take extra care when deworming your horses if you have dogs that may have the MDR-1 gene mutation that is present in some Collies, Aussies and a few other breeds. Dogs with this mutation are sensitive to Ivermectin and Moxidectin which can cause neurological signs and death. Be sure to properly dispose of deworming tubes, clean up any dropped paste, and don’t let your dog have access to horse manure for 72 hours post deworming.
• For more information you can visit aaep.org and click on Parasite Control Guidelines.

Mare & Foal Deworming

Recommendations:

• Pregnant Mares:
  • Deworm as usual for beginning of pregnancy, but when the last set of pre-foaling vaccines are administered at 4-6 weeks pre-foaling, please deworm with a product containing an Ivermectin with Praziquantel (Equimax) or Moxidectin with Praziquantel (Quest Plus)
• Foal Schedule: *important to dose off of weight
  • 2 months of age – Fenbendazole (double dose of Panacur or SafeGard)
  • 4-5 months – Pyrantel Pamoate (Strongid)
  • 6 months – Ivermectin with Praziquantel (Equimax or Zimecterin Gold)
  • 8-9 months – Fenbendazole (double dose of Panacur or SafeGard)
  • 10 months – Ivermectin (Zimecterin)
  • 12 months – Pyrantel Pamoate (Strongid)

General Deworming Goals:

• A few worms are OK. Today’s deworming strategies focus on keeping parasite burdens below harmful levels, treating clinically affected horses and reducing the transmission of parasites. Our goal is NOT to eliminate all parasites from an individual horse. In this manner, a population of susceptible parasites is maintained to dilute the resistant genes in the population. Equine parasite resistance is a real threat, therefore it is crucial that we try to maintain the effectiveness of the drugs that we have now.
• Identify high shedders. Conventional deworming strategies over-treat many horses, but under-treat high shedders. High shedding individuals have less natural immunity to internal parasites than others. While high shedders only account for 20% of the horse population, they produce 80% of the parasite eggs on the pasture. High shedders need to be dewormed more often than their low-shedding herd mates, which is why it is important to utilize FEC testing to identify them.

As every horse is unique, it is best to work with your veterinarian to develop the ideal deworming program for your horse!