Deworming your Horses

1. Determine FEC from group of horses grazing together
   • Minimum of 5 horses recommended (although can use FECRT on one horse)
   • Recommend counting as many parasite eggs as possible pre-treatment
     • 40 counted eggs/horse or more
2. Deworm horses
3. Determine FEC from the same individual horses at 14 days post treatment
4. Make an assessment of the percent reduction for the overall population
   • Unless only a single horse is tested, do NOT make interpretations for individual horses of the group tested
   • If the mean FECRT falls below expected levels, do these steps
     • Check storage conditions, expiration dates, dosage of product
     • Repeat treatment and determine new FEC at 14 days post treatment. If efficacy still falls below expected levels, it is strongly suggestive of anthelmintic resistance
     • Choose a different anthelmintic class and repeat exercise
     • If documented resistance for all available drug classes, use class w/ highest observed efficacy

• ERP = the time it takes from the date of an effective deworming in a group of horses w/ positive strongyles FEC until eggs can be found in the feces again.
• Only relevant for ivermectin and moxidectin.
  • Because resistance is widespread to the other two anthelmintic classes, which means that they most often do not effectively reduce strongyle FEC to begin with.
• Shortened ERP does not necessarily mean a sign of emerging resistance

Mature Horses (5-15 years old)

• Primary target= strongyles & tapeworms
• FECRT annually
  • Evaluate efficacy of products used on EACH OPERATION instead of individual horse
• Low shedders (<500 EPG)
  • 1-2 macrocyclic lactone treatments per year (ivermectin or moxidectin)
  • Include praziquantel in fall for tapeworms
• High shedders (>500EPG)
  • 1-2 additional treatments during “active transmission season” (May-September)
• For seniors (>15years), keep in mind that they can revert to high shedders
  • Especially if PPID

Young Horses ( < 5 years old)

• Primary targets = ascarids, strongyles, tapeworms
• FECRT yearly
  • Aim for around 4-6 months old for foals
  • Notes:
    • Treatment based on FEC is NOT recommended
    • For yearlings, FEC over 1000 EPG is normal
• 2-3 months old
  • Treat for ascarids with fenbendazole or oxibendazole at 10mg/kg orally once
• 5 months old
  • Treat for ascarids with fenbendazole or oxibendazole at 10mg/kg orally once
• 6-9 months old
  • Treat with macrocyclic lactone (for strongyles) + praziquantel (tapeworms)
  • +/- fenbendazole if ascarids on FEC
• Yearlings-5 years
  • Treat as high shedders
    • 3-4 macrocyclic lactone treatments
    • 1 praziquantel treatment in fall