Readers Share Experiences with Parasite Resistance

More than 280 readers of responded to a poll asking, "Have you experienced parasite resistance to anthelmintics with your deworming program?"

results of poll on resistance to deworming

Results were as follows: 

  • No: 59.64% (167)
  • I don't know: 30.00% (84)
  • Yes: 10.36% (29)

Readers shared their experiences with parasite resistance in the comments below.

Results of weekly polls from are published in The Horse Health E-Newsletter. Published every week, this e-newsletter offers news on diseases, veterinary research, health events, and in-depth articles on common equine health conditions and what you can do to recognize, avoid, or treat them. Sign up for our e-newsletters using the form above or on our e-newsletter page.  

Poll sponsored by Intervet Schering-Plough Animal Health.

Look for a new poll on every week!

  • Seems that Panacur and Strongid don't work anymore. Never knew until we tested.
  • No problems with worms BUT the horseflies are totally resistant to every spray I can find this year!
  • No resistance to date....
  • every other month rotation worming
  • My horses have not needed to be wormed in 8-9 years, so probably not.
  • ERP is 6-8 week in small strongyle but I do not have previous data about ERP,so can not say itshort
  • my horse do not show parasite in testing
  • I do rotational deworming, so far, so good.
  • very low key, Ivermectin is mostly still effective
  • But closed herd. No travel. No issues.
  • Negative fecal counts. Why worm when you don't have too. Only worm when needed.
  • Roundworm resistance to ivermectin products in foals
  • developed a resistance to ivermectin
  • I had a horse colic due to encysted strongyles, despite a typical rotation program
  • I now do rotational worming--hope it helps to prevent parasite resistance
  • I do not worm unless the egg count warrants it.
  • We worm daily with strongid C2X, and paste worm 2 times a year with great results.
  • I home test before using or not using anthelmintics
  • most especially ivermectin
  • FEC are essentially 0
  • Just did fecals and we're good.
  • now vet recommends fecal egg counts/my horses heavy egg shedders
  • Living in Houston,TX. we must rotationally worm monthly in the hot months.
  • how do you find out?
  • My fecal egg counts were negative on both my horses,.
  • low incidence of resistance to ivermectin
  • I use a fecal egg count program in order to avoid resistance to deworming products.
  • not yet, but I am concerned about it!
  • I am lucky to have a great veterinaian.
  • But I expect it to happen fairly soon now.
  • Thankfully, no
  • doing FECs to (hopefully) prevent resistance
  • We only worm if a stool sample comes back positive for worms. It's been 2 years now and no worms.
  • pinworms three years ago , had dewormed two yearlings every 8 weeks with ivermectrin and another
  • Exams by equine hospital show our deworming program (rotation) is effective.
  • I do rotational worming that is very effective.
  • I do rotational worming that is very effective.
  • bith roundworms and strongyles unaffected by ivermectin

About the Author

Megan Arszman

Megan Arszman received a Bachelor of Science In print journalism and equine science from Murray State University in Murray, Ky., and loves combining her love of horses, photography, and writing. In her “free time,” when she’s not busy working as a horse show secretary or riding her American Quarter Horses on her parents’ Indiana farm, she’s training and competing her Pembroke Welsh Corgi and Swedish Vallhund in dog agility and running.

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