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What You Need to Know About Horse Colic and Worms

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I've always had a horse in my life, I don't feel complete without one. I enjoy sharing what I have learned over the years to help others.

Horse With Colic Rolling

Horse With Colic Rolling


I've always had a horse in my life. I'm not complete without one. One thing I was taught early on was to keep a regular worming schedule for my horses. A worming schedule is as important for your horse as providing clean water. It's not an option, it's a part of keeping a horse.

Another part of keeping a horse is the concern for colic. Worms, oftentimes, are the source of colic, especially for horses in a pasture. Implementing a regular worming schedule for your horse(s) will eliminate or greatly reduce the chance of your horse developing colic from worms.

If you have a horse suffering from colic and you have a regular worming schedule in place, you will need to explore various causes that are not worm-related. This article is written for the horse person that does not regularly worm their horse or does not know that worming needs to be a part of their regular grooming chore.

Type of Worms That Infect Horses and When

Type Of WormSeasonSymptomTreatment


Spring and Summer

Sudden weight loss, diarrhea, rumbling in stomach.

Ivermectin (kills large and small strongyles), Moxidectin (large only)

Ascarids (Roundworm)

Year round

Mostly in foals

Pyrantel Pamoate, Moxidectin

Stomach Worm

Year round

Coughing, nasal discharge. Foals mostly.

Fenbendezole, Ivermectin


Year round





Intense itching

Ivermectin, Moxidectin


Late Summer & Early Fall

Indicated by small light yellow eggs mostly on legs.


Horse Owner Responsibility

If you decide you are going to have a horse or several horses, as a responsible horse owner, you must implement a worming schedule for your horses. You can find literally hundreds, if not thousands, of worming schedules online. The most important thing to remember is to have a fecal egg count performed in the Spring and Fall. This is a routine count to determine how infested the horse is (Spring), and whether the treatment is working (Fall).

I have found the following schedule to work well for horses I've cared for. My horses have always lived in California, so if you live in an area where the climate differs, adjust the schedule accordingly.

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  • Spring (March): Use an Ivermectin, or moxidectin, based wormer. Or use a double-dose of fenbendazole for five days.
  • Late Summer (July): Pyrantel pamoate, fenbendazole.
  • Early Winter (November): Ivermectin with praziquantel, or moxidectin with praziquantel. (If using brand name Zimectrin make sure to use the GOLD brand.)

Worming Schedule for Foals

A worming schedule for foals is going to be different from a horse. In the first year, foals need to follow this worming schedule:

  • 2 months: Ivermectin
  • 5 months: Pyrantel Pamoate
  • 6 months: Moxidectin with praziquantel
  • 9 months: Fenbendazole
  • 10 months: Ivermectin
  • 12 months: Fenbendazole
Worm Schedule: Free to copy schedule.

Worm Schedule: Free to copy schedule.

Sample Worming Schedule

Horses kept in a paddock can be wormed less often, because they are not out grazing the pasture where worms and eggs are most often picked up. I don't personally like to have two different schedules for pasture and paddocked horses. The safest bet is to worm them all regularly.

The sample worming schedule above can be copied, or you can make your own. Once you fill in the horses' names, you can hang it on the office or barn wall. I suggest laminating it if it will be outdoors. When the horse is wormed, circle which product was administered and fill in the date. It makes keeping track of one, or multiple horses, a lot easier and your herd healthy!

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

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