For the love of you pet: Tips for best parasite control for horses

By Shana Bohac
Nov. 21, 2013 at 5:21 a.m.

I used to tube worm my horse, but I have been hearing that this is not the best method of deworming. What is the best dewormer to use, and how often should I be deworming my horse?

Effective internal parasite control is an important aspect for any horse owner. Parasites can negatively affect your horses' health in many ways. Common problems associated with parasite overload include diarrhea, weakness, anemia, muscle wasting, colic, rough hair coat, slow growth, pot-bellied appearance, lethargy and weight loss.

There are several changes that have been made in the world of parasite control over the last few decades. The reasons for this change include a shift in the most common parasites seen and reduced effectiveness of popular drugs.

Deworming via a stomach tube used to be a common practice, however this technique has fallen out of favor. Not only does it require a trip to your veterinarian, but it also is a not-so-fun experience for your horse.

The medication used for tube worming has significant parasite resistance. This means that parasites are no longer being killed; therefore, it is a waste of your time and money.

The previous practice was for some horse owners to deworm every six to eight weeks, with rotating medications. This may be a great way to keep you on schedule; however, this is no longer an appropriate treatment plan simply because the most common parasites have shifted.

Large strongyles used to be the primary problem in our horses, but in recent years, small strongyles and tapeworms are more significant and prevalent. The six- to eight-week protocol was designed around the large strongyle life cycle.

Overuse of the dewormers has caused widespread resistance in some parasite populations. This could become a touchy situation since there are only a few drugs currently available for deworming. If we are not cautious, we could be left with no effective drugs.

The best way to approach deworming is to do it only when necessary and with the proper medications. Ideally, you should use a fecal egg count to determine which dewormer is needed and how frequently you need to deworm. Your local veterinarian can evaluate a fresh fecal sample and determine whether your horses are low, moderate or high shedders.

With this protocol, you will only need to deworm moderate or high shedders. The goal is to reduce the amount of dewormers given to your horse and to determine resistance in your horse herd. You can then eliminate all drugs that are no longer effective.

A basic plan is to deworm twice a year using your fecal egg count to determine which worms are most prevalent in your pasture. A follow-up fecal egg count will allow you to see if your drug of choice is truly effective. In the long run, this should save you time and money.

If you have any inquiry regarding parasite control, fecal egg counts or any questions regarding your pet's health, please contact me at

Dr. Shana Bohac has a veterinary practice at Hillcrest Animal Hospital in Victoria. She works on both small animals and equine patients. Submit questions to



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