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Spring Has Arrived Which Means…It’s Time for Horse Deworming!

Last updated on April 12, 2024

Spring Has Arrived Which Means…It’s Time for Horse Deworming!

We all know regular horse deworming is a key component of your horse’s overall health. But have you ever stopped to think about WHY and HOW horses pick up parasites and worms? Do you know what it looks like to have parasites overrun your horse’s digestive system? Or how to restore their health after that happens? It’s a pretty unpleasant subject to think about, much less read about, but we think it’s super important. So in an effort to be the best horse owners we can be, we went down a deep research wormhole (see what we did there?) to bring you aaaallll the information on the ins and outs of horse deworming you could possibly ever want. 

Common Parasitic Infections for Horses

Parasites are organisms that feed off a host organism to the detriment of the host. Numerous types of internal parasites can infect a horse and cause serious health problems if not addressed immediately. The most common ones include strongyles, acarids, pinworms, tapeworms, and bots. [1]

​While most horse owners have integrated deworming into their horse care program, there is always more to learn, and increased availability of fecal count and new research in recent years may change your approach to your parasite control program. 


There are both large and small strongyles. The larvae live in pasture grasses and are ingested through the horse’s mouth, where they make their way through the body. Some species of large strongyles are commonly called bloodworms since they disrupt blood flow in the vessels and arteries. Small strongyle larvae don’t migrate but rather burrow into the large colon, where they can stay for up to 2 years until conditions are ideal to release eggs. According to Pennsylvania State University Extension Office, it’s assumed that all grazing adult horses are infected with small strongyles which is one of the reasons deworming schedule recommendations have changed over the last decade. [2]


Ascarids are roundworms that primarily affect young horses as immunity to acarids happens around the first year of life. They can be found not just in pastures and contaminated soil, but on other surfaces like buckets and stalls. Heavy ascarid load can cause respiratory infections known as “summer colds” in foals. [3]


These are not considered intestinal parasites but rather travel through the digestive tract and lay eggs outside of the horse’s body around the anus. This causes itching and discomfort, making the horse rub its tail vigorously enough to lose hair. [4


Tapeworms use two hosts during their life cycle. Oribatid mites eat the tapeworm eggs, hatching them to larvae. Then the horse ingests the mites while grazing and the larvae move to the small intestine where they mature into a tapeworm. Mature tapeworms will continue to move throughout the intestine until they attach to the intestinal wall, causing inflammation and sometimes colic. [5]


Often called stomach bots, these parasites are both external and internal. According to the Merck Veterinary Manual, “Three common species are distributed worldwide, and a number of others are found in parts of Europe, Africa, and Asia. The adult flies lay eggs that stick to the hairs of the horse’s body. When the larvae hatch, they crawl or are carried by the tongue (after grooming) into the mouth. The larvae stay embedded in the tongue or the lining of the mouth for about 1 month, after which they pass to the stomach, where they attach themselves.” 

Symptoms of a Parasite Infection

Each type of worm or parasite has different symptoms and problems, but there are common signs to be on the lookout for. If your horse has a large parasitic burden (too much for its body to handle), the nutrients it ingests will be taken by the parasites and not the horse’s body. Obviously pretty problematic right? As mentioned above, there are also external parasites that can cause hair loss, skin issues, and swelling. Some worms can live in the horse’s body for a considerable amount of time before your horse shows symptoms, although the damage is still being done on the inside. This is why it’s incredibly important to stay consistent with your horse deworming schedule. Some clinical signs of a large parasite load include:

  • distended belly
  • weight loss
  • lethargy/decreased stamina
  • dull/patchy coat and hair
  • tail rubbing
  • colic
  • coughing
  • rapid change in body weight or composition
  • diarrhea [6]

If you notice these symptoms in your horse, contact your veterinarian right away to begin a fecal egg count test and decide on a deworming medication that will work best for your situation. Horses that have struggled with a high parasite population for an extended amount of time, may need a more aggressive and strategic deworming plan. Again, fecal testing should reveal the specific parasites that your horse is dealing with, so that you can lay out a plan to help your horse recover optimum health. 

Horse Deworming Is Key To Prevention

The number one way to prevent worms is by establishing a regular horse deworming schedule (but you already knew that). Getting a fecal egg count test to determine the amount and type of parasites in your horse helps your vet determine exactly which dewormer product to recommend for your specific deworming program. For horses that are low shedders (meaning there’s a small amount of eggs present in their manure), it’s most likely you will only have to deworm twice a year, usually in early spring and late fall. For high shedders, deworming more frequently is probably in the best interest of your horse (and the rest of the herd). However, performance horses that travel often for competition are at greater risk of exposure to a wider variety of parasites and may need to be dewormed at more regular intervals. 

A Targeted Approach is Best

Knowing, and medicating against, exactly which types of parasites your horse is fighting is extremely important. A targeted antiparasitic medication not only lessens the parasitic burden in your horse but also prevents the parasites from becoming drug-resistant. Blanket deworming can lessen the effectiveness of dewormers, which can be detrimental to the health of all horses and other livestock. Work closely with your vet to determine the best deworming products and schedule for your horses.  [7]

(For more information on the different types of deworming medicines and which parasites they target, check out this article from the University of Minnesota Extension Office.)

Aside from a regular deworming schedule, making sure that manure is properly cleaned up and disposed of in grazing areas and stalls greatly reduces the parasitic population. This is especially important when traveling for competitions, as your horse will be around numerous other unfamiliar horses and their little wormy “buddies.” 

It’s also important to note that the goal is not a zero fecal egg count. Due to the nature of, well nature, achieving a zero egg count when your veterinarian conducts a fecal exam is impossible.  You just want to keep the parasitic burden low enough that it does not cause health issues and overburden their immune systems. 

How to Recover From a Heavy Worm Burden

After discovering a heavy burden, and administering the appropriate horse dewormer, focus on GUT HEALTH! A healthy digestive system will make it hard for parasites to thrive and repopulate and allow the horse to get the nutrients instead of the parasites. As a standard practice, we always suggest feeding Foundation Daily Detox and NuTrack Digestive Support together. The detox flushes the system of all toxins, allowing organs and systems to function properly. In fact, many religious FDD and NuTrack users report having to deworm their horses less often than before with faithful use of FDD and NuTrack. Bonus: the diatomaceous earth in the ingredients is a fantastic all-natural insect and parasite killer.  NuTrack is packed full of amino acids that aid in healthy digestion and proper nutrient absorption, which is critical after a severe parasitic infection.

(To read more about how these two products work within the body, read “Do I Need to Detox my Horse?” and “Amino Acids for Horses: What They Are and Why They’re Important”)

Allow ample time for your horse to fully recover from their infection, with an emphasis on nutrition and not overdoing it before their body is ready.

A Healthy Horse is a Happy Horse

Horse deworming is a vital part of keeping your horse healthy and fit for competition! They can’t run their hardest when all of their energy and nutrients are literally being sucked from them. Keeping your horses’ environment as clean and dry as possible, getting on a regular deworming schedule, and working with your vet to monitor the amount and types of parasites in your horse’s fecal sample are the keys to keeping them healthy and (mostly) worm free. Deworming is quick and relatively easy but has potentially severe repercussions if it doesn’t get done. 

You can order FDD and NuTrack straight from our website, or contact your local dealer. If you are interested in becoming an authorized AE dealer, please contact Mark Kaylor at (509) 301-1798 to start the process! We’d love to have you join the team. 

All content is intended for informational purposes only. Please consult with your veterinarian. Proudly written for Animal Element by the team at

FAQ’s About Horse Deworming:

When is the best time to deworm?
According to the James L. Voss Veterinary Teaching Hospital at CSU, for low shedders, it’s recommended to deworm in the spring with an Ivermectin product and moxidectin, and again in the fall (generally after the first frost). The frequency will change depending on the amount of eggs present in your horse’s fecal sample. To read more about deworming schedules and products, check out the article from CSU. 

Are antiparasitic drugs helpful?
When used properly antiparasitic drugs (dewormers) can be key to ridding a horse of potentially dangerous worms and parasites. However, they can be damaging to the environment if not administered and disposed of properly. Blanket deworming can also cause antihelmintic resistance in parasites. So it is important to work with your vet to determine which dewormers to use and when.

What are the most common active ingredients in the different horse dewormers?
The ingredients and dewormer you use will depend on the type of parasite you are trying to kill. The most common active ingredients for an equine dewormer are ivermectin, moxidectin, pyrantel pamoate, piperazine, oxibendazole, and fenbendazole.

How long does it take to kill off adult worms?
How quickly the parasites are killed depends on the burden, the type of parasites, and the dewormer used. Some dewormers start killing right away, others take a few days to weeks to kill off the parasites. It’s recommended to do another fecal sample 14 days after deworming to check on the effectiveness of the dewormer used. 

Does a horse’s age come into play with deworming?
Young horses (0-3 years) and geriatric horses (20+ years) are more susceptible to heavy parasite burdens. Foals and senior horses should be dewormed more frequently than other horses.


  1. Smarsh, Danielle “Prevalent Parasites: Common Types of Equine Internal Parasites.” Penn State University Extension Office, April 2024. Accessed online at on April 8, 2024
  2. Smarsh, Danielle “Prevalent Parasites: Common Types of Equine Internal Parasites.” Penn State University Extension Office, April 2024. Accessed online at on April 8, 2024
  3. Klei, Thomas “Gastrointestinal Parasites of Horses.” Merck Veterinary Manual, May 2019. Accessed online at on April 8, 2024
  4. Smarsh, Danielle “Prevalent Parasites: Common Types of Equine Internal Parasites.” Penn State University Extension Office, April 2024. Accessed online at on April 8, 2024
  5. Smarsh, Danielle “Prevalent Parasites: Common Types of Equine Internal Parasites.” Penn State University Extension Office, April 2024. Accessed online at on April 8, 2024
  6. Hiney, Kris & Elizabeth J. Giedt “Common Internal Parasites of the Horse.” Oklahoma State University Extension Office, March 2017. Accessed online at on April 8, 2024
  7. “Worms: How to Control Them in Horses.” World Horse Welfare. Accessed online at on April 8, 2024