How Often Should You Deworm Your Horse?

1. Each horse should be dewormed every 6 months with an Ivermectin product (Spring and Fall). Ivermectin is a larvicidal (will kill parasite larvae), and if used every 6 months on each horse, large strongyles will be eliminated from your farm.

What is the best worming schedule for horses?

Traditionally horses have been dewormed every two months, but this has led to parasite resistance among horses. For this reason, we recommend performing Fecal Egg Counts (FEG) in the spring (ideally spring and fall) to determine the number of eggs a horse has in its manure.

Can you deworm a horse too much?

The active ingredient in a horse wormer kills the sensitive parasites in the population, but those parasites not affected go on to create new generations of resistant parasites. Frequent dosing or under-dosing can cause resistance to occur as can the effectiveness of the wormer.

Can you worm horses too often?

While different parasites can be beneficial to keep the gut healthy, an overload of worms can cause a wide variety of potentially dangerous problems for your horse. Setting a proper deworming schedule can help keep horses healthy and minimize the risk of spreading worm contamination.

What is a good deworming schedule for horses?

Rotation Deworming Schedule

  • 1January/February. Pyrantel.
  • 2March/April. Benzimidazole.
  • 3May/June. Ivermectin.
  • 4July/Aug. Pyrantel.
  • 5Sept/October. Benzimidazole.
  • 6November/December. Ivermectin.

What month do you worm horses?

All horses should be wormed in the late autumn with a combined round/tape wormer to remove bots, tapeworms and any adult roundworms. 4. For many horses once a year worming will be sufficient. Horses identified with higher worm burdens will need to be wormed more frequently.

How much does it cost to deworm a horse?

The cost is $12 for each quantitative fecal egg count and approximately $15.50 for each dewormer. Total yearly cost is $55.00 per year. Other horse owners prefer the older way to deworm a horse by administering a paste dewormer every 8 weeks at a cost of $93.00 per year.

What are the signs that a horse has worms?

Symptoms of worm infections in horses

  • Weight loss.
  • Colic.
  • Diarrhea or constipation.
  • Rough hair coat.
  • Poor growth in foals.
  • Respiratory problems. (nasal discharge, cough)

Can I deworm my horse twice?

Here are the basics: You will need to deworm all horses twice yearly (after the first frost and again in the spring) with an ivermectin or moxidectin product to kill large strongyles and bots.

What happens if you worm a horse twice?

Worming twice in two weeks won’t poison the horse. It is commonly done if a worming resistance test shows that the first wormer didn’t zap everything.

What shots do horses need yearly?

Summary. To recap, your horse should at least receive EWT/WN and Rabies vaccinations once a year. In general, we recommend that your horse receive EWT/WN, PHF/Rabies, Strangles, and Flu/Rhino in the Spring, and PHF and Flu/Rhino in the Fall.

How often should we Deworm?

Worms being a very common health problem for children and adults alike, experts recommend that deworming should get done twice a year or every six months, starting from the age of two years old. Deworming is the process that involves the use of medication to get rid of intestinal parasites like worms.

How soon after worming a horse can you worm again?

Many of the data sheets for wormers, notably those that contain praziquantel, ivermectin or moxidectin, advise stabling for two – three days after worming.

How often should horse teeth be floated?

Your horse should be examined and have a routine dental float at least once a year. Depending on your horse’s age, breed, history, and performance use, we may recommend that they be examined every 6 months.

What horse wormer should I use in June?

Summer (May-Aug): carry out FEC and worm if necessary with Fenbendazole, Ivermectin or Pyrantel.

What horse wormer kills all worms?

Prominent in this class, ivermectin is effective against adults of all the common equine parasites except tapeworms. It is also effective against some larvae and is credited with greatly reducing colic associated with the migrating larvae of Strongylus spp., but it does not kill encysted small strongyle larvae.

How Often Should I Deworm My Horses?

Internal parasites are a normal component of the digestive systems of horses. While certain parasites might be useful in maintaining the health of the intestine, an overabundance of worms can create a broad range of potentially serious difficulties for your horse’s health and wellbeing. Setting up a good deworming regimen can assist to keep horses healthy while also reducing the likelihood of worm infection spreading.

How Horses Get Worms

Worms are very easily picked up by horses. Feces from the animals’ grazing pastures include both mature worms and larvae, which are discovered in the feces. Horses ingest the worms and pass them back into their digestive tracts along with the grass they eat, so keeping the cycle alive and well. Even when kept in a stable, horses can become infected with worms through their manure, which can contaminate feed and bedding. Horses are susceptible to a number of different forms of worms, including bloodworms, roundworms, tapeworms, bots, and pinworms.

  • Increased appetite
  • Weight loss that occurs suddenly
  • A dull or out of condition coat
  • Lethargy
  • Anemia
  • Diarrheal obstruction
  • Intestinal blockage.

In extreme circumstances, symptoms might increase to the point where they are potentially lethal. Veterinary diagnosis is recommended if you believe your horse has worms. This will help you discover the particular type of worms implicated as well as the degree of contamination, which will help you develop an appropriate treatment strategy. To check for worms, a veterinarian will do a fecal examination or a blood test on the animal.

How Often to Deworm Your Horse

A single, perfect horse deworming program that will work for every animal in every environment or for every type of worm does not exist, nor will there ever be. Traditionally, deworming regimens included treatments every two months, with the types of dewormers being rotated to reduce the likelihood of parasites developing resistance to the chemicals. Some horses, on the other hand, can be kept in excellent condition by merely deworming them in the spring and fall. In some cases, other animals may require continuing deworming treatments to be given to their feed, particularly to avoid the reappearance of worms after the initial problem has been resolved.

  • As a result, animals that are extremely young or very elderly may require more frequent deworming since their internal barrier to contamination is more vulnerable
  • Optimal health: Horses in good overall condition may require fewer deworming treatments because they are better equipped to withstand the harmful effects of worms. Smaller herds may require less deworming than larger herds, which may unwittingly contaminate one another. Herd size is also important to consider. Poor Pasture Conditions: A filthy, tiny pasture is more likely to house higher populations of worms than a larger field that has been appropriately treated to reduce parasites. Pasture Management: Climate: Worms grow in warm, damp conditions, therefore horses in cooler, drier climates are less likely to require deworming on a regular basis. When Your Horse Comes into Touch with Unknown Horses: If your horse comes into contact with strange horses at shows or boarding facilities, more regular deworming treatments may be necessary.

Keeping Your Horse Worm-Free

Additionally, it is critical to create a regular deworming regimen for your horse and to take easy precautions to reduce the risk of worm infestation. This will allow you to use deworming treatments less regularly, which will prevent the parasites from becoming resistant to the deworming treatments in the future. In order to keep your horse free of worms.

  • Maintain a regular harrowing schedule in the pasture to break up manure and enable it to dry out, killing any worms or larvae that may be present. Mow the pasture frequently to expose the dung and worms to more direct sunlight and drier circumstances that are less conducive to worm growth and reproduction. Ensure that manure is dumped in a location that is separate from where your horse will feed or graze in order to reduce the possibility of contamination. If feasible, rotate pastures every few weeks, allowing each pasture to remain unused for 6-8 weeks before returning horses to the herd. Reduce the number of horses in each field at the same time to reduce waste and cross-contamination between animals. Elevated feeders should be used to prevent your horse’s feed from coming into touch with the ground or any surrounding dung, which might lead to contamination.

It is simple to maintain control over these troublesome parasites and to keep your horses healthy throughout the year by developing a deworming regimen that matches your animals’ needs and taking precautions to keep them worm-free.

Equine Deworming Schedule

Not many people are aware that horses have a low number of parasites in their digestive tracts all of the time, and that this is quite normal. The objective of parasite control in horses is to maintain a healthy balance in the number of parasites present so that we do not experience clinical signs (weight loss, colic), while at the same time avoiding the development of drug resistance. Horses have traditionally been dewormed every two months, however this has resulted in parasite resistance among horses as a result of the practice.

In order to assess the quantity of eggs present in a horse’s dung, we propose doing Fecal Egg Counts (FEG) in the spring (preferably, both spring and fall).

Red Hills Veterinary Hospital Recommends the Following Paste Deworming Protocol:

Unless otherwise stated, all egg count levels listed below are recommendations based on the average range of counts achieved using the McMaster procedure.


Prior to deworming in the spring, a fecal egg count is conducted (ideally spring and fall)

  • Ivermectin (Equell®, Zimectrin®, Rotectin®, IverCare®), moxidectin (Quest®)
  • SPRING (March) – ivermectin (Equell®, Zimectrin®, Rotectin®, IverCare®)
  • PREVENTION: Ivermectin with praziquantel (Equimax®, Zimectrin Gold®) or moxidectin with praziquantel (Quest Plus®) in the FALL (October).


Prior to deworming in the spring, a fecal egg count is conducted (ideally spring and fall)

  • In the spring (March), use ivermectin (such as Equell®, Zimectrin®, Rotectin®, IverCare®, and other brands), or moxidectin (such as Quest®)
  • In the late summer (July), use ivermectin
  • In the fall (October), use ivermectin w/praziquantel (such as Equimax®, Zimectrin Gold


Pre-deworming fecal egg counts are conducted before to deworming in the spring and fall to detect signs of resistance.

  • Before deworming in the spring and fall, a fecal egg count is performed to detect any signs of resistance.

In general, fecal egg counts should be used to assess therapy effectiveness. Unless otherwise specified, the treatment recommendations provided below are broad suggestions based on current medication resistance discoveries from throughout the world. It’s possible that other forms of dewormers will still be useful on your farm, and you can use them if you’ve determined that they’re successful through a fecal egg count reduction test.


  • Fenbendazole (Panacur) or oxibendazole (Anthelcide) for children under 2 months of age
  • Four to five months — Fecal egg count to track the incidence of ascarids vs strongyles in the stool. Fenbendazole (Panacur) or oxibendazole (Anthelcide) should be used to treat ascarid infestations. Strongyles should be treated with ivermectin after roughly 5 months. Use ivermectin and praziquantel to treat a tick infestation before the end of the calendar year. Assessing for the presence of ascarids in short yearling feces and treating those found with fenbendazole or oxibendazole should be done as soon as possible. Strongyles should be treated roughly three times with ivermectin throughout the yearling year, followed by one treatment with moxidectin + praziquantel towards the conclusion of the grazing season. Assays to determine treatment effectiveness include fecal egg count reduction tests.

When to Deworm your Horse – QUEST® and QUEST® PLUS

WHEN SHOULD YOUR HORSE BE DEWORMED? Every horse is a one-of-a-kind individual. Collaborate with your veterinarian to establish an Individualized Deworming TMprogram for your horse, which should begin with an examination of the fecal egg count (FEC). Establish a baseline fecal egg count for comparison purposes. An FEC test will establish the degree of parasite shedding that is currently present in your horse. The results of the FEC test reflect the number of parasite eggs in one gram. It is possible that less than 200 eggs per gram indicates a minimal danger.

Understand the risk factors associated with parasites in your horse.

These should be discussed with the veterinarian on your team.

  • Results of the FEC test
  • Horse’s age
  • Local climate
  • Manure removal
  • Pasture rotation
  • Pasture population
  • And more. Lush, overgrown, dry lot or a mix of these types of grassland
  • Feeding can be done individually or in groups, on or off the ground. Show/performance, recreation, and companionship are some of the ways horses are used. horses are moved throughout the property on a daily basis

Deworming Your Horse Should Be Individualized Following an evaluation of FEC shedding levels and your horse’s individual risk profile, you and your veterinarian will be able to build an Individualized Deworming regimen for your horse to meet his or her needs. Deworming treatments, which target important equine parasites of concern, are recommended by the American Association of Equine Practitioners (AAEP) for all horses in the spring and autumn, according to their guidelines. 1 The American Association of Equine Practitioners (AAEP) recommends high-risk deworming treatment strategies for young horses (ages 3 and younger).

  • QUEST ® is a single-dose treatment that efficiently cures and controls encysted tiny strongyles.
  • 2,*Autumn DEWORMING —Tapeworm therapy is advised once a year, in the late fall or early winter, when tapeworm transmission has ceased as a result of the winter’s chill.
  • It is possible that these two treatments are all that is required depending on your horse’s parasite risk factors.
  • Consult with your veterinarian to have a fecal egg count (FEC) test performed on your horse prior to purchasing a deworming medication.

Use of QUEST Gel or QUEST PLUS Gel in foals younger than 6 months of age, as well as in ill, debilitated, and underweight horses, is not recommended. It is not recommended for usage in other animal species due to the possibility of serious adverse responses, including deaths in dogs.

13 guidelines to follow when deworming horses

Equine practitioners are particularly concerned with the control of internal parasites in their patients. The availability of readily available, easily administered, and effective deworming agents, combined with the recognition that a specific parasite, S. vulgaris, can cause a destructive colic problem (verminous arteritis), has resulted in a deworming frenzy, particularly among horse owners and breeders of horses. Parasite resistance, which has developed in part as a result of the frequent deworming, has become a big concern.

  1. Because of prior deworming procedures, parasites that were formerly a major source of worry, such as S.
  2. With adult horses, the focus is currently on small strongyles (cyathostomins), with tapeworms and other parasites thrown in for good measure.
  3. At this time, it is recommended that horses should only be treated if they exhibit indications of a high parasite load.
  4. Due to the fact that horses with a high degree of immunity do not shed many eggs, deworming all horses on the same timetable is not a good idea.
  5. Internal parasites are not efficiently controlled by deworming every couple of months, switching dewormers each time, or deworming every other year, among other methods.
  6. While it was originally the objective to completely eliminate all parasites from a single horse, this is now unachievable.
  7. Some general guidelines are as follows: 1.Horses, particularly those older than three years old, should be handled as individuals rather than as part of a herd or as part of a routine.
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If the horse lives alone or in a stable, the frequency of the visits may be reduced or eliminated altogether.

Acaricides such as pyrantel, fenbendazole, and oxibendazole are effective in the treatment of ascarids in young horses.

3.In herd circumstances, fecal egg counts should be utilized to choose moderate and high egg shedders for deworming, with moderate and high egg shedders being selected first.

Not all horses must be tested in order to be qualified.

4.Large shedders very definitely require more than one or two treatments each year, depending on their size.

The administration of any subsequent therapies would be done on an as-needed basis.

deworm at the proper time of year Deworming should be avoided during severe temperatures such as winter or summer, as well as during droughts.

Worm-control efforts should be considered as an annual cycle that begins when the likelihood of worm transmission to horses increases from minimal to likely.

If the time between dewormings is too short, the findings of the fecal egg count will only reflect how effectively the last dewormer performed, rather than measuring how well the horse’s immune system lowered levels of cyathostomin egg shedding during that period. As an illustration:

  • After receiving moxidectin, you must wait at least 16 weeks before collecting a fecal sample. After using ivermectin, you should wait at least 12 weeks before collecting a fecal sample. Wait at least nine weeks after using benzimidazoles (fenbendazole/oxibendazole or pyrantel) before collecting a fecal sample.

The deworming of stabled horses that do not have access to other equids on pasture may only be necessary on a rare occasion or not at all. 9.When compared to older horses, horses less than three years of age are more susceptible to parasite infestations than older horses. Among the particular recommendations for children are:

  • Foals should get at least four deworming treatments throughout their first year of life. The first should be performed when the baby is two or three months old, and the second should be performed three months later. Check for parasite eggs before weaning to determine whether or not the foal has parasites
  • The third and fourth treatments should be considered when the child is nine and twelve months old, respectively, and should target the worms that have been discovered. It is recommended that tapeworm therapy be included in one of the latter treatments. Perform fecal testing on a yearly basis to see how effectively the dewormers are working. It is not recommended to deworm an 8-day-old foal. Worms are not the source of the diarrhea. Recent weaned foals should be sent out on the cleanest pastures. In the case of yearlings and 2-year-olds, they should be treated as high shedders and should have three to four yearly treatments with medications that have been proven to work by a fecal examination.

Deworming should be performed on horses displaying indications of parasitism using either moxidectin, which has shown no evidence of parasite resistance, or a larvicidal regimen of fenbendazole (10 mg/kg for five consecutive days) if possible. Do not rely on dewormers alone to keep your pets healthy. Controlling the environment is essential. Manure should be removed from the pasture rather than being spread there. If there are cattle or goats available, allowing them to rotate onto the horse pastures for a few weeks will aid in the removal of eggs from the pastures.

  1. Tradition dictates that botox therapy be administered 30 days after the first frost occurs.
  2. Diatomaceous earth and other alternate dewormers are not recommended.
  3. There is no single deworming program that works for everyone.
  4. More information may be found on the website of the American Association of Equine Practitioners, which also has recommendations.
  5. Did you find this article to be interesting?

Deworming Horses

What is the frequency with which you deworm your horses? Infected and breeding parasites may infect and breed in even the most well-cared-for horses, so if you just deworm your horses twice a year, you may be leaving them open to the dangers of parasites that can infect and breed in even the most well-cared-for horses. The season for equine parasites is constantly in season, and they may lay anywhere from 5,000 to 100,000 eggs each day, 365 days per year. It can take up to six months from the time of infection until visible indications show, by which time internal damage may have occurred and may be irreparable.

Choose a Deworming Schedule

When creating a deworming program, you must choose between two main strategies: daily deworming and interval deworming. Daily deworming is the most common strategy.

Daily Deworming

Incorporate a daily dose of the deworming ingredient into your horse’s feed to ensure maximum effectiveness. Dosing is determined by the weight of your horse; it is critical that you obtain an exact weight and that you adhere to the program’s guidelines.

You will need to use a botacide wormer such as ivermectin once or twice a year to keep your horses healthy. If you select daily deworming, consult with your veterinarian to determine the most effective plan for your horse’s health.

Interval Deworming

This is purging deworming, which is aimed to rid the horse of the majority of parasites he has been exposed to with a single dosage of wormer paste and water. The importance of timing cannot be overstated, and it is suggested that you deworm every 8 weeks. Using a dewormer too soon may result in the worms being too immature to be impacted by the dewormer. If you treat your horse too late, the worms may have had the opportunity to lay eggs, which may then infest the environment around your horse.

Get Rid of Parasites Before They Become a Problem

The American Association of Equine Practitioners has provided the following recommendations:

  • Ensure that manure droppings in the pasture are picked up and disposed of at least twice weekly. Frequently mowing and harrowing pastures can help to break up dung mounds and expose parasite eggs and larvae to the outdoors. Allowing other animals, such as sheep or cattle, to graze on pastures will help to rotate pastures and break the life cycles of parasites. Horses should be divided into age groups to decrease exposure to specific parasites and to enhance the effectiveness of the deworming regimen tailored to that age group. To avoid overgrazing and to decrease the amount of fecal pollution per acre, keep the number of horses on the property to a minimum. Feeding hay and grain on a feeder rather than on the ground is recommended. Remove bot eggs from the horse’s haircoat as soon as possible and on a regular basis to avoid consumption. It is important to rotate deworming chemicals rather than merely brand names in order to avoid chemical resistance. Whatever program you select, make a commitment to it.

Equine Recommended Deworming Schedule

Obtainable as a printable resource Unless otherwise stated, the egg count levels provided here are only recommendations based on the average range of counts achieved by the McMaster procedure.

Adult Horse Schedule

  • Performing a fecal egg count before to deworming in the spring (preferably, both spring and fall)
  • The following medications are used in the spring: ivermectin (Equell®, Zimectrin®, Rotectin®, IverCare®), and moxidectin (Quest®)
  • The following medications are used in the fall: ivermectin with praziquantel (Equimax®, Zimectrin Gold®), and the following medications are used in the winter: moxidectin (Quest Plus®

Moderate Shedders (200-500 EPG)

  • Performing a fecal egg count before to deworming in the spring (preferably, both spring and fall)
  • The use of ivermectin (Equell®, Zimectrin®, Rotectin®, IverCare, and other brands), as well as the use of moxidectin (Quest®), is recommended in the spring (March). Late summer (July) – ivermectin
  • Fall (October) – ivermectin w/ praziquantel (Equimax®, Zimectrin Gold®) or moxidectin with praziquantel (Quest Plus®)
  • Winter (November) – ivermectin w/ praziquantel (Equimax®, Zimectrin Gold®)
  • Spring (April

High Shedders (500 EPG)

  • In the spring and fall, a fecal egg count is conducted prior to deworming to check for signs of resistance. The following medications are used in the spring: ivermectin (Equell®, Zimectrin®, Rotectin®, IverCare®), moxidectin (Quest®)
  • The following medications are used in the summer: ivermectin
  • The following medications are used in the late fall: ivermectin with praziquantel (Equimax®, Zimectrin Gold®)
  • The following medications are used

In general, fecal egg counts should be used to assess therapy effectiveness. Unless otherwise specified, the treatment recommendations provided below are broad suggestions based on current medication resistance discoveries from throughout the world. It’s possible that other forms of dewormers will still be useful on your farm, and you can use them if you’ve determined that they’re successful through a fecal egg count reduction test.

Foal Schedule

  • Fenbendazole (Panacur) or oxibendazole (Anthelcide) for children under two months of age
  • Four to five months — Fecal egg count to track the incidence of ascarids vs strongyles in the stool. Fenbendazole (Panacur) or oxibendazole (Anthelcide) should be used to treat ascarid infestations. Strongyles should be treated with ivermectin after roughly five months. Use ivermectin and praziquantel to treat a tick infestation before the end of the calendar year. Assessing for the presence of ascarids in short yearling feces and treating those found with fenbendazole or oxibendazole should be done as soon as possible. Strongyles should be treated roughly three times with ivermectin throughout the yearling year, followed by one treatment with moxidectin with praziquantel before the conclusion of the grazing season, according to the manufacturer. Assays to determine treatment effectiveness include fecal egg count reduction tests.

Deworming Protocol Guidelines

The following are some of the most essential points and recommendations:

  • Maintain pasture rotation
  • Cross-graze grasslands with ruminants wherever possible. Remove manure on a regular basis. During hot and dry weather, harrow or drag pastures and keep horses out for two months. Overstocking pastures should be avoided.
  • Fecal analysis should be performed at least once a year to assess the effectiveness of parasite management.
  • Fecal egg count is an estimation of the amount of parasite eggs released by the horse in his feces. Before doing a fecal analysis, consult with your veterinarian to ensure that enough time has gone since your horse’s last deworming for eggs to have re-appeared in the stool. Each dewormer has a different Egg Reappearance Period, so check with your doctor to find out what yours is. Fecal egg count reduction test—depending on the product used, the number of worm eggs in the feces should reduce by 90 percent when evaluated 14 days after deworming.
  1. Once a year, use a dewormer containing praziquantel (such as Zimectrin Gold® or Quest Plus®) to treat for tapeworms. Small strongyles (cyathostomes) are only sensitive to a few different types of dewormers while they are in their encysted larval stage. In light of medication resistance studies throughout the world, moxidectin (Quest) would be the medicine of choice in the vast majority of instances. Enthusiastically treating the encysted larvae is suggested in the fall, at or at the conclusion of the grazing season, just before the animals enter the winter. Don’t keep mares and foals in the same pasture or paddock year after year to save money. There is an increase in the number of ascarid eggs produced, which might survive between years and infect fresh foals born during the spring breeding season

To be clear, the two parasites that cause the most worry in adult horses are tiny strongyles (encysted strongyles, cyathostomes) and tapeworms (see below). The ascarid is the parasite that causes the most worry in young horses. For the best results, consult with your veterinarian and do fecal egg counts to determine: 1) dewormer efficacy in your equine business, 2) the existence of ascarids in young horses, and 3) the presence of weakyle egg shedders at low, medium, and high levels in adult horses.

TheEquine Servicessection was responsible for its creation.

Martin Nielsen was in charge of editing.

Deworming your horse

  • Considering that every horse is an individual, various horses within the same herd will have varying worm (parasite) loads. While the vast majority of horses shed very few worm eggs, a small number of horses shed large quantities of eggs and are therefore more responsible for infecting the remainder of the herd
  • Yet, It is critical to deworm horses in a planned manner so that owners may target their high-shedding horses wisely and avoid overusing dewormers.


  • Resistance develops as a result of overuse of deworming products. Worms have the ability to produce genes that make them resistant to dewormers, rendering the therapy useless. Our capacity to treat horses with worm issues is limited by their resistance. These problems can cause severe colic and even death in horses that are affected by them.
  • The majority of horses only require deworming once or twice a year. We recommend that you get a fecal egg count (FEC) done before deworming your dog in the spring. A horse’s feces are sampled using this process, which allows us to count the amount of worm eggs the horse is shedding. On the basis of the results, we will provide a recommendation on whether or not you should deworm your horse. We recommend that horses be dewormed in the late fall, following a heavy frost, with an appropriate deworming product. It is best to consult with your veterinarian about which deworming product to use in the fall, based on the parasites that are prevalent in your area. Although we strongly recommend that you conduct an additional fecal egg count in the fall, many pet owners choose not to perform this second procedure. In many local boarding facilities, a fecal egg count is included in the spring herd health packages that they provide their clients. When pregnant mares are dewormed in the spring, before they give birth, the dewormer should be chosen in accordance with the findings of a fecal egg count. A deworming medication containing ivermectin should be administered to the mother within 24 hours of the birth of the foal
  • Foals require significantly more frequent deworming than other horses. They should be dewormed with fenbendazole for the first time at two months of age, and then retreated with this product every two months until they are yearlings. When temperatures are below freezing in the prairie provinces, foals do not require deworming throughout the winter. Foals should be dewormed with an ivermectintype product about 12 months of age, and then every three to four months with a product chosen depending on their fecal egg counts.
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Roundworms(Parascaris equorum)

  • As a result of weakened immunity, it is most prevalent in horses less than one year old and in extremely elderly animals. They pass via the trachea and spend their lives in the small intestine. Roundworms in young horses are associated with stunted growth and development, as well as respiratory symptoms. Young animals carrying extremely large loads may have clogged intestines, which can result in colic and, in severe cases, death. Older horses who are impacted may have a poor hair coat, lose weight, or perform worse than usual.

Bloodworms(Strongylus vulgaris)

  • It is possible for bacteria to travel via the arteries surrounding the big intestine and induce colic. Historically, bloodworms were a significant concern in horses, but their prevalence and impact have diminished as a result of proper deworming.


  • These organisms live in the big intestine and migrate into the gut’s wall. Cyathostomins are known to produce severe gastrointestinal symptoms such as nausea, vomiting, and diarrhea. In this species, resistance to dewormers is rising, making targeted deworming even more critical

Pinworms(Oxyuris equi)

  • Horses less than two years old, as well as horses under inadequate supervision, are most susceptible. Despite the fact that worms dwell in the big intestine, they lay their eggs near the horse’s anus, causing the horse to scratch at its hind end. Due to the difficulty in treating and controlling pinworms, proper management of horses and pastures is essential


  • Tapeworms are infrequent on the prairies, but the Anoplocephala perfoliata, which is the most prevalent tapeworm in Canada, is the most common tapeworm in the world. As a result of the fact that these worms spend part of their lives feeding on mites, they are difficult to eradicate
  • Yet, tapeworms do not appear to cause significant illness in horses. While colic is considered a possibility with this type of worm, the likelihood of experiencing it is extremely low.

Bots flies (Gasterophilus)

  • Bot flies deposit their eggs on the horse’s coat in the late summer and early fall, when the horse is most active. The eggs appear as minute yellow dots on the horses’ legs, with the majority of them being on the hind legs. During the course of licking or scratching their legs, horses consume bot egg larvae, which develop in the equine stomach and small intestine to become full-grown horses. Bots seldom produce clinical indications in horses, although they can cause gastrointestinal ulcers if the larvae are carried out through feces and hatch in the spring.

Consult with your veterinarian for recommendations on which exact products to use. Fenbendazole: This medication is effective against roundworms, bloodworms, and pinworms. Ivermectin: Ivermectin is effective against all parasites with the exception of tapeworms. Roundworms, on the other hand, have a high level of resistance to ivermectin. Ivermectin and praziquantel: These medications are effective against all parasites. Roundworms, on the other hand, have a high level of resistance to ivermectin.

Roundworms, on the other hand, have a high level of resistance to moxidectin.

Moxidectin and praziquantel: These medications are effective against all parasites. Roundworms, on the other hand, have a high level of resistance to moxidectin. Pyrantel: Pyrantel is a worm killer that targets bloodworms, pinworms, and roundworms.

Do I Need a Deworming Schedule for My Horse?

There are some drawbacks to deworming by the calendar, according to Craig R. Reinemeyer, DVM, PhD, Dipl. ACVM (Parasitology) and president of East Tennessee Clinical Research, who believes that deworming by the calendar has some advantages. As Dr. Reinemeyer explains, “Traditional, calendar-based control programs are fatally flawed because they make the incorrect assumption that the parasitic status of all horses in a herd is the same.” In reality, various horses have varying amounts of parasites, which may be diagnosed by counting the number of parasite eggs contained in a fecal sample.

  • There aren’t enough eggs. Approximately half of the horses in a herd will likely be “low contaminators” (also known as “low shedders”), which require little or no parasite treatment, according to Reinemeyer. The number of eggs is on the average side. Horses in a herd that are classified as “moderate contaminators” or “moderate shedders” will lie between the other two groups in terms of their egg-shedding tendencies
  • They will also produce large quantities of eggs. In addition, Dr. Reinemeyer points out that around 20% of the horses (referred to as ‘high contaminators’) typically have extremely high egg counts, and that this subgroup may potentially shed more total eggs than the rest of herd combined.

It stands to reason that high shedders will require more deworming treatments than low shedders in order to maintain their health. “The majority of management efforts should be concentrated on the herds with the highest concentrations of contaminants,” Dr. Reinemeyer advises. But a planned deworming program disregards all of this and mandates that all horses be treated at the same, equal times,” says the veterinarian.

The problem of resistance in a calendar schedule

Calendar deworming regimens that are “one-size-fits-all” might result in the following problems:

  • Some parasites will be able to survive. The deworming products will very certainly kill the majority of the parasite population, but not all of it. In Dr. Reinemeyer’s words, “anthelmintic resistance” is a genetic trait of a target parasite that makes it resistant to the activity of a dewormer that has previously been successful in the same worm population. As a genetic characteristic, resistance is passed on to offspring of a resistant worm, according to the researchers.
  • These parasites that are resistant to treatment reproduce. Because resistant worms in the population are not killed by the current treatment, they have a better chance of reproducing because they are not competing with their regular predators, explains Dr. Reinemeyer. “As a result, the frequency of its resistant genetic traits increases within the population as a whole,” the researchers write.
  • The cycle begins all over again, only this time it is much worse. Controlling the parasite population that has established itself on the farm might become a significant difficulty as time goes on. In Dr. Reinemeyer’s opinion, the more frequently one deworms, the more advantageous the resistant worms become, at least until they reach a population frequency that results in failures that can be identified in the lab, and maybe on the farm. The author notes that “it’s possible that the only worms permitted to breed would be resistant, therefore increasing their dominance within the worm genetics of that farm” under a particularly stringent, interval-based approach.
  • It’s more expensive than it should have been.
  • “It should be evident that this treatment is economically inefficient,” says Dr. Reinemeyer, who points out that the whole herd is dewormed numerous times a year despite the fact that around half of the horses would receive little, if any, benefit from the procedure. “However, the tendency for rote control efforts to select for anthelmintic resistance in the target worm populations has the potential to have a bigger impact than the monetary loss,” he continues.

Testing, testing …

After all, in the face of parasite resistance on a calendar rotational cycle, what can we do to appropriately deworm our horses while also minimizing the hassle? A deworming strategy that is specific. The high-contaminator animals within a herd would be identified and given the bulk of antihelmintic treatments at intervals calculated to limit egg contamination in light of local climate and management circumstances, adds Dr. Reinemeyer. There would be less, if any, treatments given to the rest (majority) of the herd.

  • Step one is to do FEC testing. First and foremost, each horse on the site is subjected to an afecal egg count test (FEC). As previously stated, this is used to determine if a horse is a low, moderate, or high shedder. “Typically, a fecal egg count performed about 3 to 4 months after the most recent deworming can be used to determine shedding classification. This test should not be performed during the winter, when egg counts tend to decrease due to the natural cycle of aging among adult worms,” explains Dr. Reinemeyer. FECR testing is the second step. A few months later, the horse is dewormed with a specific substance, and the test is redone as an afecal egg count reduction (FECR) test, which is more accurate. This time, your veterinarian will use the results to compare them to the results of the first test in order to determine how effective the treatment was. As Dr. Reinemeyer points out, “one can only execute an FECR for one dewormer at a time
  • Assessing the susceptibility of all three chemical classes would need three individual FECRs.” Step 3: Was the experiment successful? If the dewormer is still effective and there is no evidence of resistance, your veterinarian should notice a reduction in parasite eggs of 90 percent or greater, according to the manufacturer. In addition, Dr. Reinemeyer estimates that 98 percent of the time when testing ivermectin or moxidectin will be positive. According to the researchers, “FECR readings of 80 percent or more very likely suggest resistance, whereas values between 80 and 90 percent are ambiguous and should be repeated at some time in the future.” Step 4: ERP testing and evaluation. Finally, the set of tests might offer another figure known as the egg reappearance period, which is calculated based on the results of the previous tests (ERP). As explained by Dr. Reinemeyer, “the ERP measures the amount of time that elapses between an efficient deworming and the horse’s ability to severely pollute its surroundings with new worm egg infestations.

There will be no need to repeat the testing if an individual horse does demonstrate parasite resistance to a certain chemical class. “Antihelmintic resistance is a lifelong condition that will never spontaneously return to susceptible status,” Dr. Reinemeyer explains. It is OK to continue to use the dewormer, preferably with a selective approach, but it would be prudent to conduct another FECR with that class of compound about every two years if the dewormer is still effective.”

  • Shedders of a moderate caliber. “Moderate shedders might definitely benefit from one more treatment around the middle of the grazing season (summer in the north, winter in the south),” he continues. High shedders are a good thing. The major targets, according to Dr. Reinemeyer, are “high shedders,” and he may administer one additional treatment to this group throughout the grazing season. He does warn, though, that every horse should spend at least one season without receiving a deworming medication, regardless of environment. “We recommend winter for horses in the northern hemisphere and summer for horses in the southern hemisphere.” Additionally, understanding how fast eggs begin to return following a therapy might be beneficial when dealing with the horse’s ERP. In the case of a high-contaminator horse, Dr. Reinemeyer explains that knowing the ERP would assist to establish the shortest possible gap between consecutive treatments. It is also important to consider the climate. Dr. Reinemeyer says that your geographic location has an impact on the timetable. Despite the fact that some parasites’ life cycles take place outside the horse, he explains that infective stages can survive even in sub-zero temperatures. “Climate does not impact the types of parasites as much as it does the timing of infections with the most common worms in various climates,” he says. “Despite the fact that pastured horses can take up new parasites at any time of year, the overall risk of infection is typically lowest during the warmest days of summer, particularly in the southern United States. Because of these seasonal variations in parasite transmission, parasite management techniques must be tailored to the specific geoclimatic circumstances of each farm “he explains

Work with your veterinarian

The question of “Do I require a deworming regimen for my horse?” has been answered. is…yes. However, in an ideal situation, each horse’s program would be adjusted and personalized to meet his or her specific requirements. The veterinarian who will be treating your horses is obviously going to be an important partner in this process, so make sure to receive specific recommendations for your horses and circumstances. Aside from that, your veterinarian will advise you on which chemical class to use.

How often do you de-worm your horses?

The question of “Do I require a deworming regimen for my horse?” has been answered. is…yes. However, the ideal timetable would be one that is adapted to the specific needs of each horse and is unique. The veterinarian who will be treating your horses is obviously going to be an important part of this process, so make sure to receive specific advice for your horses and circumstances.

Aside from that, your veterinarian will advise you on which chemical class to utilize. And you can rest assured that taking these precautions will go a long way toward protecting the long-term health of your entire herd of animals.

  • Expansion of the stomach or the appearance of a pregnant abdomen
  • Dull coat
  • Delayed or atypical shed
  • Low energy level
  • Depressed demeanor Growth and development that is abnormal
  • Coughing that is not explained and indicators of a reduced immune system Problems with weight control
  • Constipation and/or diarrhea

Paste Dewormers are classified according to their chemical composition. Active IngredientsWorks Against (Types of worms)Products (Brands) (Brands) The insecticide Ivermectin is used to treat large and small strongyles, pinworms, hairworms, and threadworms as well as stomach worms, lungworms, ascarids (roundworms), and bots. Jeffers Ivermectin Horse Well-Being Strongyles, pinworms, hairworms, stomach worms, ascarids, bots, and Encysted little strongyles are all treated with IvermectinBimectinTMZimecterin®Equimectrin®Rotectin 1.87 percent Iver Ease TMIverCare® MoxidectinLarge and small strongyles, pinworms, hairworms, stomach worms, ascarid Ivermectin and Praziquantel (Quest®Ivermectin & Praziquantel) for the treatment of large and small strongyles as well as pinworms, hairworms and threadworms as well as stomach worms, lungworms, Ascarids, Bots, and Tapeworms The use of EquiMax®Zimecterin Gold®Moxidectin and Praziquantel against large and small strongyles, pinworms, hairworms, stomach worms, Ascarids, Bots, Encysted tiny strongyles, and Tapeworms is recommended by the American Veterinary Medical Association.

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Quest® PlusPryantel pamoate is a prescription medication.

Pyrantel Tartrates, Anthelcide®EQ, Large and Small Strongyles, Ascarids and Pinworms, Daily Wormers, Anthelcide®EQ Strongid® C,Continuex™,Equi Aid CW®​Fighting the Dewormer Resistance – The Threat of the Tapeworm –

How Often do I Need to Deworm My Horse?

Equine owners were eager to adopt new anthelmintic (deworming) remedies when they were first developed and released onto the market in the 1960s and 1970s. They also accepted the practice of deworming their horses on a regular basis throughout the year at that time. However, misuse of deworming medicines over the past five decades has resulted in resistance, which means that worms can acquire genes that allow them to become resistant to the medications. Our capacity to treat horses with worm issues is limited by their resistance.

  1. It is no longer regarded acceptable practice to provide deworming products to your horse without regard for the animal’s needs.
  2. Strategic deworming takes into account all factors, including the parasite life cycle, the horse’s surroundings, and the horse’s health.
  3. As a result of our research, we have discovered that different horses within the same herd will have varying parasite loads.
  4. That is why it is critical to tailor your deworming techniques to the specific needs of each horse in your herd.

You should treat horses as individuals – or in groups depending on age, immunological response, and overall health – and correctly target your high-shedding horses to avoid overusing deworming medicine.

Fecal Egg Counts for Horses

The majority of horses only require deworming once or twice a year. Prepare your horses for deworming in the spring by having a fecal egg count (FEC) performed on each of them. When your veterinarian does this process, it will be able to determine the quantity of worm eggs deposited in the horse’s feces, which is an indication of the horse’s parasite load. Your veterinarian will be able to tell you whether or not you need to deworm your horse based on the findings of the test. The use of an adequate deworming treatment on horses is suggested in the late fall, following a strong frost, to prevent worm infestations.

Your local veterinarian may advise you on which deworming medication to use in the autumn based on the parasites that are widespread in your region and what products to avoid using.

Horses that are Vulnerable to Parasites

When pregnant mares are dewormed in the spring, before they give birth, the dewormer should be chosen in accordance with the findings of a fecal egg count. A deworming treatment containing ivermectin should be administered to mothers within 24 hours after giving birth. Foals require deworming on a much more frequent basis than other horses. They should be dewormed with fenbendazole for the first time at two months of age, and then retreated with this product every two months until they are yearlings.

Foals should be dewormed with an ivermectin-type product at the age of 12 months, and then every three to four months afterwards with a product chosen based on their fecal egg counts, according to the manufacturer’s recommendations.

Ensure that your horses have access to clean water at all times and that they are fed high-quality hay and feed.

Make sure that their vaccinations are up to date, and have your veterinarian do regular dental checks on your pet.

Controlling Parasites in Your Horse’s Environment

It is possible to find parasites in pastures as well, where they develop from eggs in excrement to larvae that can infect your horse. Because parasites require precise temperatures, humidity, and other environmental conditions in order to develop into infective larvae, one effective method of managing them is to interrupt the parasites’ life cycle before they reach your horse’s intestine. Use the following techniques to keep parasites under control:

  • Pick up the dung and remove it from your horse’s environment as soon as possible. By restricting the number of horses allowed on an acre, you can prevent overgrazing and decrease pasture pollution. If you have a pasture that is currently being utilized for grazing, avoid depositing non-composted dung in it since this technique distributes parasite eggs. Rotate pastures with other species to interrupt the life cycles of parasites and other pests. Because they contain various parasites, young animals should be housed apart from adult animals.

By focusing on high-shedding horses in your herd, keeping your horses’ health in good condition, and regulating their surroundings, you may lessen your reliance on deworming medication and your role to the development of parasite resistance while still keeping your horse healthy.

Deworming your horse

  • Deworming is an important part of every horse and foal health care regimen. According to some research, parasites are responsible for 80 percent of colic occurrences, with larval strongyles being the most common cause of colic in adult horses. With the exception of tapeworms and bots, fecal samples can be used to screen for internal parasites.


Roundworms (Parascarus equorum) are most commonly found in horses between the ages of 3 and 9 months.

Eggs in the horse’s feces might be discovered by a veterinarian or diagnostic laboratory. Symptoms of roundworms in foals include:

  • A decrease in appetite
  • A slowing of the rate of growth
  • Potbelly look due to a dull, dry hair coat.


To kill mature roundworms, use pyrantel pamoate or fenbendazole as a treatment. If there is a suspicion of a significant burden, fenbendazole will perform better. In order to destroy the larval stages of the worm, ivermectin or piperazine should be used.

Large strongyles

Strongylus vulgaris, a big strongyle that infects the cecum and ventral colon, is present (large intestine). Large strongyles can be detected using fecal flotation assays. It is possible for the horse to become clinically ill when huge numbers of larvae infiltrate the gut. Signs of illness caused by huge strongyles include:

  • Fever, diarrhea, lack of appetite, weight loss, colic, and death if left untreated are all possible outcomes.

When a child has a persistent infection, random, recurring colic is a significant symptom of illness.


To treat against larval stages, ivermectin and moxidectin should be used. Adult worms should be treated with oxibendazole, fenbendazole, or pyrantel pamoate, among other medications.

Small strongyles

Little strongyles (Cyathostome) develop in the lining of the cecum and colon, causing small growths to appear. As they emerge, they cause damage to the lining of the stomach and swelling, which can impair digestion and the absorption of nutrients. Small strongyles can be detected using fecal flotations. Symptoms of tiny strongyles include:

  • If left untreated, anorexia, weight loss, diarrhea, and colic might result, as can becoming very underweight.


Adult worms can be treated with ivermectin, oxibendazole, pyrantel pamoate, or piperazine, among other medications. To cure larvae, you can use ivermectin, moxidectin, or pyrantel tartrate, among other things.


In humans, tapeworms (Anoplocephala perfoliata) may be found in the large colon and near the end of the small intestine. Tapeworms can be seen in horses older than 6 weeks of age. It is possible to find tapeworm fragments in the horse’s feces. It is possible that a fecal test will not find tapeworm segments or eggs since horses do not consistently excrete them in their dung. If you live in Minnesota, the rate of tapeworms in horses is the greatest, so make sure to include treatments that target the tapeworm in your deworming regimen.

However, tapeworms can induce the following symptoms:


When treating against tapeworms, double the usual dose of pyrantel pamoate is recommended.

Stomach bots

Horses infected with stomach bots (Gasterophilus) frequently exhibit no signs of illness. Bacterial infections of the mouth, esophagus, and stomach might result in the horse becoming unable to feed.


After the first heavy frost, treat with ivermectin or moxidectin to prevent stomach bots from developing.


Pinworms (Oxyuris equi) are a parasite that may afflict horses of all ages. Pinworms can be identified by looking for eggs in the anal discharge or by “capturing” the worm with scotch tape and observing how it moves. Pinworm symptoms include:

  • Anal irritation, restlessness, poor eating habits, and yellow/gray discharge from the anus are all possible symptoms.


Adult pinworms can be treated with fenbendazole, oxibendazole, pyrantel pamoate, piperazine, or ivermectin, among other medications. Fenbendazole can be used to treat pinworms in foals.


Threadworms (Strongyloides westeri) are most commonly found in young foals between the ages of 10 days and 6 months.

Threadworms can be detected by fecal flotation. Threadworms infect the small intestine and cause swelling and damage to the lining of the small intestine. This has the potential to impede digestion and nutritional absorption. Symptoms of threadworms include:


Threadworms are transmitted to foals through the mare’s milk. Infection can be reduced if the mare is treated with ivermectin within one week after giving birth. If you suspect threadworm in a foal, treat him with oxibendazole or ivermectin immediately. When choosing a dewormer, it is important to understand which parasite groups each active component targets (Table 1.). Some veterinarians have discontinued the use of moxidectin because of rare but serious side effects.

Table 1. Deworming products and parasites they control

This technique entails determining the overall number of parasites present in each animals through testing.

  • Fecal egg counts should be conducted once a month according to standard practice. Tapeworm testing should be performed twice a year, either by fecal testing or blood testing (serology). The treatment of all animals that test positive over a specified threshold level is recommended. Botfly larvae (bots) should be treated once a year, and this should be done during the winter months.

It is only acceptable for mature horses to participate in this program, and it should only be considered on a farm with a dedicated manager and sound grazing management practices.

Strategic dosing

This technique entails treating all pastured animals with a suitable product on a regular basis at intervals determined by the producer.

  • The egg reappearance period (ERP) of the medicine, which is shorter in young animals, can be used to calculate the interval between doses of the medication. The ERP is defined as the time period that elapses between the administration of a dewormer to an animal and the occurrence of substantial quantities of parasite eggs in the feces. Animals are only treated during the spring and summer seasons, when the danger of increasing egg burdens is greatest.

Interval dosing

This is the method that is most frequently employed. It is comparable to the concept of strategic dosage.

  • Animals are treated at regular periods throughout the year. Given that parasite kill time varies from product to product and even from farm to farm, the interval between doses should be decided by the ERP or by guidelines established by your veterinarian based on the products utilized. Farms where there are frequent new recruits to the group, more informally managed (hobby) farms, and young animals are also good candidates for this treatment.

Daily deworming

The addition of a parasite control medicine to the horse’s daily feed is the goal of this technique.

  • Suitable for the majority of mature grazing horses
  • A low amount of the medicine is constantly present in the environment of the parasite, increasing the likelihood that they may develop resistance over time. In most cases, further deworming with various treatments is required on a regular basis. Inquire with your veterinarian about the most recent guidelines.

How often should I deworm my horse?

Fecal egg counts can assist you in determining whether or not your horse need deworming. If your horse is losing a significant number of eggs, you can deworm them for the specific parasite(s) that are causing the problem. In an ideal situation, you’ll discover a happy medium where you can control the parasites but not excessively deworming. Excessive deworming can encourage the development of parasites that are resistant to deworming. The majority of farms provide a double dosage of pyrantel or a praziquantel medication once a year to control tapeworms.

When should I deworm mares and foals?

After foaling, deworm mares to limit the risk of Strongyloides being passed to the foal through the milk. Begin a deworming regimen for foals before to weaning (about 2 months of age). Roundworms should be targeted in this approach.

How else can I manage parasites?

Parasite control strategies must include the use of dewormers, but management is also important in the prevention and control of parasites. The management strategies outlined here can help you enhance parasite control on your farm.

  • In order to prevent severely infected animals from shedding parasites into the environment and infecting other horses, it is necessary to isolate and treat new animals on the farm. Another option is to demand deworming of all incoming animals when they first arrive at a boarding facility. Young horses should be closely monitored since they are more susceptible to parasite illnesses. Try to avoid eating from the ground, especially in filthy locations and box stalls
  • Routinely pick or pull dung from pastures, and mow pastures on a regular basis. As a result of drying, sunshine exposure, or freezing, this will break up manure mounds while also destroying eggs and parasite larvae. If grazing is the major source of fodder for your horse, ensure sure the animals are not overcrowded and the pasture is not overgrazed. Each 1,000-pound horse requires two acres of pasture, according to a widely accepted standard. Grazing on a rotational basis will assist to limit parasite exposure in the following ways:
  • Extending the use of manure
  • Allowing manure to break down
  • And reducing overgrazing.

How can I tell if my parasite control program is working?

Sending in fecal samples on a yearly basis will assist you in monitoring parasite burdens in your horse as well as the efficiency of dewormers. You can also determine whether or not your horse is a heavy egg shedder or whether or not the parasites are resistant to treatment. It is vital to monitor the efficiency of a parasite prevention program. At the very least, you should check your fecal egg counts once a year. In addition, testing and monitoring will aid in the detection of atypical parasite infection.

As a committed horse owner or stable/farm manager, you and your veterinarian may work together to establish a comprehensive and cost-effective parasite management program that is tailored to your farm and its animals’ specific needs and requirements.

Jeremy D. Frederick, DVM, previously of the University of Minnesota, and Julie Wilson, DVM, also formerly of the University of Minnesota, are the authors of this paper. In 2021, the situation will be reviewed.

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