Deworming Your Horse


woman deworming her horse with ivermectin

If you are a barn owner or a horse parent, you may have heard about deworming. So, let me tell you why deworming has got so much importance for the health of equines. Horses harbor microorganisms in their intestines; some of these microorganisms are parasites. Most of the time, parasites living normally in the intestine of horses do not cause serious implications.


But if the number of parasites inside the intestine exceeds the normal range, it creates health hazards for the horses. It is important to keep the number of parasites and other microorganisms inside the intestine in check for the better health of your horse.


Horses have different capacities to counter the worm infestation depending on the age, immune system, and breed. Horses can tolerate the normal level of infestation easily, but it becomes a real threat to their health when parasites overcome the immune system. In that case, you need to implement some management approaches to limit the exposure of parasites. Additionally, you need dewormers to help your horse win the fight against the worms.


How can I know my horse is infested with worms?

The signs of worm infestation differ in different horses. Some worms express typical signs and symptoms that a professional can easily see and diagnose. However, as a horse owner, there are general signs and symptoms which may indicate parasitic infestation in horses. Please note that these signs and symptoms may also be related to other diseases as well. Therefore, the advice of a professional is essential before any treatment.

  • Poor growth

  • Rough or dry skin/coat

  • Loss of appetite

  • Weight loss

  • Itching

  • Tail rubbing

  • Anemia

  • Colic

  • Diarrhea

  • Pot belly

You can also get a fecal exam to determine the presence and the load of parasites in your horse. This can help you determine an effective deworming program.

What are the common parasites found in horses?

Following are the common types of parasites that cause diseases in horses.


1. Small redworms (cyathostomes): are transmitted through grazing. Horses get the larvae of this parasite from pasture grazing, and these larvae develop in the intestine from where they are transferred back into the environment via feces. Damage in the intestinal walls could cause anemia.


2. Large redworms (strongyles): these parasites follow the same pattern as small redworms. The only difference is that the larvae move into the blood stream, heart, lungs, pancreas, and liver, causing severe damage. They can cause damage to the walls of the blood vessels and could cause blood clots.

strangle life cycle in horses diagram
Photo credit: Bimeda Equine

3. Ascarids or roundworms: mostly affect younger horses and live 8-14 weeks. The adults live in the small intestine laying tons of eggs. The eggs are spread to the environment via feces. The horse ingests the larvae where they migrate to the blood stream, lungs and liver. They can be coughed up and swallowed where they mature in the small intestine.


4. Threadworms (Strongyloides westeri): Are a threat to foals and can be transmitted by the mares milk, food, and by penetrating skin. They mature in the lungs, coughed up, swallowed and produce eggs. Can cause diarrhea, fever and colic.


5. Tapeworms: Spend most of their lifecycle outside of the body. Orbatid mites eat the segments of tapeworms and when the horse grazes, it chews and swallows grass and mites. The segments attach to the small and large intestine. They mature in 6-9 weeks. They usually cause diarrhea, weight loss, and can cause ruptures of the cecum wall.

horse itching and licking bot fly eggs on the front legs

6. Bots (Gasterophilus spp.): Bot flies lay eggs on the front limbs and chest of the horse. The horse then itches or licks these areas and ingests the eggs. Eggs hatch into larvae inside the mouth where they are then swallowed and attach to the stomach walls. They can live inside the body up to 9 months before being expelled in the manure.


7. Lungworm (Dictyocaulus arnfieldi): they live in the lungs of horses who live with or near donkeys and burros. They lay eggs near the bronchi where they can be coughed up, swallowed and passed in the manure. They mostly cause bronchitis and bronchopneumonia. Look for coughing, labored breathing, weight loss or similar signs of Chronic Obstructive Pulmonary Disease (COPD).


What is the best time to deworm my horse?

Generally, the best time to deworm your horse is spring and fall. However, if your horse is heavily infested with parasites, you can deworm your horse in summers, too. However, the deworming schedule is not so specific because it differs from the area. Horses living in different areas of the country may infest with different types of parasites.

deworming horse with syringe in the mouth

Keep in mind there are different factors when determining the deworming schedule and types of dewormers for horses. These factors include age, breed, area, and stocking density. These factors are essential to devise an effective parasite control plan for your horse. You should avoid taking the advice of sales representatives. A veterinarian can better devise an effective parasite control plan.


There are three types of worming schedules: interval, seasonal and daily.

  • Interval - rotating between 3 classes of dewormers: Oxybendazole, Ivermectin, Pyrantel Pamoate.

  • Seasonal - using the dewormers during the peak time of the worm lifecycle. For example, using Ivermectin for controlling the midsummer bot flies.

  • Daily - used for horses who can not tolerate higher doses of dewormers. Can create drug tolerant worms.


Therefore, it is essential to take the advice of your veterinarian before deworming your horse. Your veterinarian can best tell you the exact time and type of wormer for your horse. However, most of the wormers are used in the spring and fall seasons.


How can I make sure my horse does not suffer from parasites?

Whether you are a barn owner or you have one or two-horses, you need a parasite control policy to keep your horse healthy. You can contact a veterinarian for a parasite control policy. We have listed a few protocols that help minimize exposure to the larvae and eggs below.

removing horse poop can help manage flies and worms in pasture
  • Use dewormers to control parasitic proliferation in the intestine.

  • Reduce or completely remove manure in stalls and paddocks.

  • Give enough pasture space per horse (1-2 acres each).

  • Maintain good nutrition for your horse.

  • Fly control - traps, parasitic wasps

  • Remove bot fly and pinworm eggs from the coat when present.

How can acupressure be helpful?

Acupressure is one of the Chinese alternative medicine approaches. According to the Chinese belief, the body suffers from disease due to an imbalance of body energy. The body energy or "chi" is the vital energy of life. If somehow it gets disturbed, the body gets distressed.

acupressure practitioner touching an acupressure point on horse to support health

It becomes essential to balance the body's energy. Acupressure helps to bring balance the body's energy. It is a technique in which different pressure points on the body, called acu-pressure points, are pressed. The applied pressure helps to maintain a continuous flow of body energy and increases the blood flow.


One of the main self defense mechanisms in all animals is the immune system. Using acupressure to support the body's natural ability to heal and defend is key to helping your horse. Nationally Certified Animal Acupressure Practitioners at Poll to Pastern support the body with acupressure by boosting the blood flow, supporting the immune system, clearing the body of chi blockages, and maintaining healthy body functions.


This method has been used as an alternative approach to help animals in this modern world. Veterinarians advise both the modern medicinal approach and alternative medicinal approach for better results. Complementary care is an amazing method of helping support the body in many ways.


Final thoughts

Modern science has developed itself very much, but still, worms are a main health hazard for domestic animals. More than half of the focus of veterinarians in the industry is on parasitic infestations and their related health concerns.


The problem lies in the management practices to overcrowd horses in a small area with poor hygienic conditions. Barn managers who cannot make the grazing area free from fecal deposits face this issue.


Additionally, the use of poor-quality dewormers without the advice of your veterinarian is also one of the main causes. Owners need to understand that good deworming selection is based on the health conditions, management conditions, and the surrounding area where the horse is living.


And a veterinarian can assess the situation and advise the best suitable dewormer for your horse. Therefore, it is essential to take the advice of your veterinarian in this matter. Also note, dewormers are poisons and should be treated with care.

girl giving horse a treat after deworming

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