Horse Deworming

Every year the topic of Horse Deworming comes up regularly.  If you have a horse, you will no doubt come across a natural terror of horse ownership, and that is parasites! Worm or parasite infestation can be very taxing on your horse and can even kill, but with that being said we must put some things in perspective.

Parasites have been around longer than horses. In fact horses have evolved with parasites and when we have a healthy horse it can prevent infestation. Their digestive system and immune system is well designed to deal with worms of all kinds. And a small amount of worms don’t seem to pose any harm in the horse. It is not realistic for us to believe that we can keep our animals completely free of parasites, bacteria, viruses etc. as that would be impossible. What we can do however is to keep our horse’s as healthy as possible so they have a viable enough immune function to deal with any parasitic assault.

Most of us are familiar with chemical wormers and worming schedules. Whether it be done every few months or in some cases daily it has to be realized that chemical wormers are harsh and do damage to the horse as well as the worm.

As some parasites are becoming resistant to the chemicals more stronger and potent and therefore dangerous dewormers are coming on the market that are making things even more risky.

When our horses are showing signs of having a worm problem we must ask ourselves a few questions.

  1. What is causing the horse to be ill? A healthy horse does not succumb to heavy parasite load.
  2. How can I do this gently so I don’t hurt my horse in the process?

In order to answer these questions sufficiently we have to learn more about the typical horse worms.

There Are Many Types of Worms
the Most Common Ones Are:



  • Large Strongyles (ex. Strongylus equines): also known as blood worms and some types of hook worms – can do much damage in the horse’s digestive system and liver. They actually bite and feed off of flesh pieces that they attach themselves to. They can weaken artery walls, cause blood clotting, colic, diarrhea, anemia and fever from open wounds.


  • Small Strongyles (Cyathostomes): also known as red worms can damage intestinal walls causing wasting, anorexia, diarrhea and colic symptoms.


  • Neck Threadworms (Onchocerca cervicalis):There are different types of threadworms but the neck threadworm can burrow into the skin and into tendons and ligaments causing painful swelling and irritation. When immature as microfilariae they can also invade they eyes and sometimes cause blindness.


  • Intestinal Threadworms (Strongyloides westeri):These threadworms in their larval stage can invade the lungs causing bleeding and breathing problems. Very young horses are the most prone and threatened by them.


  • Lungworms (dictyocaulus arnfieldi): As the name implies the these worms are found in the lungs. They can cause a severe cough and respiratory distress. Foals are most susceptible. Some horses can be infected and show no signs however.


  • Pinworms (oxyuris equi): can cause the classic tail rubbing and skin itching most often associated with worms. The pinworms actually can be found around the rectum on close inspection if the horse is heavily infested. They live in the large intestine and can damage intestinal walls.


  • Round Worms, Ascarids, (parascaris equorum):Mostly contracted by the young due to an immature immune system round worms can rather quickly damage the lungs, liver and intestines. Symptoms can be flu-like with coughing, respiratory infections, fever even bleeding from the lungs when the worm is in the larval stage, later on as they migrate they settle in the small intestine and can cause symptoms of colic and if there are too many of them even blockages that can cause death.


  • Tapeworms (anoplocephala perfoliata): can grow to several feet as they feed and grow. They take much of the horse’s nutrition to feed themselves and thus cause the horse to lose weight no matter how much food is being given. This is particularly so if the horse is not well and the problem leads to an infestation – then they can cause anemia and severe intestinal blockages that can kill the horse.


  • Bots (gastrophilus spp.): Bots are not truly worms they are flies that deposit their eggs on the horse’s legs and mouth areas. The eggs are either ingested through grooming or they hatch and the larvae burrow under the skin to migrate to the intestine. They can cause inflammation, infection, ulcers, colic and intestinal blockages if there is an infestation.

Most worms have a typical life cycle. First the larvae are eaten from contaminated food, grass, pasture etc. They go on into the gut and then bury into blood vessels to feed until fully developed. They then return to the intestines to lay their eggs which are excreted along with fecal matter and await a new or same host.


Signs and Symptoms of Worms in the Horse:


An interesting phenomenon has been cited by parasitologist’s that 20% of the horses in a typical herd carry 80% of the worm burden. If one were to take a closer look it could be speculated that these 20% have an underlying health issue as well causing a weakness that allows the worms to grow and reproduce. Examples of symptoms of a horse with worms could be as follows:


  • Rough and dull coat
  • Tail rubbing and overall itching
  • Moody or change in behavior normally quiet
  • Weight loss, unthrifty
  • Bloated abdomen
  • Coughing
  • Eye problems
  • Allergies
  • Cancer or tumour growths
  • Light coloured discharge around rectum
  • Colic, digestive disturbances
  • Diarrhea and/or constipation
  • Anemic, low energy and stamina
  • Worms found in stool or around anus


It is important to note that worm symptoms are often either complicated with another disease condition as that precedes the worm problem. Or what may appear to be worm problems may in fact be another disease. One should not automatically reach for dewormers, all of the horse’s symptoms should be taken into consideration and treated as a whole.

There are ways to test for worms but even those are not 100%. The most common is the Fecal Flotation and then blood work. The Fecal Egg Counts estimates the number of internal parasites in 1 gram of manure. If the ‘epg’ (eggs per gram) is greater than 200 then the horse is considered to have a serious parasite infestation.

The Fecal Egg Count test normally screens for nematode eggs such as pinworms, roundworms and strongyles. These tests will not be able to detect tapeworm, bot or any worms in the larval stage. So these tests can be helpful but should not be totally relied upon.

It is estimated in order to get a more accurate test one should have close to 10 samples from different manure piles for each horse. This is not very economical nor feasible for the average horse owner. Both physical symptoms and fecal counts and possibly blood work if needed should be taken to make sure there is a worm problem before deworming.

It is more of an art than a science but conscientious horse owners soon learn how to maintain their horse’s health and thus keep the worms from ever becoming a real problem.


Please Weigh the Risks Before Using Chemical Horse Dewormers!

If you are going to use a chemical horse dewormer please weigh out the risks and consequences for doing so carefully. In some cases chemical wormers will be needed particularly when the situation seems dire and time is of the essence. But even in these cases chemical wormers are not a replacement for proper health care.

One should not think about treating the worms but treating the horse to bring it to better health so it can deal with the parasites and prevent future problems.

The other problem with liberal use of chemical wormers is parasite resistance. Already we are finding that the drugs we are using are immune and useless against the worms. The chemical worming agents are getting stronger and thus more dangerous and are in fact causing major health problems in our horses, and in some instances can kill. Some contain known pesticides that come with warning labels when used in other products so caution is strongly advised.

It is also important to realize that the wormers meant for horses such as the Avermectins for example, can be extremely dangerous when accidentally ingested by dogs or cats or some other animal species. One of the Avermectin has a warning label with “may not be well tolerated in all non-target species (cases of intolerance with fatal outcome are reported in dogs, especially Collies”. There have been examples of dogs licking used syringes and later going blind and succumbing to illness if not death.

Another label for Panacur lists: “User warnings, direct contact with skin should be kept to a minimum. Wear impermeable rubber gloves while administering the product. Wash hands after use. Disposal warnings Dangerous to fish and aquatic life. Do not contaminate ponds, waterways or ditches with the product or used container. Dispose of any unused product and empty containers in accordance with guidance from your local waste regulation authority. Withdrawal periods; Not to be used in horses intended for human consumption. Treated horses may never be slaughtered for human consumption. The horse must have been declared as not intended for human consumption under national horse passport legislation. For animal treatment only. Keep out of reach and sight of children.”

Chemical wormers are so toxic that they kill both the parasites and beneficial soil nematodes and insects when excreted later in the manure. If you do deworm your horse place in a different area (ie. sacrifice or winter paddocks) for a day or two at least till the horse is no longer excreting the chemical with its manure.

The chemicals are so potent that some people have tested the land years later to find the soil still dead of important soil inhabitants that are critical for proper soil health. If you need to wear rubber gloves while administering and you have to ask how to properly dispose of the empty containers because it is considered a hazardous waste. Why are we still putting this into our horses with such little thought of consequence?


Some of the Side-effects Chemical Horse Dewormers can Cause in Horses:


  • Liver damage
  • Kidney damage
  • Seizures
  • Digestive problems (kills good bacteria)
  • Colic
  • Allergies & Anaphylaxis
  • Parasite Toxicity from mass die-off
  • Laminitis
  • Swollen neck, glands
  • Immune System Dysfunction
  • Death



The Most Common Chemical Horse Dewormers on the Market Are:

  • Pyrantel’s (Strongid-P, Pyratape P, Continuex)
  • Benzimidazoles/Fenbendazole (Panacur, Equine Guard)
  • Moxidectin (Quest)
  • Ivermectin (Panamec, Eqvalan)
  • Oxfendazole (Equi-cide)
  • Oxibendazole (Anthelcide)
  • Praziquantel (Droncit, Cestex)


Don’t Forget The Paddock!

99% of worm larvae exist on the pastures and only 1% in the horse. Picking up after your horse is mandatory especially around feeding areas. If you want to have a successful worm program you MUST keep your pastures clean.

By the way, cold temperatures do not kill worm eggs, but hot dry weather does. So if you own more than a couple of horses make sure you rotate the paddocks frequently and harrow the manure to expose the eggs to the hot sun. Never let horses eat from manure laden pastures.

For further information on Horse Pasture Care, check out ourPasture Care page

Natural Alternatives to Horse Deworming

So your horse has worms what are your options. First get to the underlying reason your horse has a lowered immune system to allow for worms to take hold. This means there is usually an underlying disease condition, and/or toxicity is present. Many times heavy metal, pesticide, insecticides and herbicides and other chemicals are a big problem in your horse that it lowers his immune system and becomes a target for parasites.

Poor nutrition is a major concern that should be the first thing to consider. Today’s foods are much depleted in crucial vitamins, minerals and other nutrients that is taking a very detrimental toll on our horses health.

Get your horse’s hair tested to see what his mineral levels are and if there are any heavy metals present in his body. So from a natural standpoint a horse deworming program should consist of:


  • Address nutritional deficiencies and toxicities
  • Clean your horse living quarters free them of chemicals, pesticides, unnecessary plastics, aluminum etc.
  • Clean your pasture – manure means more worms!
  • Detoxify your horse! Liver and kidney are probably very stressed due to presence of toxins and worms themselves create a toxic environment
  • Detoxify heavy metals
  • Address underlying health condition, chronic disease. Treat with Homeopathic medicines and other gentle natural medicines whenever possible.
  • Use Homeopathic & Herbal De-wormers first. Only consider chemical worming if above has failed or there are no other choices.


There are many wonderful herbal and homeopathic horse dewormers on the market. But it is best to devise a specific program tailored to your horse for better success. Get the help of a qualified homeopathic or holistic veterinarian to help you.


Would you like a more Natural
Horse Deworming Program?

Our 3 step process addresses your horse deworming on a individual basis. We utilize both homeopathic remedies and Herbs that have a very unique balance that eliminates the Parasites, Naturally without the concern of side effects.

Our program eliminates the need for those expensive stool samples needed for chemical dewormers that can be over $150 with multiple samples needed. Also, you avoid the potentially deadly side effects that come with Chemicals.

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