How Long After Worming Horse Are Worms Expelled?

Last Updated on December 21, 2022

If you care for or own a horse, you will know that worm control is an essential part of horse maintenance. It is very likely that at some point you will need to give your horse a dewormer. But how long after worming horses are worms expelled?

Is It Normal To See Worms In Poop After Deworming?

Every horse will come into contact with parasites during their lifetime. This includes worms, and it is normal for horses to carry a small number of worms most of the time. However, if these worms multiply and numbers start to rise, they can become a problem.

When your horse has a high level of worms, you will need to administer a dewormer. These normally work by either killing or paralyzing the worms, stopping them from multiplying. When the wormer has been administered there is only one way out for the worms – via the feces!

So if you need to administer a dewormer to your horse, it is completely normal to see worms in poop after deworming. It is a good idea to monitor the feces for several days after deworming, to see the type and number of worms being passed. Not a pleasant task for any horse owner, but it will help you see how many worms your horse had!

Are Live Worms In Stool After Deworming A Problem?

It is entirely normal to see live worms in stools after deworming. Not all wormers work by killing the worms whilst they are in the body.

If you see live worms in the feces after deworming, don’t panic! These worms will not be able to survive and reproduce outside of the horse’s intestinal system. However, it is a good idea to figure out what type of worms they are to help your veterinary surgeon decide which wormer you should use in the future.

Here are the most common types of worms you might see in your horse’s feces:

  • Redworms – small, thin worms, which are either red or white in color
  • Roundworms – large, stringy yellow-white worms, up to 30cm in length (yuck!)
  • Tapeworms – a long worm that is normally excreted in smaller segments
  • Pinworms – small white worms, very similar to beansprouts in appearance

Safeguard Horse Dewormer – 25 Gm

How Long After Worming Horse Are Worms Expelled For?

After you administer a dewormer to your horse, there will be a short period – from hours up to a couple of days – before it begins to take effect. Once the wormer begins to work its magic, it will continue for 24 to 48 hours. During this time you may start to see worms expelled in the feces.

But how long after worming are worms expelled? Well, this varies from horse to horse. If your horse has a low worm burden, you may not see any worms being expelled at all. For horses with a large worm burden, they may expel worms for 3 to 4 days after deworming. This is because the dead or paralyzed worms can take a long time to exit via the digestive system. So don’t panic if you are still seeing worms after a few days, the wormer is still doing its job!

If you continue to see worms in your horse’s feces after this time, you should seek advice from your veterinary clinic. This is because you may need to get a fecal analysis done, and possibly use a different type of wormer. Never give another wormer without consulting a veterinarian first.

How To Check For Worms After Deworming Your Horse

Although it is not uncommon to see worms in horse poop after deworming, this isn’t always an accurate way to check for worms. If the droppings are not collected straight away then other creatures may have eaten the worms, so you may not always see them. It is also virtually impossible to check the sheer volume of manure that horses produce!

Is It Normal To See Worms In Poop After Deworming

The most accurate way to check for worms after deworming your horse is by carrying out routine worm testing on your horse. This is a great way to figure out if a horse needs worming or not, and helps us to ensure that we give the right wormer at the right time. This is known as a targeted worming strategy.

Various tests can be used to check for worms in horses. The simplest one is to take a dropping sample to check for worm eggs. Saliva and blood tests can also be used, particularly for hard-to-spot worms such as tapeworms.

How To Stop Your Horse from Getting Worms

With horses, prevention is always better than cure! In the past, wormers would be given all year round, whether the horse had worms or not. This has led to a lot of worms that are resistant to wormers, and we now aim to worm only when absolutely necessary.

So, what are the best ways to stop your horse from getting worms? The number one most effective thing you can do is collect your horse’s droppings. It takes only five days for worm eggs in a dung pile to turn into larvae, which can then be eaten by your horse.

How To Stop Your Horse Getting Worms

Droppings should be collected regularly from the pasture, daily if possible. These should be disposed of on a muck heap located well away from the field. Amazingly, worm larvae can travel considerable distances in the right conditions!

It is also important to avoid overgrazing – this is where there are too many horses on a small patch of land. Rotate fields regularly to minimize the worm burden on the land, and remember to test your horses regularly for worms.

Should I Feed My Horse Before Worming?

For the vast majority of horse wormers, it does not matter if the horse has feed before the wormer is administered or not. If you are in any doubt, check the datasheet for the wormer you are using or ask your veterinarian for advice.

There is one good reason to withhold food for a short period before giving wormer to your horse. When worming a horse with a paste syringe that is squirted directly into the mouth, this is best given when the horse’s mouth is completely empty.

Many horses store balled-up food in their cheeks for some time after they take a mouthful of food. They will then use this to help them to spit out the wormer, making it hard for you to be sure if they received the correct dose or not.

Can You Worm a Horse That Has Ulcers?

Controlling worms and other internal parasites in horses that have ulcers is particularly important, as they can be the cause of ulcers or may make an existing problem first. It is suspected that there is a link between botfly larvae and gastric ulcers in horses, and strongly may cause ulceration of the colon.

If your horse is undergoing treatment for ulcers, it is a good idea to consult with your veterinarian before giving a wormer. They will be able to decide on a targeted worming strategy and make sure that the wormer is safe to be used alongside any medication your horse is receiving.

How Often Are You Supposed to Worm Your Horse?

There are no hard and fast rules on how often it is necessary to worm your horse. In the past, specific wormers were given to all horses at certain times of the year, whatever the situation. This was called blanket worming but is no longer advisable as it is thought to increase the risk of wormer resistance.

Instead, most veterinarians now recommend a targeted worming strategy. This involves testing the horses beforehand for the presence of worms and only treating those with a high worm burden or those considered to be at increased risk.

Targeted worming is very effective when carried out in conjunction with other worm control strategies, such as a collection of droppings and pasture rotation. Your veterinary clinic will be able to advise you on the best time of year to test your horse for worms, and also which wormer if any, should be given in light of the test results.

Can You Overdose a Horse on Wormer?

Most horse wormers have a reasonable safety margin and a slight overdose will not cause any ill effects. However, accurate dosing is key to reducing the risk of wormer resistance. Both under-dosing and overdosing can contribute to this problem, but under-dosing is considered to be worse.

The most common method of estimating horses’ weight is using a weigh tape. These are not always very accurate, so if you ever get the chance to weigh your horse on a weighbridge you should take it – you might be very surprised!

A lot of veterinarians now advise that you add 10% to your horse’s body weight when calculating the dose of wormer to give. So, if your weigh tape tells you that your horse weighs 600lb, you should add another 60lb to the dose given.

When to Worm Horses With Panacur?

Panacur is a type of horse wormer used to control large and small strongyles, ascarids, and pinworms. Its active ingredient, fenbendazole, is particularly effective at treating encysted small strongyle larvae, which can cause a lot of harm to young, susceptible horses.

Panacur is commonly used in young foals as the first wormer, normally given at around 6 weeks of age. After this, Panacur and all other wormers should only be given as part of a targeted worming strategy. This means testing the horse for the presence of worm eggs in the droppings first, then deciding on the most appropriate wormer according to the time of year.

If worm egg count tests come back positive, then fenbendazole (Panacur) is commonly given as a five-day course as part of a winter worming program. Alternatively, a one-off dose of moxidectin (Equest) may be advised.

Fenbendazole wormers (Panacur) are sometimes also recommended if summer worm egg count tests come back positive.

Can I Worm My Horse if it Has Diarrhea?

If your horse is suffering from diarrhea, it is a good idea to seek advice from your veterinarian before worming it. Worms can sometimes cause diarrhea in horses, so it may seem logical to give a wormer, but this may make the situation worse.

The reason for this is that many horse wormers will cause low-grade diarrhea in horses. So, if your horse is already suffering from diarrhea, giving a wormer may make this worse. Severe diarrhea can be very problematic for horses and may lead to dehydration.

If a horse has a high worm burden, then any worm must be only given under veterinary advice. Worms often burrow into the intestinal walls, and administering a wormer can lead to severe gastrointestinal inflammation. In younger horses, this may lead to chronic diarrhea, weight loss, and even death.

Your veterinarian may prescribe medication to give alongside the wormer, such as steroids. These will help to reduce inflammation and limit the chance of permanent intestinal damage.

How Much Wormer to Give to a Horse?

The amount of wormer to give a horse is normally calculated according to the body weight of the horse. Luckily, most wormer manufacturers provide their products in handy dosing syringes, with the body weight of the horse marked in increments on the side. All you need to do is set the dial to the body weight of your horse, and administer the wormer!

Accurate dosing of wormers is essential to ensure they are as effective as possible. So, don’t be tempted to guess the weight of your horse, as there are far easier ways to figure this out.

If you have a weighbridge in your local area, this can be a good option for weighing your horse. Your veterinary clinic may also have weighing scales for horses you can use.

Another option is to use a weigh-tape. These go around the girth of the horse, estimating the body weight according to this measurement.


So, as we’ve learned, some horses may expel worms for three to four days after worming. How long after worming horses are worms expelled depends on how high the worm burden of the horse was before worming. It is important to check your horse’s feces for worms, especially after deworming.

We’d love to hear about your experiences – do you worry when you see worms in your horse’s poop? Or maybe you have a question about how to reduce your horse’s worm burden? Add a comment below this post and we’ll get back to you!

What are the signs that a horse has worms?

Worms are one of the most common problems in horses. The symptoms of worms can be very subtle and it can be difficult to know when a horse has worms unless you are an experienced horse owner. Most often you will notice that your horse might be loosing weight, his hair coat might become rough and brittle, he might have issues with diarrhea or constipation and might even experience colic or develop respiratory problems. These symptoms are not specific only to worms so it is important to rule out other causes such as inflammation or infection before making the diagnosis of worm infestation. If you suspect your horse may have worms it is important to make sure that you get a fecal sample from him and have your veterinarian examine him to confirm the diagnosis. 

Can worming a horse cause colic?

Yes. The roundworm larvae usually enter the intestine when swallowed with grass. Roundworms then grow and live in the small intestine and when a horse is wormed, they are killed in large numbers. This can form an obstruction within the small intestine and it often results in the horse experiencing impaction colic. A horse that has been wormed regularly is much less likely to have an impaction colic, though. In general, this kind of reaction to wormer is more common in young horses and horses that haven’t been regularly de-wormed.

How do you get rid of worms in pastures?

The most effective way to reduce larval numbers in your paddocks is by removing the manure regularly. By removing the manure, you’ll keep the eggs from hatching into larvae. In warmer climates and higher summer temperature it is recommended to remove manure every three days. If this is not possible, there are other ways to control worms population in pastures. However, if possible, it is best to avoid using chemical pesticides and fungicides that can impact the environment. You can use pasture plants instead. There are a variety of chemical compounds in those plants that have shown some degree of efficacy against parasites, including thujone and tannin. Another good example of a non-chemical method is pasture rotation. Rotating your animals between pastures every month or so helps keep the parasites under control by limiting the amount of time your animals spend grazing on one particular pasture.

Which horse wormers contain moxidectin?

Equest contains the drug moxidectin and is one of the few wormers that can control the important encysted larval stages of small red worms. It has a long period of action against worms, helping to reduce contamination in the pastures for grazing animals. This means that it is less likely to lead to over-dosing and the need for repeated treatments. It is also a long-lasting drug with low toxicity and a wide margin of safety. Moxidectin is used in equine wormer products because it is more stable than other drugs in water solutions, and is particularly effective when used at the correct dose. This makes it an ideal choice for use in horse wormers. It can be used in both feed and water based products, and has been proven effective in both types.