How Do I Deworm My Horse?

Worming your horse is quick and easy to do as most deworming treatments come in the form of a syringe that can easily be squeezed into the corner of his mouth.

To worm your horse make sure you’ve got a firm grip on his halter then place the syringe in the corner of his mouth and gently squeeze the paste into his mouth. I always follow this up with a syringe of honey, that way the horse is left with a sweet taste and thinks of the whole process as a positive one.

How often should I deworm my horse?

Until very recently the general consensus was that you should worm your horse every 6-8 weeks. While this is still recommended in some cases it’s not always a good idea. Like most bacteria, parasites have also started to develop a resistance to treatments. To help prevent resistance it’s advisable to have a natural method for reducing the number of larvae while also only worming horses that have a large number of eggs. In the long run, this will not only be cheaper but it’ll also help to increase the effectiveness of wormers 

How do I test my horse for worms?

There are two main ways to tell if your horse has an infestation of worms. All horses will have some worms in their digestive system and you don’t want to completely remove all worms so testing to see if the worms are a problem is a good idea.

You can use the fecal egg count method to count the number of eggs your horse has per gram of droppings (known as EPG – eggs per gram). The baseline for worming is anything over 200 EPG. The problem with this method though is that only adults lay eggs so if your horse has a large number of larvae but only a very small number of adults the count won’t be reliable.

The other way of testing for worms is to use a tapeworm antibody test. This is a blood test carried out by a vet. The problem with this method though is that the results can still be positive for up to six months after all of the tapeworms have been killed.

Horses infected with worms can appear to be in good health but there are a few things to look out for that can indicate a worm issue:

  • Lethargic
  • Lack of appetite and loss of weight
  • Loss of condition, especially a dull coat
  • Diarrhea
  • Colic

Are there natural ways to prevent my horse getting worms?

In recent years parasites have increased their resistance to anthelmintics (the active ingredient in worming products) so many people opt to reduce or even prevent the risk of worms instead of worming. This might sound impossible but is actually easier (and more effective) than you might think.

  • Remove droppings every day – If you clear droppings from the paddock every day it’ll prevent larvae from hatching and then being ingested by your horse while he’s grazing. As an added bonus this will help to reduce the number of flies in the summer as well.
  • Use a hay net or rack – Feeding hay off of the ground will help to keep it free from larvae.
  • Fecal egg count (or FEC) – Some horses will carry more eggs than others. Counting the number of eggs in each horse’s droppings will help to establish which horses need to be wormed and which don’t. Worming only those horses will not only help to reduce the chance of infection it’ll also increase the effectiveness of the wormer. Horses with 200 or more eggs per gram (EPG) are considered to have a large number and need worming. A recent survey discovered that around 90% of fecal egg counts were below 200 EPG, so, therefore, didn’t need worming.
Grazing horses and sheep together can help reduce the number of larvae
Grazing horses and sheep together can help reduce the number of larvae
  • Rotate paddocks – If you have access to more than one paddock try to switch which one you use regularly, every 3-6 months is fine. Doing this means that most of the larvae will be killed off by the extremes of temperatures during the summer and winter. If you only have one paddock then consider fencing half of it off and then rotate between the two halves.
  • Cross grazing – Sharing a paddock with sheep will drastically help to reduce the number of larvae. This is because sheep can eat horse worm larvae without any effect.

What parasites can cause my horse to have worms?

There are a number of different parasites that can affect your horse but the most common ones are:

  • Redworms – Known as strongyles, this parasite infects the horse when the larvae are ingested and transform into parasites as they make their way to the horse’s intestine. Common symptoms are anemia, lethargy, and diarrhea.
  • Roundworms – Roundworms or ascarids grow in the small intestine then migrate through the liver to the lungs and then the throat before being swallowed again. When they’re back in the small intestine they mature and reproduce. A real problem in horses that are under a year old because they haven’t developed an immunity to them yet.
  • Tapeworms – The eggs of tapeworms are eaten by mites who then inadvertently incubate the eggs as they develop into larvae. While grazing horses will eat the mites which allow the larvae to mature. Once they’ve matured they attach themselves to the wall of the gut where they can cause an obstruction and inflammation.
  • Bots – Adult bot flies lay yellow-colored eggs on the chest, shoulders, and forelegs of horses, as the horse grooms itself it ingests the eggs which then attach themselves to the stomach lining causing irritation and digestive problems. Around 9 months later the larvae leave the horse via droppings and burrow into the ground to mature, only to return as adults and repeat the cycle. 
  • Pinworms – Pinworms lay their eggs on the skin around a horse’s anus which makes the area extremely sore. Although they don’t often cause disease they can irritate the skin so much that the horse can rub the area raw.
  • Threadworms – After around six months horses develop a natural immunity to threadworm but in foals, it can affect their growth rate. Threadworms are often dormant in older horses but mares can pass it to their foals via milk.
  • Lungworms – Often present in horses who share a paddock with donkeys. Donkeys can tolerate a large number of lungworm larvae but in horses, they create respiratory issues.

How do I treat worms?

The best way to treat worms is to use a worming paste but which paste you use will be dependant on the type of parasite your horse has a problem with. The table below should help you to know which ingredients help to remove which worms.

RedwormsRoundwormsTapewormsBot LarvaePinwormsThreadwormsLungworms

Can worms be good for my horse?

Historically we’ve tried to eradicate worms by use of a strict worming program but can worms actually be a good thing? I know you think I’ve gone mad but there’s a lot of evidence to show that a small number of worms can actually be a good thing. A low fecal egg count (approximately 100 to 200 EPG) can in fact help your horse. This is because they help to strengthen your horse’s immunity which is obviously a good thing.  


You don’t have to religiously worm your horse every few months, in fact doing so can lead to the parasites becoming immune to the treatment. Instead, it’s better to have a worm management plan where you regularly test for worms and then treat them accordingly. At the same time as doing this, you should be keeping the paddock as free of droppings as possible and rotate paddocks at least every six months.

I hope you found this article helpful. If you did I’d be grateful if you could share it please as it would really help me.

Recent Posts