Horses nearly always have a worm burden, meaning they nearly always have some parasitic worms in their digestive system. Controlling the worm burden is very important as a major worm burden can impact the health of your horse. It could be something which seems something minor, such as losing a bit of weight and condition. But they can also have serious health risks such as colic. Some conditions have a mortality rate of 50% and will the horse may recover, there can be permanent damage. Therefore it is important to have your horse on a worming programme.
What worms affect horses?
- Redworm (small, large and encysted.)
- Tapeworm
- Pinworm
- Roundworm
Proactive and Reactive Worming Programmes.
Worming used to be very proactive, advice being to worm every 6-12 weeks regardless. We then moved away from this to using certain wormers at certain times of year. However, using lots of wormers allows the worms to build up immunity over time. This is now a big issue in the equine population.
So now the advice is moving to a more reactive method. There are now a few different testing methods available, such as worm egg counts, saliva and blood tests. Horses should be tested throughout the year, usually more regularly during the main grazing season. Horses with high results or regularly test slightly above average should be wormed. This means that most horses are wormed less often and therefore worms are less likely to build up immunity.
When to worm?
There is no one size fits all method for worming horses. All horses have different needs with young and old horses needing more regular worming. But this is a rough guide for the average horse.
December / January: Worm for encysted small redworm
Encysted small redworm is one of the most dangerous types of worm to infect our horses. Unfortunately the normal worm tests such as worm egg count test using a poo sample or saliva tests do not detect them. So the current advice is to worm your horse once a year, targeting these worms specifically. Traditionally you would worm after the first frost of the winter. But any time in December or January should be fine.
There is a relatively new blood test what can test for encysted small redworm. So if you can test for it, you should. But this isn’t widely available yet.
Use Moxidectin or 5 day course of fenbendazole.
Spring: Tapeworm & Egg Counts
Spring, especially March, is a good time to start your worm tests for the year. This is about 2-3 months or 8-12 weeks since you last wormed your horse. So the perfect time to test. You should perform a worm egg count test but also a saliva test for tapeworm. There is also a blood test available for tapeworm, but the saliva test is more widely used.
You should only worm if the test results come back suggesting you should. The test results will also tell you what type of wormer you should use.
Summer: Regular Worm Egg Counts
Throughout the summer, you should perform word egg counts every 8 – 12 weeks. So if you did your spring tests in March/April, your next counts will be in May/June, then July/August. Once again, you should only worm if the test results suggest you should.
Autumn: Tapeworm & Egg Counts
By now roughly 6 months will have passed since your last Tapeworm test. So in Autumn you should repeat the tests you did in the spring, combing your final worm egg count of the year with a Saliva test. This will be in September/October, roughly 8 – 12 weeks since your last worm egg count.
Do I need to do this all myself?
Most yards, especially livery yards, will have a yard programme so all the horses are doing the same thing. This means you shouldn’t have to worry too much about what you should be doing and when as usually the yard owner will organise this for the entire yard. But it never hurts to be aware of what should be happening!
This can be a lot to remember and it can be easy to loose track of what you did last and when! My latest tactic has been to put up repeat reminders in my calendar for when to worm and when to test. I worked this out from when I last wormed for encysted small redworm and counted forward based on the above timelines.
If you have your horses by yourself or have to be responsible for your own worming programmes, there are still plenty of options out there to support you. Many vets will offer a worming programme where they will remind you when to worm and will provide the correct wormers and tests. Alternatively, many testing companies offer worm packages. These will usually include tests at certain times of year and suggestions of what wormers to use. However, you do end up paying a little bit more for this than if you were to just buy the tests when you need them.
Other considerations
While worming your horse at the right times with the right wormers is very important for their health. There are other things what should also be considered when it comes to worming horses.
Your horses weight
How much wormer you give your horse is determined by their weight. Before giving your horse a wormer you should check their current weight. Ideally we would all have access to a weighbridge which is by far the most accurate way to get our horses weight. But at the bare minimum you should use a weight tape to get a rough idea.
Manage your fields
Poo picking regularly and if possible, rotating your fields will help keep the number of worms in your grazing down. Ideally fields should be cleared of droppings at least once a week. But at the very least your horse should have plenty of areas in the field clear of poo. Sharing your grazing with other animals such as sheep can also keep the worm numbers down.
Last Updated on 15/03/2023
