Worming Information

When horses graze it is impossible to avoid worms in the environment. With a low burden in the environment combined with the horse’s immune system this usually keeps the worm levels in the gut low. It is important to understand that it is normal for a horse to carry a small worm burden as that helps them to develop immunity. Important factors to consider when worming your horse include: 

  • Whether your horse needs worming 
  • Which wormer is most appropriate for that time of year/ type of worm burden 
  • The weight of your horse – underdosing risks increasing the chances of resistance forming 

The best way to tell if your horse needs worming is a worm egg count. We ask for a small amount of fresh faeces from multiple balls which we then look at under a microscope. Worm egg counts allow us to target treatment more effectively. Your horse may show no clinical signs of a high worm burden which is why a worm egg count is much more useful. However very high burdens may cause the following clinical signs: 

  • Weight loss 
  • Colic 
  • Diarrhoea 
  • Rough hair coat  
  • Poor growth 
  • Respiratory problems – nasal discharge or cough  
  • Itching of the tail  
  • Visible worms in the faeces  

We would recommend your horse has a worm egg count 3-4 times a year. A worm egg count will show the presence of many adult worms such as large and small red worm.  Worms which do not show up on a worm egg count: 

  • Tapeworm – blood or saliva tests are available as an alternative  
  • Pinworm – cellotape test around the tail area  
  • Encysted stage of the small redworm – blood test   

A worm egg count can also be used to test for resistance, after worming your horse a reduction in eggs of less than 95% suggests resistance to the wormer is forming. Modern worming treatment has been around for approximately 50 years and ongoing use has led to resistance. This occurs through natural selection. Some worms will be naturally more resistant to the effects of the wormer, these worms will then reproduce passing the resistant genes on, contaminating the pasture with a population of resistant worms. By regularly using wormers we then select for a population of worms which can’t be killed. The medications will then become less and less effective leading to increased worm burdens. Therefore, is it of vital importance we use wormers responsibly and slow the resistance down. We can do this by: 

  • Only worming when required – blanket worming is not recommended  
  • Rotating type of wormer 
  • Worming correctly – accurate weight, always give slightly more than slightly less 
  • Reduce the environmental burden – regularly remove droppings in paddocks, rotate pasture, avoid over stocking 

We have worming protocols which we discuss and email out to you based on your management systems. They highlight when to worm and which wormers we would advise based on your worm burden. If you would like more information please contact us on: