Worming your horses to keep them healthy with the 3D worming approach – Direction, Dosage & Delivery.

Correct worming protocols are a vital part of keeping horse in good health and top condition.

The over use of wormers over the past 40 years has led to the development of resistance to many types of wormer drugs. It is now imperative that equine worming regimes are designed to identify and target only the horses that specifically need worming and use the most appropriate drug when treating them at the correct time of the year.

The Horse Health Programme allows you to be in control of your horses worming requirements.  The programme includes four faecal worm egg counts (FWEC’s) along with an autumn tapeworm saliva test and an autumn wormer where required.


It is critical to take expert advice when designing your worming programme. This should be tailored to your horse, taking into account their environment, management, health status and other risk factors. Your vet will also have knowledge of local worm resistance patterns that will help to select effective treatment as required.

The number of different types of worms and wormers available for horses can be confusing. A good worming programme for adult horses will include testing/ treatment for tapeworm once a year We recommend a once yearly treatment (late autumn / early winter) unless there is a known history of tapeworm problems on the yard or in the individual horse.  We also advise regular testing for strongyles throughout the year utilising faecal worm egg counts with an annual treatment for encysted red worm larvae and bots in the winter. Young stock and breeding animals will require more regular worming - speak to your vet for advice.

Spring and autumn

During the spring and autumn months worming for tapeworm is recommended. Tapeworm infestation will not be picked up by routine faecal egg counts; however, there are new tests available that can detect antibodies to tapeworm, in blood or saliva. We include a tapeworm saliva test in our Horse Health Programme.


Faecal worm egg (FEC) counts should be used every 2-3 months throughout the year, to assess the roundworm burden. Your vet will be able to advise you on whether your horse requires worming, usually only horses with a FEC of >200 eggs per gram are treated.


The annual treatment for encysted small redworm larvae is usually given over winter.  The encysted larvae can emerge from the intestinal wall in the spring and cause damage which leads to diarrhoea and weight loss. As there are only two effective treatments for encysted redworm (moxidectin and fenbendazole) and resistance is a big concern, many experts recommend that the use of moxidectin should be reserved for a single annual treatment at this time. Winter treatment should also cover bots, which are the larval stages of Gasterophilus flies. As the bot larvae overwinter in the horse, treatment during the winter months should remove the larvae without the risk of reinfection as fly activity has ceased. 

Pasture management

Reliance on drugs for worm control can be drastically reduced if sufficient attention is given to pasture and horse management.  This not only makes worming more cost effective, but also helps to prevent resistance developing.

  • Avoid overstocking pasture (one horse per acre is an appropriate rule of thumb)
  • Poo pick at least three times per week.
  • If possible, co-graze horses with sheep or cattle.
  • If possible, rotate pasture and rest fields year by year.
  • Keep young horses grazing separately from older horses. Young horses are likely to have the highest parasite burdens and be responsible for the majority of pasture contamination.


Where worming is deemed necessary, it is vital to ensure horses receive the correct amount of wormer for their weight. Visual estimation of a horse’s weight could lead to inaccuracies and most often under-dosing.  When a weighbridge is not available, a weight-tape can be used. Ask your vet about how to correctly use a weight tape, or watch the ‘how to’ video at www.3dworming.co.uk.


In each syringe of wormer there is approximately one or two teaspoons of paste containing the total dose of the active ingredient.  Any ‘spit-out’ can represent a significant volume of the overall dose being lost and horses receiving incorrect doses.  Under-dosing has several consequences; firstly, the product will not work as it should and secondly, it can contribute to the rapid development of resistant worms.  Some wormer drugs are also highly toxic to other pets so be very careful when disposing of used syringes!

If your horse is difficult to worm with a syringe, some wormers are available in a tablet form which can be added to the feed. These are also handy for dosing small or larger horses.

Brought to you by Virbac, the manufacturers of Equimax® and Eraquell®.