Worming Advice

Advice on the use of Wormers

Over the last decade increasing resistance to antihelminthics (drugs that act against worms) has been reported. This is worrying as there are no new drugs in the pipeline and if worms become resistant to all the currently available wormers, we will have no means to treat infestations in the future.

Unnecessary worming and incorrect dosing are believed to have played a substantial role in the development of resistance. The traditional way of worming is “interval dosing”, which involves regular administration of wormers to the whole population on one yard. While this regimen is very practical, it will result in routine worming of many horses that do not need it. For certain, in the absence of particular husbandry procedures e.g. dung removal, paddock rotation etc, this approach is preferable to ‘zero worming’.

We have now teamed up with Liphook Equine Hospital to provide a faecal worm egg count service, in order to ‘target worm’ those horses that require treatment.

In order to do this, a practical “easy to use testing kit” is available at the surgery or supplied by an attending vet. You will just need to clearly fill in all your details on the bag provided, collect a faecal sample and send it to Liphook Equine Hospital using the prepaid bag provided. The lab will then send us the results and we will advise you on the appropriate course of action. If your horse has a negative count, it is likely that no further action will be required. If the worm egg count is positive, we will be able to advise you on the most appropriate wormer to use and discuss husbandry.

It is important to remember that not all worms are detectable by the worm egg count. You would still need to worm your horse yearly for bots, tapeworm and encysted larvae. There is a blood test available that can assist in the diagnosis of tapeworm.

We advise following the program below:

Year 1

Month Action Use
March Worm Egg Count  
May Worm Egg Count (if positive results in March)  
July Worm Egg Count (if positive results in May or if no worm egg count carried out in May)  
September - October Equimax (Ivermectin + Praziquantel) To target bots and tapeworms
December Equest (Moxidectin) To target cyathostomes (migrating and encysted larvae)


Year 2

Month Action Use
March Worm Egg Count  
May Double dose Pyratape (Pyrantel) To target tapeworms
July Worm Egg Count  
September - October Eqvalan (Ivermectin) To target bots
December 5 Days panacur guard To target cyathostomes (migrating and encysted larvae)


In addition to this, any new horse entering a yard should have a worm egg count performed prior to turnout, to prevent contamination of pastures.

An important part of an effective worming program is to ensure that drug treatments and faecal sample testing are combined with good pasture management (avoidance of overstocking, poo picking and harrowing during dry periods) and to minimise infection levels and reliance on wormers.

It is important to note that pregnant mares & young foals are more susceptible to a worm burden than other categories of horses and that wormers administered to the mare will not be passed to the foal via her milk. While any worm can affect foals, the most significant parasites are ascarids, also known as roundworms.

Ascarids take advantage of the na├»ve immune systems of young or debilitated horses. The more traditional interval dosing will be more appropriate for a young foal from 1 month of age although heavy roundworm burden can cause problems if a sudden and massive kill of the roundworm occurs following the worming dose. Mares should be wormed during pregnancy, particularly one month before their ‘due date’ with 5 Day Panacur Guard.

When administering a wormer, it is important to estimate the horse`s weight as accurately as possible to avoid underdosing (or overdosing in case of Equest, as it has not got a large safety margin). A weight tape could be helpful to monitor weight, especially when dealing with a growing foal.

When administering an Ivermectin or Moxidectin based wormer, it is important to dispose of any leftover product safely and contaminated faecal output as these wormers are very toxic to dogs, especially Collies.

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