Autumn Worming

As a horse owner you know you need to worm regularly. Correct dosing, faecal worm egg counts and pasture management all play an important role in keeping your horse’s worm burden low. There is evidence of anthelmintic (wormer) resistance to all drug classes so you need to ensure that you use the right product at the right dose and at the right time of year, to help prevent this from becoming commonplace. Strategic dosing for specific worms at specific times of year should be performed on all horses and will help make a difference.

In the autumn we would advise you to focus your efforts on tapeworm and encysted small red worm control. Bear in mind that not all products will kill these two worms, so you need to make sure that you use an effective product. It is important to treat all horses on the same yard at the same time. Working out a specific worming protocol for your horse will mean you can develop the most efficient system and can mean that some horses need to be wormed less frequently than others. We can help you do just that.

Young stock are particularly prone to worm infestation and, if possible, they should be grazed separately from older horses. We know that this isn’t always possible, in which case, you need to take special measures. Small red worm (Cyathostome) infestation is a particular problem in younger horses. In the larval stage they encyst in the intestinal wall and emerge ‘en masse’ when conditions are right – usually late winter or spring, causing diarrhoea, weight loss, colic and even death. To complicate matters, faecal worm egg counts, which are a useful tool in detecting adult worm population, will not pick up encysted larvae, because only adult worms produce eggs. The only way to be sure your horse is not infested is to use a product with proven effectiveness against the encysted stage of the small red worm.

Tapeworms are also common in UK horses and, once again, heavy infestation can cause colic. Autumn is a good time to treat against tapeworms to clear the horses at the end of the grazing season. Not all wormers are effective against tapeworm. We are happy to advise you to make sure that you worm your horse appropriately to get the best results in terms of effectiveness and your horse’s welfare.

Under dosing is thought to have contributed to certain wormers becoming less effective. A weigh tape will help you determine how much wormer you need to administer for it to be effective. Worm counts help us ascertain if your horse responds well to the wormer and by their use we can suggest a protocol which may mean worming less but targeting specific types of worms with the appropriate wormer. Faecal worm egg counts are also useful during the grazing season to identify the horses which require a wormer and they can also be used to help identify potential anthelmintic resistance. In any case, it is important that you rotate the wormer after each grazing season and use a product that contains a drug of a different class. The three main classes of anthelmintic are; the benzimidazoles; the tetrahydropyrimidines (pyrantel); the macrocyclic lactones (iver/avermectins). Using the same class of wormer every season will help increase the chance of resistance developing.

Grazing/pasture management can also help control worm burden on the pasture:
• Picking up dung at least twice a week is one of the best ways to limit the level of worm infestation on the pasture.
• All horses grazing together need to be wormed at the same time, otherwise they will just re-infest the pasture and each other.

We offer a worming programme service including worm egg counts and a tailored worming programme for your horse. Please contact the practice for further advice about developing an effective worming protocol. We can advise on introducing new arrivals, seasonal risks or local conditions regarding resistance. Yards offer a particular challenge when it comes to effective worming programmes. We welcome the opportunity to work with yard managers to create a yard worming protocol to protect all the horses that share the same pasture.


Autumn Worming