Worming: Worming Programmes

A diagnostic-led, targeted worming programme and only worming your horse when necessary is better for your horse and reduces the risk of resistance to the ingredients used in wormers.

A basic targeted worming programme

The worming programme for individual horses may vary depending on their age, pasture management, previous worming history and worm burden. However, a basic targeted worming programme for an adult horse may look like this:

• Spring/summer grazing season (March – September):Carry out a faecal worm egg count approximately every 12 weeks. Your vet will be able to recommend an appropriate wormer if your horse needs to be treated.
• Once the grazing season is over and the weather starts to get colder (October – December), this is the best time to test for tapeworm and carry out a risk assessment, and possibly a blood test, for the presence of encysted small redworm. These tests will determine whether you need to treat your horse for either of these parasites, neither of which can be identified using a faecal worm egg count.
• It is then recommended that you carry out a faecal worm egg count 12 weeks after testing/treating your horse in the Autumn/Winter.

If the worming history of a horse is unknown or the horse is starting on the worming programme, then your vet may suggest treating with moxidectin once and then following the targeted worming programme. This also applies to new arrivals on the yard.

There are also other things you should do to help reduce your horse’s worm burden, such as regular poo picking, rotating grazing paddocks, not overstocking pasture and grazing horses with other livestock. Find out more Worming: Top Tips For Worm Control – Horse Health Programme

The worming of foals and horses up to two years old differs from that of adult horses. Speak to your vet for advice on worming youngstock.

Faecal Egg Count Reduction Tests – why they are important

The faecal egg reduction reduction test (FECRT) is the only sure way that you can tell if the wormer (anthelmintic) that you are using to treat small redworms is effective, or if the worms have developed resistance to the drug. If the worms have developed resistance, the wormer won’t be working as well as it should, and there is a risk that your horse will accumulate dangerous numbers of redworms.

• Ideally you should perform a FECRT once a year (in the Spring, Summer or Autumn) when a routine faecal egg count from your horse is high e.g. more that 4-500 eggs per gram.
• If your horse is grazing pasture with other horses which also have high worm egg counts, then the test should be done simultaneously with some or all of the other horses that have high counts.
• Ideally, you should perform the test on at least five horses in the herd – the higher the worm egg counts and the more horses that you can test, the more reliable the results will be. However, it is still valuable to do the FECRT on individual horses on a pasture or small groups of horses if they are grazing the same pasture.
• Your vet or SQP can advise you about exactly how to do the FECRT, but in short, it involves running a faecal egg count just before giving your horse a wormer and then repeating another faecal egg count 14 days later. If the anthelmintic is working well, then there should be a reduction in the egg count of at least 90-95%, whereas if there is a resistance problem, the reduction will be less than 90%.
• It is really important that you administer the correct dose of wormer (anthelmintic drug), based on the weight of the horse. Your vet can help you with how to assess your horse’s weight.
• There are three main types of anthelminitc drugs that are commonly used to control redworms – the benzimidazoles, the pyrimidines and the macrocyclic lactones (includes ivermectin and moxidectin). You should discuss which drug class it would be appropriate to test with your vet or SQP.