Valley Veterinary Group

Why should we worry about worms and horses? 

A large percentage of horses and ponies carry some internal parasites (worms) which, in small numbers cause very few ill-effects. However, if left unchecked and numbers increase beyond a certain level, they pose a major threat to the general health and well-being of the animal. Sadly, it is not always possible to tell that a horse is carrying these parasites just by looking at it from the outside and even an apparently healthy looking animal can have a high worm burden which could develop and cause illness, even death. Horses such as these are also a liability to other owners as they are contaminating shared grazing by passing out worm eggs in their droppings.

One problem which is causing more concern nowadays is the development of resistance to certain worming chemicals. It has been shown with other animals, such as sheep, that using currently established worming practices can encourage the increase of resistance, leading to a population of parasites which cannot be controlled by the known range of chemicals. In the UK, worms with resistance to benzamidazole and pyrantel based wormers have been shown to be a growing problem in horses and ponies.

What is a worm count? 

Although it is called a "worm count", the test counts the number of worm eggs found in a sample of the horse's dung. The test is mainly for eggs of large and small Strongyles, although occasionally eggs of roundworm and tapeworm are seen. If you want a specific test for tapeworm then please contact us and ask for a tapeworm antibody test to be done.

Why do a worm count? 

Primarily, the reason for having a worm count done is to check one aspect of the internal health of your horse or pony. Overlooking a worm problem can lead to the development of a heavy worm burden and the typically described "Poor do-er" which may show diarrhoea, colic, loss in weight, lethargy and, in the worst cases, death. A worm count is one way of checking to see that these parasite burdens are not waiting in the background to cause you and  your horse problems a little further down the road. Once this has been ascertained, you are then in a good position to plan a worming strategy in consultation with us. A worm count can help to recognise that there is a potential problem so that you, the owner, can take steps to prevent things progressing. Other reasons for getting a count done are:

1. To give you peace of mind that your horse is not shedding eggs onto the grazing area and so contaminating the pasture and creating recurring problems for you and other owners.
2. To give confidence that the worming and pasture management strategy which you and/or your livery yard are using is successfully controlling the parasites.
3. To check newly acquired horses and ponies upon arrival at a yard before turning them out onto communal grazing so that pasture contamination is kept to a minimum.
4. To make sure that your animal is not carrying worms which are resistant to (i.e. not controlled by current worming chemicals.
5. To monitor horses which are travelling to different venues as part of their routine, and grazing on potentially contaminated grassland.
6. As part of a pre-sales or pre-loan health check.

In conjunction with us, you can adopt a strategy which aims to decrease the quantity of chemicals given to your horse. In these cases, regular worm counts are done and worming chemicals are given only if the count reaches a threshold level. This technique not only reduces costs, but is also considered helpful in combating the problems of resistant worms developing.

Strategic worming means you only worm the horse if the faecal worm egg count (WEC) is greater than 200 eggs per gram. It has been suggested that a low worm burden    encourages the horse to improve its own immunity against worms.

If the horse does not require worming, a repeat sample is taken 12 weeks from the original sample. If the samples continue to be negative the intervals between sampling can be increased.

Advantages of strategic worming:-

Cost effective – only treat those that need worming.

Less resistance – worms are not exposed to excessive worming drugs so take longer to become resistant to the drugs.

Environmentally friendly – less build up of drugs on the pasture.

If you decide to use strategic worming, do bear in mind that:-

All horses need to have repeated WEC.

Youngstock have less natural resistance to parasites so regular sampling is vital.

Tapeworm levels not assessed – either worm in spring and autumn for tapeworm or use blood samples to detect tapeworm infection.

Small redworm encysted larvae not assessed - use a larvicidal dose once yearly between November and January.

We would recommend worm egg counts to be carried out in February, May and August to establish whether your horse needs treated with a wormer. May would also be a sensible time to treat or test for tapeworm. Around November - January after the first frost we recommend worming for tapeworm, and larval stages of cyathastomes.

It can be useful to mark a calendar to plan the next date of worming or worm egg count.

Is your wormer working?

• Check how your worming programme is working by collecting a fresh dropping sample 2 weeks after worming and bringing it into the practice for a worm egg count (WEC).
• A blood sample is required to test for tapeworms and to show tapeworm levels in the previous 12 weeks.

How do I get a worm count done? 

Getting a count done could not be easier. All you need to do is:

1. Contact us by telephone or e-mail and tell us how many horses you want to test.
2. We provide you with the number of sample pots that you need.
3. Once you have taken the sample, hand it back into the surgery and we will provide you
   with the results as soon as possible.