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Emergency 01620 822262
Haddington 01620 822262
Musselburgh 0131 6653343
Dunbar 01368 860461
North Berwick 01620 894471
Prestonpans 01875 814772

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Parasite Control

Parasite Control

Horse owners know that controlling worms is essential for the health and wellbeing of their horse. It’s important to carry out the appropriate worming programme depending on the season, the particular worm threat and the size of your horse. Getting any of these wrong can lead to issues of resistance causing bigger problems in the future and can lead to unnecessary expense.

Links’ equine vets provide straightforward advice to ensure that you:

  • Follow the most up to date guidelines
  • Worm responsibly
  • Avoid problems of resistance
  • Avoid unnecessary treatment – saving you money

The Threats Worms Pose:

Parasites in horses can lead to:

  • Colic
  • Serious diarrhoea
  • Other gut disorders
  • Weight loss
  • In extreme cases death

How to Control Worms:

A 3-pronged approach is most effective:

  • Horse Wormers
  • Reducing Environmental Levels
  • Monitoring Infection Levels.

Horse Wormers:

This can be done in several ways:

  • Interval Dosing
  • Strategic Dosing
  • Targeting Dosing or a Combined Programme

Some wormers also help in the control of mange, lice and the winter eradication of stomach ‘bots’.

How do I worm my horse?

As the information on equine worming can be complex (see the page Parasite Control in Horses) it can be difficult to decide how and when to worm your horse.

This problem is simplified if we consider different age groups and the horse's environment and also the desirability of using antparasitic drugs in cases where they may not be totally necessary. This unnecessary usage is expensive, potentially detrimental to the horse and ultimately can lead to uncontrolled resistance in the worm population whereby no wormers work. This situation can be put off as long as possible by responsible worming which has a good chance of saving you money too!

Pregnant Mares and Foals

Pregnant mares should be wormed throughout their gestation with suitable equine wormer and a final dose given 2-4 weeks prior to the foal being due.

The foals themselves should be wormed as they start grazing and this should be repeated in their first year again with a suitable equine wormer at manufacturer's recommended intervals. Tapeworm infection is less likely in horses less than two months of age so a narrow spectrum wormer is suitable at this point.

Adult Horses over 3 years

Many inaccuracies are often quoted with regards worming programmes in adult horses. These include that tapeworm need treated for twice yearly, that only young and old horses need to be treated for cyathostomes and that all horses need regular roundworm treatment. The facts of the matter are very different and are often surprising to people who have wormed their horses religiously in the past (to the obvious benefit of the wormer manufacturers and their shareholders!).

These facts are:

Horses in the UK only need to be treated for tapeworm once a year (there is no evidence to support twice yearly tapeworm treatments being necessary).

All horses should be treated for cyathostomins in the winter to prevent accumulation of encysted worms in the gut wall.

On average 80% of horses do not need regular roundworm treatments as their burden is so so low that worming makes no difference to the horse but only promotes resistance in the roundworm population as a whole.

Horses up until 3 years old tend to have higher roundworm and tapeworm infestations than older horses (until they get to 15-20 years) and so these young stock are more likely to need regular worming based on the results of faecal egg counts.

The only extra advice is that any treatment given should alternate year to year to avoid the problem of resistance occurring.

So we get to this outline for worming an adult horse:


Worm against tapeworm (Double dose Strongid P or Pyratape P one year, Equimax or Eqvalan Duo the next year).


Collect faeces from every horse and check roundworm output by faecal egg count. 80% of horses on average will not need wormed. If they don’t move to the Winter worming for Cyathostomins. If they do need wormed against roundworm then use a usually effective product (Eraquel, Eqvalan, Strongid P, Pyratape) but always follow up with a repeat worm egg count 2 weeks later to ensure the product used is actually working. Without this follow up egg count the product may already be ineffective and the money spent on it is 100% wasted.


Protect against cyathostomins with Equest or similar one year and a 5 day course of Panacur Equine Guard the next year.

Stomach Bots

Bots are the larval form of certain flies (Gasterophilus spp.) which attach themselves to the stomach lining and can in thankfully rare cases cause stomach ulceration and even perforations with devastating consequences. Modern equine wormers of the avermectin family (eg Eraquell and Equimax) will kill Bots so removing this problem.

For the latest prices on equine wormers and faecal egg counts as standalone items or in conjunction with a yearly booster or vaccination course please contact us.

Reducing Environmental Levels:

Good Pasture management to reduce the risk of infection:

  • Twice weekly clearing of droppings
  • Regular pasture resting
  • Only 1 or 2 horses per acre of grass
  • Mixed grazing where possible.

This is basically good pasture management to reduce the exposure of grazing horses to infectious material.

Pastures should be cleared of droppings twice a week - this can have a dramatic effect on reducing levels of parasitism. Pastures should be regularly 'rested' to allow the worm eggs present to die off. This should be no less than 3 months without horses present. Mixed grazing using cattle and sheep can have a good effect on reducing contamination as these species take up the eggs present but don’t become infected by them and so produce no equine parasite eggs in their droppings.

Stocking density should also be carefully monitored and this means no more than 1 or 2 horses should graze per acre of grass.

Monitoring Infection Levels

Faecal egg counts and blood tests can be useful in monitoring a worming programme’s effect. Plus:

  • Faecal egg count on new arrivals before mixing with current horses.
  • A tapeworm ELISA blood test in cases of recurrent colic.

Monitoring levels of infection

Faecal egg counts are regularly used to monitor parasite levels. The test is useful to check new horses, to ensure worming programme is working, to investigate illness and to identify particularly high 'shedders' of worms. However the test does not pick up larval forms and can does not differentiate between certain worm types.

A blood test can be used to show antibody levels against tapeworm which again can be used to monitor worming programmes, check new horses and investigate illness (colic specifically). Limitations of this test chiefly reflect the fact that antibody levels to tapeworms stay increased in horses for up to 4 months so a high level today may actually reflect increased infection some months ago.

At the Links Veterinary Group we would advise a faecal egg count to be performed on new arrivals before mixing with current horses, and also a tapeworm ELISA blood test in cases of recurrent colic.