Advice & FAQs

Which worms are most likely to affect horses?

Redworm - extremely common. Likely to cause ill-thrift and disease. Migrate through the gut wall - large strongyles enter the circulatory system while small stongyles can encyst in the gut wall.

Ascarids and threadworm - more common in foals and young horses.

Tapeworm - implicated in some forms of colic due to where in the gut tapeworm inhabit.

Lungworm - usually only a problem in donkeys.

Pinworm more of an irritant than a significant health problem. 

Bots - fly lays eggs on the skin which can cause local irritation. Larvae in the stomach rarely result is disease. 

When should my horse be wormed?

Wormer should be administered as infrequently as possible and their worm burden monitored using worm egg counts or Equisal tapeworm tests. Wormers should then be used strategically throughout the year to ensure the worm burden in controlled but that the worms are not exposed frequently to the various wormer ingredients. This will help ensure resistance to wormer groups is reduced while maintaining horse health. 

What treatment can I use to combat encysted small redworm?

Moxidectin based wormers are licensed to treat all stages of redworm including the encysted stages. The advantage this wormer group offers is that it will treat the encysted stage whilst it is still encysted in the gut wall. This means there is reduced likelihood of mass emergence and the potentially fatal consequences which can result.

Alternatively a 5 day course of a Fenbendazole wormer can be used. This more traditional course has advantages if you do not know the current worm burden of your horse. As the worms will be killed over the course of 5 days there is a reduced likelihood of colic caused by the gut having to digest all of the worms in one go. However, this course will not prevent the emergence of redworm from their cysts, which can be more dangerous than using a Moxidectin which will kill them in situ. 

If in any doubt consult your veterinary surgeon who will be able to advise. Alternatively carry out a faecal worm egg count before treatment which will allow you to establish an approximate worm burden - though it is important to note this will not show the encysted stages as these do not shed eggs whilst in their cyst.

Tapeworm - when should I worm and do I need to double dose?

The ideal time to treat for tapeworm is the beginning and the end of the grazing season - Spring & Autumn. The reason for this is that exposure to tapeworm is greatest during extended periods of grazing - therefore treatment at the end of the grazing season and again 6months later is most effective. 

If you do not wish to treat as a matter of course then use of an Equisal Saliva Test will indicate the presence of tapeworm antibodies and allow you to make an informed decision on whether or not to treat. 

Tapeworm can be effectively treated in a single dose using a wormer containing praziquantel. Alternatively a double dose of a wormer containing Pyrantel can be used. 

What is the most common internal parasite that can affect my horse?

Small Redworm (small strongyle/cyathostomin) are the most common internal parasite to affect horses in the UK. These parasites can cause diarrhoea, rapid and severe weight loss as well as life threatening colic. 

What shall I do if my horse has a high worm burden?

If you know that your horse has a high worm burden, from results from a faecal worm egg count for example, and are concerned as to what the best course of action is to treat this, we would always recommend consulting your veterinary surgeon before treatment. A possible course of action would be to treat with a wormer which will only control the adult stages such as pyrantel wormer. This can then be followed up in 7-10days with a moxidectin based treatment to treat the remaining larval parasites. Tapeworm treatment can be included if necessary. 

How are routine worming and strategic worming programmes different?

Routine worming is a programme which uses anthelmintics throughout the year according to the dosing interval recommended by the manufacturer to treat for roundworm, tapeworm and bots. 

Strategic worming uses faecal worm egg counts to establish the need for treatment with anthelmintics. Treatment is only administered when the result of the worm egg count is above a specified level. This means that the interval between dosing can be extended where appropriate. Care must be taken using this method as not all worm species will be indicated by a worm egg count eg. encysted small redworm or tapeworm. 

Why do tapeworm not show in a faecal worm egg count?

As tapeworm only release their eggs sporadically a faecal worm egg count could show a false negative - ie no eggs may have been shed on the day the sample was taken, suggesting there is no tapeworm burden. The reality may be that there is tapeworm present. There is a test available specifically for tapeworm - Equisal measures antibodies produced by the horse in response to a tapeworm infection which will give an indication as to whether or not to treat.  

What if I overdose my horse?

All medicines should be dosed accurately and in accordance with the manufacturers recommendations or those given by your veterinary surgeon. Although a slight overdose is unlikely to have harmful effects, if in any doubt contact your veterinary surgeon. 

What about underdosing?

Whilst this will do no harm to the horse, you would be administering a sub theraputic level of the drug to the animal. This would expose the parasites to the drug but perhaps not sufficiently enough to kill them. Survivors of the treatment may then pass on their 'immunity' to subsequent generations leading to potential resistance to that drug. 

I don't know the weight of my horse, is this a problem?

In order to accurately dose it is imperative that you know how much they weigh. Weight should be established by the use of a weight tape or weigh bridge. Horse weight should never be guessed or estimated. Often guessing or estimating will lead to underdosing and the problems outlined above. 

My horse is difficult to dose with a syringe wormer. What are my options?

In-feed wormers are available such as Panacur Horse Granules. It is essential to ensure that all of the feed is eaten in order to prevent under dosing. If the ingredient you need is only available in a syringe formulation then we would suggest seeking advice from your veterinary surgeon as to the best way forward for your animal. 

Can I keep part used syringes for next time?

Generally wormers can be stored according to the manufacturers instructions up until the expiry date once opened. However, always check the packaging information as this is not always the case. 

Is rotating wormers each season a good idea?

The strategy of wormer rotation in horses has yet to be shown to make a significant difference to the development of resistance in the worm population. (Barnes E et al, 1995) While not without merit, there are many other factors which have more baring on the development of resistance than changing ingredients would have. 

Essentially, the most effective way to prevent resistance is to ensure a highly effective initial kill of the resident worms, alongside dosing with anthelmintics as infrequently as possible. (Dobson R et al, 1996). Therefore the ideal anthelmintic is a highly potent one which can be given as infrequently as possible. 

Additionally, good pasture management and the use of targeted worming programmes which use faecal worm egg counts to establish the need to treat can help prevent resistance developing. 

How frequently do I need to pick up the dung from the pasture?

Dung should be removed regularly, at least twice weekly during the grazing season, and once a week between November and March. Although harsh frosts may kill infective larvae on the pasture, with the milder and wetter climate now experienced in the UK, high levels of infective larvae can occur at any time of the year (Love S, 2003). Thus, there is an increased likelihood of grazing animals acquiring parasite burdens throughout the year. Therefore if the autumn and winter remain mild and wet, the twice-weekly removal of dung will be necessary all year round.

Should I worm my pregnant mare?

It is very important to worm pregnant mares, not only for their own health, but also that of the foal when it is born. Always check that the product you want to use is licensed to treat pregnant and lactating mares and try to worm her before foaling and throughout lactation according to manufacturer’s instructions.

What wormers can I use on pregnant mares?

Horse womerPregnantLactating

Eqvalan PasteYesNo
Eqvalan duoAfter 3 Months Of GestationYes
Panacur GranulesyesNo
Panacur PasteYesNo
Panacur 10% LiquidYesNo
Panacur 5 Day GuardYesNo
Pyratape P PasteYesYes
Strongid p pasteYesYes


Should I worm foals?

Yes foals should start to get wormed from 4 weeks of age + , they need special treatment as they have no resistance to worms. Mares with foals should be treated before to foaling with an appropriate wormer and preferably grazed on pasture that has not been grazed by other horses in the previous 12 months if this is not possible delay turning them out until June.

What horse wormers can I use on foals?

IngredientAge of foalSuitable wormers to use
Pyrantel Embonate 4 weeks Embo tape, Pyratape p, Strongid p
Ivermectin 6-8 weeks Eqvalan, Eraquell, Animec, Noromectin, Nexmectin, Bimectin
Fenbendazole** 6-8 weeks Panacur 5 day guard, Panacur granules, Panacur paste
Moxidectin 4 months Equest


From what age should I start worming my foal?

As foals have a low tolerance to worms they can quickly acquire massive worm burdens; therefore worming of foals should start at four to six weeks of age, and repeated every four weeks until 6 months of age. Thereafter worming can continue as per wormers recommended dosing interval. Always check 'the age from use' of any wormer prior to use.

What can I use for my donkey?

Donkeys should be wormed on the same basis as other horses but it is important to note that there are only a limited selection of wormers which are licensed for use in donkeys. 

There is a limited range of worming products available for worming donkeys on the UK market.

Here is a list of those prducts currently licensed for donkey treatment and available from our online store

Brand NamePackage Declaration
Panacur Equine Horses and other Equines
Panacur Equine GranulesDonkeys and Horses
Panacur Equine PasteHorses and Other Equines
EqvalanHorses and Donkeys

Strongid P PasteDonkeys and Horses
Pyratape PHorses and Other Equines


How do I report a suspected adverse reaction to a product?

Please follow the following link :-