Equine Worming | Chine House Veterinary Hospital

Chine House Veterinary Hospital

EQUINE WORMING
Types of worm:
1.	Redworms: Theses can be divided into large redworms (strongyles) and small redworms (cyathostomes). Both these parasites colonise in the intestines after the horse grazes contaminated pasture. Here they evolve into adults, producing eggs passed in the droppings to further contaminate the pasture. The large redworms migrate as larvae through the intestines and liver, before become adults, causing inflammation. The small redworms can go into cysts in the intestinal wall to hibernate over the winter to emerge again in the spring. This is the dangerous time for horses as the mass emergence of larvae can cause severe damage to the intestines. This condition is known as larval cyathostomosis.
2.	Tapeworm: The tapeworm, anoplocephala perfoliata, lives at the junction between the small and large intestines, ileo-caecal junction. Tapeworm infestation can cause varying degrees of colic.
3.	Bots: Bots, gasterophilus, live in the stomach of horses as larvae. These are later passed in the droppings and hatch out into adult flies. These flies then lay their eggs on the horses coat, especially legs. The larvae can cause stomach ulcers.
4.	Lungworm: The larvae of lungworm, dictyocaulus arnfieldi, migrate to the lungs and can cause respiratory disease. This is seen very rarely, however, horses that live with donkeys are at greater risk.
5.	Strongyloides westeri: This worm can be transmitted from the mother to her foal in the milk and can cause severe diarrhoea if the foal is weak with a poor immune system.
6.	Parascaris equorum: This worm usually affects younger animals.
Diagnosis:
	A veterinary surgeon can often assess that worms are a problem in horses with the typical signs such as ill thrift, colic, diarrhoea and weight loss alongside inadequate worming and poor pasture management, however, samples of the droppings can be used to count the number of worm eggs. A blood sample is also available to help diagnose tapeworm infestation.
Prevention:
1.	Good pasture management: The pasture should not be overcrowded and droppings should be regularly picked up.
2.	Resting the pasture can allow time for worm eggs on the pasture to die. To be effective the pasture should be rested for at least six months
3.	If it is possible grazing with other species such as sheep or cattle should be done in rotation. Parasites from these species don't affect horses and their droppings promote good grass growth.
4.	New horses, with an unknown history, should be wormed on arrival and should be stabled for two days before going onto the pasture to reduce contamination. (Please speak to one of our vets about the appropriate wormer to use).
5.	Appropriate use of chemical wormers to reduce the number of eggs passed in their droppings.
Frequency of worming:
	Worming regimes should be set up for individual horses. Every clients situation is different and so blanket wounds cannot be given. Ideally we want to bring wormer usage down to a minimum level so that costs to clients are low but disease is still prevented. Using fewer wormers should also help reduce worms become resistant to certain wormers. The main method to minimise worming is to take faecal samples and count the number of worm eggs present with or without a tapeworm blood test. Horses with high numbers should be wormed, however, if the numbers are low then worming is not necessary which reduces cost and build up of worm resistance. This technique works very well on small yards where there are not many horses present and few new horses are introduced. Unfortunately some premises have to rely on more wormer because of their circumstances. Using the correct wormer is very important as certain wormers will only kill certain worms effectively. Inappropriate use of wormers has also been seen to increase the build up of resistance.
Types of wormer:
1.	Ivermectin and Moxidectin: These wormers will kill almost all types of worm, including bots, however, are not effective against tapeworm. Although ivermectin has some action against the hibernating encysted cyathostome larvae they will not kill all of them and moxidectin has been seen to be far more effective. Moxidectin also has a longer lasting effect, therefore, can be given at three monthly intervals, however, should not be used in foals. Some trade names: Ivermectin: Eqvalan, Noromectin, Eraquell, Vectin Ivermectin and Praziquantel: Equimax, Eqvalan Duo Moxidectin: Equest Moxidectin and Praziquantel: Equest Pramox
2.	Fenbendazole: This wormer is effective against most species of worm, however, resistance has built up against cyathostomes. Fenbendazole can be given as a 5 day course to target hibernating larvae and is a safe course of treatment if the animal has not been wormed for a long while or the worming history is unknown. Trade name: Panacur Panacur equine guard (5 day treatment)
3.	Pyrantel: Is reasonably effective against many mature worms, however, is mainly used as a treatment against tapeworms at double the dose. Trade names: Strongid-P and Pyratape-P
4.	Praziquantel: This is a specific treatment against tapeworms. Some trade names: Praziquantel: Equitape Praziquantel and Ivermectin: Equimax and Eqvalan Duo Praziquantel and Moxidectin: Equest Pramox
Please see table at the end of this article, which shows some of the different wormers and their respective actions.
Worming method: The following is only a basic guide, please contact one of our vets if you require more in depth advice.
1.	Pick one class of drug to use for one to two years as your routine wormer and then change to another the following year to help reduce resistance.
2.	Use this wormer throughout the year when the faecal egg count results indicate that the horse needs worming or, if this is not possible e.g. large yard, treat at intervals recommended by the individual wormer.
3.	Treatment against tapeworms should be given in the autumn. Either praziquantel or a double dose of pyrantel.
4.	Ivermectin should be given in December to treat bots.
Amount to give:
	It is very important that the correct amount of wormer is given to every horse as it may not be effective and in some situations toxic. To calculate the correct amount of wormer to give you can weigh your horse using a set of scales (there is a set a Chine House Veterinary Hospital) or using a weight tape.
Disclaimer

Wormer Name	Active ingredient	Activity against
Noromectin	Ivermectin	O, B
Equimax	Ivermectin & Praziquantel	O, B, T
Eraquell	Ivermectin	O, B
Eqvalan	Ivermectin	O, B
Eqvalan Duo	Ivermectin & Praziquantel	O, B, T
Vectin	Ivermectin	O, B
Equest	Moxidectin	O, B, EC
Equest Pramox	Moxidectin & Praziquantel	O, B, T, EC
Panacur	Fenbendazole	O
Panacur equine guard	Fenbendazole	O, EC
Pyratape-P	Pyrantel	O, T (at 2x dose)
Strongid-P	Pyrantel	O, T (at 2x dose)
Telmin	Menbendazole	O
Equitape	Praziquantel	T
T= Tapeworm B=Stomach bots EC= Encysted cyathostomes O= All other worms

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