Worming

Management of worms and wormer choice.

OPTIMISING ANY HORSE WORM CONTROL PROGRAMME

WHICH WORMER TO USE?

It has been shown in surveys that most owners worm their horses frequently enough to prevent a significant worm burden developing. However, it would seem that often the decision as to which wormer to use is made on the basis of advertising or cost. Currently there is real concern over the problem of worms becoming resistant to the types of wormer we use. In Britain, there is already significant worm resistance to certain classes of drug used. In countries such as Australia and South Africa, the problem is worse and farms have had to be abandoned due to the worms being resistant to all classes of drugs available. It is therefore important that we not only worm our horses to prevent disease, but that we do it in a responsible way. In order to slow the development of resistant worms in the population, it is important to understand a little about the wormer you are giving.

Use the correct dose for weight

A weighing tape can be used to give an indication of a horse’s weight.

Breed type/Height – a rough guide to weights.

Mature Shetland - 100kg
12.2hh pony - 250-300kg
Donkey - 250-300kg

14.2 pony - 400kg
15.2hh TB - 450-500kg
15hh Cob - 550kg
16.2hh TB - 550 - 600kg
16.2hh Hunter - 600-650kg
Shires/Clydesdales - 800kg

New arrivals to the yard

Worm as the horse arrives for all parasites.
Ideally isolate for 7 days in a stable or separate paddock so any worms excreted do not become a new resident population.

Remember other infectious diseases require approximately 2 weeks of isolation e.g. strangles, ringworm, herpes virus, equine influenza.

Pick up droppings

At least twice weekly.
Especially important if on restricted grazing as worm larvae migrate from droppings onto the surrounding grass.

Paddock rotation

Rest pasture for at least 3 months if possible
Clean pasture reduces the worm burden the horse is exposed to
Do be aware if the horse/pony is prone to laminitis or tying up

Graze with sheep or cattle

Horse worms are unable to survive in these animals

Foals

Worm at 2 and 6 weeks of age with Panacur paste if high risk of worm exposure.
Worm at 12 weeks if foal is in a low risk situation.
Keep foaling boxes disinfected.
Tapeworm treatment should only be necessary from the autumn of the year of birth (spring if the foal is very late).

HORSE WORMING DRUGS AVAILABLE

CLASSES OF WORMERS

Avermectins e.g. ivermectin or moxidectin based wormers
Pyrantel based wormers
Benzimadazoles e.g. fenbendazole based wormers

The following table shows you the worming drugs available and their duration of action. It must be noted that duration of action differs between drugs, as do the parasites targeted.

Trade Name	Active Ingredient	Duration of Action	Action
EQUEST EQUEST PRAMOX*	MOXIDECTIN (*and PRAZIQUANTEL)	13 weeks	Kills all except tapeworm and effective against encysted small redworm larvae. Can be used from 4 months old (*also kills tapeworm and can be used from 6.5 months old).
EQVALAN VECTIN ERAQUELL	IVERMECTIN	8 weeks	Kills all except encysted small redworm larvae and tapeworm.
STRONGID P PYRATYPE	PYRANTEL TARTRATE	4 weeks	Double dose kills tapeworm. Can be used from 8 weeks old. Kills roundworms but not bots or encysted redworm larvae.
EQUITAPE	PRAZIQUANTEL		Tapeworm only.
EQVALAN DUO EQUIMAX	BOTH PRAZIQUANTEL & IVERMECTIN	8 weeks	Kills all at single dose, except encysted small redworm larvae. Can be used from 2 weeks old.
PANACUR GUARD	FENBENDAZOLE	4 weeks	5 day course kills encysted small redworm larvae, but there is some resistance. Does not kill tapeworm.