Equine Worming

The best way to save money, target your treatment and expose your horse and the environment to as few drugs as possible is to worm your horse as little as possible!

• Know whether your horse has worms! Worm egg counts (WEC) can be done in 24 hours on a fresh poo sample and will tell you if your horse has an active strongyle infection or not.

• Poo pick, boring but essential. Clearing fields of poo at least twice weekly will dramatically reduce the infection of the pasture.

• Graze with other animals – such as cattle and sheep. Horse worms eaten by cows and sheep will not develop as they are in the 'wrong' host.

The worm egg count will give you a crude idea of the worm burden of your horse. It will not show the small redworms (cyathastomes) and tapeworm burden, although a blood test can be used to check tapeworm infestations. Small redworms are in the encysted immature form of large redworms which hibernate in the top layer of the guts and emerge in spring ready to mature and reproduce. As such they are mostly dormant and do not show up in the faeces. They can cause massive damage to the gut lining when they emerge however causing colic, diarrhoea and in some cases permanent worm damage. Tapeworms are a potentially important cause of colic in horses when they are present in large numbers, blocking the guts at the junction between the caecum and the colon.

It is vital therefore to target both cyathastomes and tapeworm regardless of the results of a WEC.

• Worm twice a year for cyathastomes with a product that will kill the encysted stages of development – ideally before the risk time when they emerge, so late autumn and late winter- November and January are ideal.

• Worm twice a year for tapeworm. You can combine this conveniently with the cyathastome worming. Either use a tapeworm product one week after the cyathastome dose or a combination product.

That is basically all the worming most horses need.

You then have two choices:

• Check that the horse is not getting re-infected for the rest of the year by submitting a poo sample for a WEC every 2-3 months.

• Routinely worm with a selected class of wormer at the appropriate intervals.

Different Drugs

Resistance to wormers is caused by the worms adapting to the drug used. Resistance to the benzimidazole chemical group is widespread throughout much of the UK due to horses remaining on the same pasture and being treated with the same product regularly. There have been some reports of resistance to ivermectins in cattle worms but this is not yet a significant problem in horses.

Use a weigh tape to get a good idea of your horses weight – (most people severely underestimate)- and dose to the max! The different chemical groups have different lengths of action, which will affect how often they are required.

X – effective against this parasite using single dose regime.

XX – effective against this parasite using double dose regime.

Example Worming Programme

January – Product(s) effective against cyathastomes and tapeworms

Spring – WEC then treatment as necessary

Summer – WEC then treatment as necessary

Autumn – WEC then treatment as necessary

November – Product(s) effective against cyathastomes and tapeworms