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Faecal Worm Egg Counts for Your Horse

The type of worms that cause disease in our horses have developed resistance to lots of the chemical horse wormers available. Using faecal worm egg counts (FWEC) in conjunction with horse wormers means that your horse or pony will only have the chemicals that they actually need, thus helping to reduce the incidence of resistance.

Although only 20% of horses have worms, over 80% are still being wormed.

FWECs can be used to assess whether a horse has a worm burden that requires worming treatment. They can also be used to monitor the effectiveness of a particular treatment and should be a routine part of a horse’s worming programme.

What is a faecal worm egg count?

A sample of your horse or ponies faeces is viewed under a microscope to see whether any worm eggs are present in the dung. FWEC are generally performed at regular intervals through the grazing season (April-October).

Will a faecal worm egg count identify all horse worms?

A FWEC will only show up the eggs from the worms that lay eggs as part of their lifecycle. This does not include pin worm, bots and tapeworm. In addition, a FWEC will not be able to identify immature worms that are not laying eggs and cannot identify the encysted small redworm.

What does a clear result mean?

It means that there are no worm eggs in the sample of faeces that you have sent for analysis. It does not mean that your horse does not have worms.The worm life cycle includes many larvicidal stages that are not detected by faecal egg counting and some worms do not produce eggs. It is therefore very important that horses are still treated for encysted redworm, tapeworm and bots at the appropriate time of year.

It is important that horses are still treated for encysted redworm, tapeworm and bots at the appropriate time of year.
It is important that horses are still treated for encysted redworm, tapeworm and bots at the appropriate time of year.

Faecal worm egg counts should form part of a tailored horse worming programme and advice should be sought from your vet about the results and when treatment is required.