SMART rule no.2: do not kill all worms!

Horse owners are being reminded to not kill all worms when treating their animals, as keeping a low number of treatment-resistant worms in the system can be beneficial.

The posters for Merial's second rule (from the four SMART rules for effective worming) are now available for veterinary practices, and the company is keen to ensure horse owners are aware of the need for some untreated worms to stay in an equine's system.

Rule two details the importance of allowing a horse to keep a low amount of refugia – a population of worms not exposed to wormer treatment – which helps to dilute the number of treatment-resistant worms that are developing.

Worming too frequently will deplete the number of treatment-sensitive worms in the animal, leaving only resistant worms in the gut which cannot be eradicated with treatment. To avoid over-worming, Merial recommends that horse owners use faecal worm egg counts [FWECs] to determine whether their animal needs worming treatment.

If the horse in question has an FWEC result of less than 200 eggs per gram, a worming treatment is not required, says Merial, as carrying out worming on an egg count of lower than this can result in refugia being wiped out.

In refugia, both sensitive and resistant worms breed, meaning the worm population always has a good proportion of treatment-sensitive worms. As long as refugia is maintained, treatments should continue to be effective both now and in the future.

• Contact your local area manager or call the Merial customer support centre on 0845 601 4236 for details.

(Article reproduced with kind permission of www.vetsonline.com)