The parasite problem: Many horse owners struggling with deworming

Faecal worm egg counts should be used every 8-12 weeks during the grazing season.
Faecal worm egg counts should be used every 8-12 weeks during the grazing season. © Steve Bardens / Zoetis

Results from last year’s National Equine Health Survey in Britain have revealed a lack of understanding from horse owners about faecal worm egg counts and the control of parasites.

NEHS is a snapshot survey, conducted by Blue Cross in conjunction with the British Equine Veterinary Association during the month of May each year. Last year 5235 people took part and returned records for 15,433 horses.

The results of the 2017 survey revealed that 37% of respondents never carry out FWECs, and of those that do, only 25% do so at the right intervals.

The majority (39%) of those who carried out FWECs did so at four-monthly intervals; 22% did so at 8-12 week intervals and 2% did so at six-weekly intervals.

Zoetis equine veterinarian Dr Wendy Talbot said the survey results show a lack of understanding about the purpose and benefits of FWECs during the grazing season.

Only 25% of those carrying out fecal egg count tests are doing it at the correct intervals.
Only 25% of those carrying out faecal egg count tests are doing it at the correct intervals. © Steve Bardens / Zoetis

“For the most effective results FWECs should be conducted every 8 to 12 weeks between March and October,” Talbot said.

“They will indicate which horses are passing the most worm eggs in their droppings and mean that horses are only treated when necessary. Remember though that FWECs don’t remove the need to treat horses at specific times of year for encysted small redworm, tapeworm and bots, none of which will show up in FWECs.”

Talbot said this 11-point checklist can help owners take control of worms year-round.

  • FWECs should be used every 8-12 weeks during the grazing season from around March to October in the northern hemisphere and horses treated according to the results.
  • Encysted small redworm (don’t show up in FWECs) should be targeted in adult horses once a year in the late autumn or early winter using a single dose of moxidectin or a five-day course of fenbendazole.
  • Tapeworm (don’t show up in FWECs) should be targeted twice a year, usually in the autumn and the spring using a single dose of praziquantel or a double dose of pyrantel or a tapeworm test conducted.
  • Bots (don’t show up in FWECs) should be treated annually in late autumn/early winter (‘after the first frost’).
  • Beware of resistance: There is widespread evidence of resistance in small redworm to fenbendazole, including the five-day dose so a resistance test is recommended before using it.
  • Weigh before worming to ensure you give the right amount of wormer. Underdosing can encourage worms to become resistant to the wormer you use and not be killed by it, creating a strain of resistant worms on your yard.
  • Use faecal egg count reduction tests (FWECRTs) during the grazing season: The best way to ensure that your wormers are working properly is to ask your vet to perform a faecal egg count reduction test each year. This involves taking a FWEC immediately before and two weeks after worming to assess the level of worm eggs being shed.
  • Keep pasture clean: Daily poo-picking, regular rotation and resting of fields and cross grazing with sheep or cattle will help keep pasture worm burdens under control.
  • Keep a worming record so that you have a history of the wormers used and when they were administered. Share this information with your vet or suitably qualified person (SQP) to ensure you have treated effectively and to avoid overuse of the same types of wormer.
  • Foals and young horses: are more likely to suffer parasite-related disease and will require a different approach.
  • Seek advice: Never be afraid to ask for help. Always speak to your vet or SQP to discuss the best worm control programme for your horse and his environment.

The NEHS is sponsored by Dodson & Horrell and Zoetis and supported by the UK’s leading equestrian organisations and charities.

To help horse owners understand worming best practice Zoetis has produced a worm control module for the British Horse Society’s Stage 3 Care Award. See for more information.

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