Vet practice warns over parasite threat

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Kirsty MacGregor

An equine veterinary clinic in Derbyshire, England, is emphasising the importance of responsible worming after the sudden death of a seemingly healthy horse from severe worm damage.

Veterinarian Kirsty MacGregor, of Bakewell Equine Clinic, was called to examine a six-year-old horse which had suddenly dropped dead in its field.

The horse had appeared normal on the day it was turned out in the pasture. He was outwardly healthy and had relatively good body condition. He had been seen walking across the field five minutes previously but, within minutes, had fallen in mid-stride, indicating a sudden death.

A necropsy confirmed that the cause of death was “verminous thromboembolism” – a fatal blood clot caused by severe worm damage.

MacGregor explained: “The large intestine was loaded with encysted small strongyle larvae and there was evidence that other worms had migrated to the arteries and the liver, causing inflammation and damage.

“The horse also had lesions in the small intestine, which, although common, are likely to be associated with parasite migration and chronic gastric ulceration in this case.”

The horse was kept on a large do-it-yourself yard with about 40 other horses and ponies.

With so many individual owners it had proved difficult to implement a regular worm control programme, although the yard owner and her liveries had tried hard to manage the situation.

“This unfortunate case serves to highlight the tragic consequences of being unable to coordinate an effective worming programme,” MacGregor said.

“Subsequently, we have carried out emergency dosing, treating all the horses at the yard with a combination of moxidectin and praziquantel (Equest Pramox) to treat encysted small redworm and tapeworm.

“At the yard owner’s request we have also put together a worm control programme for all the horses.”

Bakewell Equine Clinic has seen several cases involving encysted small redworm infestation this year, presenting symptoms such as violent colic and weight loss which in some cases have proved fatal.

They have put together 10 tips to help horse owners make sure they keep their horses safe from worms:

  • Use diagnostics on a regular basis to build a picture of your horse’s worm burden.
  • Understand your enemies – familiarise yourself with the main types of worms affecting horses.
  • Select the wormer most appropriate for the parasite you are targeting, by looking at the chemical ingredients of each wormer, rather than just choosing the wormer for its name alone.
  • Use a weigh tape or scales to make sure you dose accurately according to weight.
  • Treat horses as individuals as well as a part of the herd to make sure they are wormed according to their need as well as for their environment.
  • Worm new horses before they mix with existing animals.
  • Don’t overstock paddocks and rest them wherever possible to let the parasites die off.
  • Grazing with sheep or cattle on the same pasture is an excellent way to cut the worm population as they will ‘hoover up’ horse worm larvae which then die.
  • Keep stables hygienic and clean feed buckets well.
  • Collect and dispose of dung from the field promptly, at least every week, as this will significantly reduce the number of worm larvae getting on to the pasture.

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