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Red Worm

Posted on 29 November 2016

By Geraldine Long

We will be focusing on the small red worms, cyathostomes, as not only are these are the most deadly of parasitic worms found in the equine species but they are the most common internal parasite of the horse. The normal lifecycle is very quick and takes place over a few weeks from ingestion of larvae to adult egg laying worms. Unfortunately they are becoming increasingly resistant to anthelmintic (anti-parasitic) drugs on the market and alongside this, cyathostomes can only be detected at certain stages of their lifecycle. When a horse swallows the cyathostome larvae from the pasture, the larvae develop within the lining of the bowel and then emerge as adults. However a proportion remains within the lining and may remain there for years. Whilst hibernating these inhibited larvae are resistant to almost all types of wormer. As the larvae do not produce eggs, they will not be detected by routine faecal worm egg counts. The larvae then re-emerge, often at the end of winter and this re-emergence may involve large numbers at the same time, resulting in enormous damage to the bowel wall and can even prove to be fatal. Other symptoms are:

  • Diarrhoea
  • Weight Loss
  • Dull/Depressed
  • Colic
  • Loss of Condition
  • Anaemia
  • Fluid build up on legs, stomach and around the sheath.

What Can you do?

  • Worm all horses late autumn/early winter with a wormer that targets small redworm and the encysted stages. Moxidectin wormers e.g or Fenbendazole wormers e.g Panacur 5 day guard are ideal. These are available to buy from the practice.
  • Follow a worm egg count protocol with worm egg count analysis carried out in spring and summer to ensure only those with significant burdens are wormed to stop resistant populations building up. We offer this at the clinic so get in touch if you would like to know more.
  • Good grazing management - rotate paddocks, don’t overstock and poo pick as often as possible.
  • Ensure your wormer doses are correct - we have a weigh bridge here at the clinic, and are happy for anyone to book in to use it, this is important to ensure you have an accurate weight for your horse and you can dose accordingly.
  • Avoid using the same class of wormer year after year, not actually as easy to do as it is to say!!
  • If you have any questions please do not hesitate to contact us at the clinic, we will be happy to help 01270 628888

The header image shows Cyathostome worms found in the droppings of a rescue horse. He has now made a full recovery and lives with one of our vets! Image property of Nantwich Equine Vets.