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Grass sickness

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With a death rate of more than 85%, equine grass sickness (EGS) is a serious, debilitating disease that affects horses, ponies and donkeys.

Grass Sickness

 With a death rate of more than 85%, equine grass sickness (EGS) is a serious, debilitating disease that affects horses, ponies and donkeys. It causes severe, extensive damage to nerves, mostly the ones that control involuntary functions, and the gastrointestinal tract is particularly affected.

EGS was first described in eastern Scotland in the early 1900s and Britain has the highest incidence of the disease worldwide, with equines in Scotland and northeast England being particularly susceptible. There is limited accurate information about how common EGS is but, on average, approximately 140 cases are reported to the nationwide Grass Sickness Surveillance Scheme each year.

 What causes EGS?

Almost all cases of EGS occur in horses with access to grazing. Scientific evidence suggests that the disease may be caused by the bacterium Clostridium botulinum type C, which is commonly found in soil and can produce neurotoxins that horses are particularly sensitive to. The disease is thought to occur when a combination of several risk factors triggers C botulinum that’s present in the horse’s intestinal tract to produce neurotoxins.

Decades of research have identified many risk factors associated with EGS, including…

  • access to grazing – this is the main risk factor for EGS, with only a couple of isolated reports of the disease occurring in stabled horses
  • EGS having occurred on a premises previously – it’s considerably more likely to recur on premises where there has been a previous case
  • the time of year – 60% of all cases occur between April and June, particularly during periods of cold, dry weather
  • recent movement to a new premises or pasture – exposure to new grazing is associated with an increased risk of EGS
  • age – young adults aged between two and seven years are at greatest risk
  • breed – it’s been suggested that native Scottish breeds may be more susceptible
  • pasture disturbance – studies have identified increased risk where there is a history of pasture disturbance, presumably due to increasing the chance of soil ingestion

Find out more about the symptoms of EGUS and how it can be treated by reading the full article, get your copy of Spring Horse&Rider here, on sale 9 February.

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