It’s vital to keep an eye out for deadly grass sickness

Grass sickness is an often fatal disease that occurs in horses, ponies and donkeys.

The disease was first recognised in 1907 following an outbreak near Dundee. Today the disease still frustrates vets as they work tirelessly to better understand it with the support of The Moredun Foundation Equine Grass Sickness Fund. The charity raises funds specifically for the research into Grass Sickness and celebrated its 30th anniversary this year by hosting an Equine Grass Sickness research conference on the 28th April 2018.

Currently there are approximately 140 cases of Equine Grass Sickness reported to the Equine Grass Sickness Fund every year in the UK. The disease is not notifiable and therefore it is believed that these statistics significantly underestimate the actual number of cases. The vast majority of cases are fatal, with only around 50% of the milder forms of the disease surviving with intensive nursing.

One of the difficulties faced by vets is distinguishing between the categories. Commenting on the categorisation Prof Scott Pirie BVM&S PhD Cert EM (Int Med) Cert EP Dip ECEIM MRCVS of the Royal (Dick) School of Veterinary Studies states: ‘Despite the categorisation of disease, it is important to remember that the different categories very much represent a continuum of severity, of which the acute and chronic forms are two opposite extremes.

‘The relevance of the categorisation process relates predominantly to the severity and therefore prognosis of the case and whether to treat or not. The acute and subacute cases are invariably fatal; approximately 50% of chronic cases will survive with appropriate nursing.

‘Therefore, it is important to make the distinction between sub-acute and chronic cases. Although this distinction is most accurately based on the extent of nerve cell depletion in the gut, this is only evident during a pathological examination – we are trying to make that distinction based on our clinical exam.

‘This involves considering the clinical manifestations of “not much depletion” versus “a moderate amount of depletion” versus “extensive depletion” and identifying clinical signs that are consistent with those three different categories.’

A proportion of horses, ponies and donkeys that are diagnosed with chronic grass sickness can be nursed; however, vets and owners are faced with a very difficult decision on whether this is possible or in the best interest of the horse.

Pictures by Angus Blackburn.

Read the full story in EQY Magazine, which comes with the July 2018 issue of Scottish Field.

The pictures accompanying this article are available to view and purchase – simply click on the image you want to view – it will open in another window.

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