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15 September 2014

EQUINE GRASS SICKNESS by Tony Comerford

Just over a year ago I lost my horse to Grass Sickness.  It has taken that year and a new horse before I felt able to write about it. 

Grass Sickness is an equine disease which causes damage to parts of the nervous system that control the whole length of the digestive tract from the throat to the rectum.  It causes partial or complete paralysis of the digestive system.

This condition was something I had always known about but had adopted a complacent head-in-the-sand attitude of "it won't happen to me" well, it did, and it happened to Dawn's horse, Magick, too so now we are embarking on an awareness raising campaign.  That is the reason behind this article and another that Dawn is to write.  We have also presented a memorial trophy to the branch to go to the most frequent volunteer helper within the branch on an annual basis.  Also there will be collecting tins displayed at the Caravan at the future rides to try and raise some funds for the Equine Grass Sickness research unit.

As an illustration my story follows.  Nik had suffered recurrent lameness so he had been referred to the Dick Veterinary Hospital in Edinburgh for investigation.  They decided he needed to stay there for a few days for tests to be carried out.  Like any stay in hospital this was a stressful situation for the patient.  However he seemed fine.  Eventually diagnosis was arrived at.  He was booked in for treatment a month hence.  The prognosis for the future was good.  So I collected him.  He trotted into the trailer and we set off home.  We got stuck in a traffic jam around the Forth Road Bridge on a hot day.  A four hour journey became 6 hours.  STRESS. 

The next day after a period turned out to grass, he did not seem quite right; listless and lacking energy.  However long this turn out period was, it was too long.  He should have been stabled. 

Day 3.  He had conjunctivitis this did not seem a problem as he was prone to this following an eye injury in his youth.  However I did not know that conjunctivitis is also a known pre-symptom of Grass Sickness. 

Day 4.  He had colic and was given symptomatic Veterinary treatment and seemed to recover. 

Day 5.  There was no colic, but he was tucked up, uncomfortable and would not eat.  The Vet mentioned Grass Sickness - I mentally dismissed that possibility. 

Day 6.  He still would not eat and was no longer passing droppings.  The Vet treated him for impaction. 

Day 7.  There was no change and the Vet administered a stomach tube and liquid paraffin to try and ease the bowel contents.  There seemed to be some improvement. 

Day 8.  He had a nasal discharge, was trembling and there were no gut sounds.  The Vet said he showed conclusive symptoms of sub acute Grass Sickness with stomach contents backing up and beginning to be expelled through the nose.  I was told that there was no option but immediate euthanasia before he suffered any more. 

Until that point I had not accepted this reality. 

The support and treatment we got from the Vets, the Dick Hospital and my insurance company were amazing.  However, why did it happen?? 

My theory and that of the Vets was that stress was a major contributory factor.  In our case there were three separate sources of stress.  Hospitalisation.  Travelling.  And the worst, too much grazing, involving a basic change of nutrition in a high risk period.  However, ever following these prerequisites for the disease rapid and conclusive diagnosis in anything but acute cases is difficult.  Not that diagnosis would have made the slightest difference to the end result. 

It has been estimated up to 1% of the horse population will contract the disease of which 90% will die.  Also, unfortunately for us, the East of Scotland has the highest incidence.  Most horses that contract Equine Grass Sickness are at grass.  By the symptoms shown it is thought that a fungal neurotoxin may be responsible but this has not yet been scientifically proven.  To date no cure or antidote has been found.  It is also thought that a selenium deficiency which results in reduced levels of protective anti-oxidents in the body may also be a causative factor.  Other factors which influence the risk of the disease occurring are, 1.  The age of the horse.  The common range of affliction is 2-7 years old.  2.  Cold and dry weather conditions in the temperature range of 7-11 Celsius, when the grass is growing.  3.  Stress may act as a catalyst triggering the onset of the disease. 

If we cannot avoid stress, e.g, from travelling, competing, new owners etc, we need to manage the situation.  It is recommended that horses at risk or potentially stressed should not be allowed 24 hour access to grass.  They should be stabled for at least 6 hours of the 24 and longer if possible.  They should then be fed hay, roughage, or concentrate as an alternative to grass.  New horses coming on to known Equine Grass Sickness premises should be stabled full time at high risk periods and allowed only very limited access to grass. 

The main line of research into Equine Grass Sickness at the moment is the role of oxidant stress as represented by an imbalance in the level of protective anti-oxidents and detrimental oxidents.  Recent work at the University of Edinburgh School of Veterinary Studies has been centred on the role of toxigenic clostridium species as the cause of Equine Grass Sickness.  In particular this work is concentrating on the soil associated bacterium clostridium botulinum type c/d. 

This is a highly neurotoxic bacterium that is normally associated with domestic and wild mammals and birds.  It is suggested that this organism is a normal component of the "microbiota" of the gastro intestine tract of horses.  In the healthy horse it is carried harmlessly being controlled by the local gut immune system.  Disease is then thought to be triggered by change in nutrition which is followed by either the number of clostridium botulinum, type organisms increasing dramatically and, or there is a massive production of toxin within the gut.  The horse’s immune system is then unable to cope. 

If this hypothesis is proved conclusively then it may be possible to develop a vaccine against Equine Grass Sickness.  Vaccination, they say, is the best hope for the future as by the time diagnosis is made, the nervous system is irretrievably damaged.  In the interim, my Vets have advised me to adopt precautionary measures of feeding a selenium supplement, restricted grazing and stress management.  These simple actions MAY reduce the likelihood of disease.

Also, we can contribute to the Equine Grass Sickness Fund.  More information can be found on their website www.grasssickness.org.uk