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Grass sickness is a disease that affects all type of horses, ponies and donkeys. The disease was first recognised in 1907 in Dundee, Scotland and now occurs in all parts of Great Britain. The disease is found in Europe and has recently been reported in Ireland and North America. A very similar disease also occurs in Chile, Argentina (where it is called mal seco or dry sickness) and the Falklands. In the UK, the disease is more prevalent in eastern counties and the incidence rate in certain regions is as high as 1 in 200 horses.
The disease can affect any equine breed that has access to grass. Statistical studies show no prevalence for breed or sex although younger horses (2-7 year olds) are more susceptible. The disease has not been reported in suckling foals and it may be that older horses have built up immunity to the causative agent. Grass sickness is associated with cool dry weather and more cases are seen between April-July with a peak in May.
A significant number of cases have a recent history of stress. These include recent change of owner and subsequent move of pasture, introduction into a new herd or other factors such as breaking and castration.
Despite a large amount of research over the last century the cause of the disease has not been identified. The type of damage caused to the nervous system indicates that some sort of toxin is involved and poisonous plants, chemicals, different bacterial species and viruses are amongst the possible causes that have been investigated. Grass sickness is not contagious and the cause of the disease is likely to be multifactorial i.e. caused by a combination of conditions and/or agents. Current research includes investigation of the association of the bacterium Clostridium botulinum with the disease and into the cyanide-producing properties of white clover.
There are three main forms of grass sickness: acute, subacute and chronic. The acute and subacute forms are invariably fatal but encouraging progress has been made in managing selected chronic cases of the disease. Symptoms of the acute phase can include muscle tremors, salivation and dysphagia (difficulty in swallowing). Euthanasia/death occurs within 48 hours. In the subacute form, symptoms are less severe than the acute although the majority will die or require euthanasia within 7 days. As the disease progresses symptoms can also include colic, reduced gut motility, colonic impaction and weight loss. A typical sign of a chronic case is severe weight loss with the horse appearing very ‘tucked up’.
It can be very difficult for a veterinary surgeon to distinguish the early stages of grass sickness from other conditions that cause similar symptoms. There is no definitive diagnostic test in the live horse, although urine analysis and one involving phenylephrine eye drops (both developed at Edinburgh University) may prove useful. Definitive diagnosis is only obtained postmortem by examination of the nerve ganglia.
The Equine Grass Sickness Fund (EGSF), which was established in 1988, is a registered charity that helps to fund and co-ordinate scientific research into the cause, treatment and diagnosis of this distressing disease.
The EGSF has funded many projects in addition to two PhD students based at Edinburgh University. Articles about current and past research as well as information, advice and merchandise can be found on the charity’s informative website.
Until recently the mortality rate for chronic cases was approaching 100%. The experience gained at Edinburgh University Veterinary School has increased the survival rate for selected chronic cases to approximately 70% and their care regimes have been successfully used by clinicians elsewhere. The mainstay of the treatment is good nursing care i.e. constant human contact and the feeding of palatable, easily chewed, high-energy food. The veterinary school has a dedicated grass sickness nurse, funded by the ILPH, and the long-term care of chronic cases is subsidised by funding provided by the Equine Grass Sickness Fund.
As mentioned earlier, the possible association between Clostridium botulinum type C/D and grass sickness is currently under investigation at Edinburgh University. The organism and its toxins are extremely difficult to detect and studies have been focused in two ways: detection of toxin and of the bacterium and detection of specific antibodies. Results are highly indicative of the involvement of this organism in the cause of the disease. This is encouraging as it raises the possibility of development of a vaccine in the future.
However, much more research is required and is expensive! If you would like to find out more, become involved or need cards and gifts please visit the EGSF website where you can purchase items to help support the charity. This disease affects all type of horses and ponies and therefore all types of horse owners. The Equine Grass Sickness Funds need YOUR help in raising money to find the cause of this devastating disease.
The disease can affect any equine breed that has access to grass. Statistical studies show no prevalence for breed or sex although younger horses (2-7 year olds) are more susceptible. The disease has not been reported in suckling foals and it may be that older horses have built up immunity to the causative agent. Grass sickness is associated with cool dry weather and more cases are seen between April-July with a peak in May.
A significant number of cases have a recent history of stress. These include recent change of owner and subsequent move of pasture, introduction into a new herd or other factors such as breaking and castration.
Despite a large amount of research over the last century the cause of the disease has not been identified. The type of damage caused to the nervous system indicates that some sort of toxin is involved and poisonous plants, chemicals, different bacterial species and viruses are amongst the possible causes that have been investigated. Grass sickness is not contagious and the cause of the disease is likely to be multifactorial i.e. caused by a combination of conditions and/or agents. Current research includes investigation of the association of the bacterium Clostridium botulinum with the disease and into the cyanide-producing properties of white clover.
There are three main forms of grass sickness: acute, subacute and chronic. The acute and subacute forms are invariably fatal but encouraging progress has been made in managing selected chronic cases of the disease. Symptoms of the acute phase can include muscle tremors, salivation and dysphagia (difficulty in swallowing). Euthanasia/death occurs within 48 hours. In the subacute form, symptoms are less severe than the acute although the majority will die or require euthanasia within 7 days. As the disease progresses symptoms can also include colic, reduced gut motility, colonic impaction and weight loss. A typical sign of a chronic case is severe weight loss with the horse appearing very ‘tucked up’.
It can be very difficult for a veterinary surgeon to distinguish the early stages of grass sickness from other conditions that cause similar symptoms. There is no definitive diagnostic test in the live horse, although urine analysis and one involving phenylephrine eye drops (both developed at Edinburgh University) may prove useful. Definitive diagnosis is only obtained postmortem by examination of the nerve ganglia.
The Equine Grass Sickness Fund (EGSF), which was established in 1988, is a registered charity that helps to fund and co-ordinate scientific research into the cause, treatment and diagnosis of this distressing disease.
The EGSF has funded many projects in addition to two PhD students based at Edinburgh University. Articles about current and past research as well as information, advice and merchandise can be found on the charity’s informative website.
Until recently the mortality rate for chronic cases was approaching 100%. The experience gained at Edinburgh University Veterinary School has increased the survival rate for selected chronic cases to approximately 70% and their care regimes have been successfully used by clinicians elsewhere. The mainstay of the treatment is good nursing care i.e. constant human contact and the feeding of palatable, easily chewed, high-energy food. The veterinary school has a dedicated grass sickness nurse, funded by the ILPH, and the long-term care of chronic cases is subsidised by funding provided by the Equine Grass Sickness Fund.
As mentioned earlier, the possible association between Clostridium botulinum type C/D and grass sickness is currently under investigation at Edinburgh University. The organism and its toxins are extremely difficult to detect and studies have been focused in two ways: detection of toxin and of the bacterium and detection of specific antibodies. Results are highly indicative of the involvement of this organism in the cause of the disease. This is encouraging as it raises the possibility of development of a vaccine in the future.
However, much more research is required and is expensive! If you would like to find out more, become involved or need cards and gifts please visit the EGSF website where you can purchase items to help support the charity. This disease affects all type of horses and ponies and therefore all types of horse owners. The Equine Grass Sickness Funds need YOUR help in raising money to find the cause of this devastating disease.
