Equine Atypical Myopathy (EAM)
This Autumn has seen an increased incidence of this frequently fatal disease in horses and ponies across Europe. It is a disease that causes destruction of the muscle tissue and involves both skeletal and heart muscle. The causative agent is currently unknown, however it is speculated to be a fungus or bacteria that lies dormant in the pasture and that is able to thrive in certain climatic conditions. One current hypothesis is that the agent is a Clostridial toxin, produced by bacteria from the same family as Tetanus and Botulism. The disease is seen most commonly in the Autumn and the Spring, especially when a dry spell is followed by very wet conditions which permit soil contamination of the pasture.
Risk Factors:
A greater number of cases have been reported in young horses (less than three years old) and older horses (greater than 20 years old), horses in poor body condition and horses with poor worming and vaccination history. Horses affected have been those which are living out and the highest risk pastures seem to be those that are heavily grazed and those with access to natural water courses such as rivers and streams.
Clinical Signs:
The most obvious clinical sign is the sudden onset of stiffness and weakness in the grazing horse. This may be accompanied by any combination of the following signs: dark coloured urine, red or purple mucous membranes (gums), depressed demeanour, muscle tremors, difficulty to stand or walk, difficulty breathing, low body temperature and collapse. Less frequently reported signs include vigorous head shaking, frenzied vocalisation (whinnying) and spasms of the neck muscles as if the horse is choking. The central nervous system does not seem to be affected and horses are often very aware of their surroundings. Many horses will still want to eat food that is placed within reach.
What to do if you suspect a case of Equine Atypical Myopathy:
In the unfortunate event that you suspect any of your ponies to be suffering from EAM it is very important to contact you veterinary surgeon immediately. The earlier the disease is detected and treatment initiated the greater the chance of survival. Whilst you await the vet’s arrival remove the affected pony from the field by the shortest route possible. Use a trailer, if necessary, as forcing affected horses to walk long distances exacerbates the damage to the muscles that takes place as part of the disease process. Warm the horse using rugs and offer water and sugary foods to eat. Your vet will examine the horse and collect a blood sample for testing to confirm the disease. They will begin symptomatic treatment.
As the causative agent is still unknown treatment of this condition involves providing supportive therapy in order to maintain organ function and limit complications whilst the disease runs its course. These treatments may include providing pain relief, administering anti-inflammatories, and using intravenous fluid therapy to restore hydration, correct electrolyte imbalances and support kidney function.
Any field in which EAM has been confirmed should have remaining horses removed immediately to stables or at the very least to another field. The remaining horses should be monitored closely for clinical signs. It would be wise to have blood tests performed on the remaining horses in order to detect sub-clinical cases before they progress to the full manifestation of the disease.
Prevention:
Maintaining your ponies in good general health is the key to preventing many illnesses and this is no exception! Adequate nutrition to maintain good body condition and regular vaccination and worming are of utmost importance. Careful grazing management in order to eliminate the grazing of “bare” fields and providing adequate supplementary feeding to reduce grazing pressure will all minimise the risks. Using mains water rather than water from a natural source is also wise.
For further information the website myopathieatypique.fr/en has good information in a user friendly format.