What is Equine Dysautonomia?
Equine dysautonomia, also known as equine grass sickness (EGS), is a neurodegenerative disease that is often fatal in grazing horses (mainly in northern European and South American countries). It is not clear what causes the disease, though it is thought that it may result from neurotoxins that are produced by the Clostridium botulinum Type C bacteria. The disease will cause significant damage to nerves in the central and peripheral nervous systems of your horse and lead to reduced motility of his GI tract as a result of degeneration of the autonomic nervous system.
While equine dysautonomia can be seen at any age after a horse has been weaned and throughout the year, it occurs most in the spring and in horses between the ages of two and seven. Typically, the disease is seen in horses that are kept only in grass; on rare occasions, it has been found in horses that are stabled.
Also known as equine grass sickness (EGS), equine dysautonomia is an often fatal neurodegenerative disease that is thought to be caused by neurotoxins of the Clostridium botulinum Type C bacteria.
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Symptoms of Equine Dysautonomia in Horses
Should your horse develop equine dysautonomia, you may see the following symptoms:
- General muscle weakness
- Rapid heart rate
- Intestinal blockage
- Significant abdominal pain
- Muscle twitching of the shoulders and flanks
- Tucked up stance
- Weight loss (significant in chronic cases)
- Drooping of eyelashes and upper eyelids
- Trouble swallowing
- Dry nose (chronic cases)
- Small, hard feces
- Distension of stomach and small intestine which can lead to gastric rupture (acute cases)
- Ulceration of the esophagus
- Empty GI tract (chronic cases)
Equine dysautonomia can occur in three different forms:
The most likely of the three forms to be fatal; onset is rapid and the disease will progress quickly. Death will typically occur in under 48 hours. Symptoms can include depression, trouble swallowing, excessive drooling, increased heart rate, muscle tremors, and significant stomach discomfort.
Symptoms are less severe and the progression of the illness is slower. A tucked-up abdomen and significant weight loss are typical symptoms.
This form has the best chance of survival. In addition to a tucked-up abdomen and significant weight loss, your horse may also display sweating, muscle tremors, increase in his heart rate and muscle weakness.
The forms are categorized by how long it takes for death to occur. Should the horse pass away within 24 hours, for example, the form of illness would be considered acute. In chronic cases, your horse can survive for weeks or months; some horses are able to recover from the chronic form.
Causes of Equine Dysautonomia in Horses
Though the cause of equine dysautonomia has not been confirmed, it is thought that the Clostridium botulinum Type C bacteria produce neurotoxins that cause the disease. These bacteria are often found in soil and have the ability to produce a variety of toxins (to include strong neurotoxins). Nearly all of the cases of equine dysautonomia exist in horses that have the opportunity to graze and it is thought that while they are grazing they are exposed to something in the soil that is ingested along with the grass that they eat. Multiple elements may be involved in the development of the illness.
Diagnosis of Equine Dysautonomia in Horses
Once you notice something is not right with your horse, you will want to seek immediate veterinary attention. With the exception of a biopsy of the intestine or rectal tissue, there is no reliable test available to diagnose the condition. The increased heart rate, difficulty swallowing, decrease in motility of the GI tract, tucked-up stance and drooping of the upper eyelid will be noticed and considered by your veterinarian as he is trying to determine the illness in your horse. Along with information regarding his history and opportunities to graze, these symptoms point him in the direction of considering equine dysautonomia.
Treatment of Equine Dysautonomia in Horses
Some horses with the chronic form of the disease can survive with a great deal of supportive care, though studies show most equines will succumb to the disease. Therefore, therapy is often intensive and sometimes aimed at comfort only; should your horse be experiencing the chronic form of this disease you will want to offer him a variety of feeds in order to motivate him to consume food. Should your horse be experiencing the acute or subacute form of the disease, your veterinarian will likely recommend euthanasia so that he may not suffer.
Recovery of Equine Dysautonomia in Horses
Should your horse develop the chronic form of equine dysautonomia, he may be able to recover from the illness. It is important that you work closely with your veterinarian and follow any instructions you are given in order to ensure that your horse has the best chance of recovering. As noted above, it is important that your horse eat in order to recover; therefore, you will want to provide him with a variety of feeds so that he may find some to be appealing.