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What is Everlasting Pea Poisoning ?

The everlasting pea (scientific name Lathyrus Latifolius), also known as sweet pea or perennial pea, is a plant that is toxic to horses as well as dogs, cats and other animals.  This plant contains a toxin called aminopropionitrile which has an effect on the neurological system of the host. The toxins or poisons believed to be involved are DABA, ODAP, amine, phenol and glycoside.

Everlasting pea poisoning in horses is a potentially fatal condition resulting from toxins being released into the horse’s system after ingestion of this plant in the Fabaceae family. These toxins can cause neurological and musculoskeletal damage.

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Symptoms of Everlasting Pea Poisoning in Horses

The symptoms of everlasting pea poisoning are primarily neurological in nature.  Here are some of the symptoms you might see in a horse suffering from this poisoning:

  • Abnormal gait
  • Weight shifting
  • Hindquarter stiffness
  • Roaring - a whistling or roaring noise made by the horse attempting to breathe after exercise
  • Weakness
  • Lethargy
  • Pacing
  • Head pressing
  • Tremors
  • Seizures
  • Death

The degree to which these symptoms may be displayed in the afflicted horse will be dependent upon the amount and duration of consumption of the plant. 

Types  

Everlasting pea poisoning, also known as lathyrism, is a condition that can affect horses, cats, dogs, turkeys, rodents, sheep and even humans.  When ingested in large quantities (and this is the case especially in large animals like horses), the toxins contained in the seeds is released into the body and can cause neurological and musculoskeletal symptoms in the host.  

This malady is more common in horses and can sometimes result in death by suffocation as laryngeal hemiplegia (a condition in which one or both of the muscles in the larynx become paralyzed) becomes an issue, affecting the ability of the equine to get enough air into its lungs. This same neurological inference causes muscular problems in the hind limbs (paralysis and weakness), affecting the horse’s gait and abilities to move around normally.

Causes of Everlasting Pea Poisoning in Horses

The cause of everlasting pea poisoning in horses is primarily the result of a toxin which causes neurological and musculoskeletal interference in the body of the host by the activities of DAPA, ODAP, amine, phenol and glycoside in the horse’s nervous system.  The condition is called lathyrism or poisoning by lathyrogens and is creates conditions in which:

  • The neurological signals to the muscles in the larynx are confused, causing the muscles to become paralyzed - this paralysis can be sudden as well as transient and will cause the “roaring” sound which indicates difficulty getting enough air into the lungs of the host
  • Liver and spleen inflammation - considered to be significant and profound
  • Hind limb paralysis - also caused by neurological inference by the toxin

Diagnosis of Everlasting Pea Poisoning in Horses

It is important to note that ingestion of any part of the plant is toxic but the seeds seem to be the most toxic to horses.  Also important to note is that a few seeds won’t hurt but the poisoning issue comes after the horse has ingested the seeds in large quantities for extended periods of time as can occur in pasture foraging in some areas of the country during some seasons of the year. 

Diagnosis of the poisoning caused by everlasting pea consumption is determined by a complete physical examination done by your veterinary professional as well as a history from you which addresses the feeding regimen (whether pasture or grain fed) and frequency and the behaviors and symptoms noted at home.  Your veterinary professional will likely need to order some lab testing of blood and various tissue samples, focusing on the balance of minerals and other comprehensive blood components.  

Imbalances of copper have been shown to mimic some of the symptoms and clinical signs of everlasting pea poisoning so ruling out that diagnosis will be important.  Once your vet has collected the information gained from the diagnostic testing, he will develop and initiate a treatment plan commensurate with the degree of severity to which your horse has been poisoned.

Treatment of Everlasting Pea Poisoning in Horses

The first line of treatment of everlasting pea poisoning includes removing the afflicted horse from the source of the everlasting pea seeds that he is eating.  There are no medications which can be given to neutralize or reverse the effects of the poisoning in horses.  It is likely that your veterinary professional will recommend providing supportive care (fluids, rest, nutritional dietary changes).  

Surgical correction of some of the neurological damage may be possible, like surgery to open the airways which have become constricted due to paralysis of the larynx muscles. Any skeletal damage or neurological damage done by the poisoning will be permanent but there are some limited surgical options available to improve the quality of life for the afflicted equine.  If the laryngeal paralysis becomes constant, the eventual suffocation of the equine will cause the death of the horse.

Recovery of Everlasting Pea Poisoning in Horses

It is imperative that, if you have a horse who is suffering from everlasting pea poisoning, you should consider a thorough review of the pasture forage and supplemental hay/grain that is being fed to your herd.  If one horse gets sick, and if the rest of the herd is also being fed or grazed in the same manner, then you will likely have other episodes with which to contend.  Monitoring your afflicted horse and providing a quiet and restful place for the equine to recuperate as well as providing the necessary supportive care will likely be your primary duties as your horse recuperates.  

Any surgical options, if any exist, will be thoroughly discussed by your veterinary professional and he will go over the risks and benefits of each of them.  The most important thing that you can do for your afflicted horse and your remaining herd is to be aware of the vegetation which is available and accessible to them as they forage and graze.  Control of harmful vegetation will need to be paramount to keeping your herd as healthy and productive as possible.