What is Black Bean Tree Poisoning?
Although black bean tree poisoning is less common in horses than in cattle, it can cause severe problems in horses that have an intolerance to the toxins within the seeds. This can be a fatal condition. Most horses avoid the seeds of black bean trees but they will be eaten if the pasture does not have adequate grazing. Generally, horses do not eat the leaves of black bean trees.
Black bean trees are native to Australia but can be found within some areas of the United States as ornamental trees that have been planted for shade.
Castanospermum australe or black bean tree is an evergreen tree that is used for shade or as ornamental. In mid-late spring clusters of red and yellow flowers will bloom on a black bean tree and then large cylindrical pods form. These pods contain large bean type seeds. The leaves and seeds of a black bean tree contain saponins and castanospermine. These are indolizidine alkaloids and if ingested, are toxic to horses.
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Symptoms of Black Bean Tree Poisoning in Horses
If you suspect that your horse is suffering from black bean tree poisoning, remove your horse from its pasture. Put them in a densely bedded stall and contact your veterinarian for an immediate assessment. Many of the symptoms of black bean tree poisoning are similar to other toxins and it can be difficult to determine what is causing your horse to be ill. Monitor your horse’s symptoms until your veterinarian arrives and give them a full list of what you have observed.
- Weight loss
- Frequent urination
- Labored breathing
- Diarrhea, may contain blood
- Dark or tarry manure
- Sudden death
Causes of Black Bean Tree Poisoning in Horses
Black bean tree poisoning will cause severe irritation of the gastrointestinal tract. In some cases, sudden death can occur in horses. Researchers have determined that the leaves of a black bean tree contain unknown toxins that can be harmful to large animals, including horses. Most horses will not eat the leaves of black bean trees.
It is the seeds of black bean trees that are the most problematic, even though horses do not generally eat the seeds unless they are foraging for food in a sparse pasture. The seeds contain the toxins saponins and castanospermine. These toxins are indolizidine alkaloids and can be extremely dangerous for horses.
Diagnosis of Black Bean Tree Poisoning in Horses
Your veterinarian will begin by doing a full physical examination of your horse. They will ask you questions about the symptoms that you have seen and about your horse’s diet and daily routine.
Many times when a horse is suffering from toxicity, the symptoms are generalized. Sometimes your veterinarian may not even be able to pinpoint what has poisoned your horse. Further testing may be inconclusive or it may point to the exact cause of the poison and allow your veterinarian to tailor treatments to that specific toxin. Blood work for example, can reveal how the toxin is affecting your horse. However, With this type of poisoning, time is important; treatment may need to be initiated before testing can be done.
To try and determine what toxins your horse has come in contact with, your veterinarian may walk your horse’s pasture looking for potential dangers. They may also ask you about the vegetation that is growing in or near your horse’s pasture as well as any treats that you might have given your horse.
Treatment of Black Bean Tree Poisoning in Horses
There are no antidotes available for black bean tree poisoning in horses. Your veterinarian will probably recommend that your horse be hospitalized for supportive care. This will allow your horse to be continuously monitored and treatments quickly given as symptoms appear. Supportive care will include intravenous fluids to keep your horse hydrated.
As symptoms present, your veterinarian will treat the symptoms. Activated charcoal may be administered if treatment was sought quickly enough that the toxins are still within the stomach.
Once your veterinarian has set a treatment plan, be sure to follow all instructions as given to ensure the best chance for your horse’s full recovery.
Recovery of Black Bean Tree Poisoning in Horses
Black bean tree poisoning can be fatal. It is important to treat the symptoms as they present to keep your horse’s health from deteriorating further. Hospitalization until your horse is stable may be necessary. Speak with your veterinarian about your horse’s expected recovery time and prognosis.
Prevention is the best way to keep your horse safe. Always walk through your horse’s pasture and look for any vegetation that might be toxic to your horse. If you are unsure if a plant, tree or shrub is toxic to your horse, ask your veterinarian. Keep fence lines clean as well to prevent any overhanging branches from dropping leaves or seeds into your horse’s pasture.