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What is Boxwood Poisoning?

Boxwood, whose scientific name is Buxus sempervirens, is from the family Buxaceae. The boxwood is a small tree that is often used as a hedge for landscaping purposes. It is native to southern Europe, northern Africa and western Asia, though can be seen throughout the world. The boxwood has a rounded shape with dark green, glossy leaves and extends in height to 15 to 20 feet. In the spring, small groups of pale yellow flowers will bloom and in summer there will be pale green to brown fruit capsules that ripen from August to September. The bark of the boxwood is light green or light gray and the tree has a dense, cordate root system that grows deep and wide. The boxwood tree contains alkaloids; while the entire tree is poisonous, the bark and leaves contain the most significant amount of poison.

A small tree often used as a hedge, the boxwood contains three alkaloids that are toxic in horses: buxine, cyclobuxine and cycloprotobuxine.

Symptoms of Boxwood Poisoning in Horses

Should your horse ingest a portion of boxwood, he may display the following symptoms:

  • Colic
  • Diarrhea (can be bloody)
  • Severe gastroenteritis
  • Seizures
  • Convulsions 
  • Respiratory arrest which can lead to death.



While the boxwood tree is toxic to horses, it has been used over the years for medicinal purposes. It is thought that the alkaloids in the tree can keep away pathogens that promote disease. For example, the wood from the tree has been boiled down to treat rheumatism and syphilis and the volatile oils were used to treat epilepsy and toothaches.



Causes of Boxwood Poisoning in Horses

All parts of the boxwood are poisonous, though the bark and leaves are more so than other portions of the tree. The tree contains butyraceous oil and three alkaloids that impact the horse: buxine, cyclobuxine, and cycloprotobuxine. The toxicity in horses is thought to be 0.15% of the plant to the weight of the horse; for an average size adult horse this is equal to the ingestion of 1.5 pounds of the leaves. How impacted your horse will be by the boxwood will depend on how much he ingested as well as how susceptible he is to the toxin. Horses tend to be very susceptible.



Diagnosis of Boxwood Poisoning in Horses

Should you witness your horse ingesting a portion of a boxwood tree, or notice troubling symptoms and suspect they may be from a poisonous plant, you will want to seek immediate attention from your veterinarian. It will be helpful to bring a portion of the tree that he consumed to the veterinarian as this will help in diagnosing your horse and beginning treatment as quickly as possible. It is likely you will be asked about the symptoms you have noticed in your horse and when you began noticing them. 

Your veterinarian will conduct a complete physical examination, which will include taking your horse’s temperature, heart rate, blood pressure, and respiration rate. In addition, your veterinarian will look down your horse’s throat to see if there are any parts of the plant still in his airway and may conduct testing to see if there are any plant remains in his stomach. Blood and urine tests may be conducted and the veterinarian may test fecal matter from your horse to confirm the type of toxicity he is experiencing.



Treatment of Boxwood Poisoning in Horses

Antidotes are not available for most toxic plants; therefore, treatment will be focused on eliminating the poison from your horse’s system along with treating the symptoms he is displaying. Your veterinarian will likely try routine decontamination procedures, like using activated charcoal (which will absorb the toxins in your horse) and giving a medication that will help your horse eliminate the plant from his system. In the meantime, your veterinarian will work on treating the symptoms he is experiencing, which may include administering oxygen to help with respiratory symptoms and intravenous fluids to flush his system and keep him hydrated.



Recovery of Boxwood Poisoning in Horses

Ingestion of boxwood can be fatal to a horse. Should your horse overcome the initial toxicity, you will want to follow the instructions of your veterinarian to work towards the best outcome for your horse. It is likely follow up appointments will be recommended to make sure that your horse is progressing in his recovery and to make any changes to his treatment that are necessary.



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