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What is African Wonder Tree Poisoning?

The African wonder tree is more commonly known by its name of castor bean or castor oil. While it is valuable as a crop, it is imperative you keep it away from your horse. It is grown naturally in tropical regions but can be found as an ornamental or introduced plant in non-tropical regions. This plant contains a highly toxic substance known as ricin that can lead to minor symptoms, such as oral irritation and trembling, or severe symptoms of kidney failure, convulsions, coma, and death. If you have the slightest suspicion your horse may have ingested a part of the African wonder tree, you need to contact your veterinarian immediately.

If your horse ingests any amount of the African wonder tree, it should be considered a medical emergency. A very small amount of ingested plant can be lethal.

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Symptoms of African Wonder Tree Poisoning in Horses

Symptoms of African wonder tree poisoning can develop 12-48 hours after initial ingestion. Symptoms may include:

  • Oral irritation 
  • Burning of the mouth
  • Burning of the throat
  • Loss of appetite
  • Increased thirst
  • Weakness
  • Trembling
  • Loss of coordination
  • Sweating 
  • Colic
  • Breathing difficulties
  • Fever
  • CNS depression 
  • Bloody diarrhea
  • Kidney failure
  • Convulsions
  • Coma
  • Death

Types

The African wonder tree has the scientific name of Ricinus communis. It belongs to the castor bean family and may be known by another name such as mole bean plant, castor bean, castor oil, spurge family, and euphorbiaceae. This plant is native to the tropic regions of the world and harvested for its castor crop value.

Causes of African Wonder Tree Poisoning in Horses

The African wonder tree contains ricin; a highly toxic substance that inhibits the synthesis of proteins. It is a glycoprotein and is believed only one ounce of seeds can be lethal if ingested. While this plant is naturally growing in tropical regions, horses of other regions come into contact with this plant via pruned foliage or as an ornamental plant.

Diagnosis of African Wonder Tree Poisoning in Horses

The veterinarian will want to complete a full physical exam on your horse and will make note of all of his symptoms. She will want to collect a history from you and get the details of when the symptoms started, if they have been progressing, and any change in diet or environment recently. 

She will then want to run lab work for diagnostic purposes. She will suggest a complete blood count (CBC) and chemistry panel to check for abnormalities within the blood and as a way to assess organ values and function. Depending on the results, she may want to run more in depth blood related tests. She may also want to run a urinalysis in addition to the blood work to check kidney function. 

If bloody diarrhea is an issue, she may want to run some tests on the feces to rule out other possible causes of this symptom. If your horse is experiencing any type of incoordination or other CNS symptoms, your veterinarian may want to run a series of neurologic tests to try and determine the cause. If your horse is experiencing breathing difficulties and the veterinarian cannot confirm the cause via auscultation alone, she may want to take radiographs to check his lungs for air, fluid, masses, or other possible abnormalities. 

There may be other tests your veterinarian will want to run in order to rule out other causes of your horse’s ailment.

Treatment of African Wonder Tree Poisoning in Horses

If your veterinarian notices increased thirst and sweating, she may want to start your horse on fluid therapy to ensure he does not become dehydrated. The fluid therapy will also keep his body temperature low if he is febrile. If he does not have much of an appetite, she may try to tube feed him in order to keep his digestive system moving. If his GI tract comes to a halt, it can lead to other secondary issues you would have to treat as well. 

For any type of muscle weakness or abnormal use of a limb, you will want to keep him in an enclosed area. This will enable you to keep a close eye on him and ensure he does not over exercise himself. Also, if he is safe in a barn-like shelter, it will keep him safe from predators versus if he was on pasture and could not move properly.

Other forms of treatment will be determined by the symptoms your horse is experiencing. If his mouth is burning, she may try to offer him something to ease the pain and discomfort. If he is suffering from breathing difficulties, she may want to supplement him with oxygen. If he begins to have convulsions, she will administer an anti-convulsion medication to stop it. She will treat symptomatically as symptoms appear.

Recovery of African Wonder Tree Poisoning in Horses

There are many factors that will contribute to your horse’s recovery. Once kidney failure begins, there is no correcting it. Also, once he begins to have convulsions and goes into a coma, there is very little chance of recovery. The amount of African wonder tree he ingested is the most important factor. If ingestion of this plant occurs, prognosis is guarded to poor. If he ingests one ounce or more of the plant, it will likely result in his death.