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What is Indigofera Poisoning?

Indigofera is typically found in temperate or tropical climates but can sometimes be found as an introduced plant in other regions as well.  It is believed clinical symptoms of toxicity do not appear until 14 days of daily ingestion of the plant.  By this time, the toxin from the plant has built up in your horse’s system and clinical symptoms can be severe.  There is no antidote to indigofera toxicity, but your veterinarian can offer your horse supportive and supplemental treatment in response to his symptoms.

Indigofera ingestion can poison your horse.  If you suspect or witnessed him eating this plant, contact your veterinarian immediately.

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Symptoms of Indigofera Poisoning in Horses

Symptoms of indigofera toxicity may include:

  • Inappetence 
  • Weight loss
  • May segregate themselves from herd mates
  • Somnolence
  • Hypermetric forelimb gait
  • Hindquarter weakness 
  • Head carried high
  • Tail held out stiffly 
  • Difficulty turning in tight circles
  • Bilateral ocular discharge
  • Corneal opacity
  • Edema
  • Dyspnea
  • Stomatitis
  • Sudden loss of control of hindquarters 
  • Pregnant mares may abort 
  • Liver failure 
  • Recumbency
  • Convulsions
  • Death 

Types

Indigofera can be found naturally in tropical and temperate climates.  This condition is also commonly known as “grove disease” when horses graze on the creeping indigo species or Indigofera spicata.  In Australia, it is referred to “Birdsville disease” as it is caused by the birdsville indigo or Indigofera dominii.  The plant flourishes with branched runners fanning out from a crown that may grow as high as 3 feet.  Stems are typically pale green with pinnate leaves and flowers in pink or dark red.

Causes of Indigofera Poisoning in Horses

It is believed your horse has to consume at least 4.5kg of plant every day for at least 14 days before clinical symptoms of toxicity appear. Indigofera produces a nitrotoxin known as indospicine; it is a protein synthesis which inhibits cellular energy production within the nervous system.

Diagnosis of Indigofera Poisoning in Horses

There are a lot of symptoms indigofera toxicity can cause so it is important your horse receives a thorough examination.  She will make note of all of his symptoms, ask you when each symptom began, and if he has been improving or worsening.  The smallest detail may help her rule out other possible causes of his symptoms.   

She will want to perform lab work so she can check his organ values and levels in his blood.  She will suggest a complete blood count (CBC) and chemistry panel to check for abnormalities.  Depending on the results, she may want to run more detailed blood related tests for additional diagnostic information.  

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.  She may even recommend diagnostic imaging such as an MRI or CT scan to determine a possible cause.  

As for any eye abnormalities, she may perform a series of tests on them individually to check for other possible ailments such as an ulcer or cataracts.  If your horse is experiencing breathing difficulties and she 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 possible causes of your horse’s ailment.  Of course, if your horse dies you can request a necropsy in order to determine the cause.  This will give you a complete diagnosis to ensure none of your other horses suffer from the same illness.  Postmortem examination can show degeneration of the brain and spinal cord.

Treatment of Indigofera Poisoning in Horses

While there is no antidote to indigofera toxicity, your veterinarian can provide your horse with supportive care.  She can administer medications and supplemental therapies in response to the symptoms he develops.  She may want to start him on fluid therapy to flush the toxin from his body quicker.  It will keep his urinary system running and flushing out the toxin.  

If he is experiencing respiratory distress, she may supplement him with oxygen therapy in addition to administering injections to ease his agony.  If he is suffering from severe CNS symptoms to where he may cause himself, you or veterinary staff harm, she may give him a mild sedative for everyone’s safety, however, this is rare since she does not know what he is suffering from.  

If the blood work comes back indicating liver failure, unfortunately there is no cure.  Your veterinarian can offer him supplements to try and slow the progression, but in time it will be a cause of death.

Recovery of Indigofera Poisoning in Horses

The severity of the toxicity will determine your horse’s chance of recovery.  There are many symptoms he can develop and it is possible he may never recover.  Some neurologic abnormalities never go away once developed and it may affect your horse’s quality of life.  Each case of indigofera toxicity is unique, but prognosis is typically guarded.