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What is Paterson's Curse Poisoning?

Echium plantagineum, also called Salvation Jane, noxious weed, and Lady Campbell weed, can be found in fields, roadsides, waste areas, and near coastal or other water areas. Native to Africa and the Mediterranean, it can be found throughout the world. This annual plant grows in the winter, and boasts broad, hairy leaves, blue flowers on stalks, curled spikes at the ends of branches, and numerous seeds that can lie dormant in soil for several years.

Like many other plants in the Boraginaceae family, the ingestion of Paterson’s Curse in your horse can lead to a toxicity. Though the symptoms can be slow to appear, digestive and behavioral changes can indicate damage being done to the liver. Over time, liver failure can occur, leading to death.

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Symptoms of Paterson's Curse Poisoning in Horses

In most cases of a Paterson’s Curse toxicity, signs are typically not seen for many weeks or months after the initial exposure to the plant, and may appear even if consumption has ceased. Symptoms you see in your horse are directly related to liver damage resulting from this toxic plant. Often, the common neurological sign of aimless wandering is referred to as “walking disease” or “sleepy staggers”. Signs include:

  • Loss of appetite
  • Depressio
  • Constipation
  • Diarrhea
  • Bloody feces 
  • Weight loss
  • Colic
  • Jaundice
  • Abdominal swelling
  • Photosensitivity
  • Dullness
  • Sleepiness
  • Loss of condition
  • Progressively weaker 
  • Reluctance to move
  • Head-pressing
  • Aimless wandering
  • Yawning
  • Chewing motions 
  • Pica 
  • Behavioral changes
  • Aggressive of frenzied behavior
  • Incoordination
  • Pneumonia 
  • Difficulty breathing
  • Coma 
  • Death 

Types

As in most cases of toxicity from a plant in the Boraginaceae family, there are two recognized types of poisoning.

  • Acute poisoning occurs when a large amount of Paterson’s Curse is ingested within a small amount of time, but is rarely seen due to the unpalatable nature of the plant; the resulting liver failure can cause sudden death within 2 to 3 weeks after ingestion occurs, often without any previous signs
  • Chronic poisoning is seen more often, as small doses of Paterson’s Curse are ingested over a lengthy amount of time, often from contaminated hay bales; symptoms can occur up to 8 months after the first ingestion of the plant, and show a progressive loss of condition and liver disease

 

Causes of Paterson's Curse Poisoning in Horses

The pyrrolizidine alkaloids within Paterson’s Curse are responsible for the symptoms and resultant liver failure seen after ingestion. While this toxic plant contains over 10 different kinds of these alkaloids, echiumine and echimidine are believed to be responsible for chronic liver damage. The levels of these two alkaloids can vary, depending on the climate and soil. Typically, pyrrolizidine alkaloids cause cell death in targeted organs, commonly the liver. Younger horses are more sensitive to these toxic alkaloids. There have been cases of fetal and neonatal fatalities from mothers who showed no signs. 

While horses will normally ignore Paterson’s Curse, there are situations when this plant can be consumed. These include:

  • Contaminated hay bales or feed
  • Overgrazed pastures
  • Lack of other green vegetation
  • Drought 
  • After a fire

Diagnosis of Paterson's Curse Poisoning in Horses

A diagnosis of a Paterson’s Curse poisoning can be difficult, due to the delay of symptoms. If you have seen evidence of your horse ingesting this plant, bringing a sample of the plant to your veterinarian can speed up a diagnosis. In these cases, any tests performed can be more targeted, and results, along with a positive plant identification and symptoms, can determine the diagnosis.

More often, your horse will begin to exhibit symptoms long after any ingestion has occurred, and you may have no knowledge of exposure. Your veterinarian will then examine your horse and run a series of tests to determine the cause of symptoms. Bloodwork and serum analysis, including an ELISA test, and possibly spectrophotometry and gas chromatography/mass spectrometry, can reveal the presence of pyrrolizidine alkaloids. Enzyme levels in the serum and protein levels in the blood can also indicate the presence of liver disease. At that point, your veterinarian may perform a more comprehensive liver test to assess its function. A liver biopsy may be ordered for further testing.

Treatment of Paterson's Curse Poisoning in Horses

There is no specific remedy for a Paterson’s Curse poisoning. Treatment is supportive and symptomatic. The plant needs to be removed from any feed, hay, or areas within your horse’s reach to prevent further toxicity. Your horse’s diet may be changed, and may include higher amounts of carbohydrates. 

Supportive treatments can include fluid and electrolyte therapy, and medicated creams or lotions if your horse is experiencing photosensitivity. In such cases, your horse will also need to stay out of the sunlight while he recovers.

Recovery of Paterson's Curse Poisoning in Horses

The rate of recovery for horses poisoned from ingestion of Paterson’s Curse is poor. Often, by the time symptoms are noticed, the damage to your horse’s liver may be irreversible. Horses are often found dead without any previous signs of a problem. If your horse receives proper treatment, and Paterson’s Curse is removed from your horse’s reach before significant liver damage has occurred, he may recover. 

Due to the fatal nature of this poisoning, prevention remains the best way to ensure the safety and health of your horse. Accomplish this by examining your horse’s feed and hay bales for Paterson’s Curse, and monitoring your pastures, fields, fence lines, and trails for signs of this toxic plant. Manage it on your property by slashing during flowering, hand pulling before flowering, and using herbicides.