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What is Sycamore Tree Poisoning?

Sycamore poisoning (atypical myopathy) is most common in autumn, simply because there are more seeds falling to the ground. The toxicity level is different in each seed or seedling, ranging from mild to extremely toxic.  Young horses are more vulnerable to the toxin. 

Symptoms of sycamore poisoning in horses can occur 12 to 72 hours after ingestion.  The toxic agent hypoglycin can cause the fast breakdown of muscle cells.  The breakdown of the muscle cells then causes high levels of muscle enzymes to enter the bloodstream. If the horse’s kidneys are unable to process the high levels of muscle enzymes, this will lead to acute kidney failure.

A horse showing signs of sycamore tree poisoning must be seen by a veterinarian as soon as possible.  Sycamore tree poisoning, if not treated promptly by a veterinarian, can be fatal to the horse.

The seeds and seedlings of the sycamore tree contain the toxic agent hypoglycin A, which causes severe muscle damage.  If a horse ingests the seeds or seedlings of a sycamore tree he will develop atypical myopathy.

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Symptoms of Sycamore Tree Poisoning in Horses

Symptoms of sycamore tree poisoning may include:

  • Lethargy
  • Reluctance to work
  • Weakness 
  • Stiffness
  • Tremors
  • Sweating
  • Difficulty breathing
  • Choking
  • Red or brown urine
  • Colic
  • Fast irregular heartbeat
  • Recumbency
  • Pain
  • Collapse

Causes of Sycamore Tree Poisoning in Horses

Sycamore tree poisoning in horses is caused by the consumption of sycamore seeds and or seedlings.  Horses usually will ingest the seeds and or seedlings when:

  • The pasture is poor with  lack of suitable forage
  • A horse who finds shelter under a sycamore tree may proceed to graze under the tree
  • The ingestion of the seeds leads to muscle myopathy
  • The kidneys cannot process the high levels of enzymes
  • Renal failure can lead to coma and death

Diagnosis of Sycamore Tree Poisoning in Horses

If you suspect sycamore tree exposure, be certain to alert your veterinarian upon his arrival. A horse with atypical myopathy will have dark brown urine when a sample is examined. Blood tests may reveal kidney damage and high levels of muscle enzymes. The diagnostic process will include, along with the urine and blood analysis, laboratory work ups to rule out possible concurrent illnesses in order to best choose the treatment plan. Clinical signs like sweating, choking and fast heart beat will be addressed according to the severity. Often, a horse who has consumed the seedlings from the tree will require transport to a large animal hospital for treatment.

Treatment of Sycamore Tree Poisoning in Horses

Your horse may need hospitalization for up to two weeks. Nutritional therapy to keep digestive motility stable and productive will be required alongside fluid administration to combat dehydration and to flush the kidneys. Ensuring that renal failure does not occur is essential. Medication for pain, drugs to reduce tremors, and supplementation of vitamins will be prescribed. Vitamin B1 and vitamin B2 are beneficial to muscle tone.  Beta-carotene, vitamins C and E may help remove oxidizing agents. With 24 hour care, horses who have suffered sycamore tree poisoning will have a 50/50 chance of survival. Younger horses, aged horses, and equines with underlying health concerns will need to be monitored very carefully. Continued therapy may be required for a few weeks.

Recovery of Sycamore Tree Poisoning in Horses

Horses that are treated for sycamore tree poisoning in the early stages have a good recovery prognosis.  The patient will need follow-up visits to monitor his progress.  The veterinarian may want to take another urinalysis, to check kidney function.  Most horses that recover from sycamore tree poisoning do not have long term effects from the toxin.

It is imperative to avoid the reoccurrence of sycamore tree poisoning.  If you decide not to have the tree removed from the pasture, a fence should be placed around the tree.  Keep in mind that sycamore seeds can fall and spread in an area 3 times the height of the tree.  

A horse needs to have long stem hay, pasture grasses and legumes available to him to forage on.  The pasture should be well maintained, fertilized and routinely checked for poisonous weeds.