What is Carolina Maple Poisoning?

The Carolina Maple is a very common tree that can be found almost anywhere in the world, but is most common in the Eastern and Southern United States. These trees can grow up to 90 feet tall and produces thousands of leaves, which are dropped to the ground in the Fall. The average Carolina Maple tree can drop between 50,000 and 75,000 leaves per year and it only takes about one pound of these leaves to make your horse critically ill and three pounds to be fatal. The bark of the tree also contains tannins, which causes gastric distress, laminitis, and possible liver and kidney damage. The fatality rate in horses with Carolina Maple poisoning is between 60% and 70%, so if you believe your horse may have eaten any amount of the leaves or any part of the tree, get veterinary help immediately.

Because the Carolina Maple (Acer rubrum) tree is one of the most abundant trees in North America, many horses have been reported as being poisoned from eating the leaves. In fact, a healthy horse can become sick and die within hours of consuming them. The toxic substances in the Carolina Maple tree leaves are tannic acid, gallotannins, Pyrogallol, and gallic acid. These are powerful oxidants that react with other substances in the body to create the formulation of methemoglobin, damaging blood cells and reducing the available oxygen in your horse’s body. These damaged cells can clog the kidneys and starve the tissues and organs of oxygen, causing the failure of vital organs. This leads to death without immediate treatment.

Symptoms of Carolina Maple Poisoning in Horses

The signs of Carolina Maple poisoning may include:

  • Appetite loss
  • Abdominal pain
  • Depression
  • Weakness
  • Dark (or pale) membranes around the eyes and mouth
  • Red or brown urine
  • Breathing difficulty
  • Spontaneous abortion in pregnant mares
  • Sleepiness
  • Lethargy
  • Laminitis (limping, refusal to work or exercise)
  • Convulsions
  • Death


The Carolina Maple tree is scientifically referred to as Acer rubrum of the Aceraceae family. However, it is also known by many other names such as:

  • Swamp Maple
  • Scarlet Maple
  • Red Maple
  • Curled Maple
  • Acer Sanguineum
  • Soft Maple
  • Rufacer Rubrum


Causes of Carolina Maple Poisoning in Horses

The toxic principle in the Carolina Maple tree are gallotannins, gallic acid, Pyrogallol, and tannic acid, which cause the destruction of red blood cells and oxygen starvation in the tissues and organs.



Diagnosis of Carolina Maple Poisoning in Horses

The veterinarian who examines your horse for signs of Carolina Maple poisoning will first need to know as much of your pet’s history as possible, including any recent injuries and illnesses, especially if this is not your regular veterinarian. Also, be sure to provide a list of medications your horse is on or has been on in the past several days. Some medications can interfere with the diagnosis as well as the treatment plan. The physical examination will include a complete body assessment, vital signs, palpation, auscultation, behavior, and a lameness examination. The veterinarian will perform routine blood tests such as a biochemical analysis, blood urea nitrogen, complete blood count, and packed cell volume.

Some of the results commonly found include low calcium and elevated phosphates, proteins, creatinine, and BUN. The PCV test will determine whether the hemoglobin concentration is decreased as these toxins destroy hemoglobin and can become as low as 8% or 50 grams per liter. A urinalysis should show protein, glucose, and a low specific gravity if your horse has been eating Carolina Maple tree leaves. The veterinarian may also perform some x-rays and an ultrasound to check for other abnormalities that may not be obvious.



Treatment of Carolina Maple Poisoning in Horses

The treatment of Carolina Maple poisoning depends on the amount eaten (if known) and the condition of your horse. Detoxification, fluids, oxygen, medication, blood transfusions, and observation may be used to treat your horse.


Your horse will be given activated charcoal by mouth to bind the toxins and a gastric lavage to wash it all away. The lavage is done by inserting a tube into your horse’s stomach and pumping warm sterile water into the digestive system.

Fluids and Oxygen

Intravenous (IV) fluids will be administered to prevent dehydration and promote circulation. Oxygen will be provided if it is needed.


Some of the drugs the veterinarian may use in treating your horse may include methylthioninium chloride to help oxidize the blood, diuretics such as hydrochlorothiazide or methazolamide, and Vitamin C.

Blood Transfusion

In severe cases, a blood transfusion will be done to introduce oxygen saturated blood into the system. This oxidizes the blood so oxygen can get to the vital organs and other tissues.


Your veterinarian will most likely want to keep your horse overnight for observation. This is the best way to provide supportive treatment as needed.



Recovery of Carolina Maple Poisoning in Horses

Although the rate of fatality is high, if you are able to obtain treatment for your horse within a few hours of consumption, your horse has a fair to good chance of a successful recovery. Of utmost importance upon recovery will be eliminating the chances of your horse ingesting the Carolina Maple; moving the paddock away from the vicinity of the tree or consistent collection of leaves in the area must be considered.



Carolina Maple Poisoning Questions and Advice from Veterinary Professionals

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