What is Red Maple Poisoning?
Red maples, or Acer rubrum, are one of the most common species of maples that grow throughout eastern North America. Other names of red maples include swamp maple, curled maple, scarlet maple, and soft maple. The red maple is a tall hardwood tree. Its leaves are characterized by three large points and five prominent veins. Though green in summer, the leaves will turn yellow and crimson in the fall. Horses are the only animal reported to have an adverse reaction from consuming red maple leaves.
The ingestion of dried or wilted maple leaves can cause a toxic poisoning in horses. Generally occurring in the fall and winter months when the leaves fall off the tree, red maple poisoning can damage red blood cells, which leads to a severe lack of oxygen circulating to organs and tissues. Symptoms of depression, a lack of appetite and colic may seem mild, but if the poisoning is not treated quickly, death can occur. Darkened mucous membranes and urine are signs of a more severe reaction, and require medical attention immediately.
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Symptoms of Red Maple Poisoning in Horses
Symptoms can begin within 12 to 48 hours after your horse has ingested wilted or dried red maple leaves. Death from toxicity can occur as early as 18 hours after ingestion, or up to 7 to 10 days later. Signs can include:
- Lack of appetite
- Lack of fever
- Abdominal discomfort
- Blue, yellow or brown mucous membranes
- Dark red to brown urine
- Foot tenderness due to laminitis
- Labored breathing
- Unable to rise
- Increased heart rate
- Increased respiratory rates
- Abortion in mares
- Kidney failure
- Acute hemolytic anemia, or the destruction and removal of red blood cells
- Sudden death
Causes of Red Maple Poisoning in Horses
The cause of red maple poisoning in horses is the ingestion of wilted or dried red maple leaves. The ingestion of fresh leaves does not seem to cause the same reaction. Toxicity in the leaves is the highest in the fall, and cases of toxic poisoning in horses generally occur in the autumn and winter months. Any leaves left until the next spring do not seem to retain toxicity. Leaves wilted due to summer storms have also been known to cause toxic poisoning.
The main toxic ingredient is believed to be gallic acid, which causes acute hemolytic anemia, or the destruction of red blood cells. This results in a lack of available oxygen to the tissues of the body, producing the symptoms seen in poisoned horses, such as darkened urine caused by the removal of hemoglobin, kidney failure due to toxic levels of hemoglobin in the kidneys, darkened mucous membranes due to lack of oxygen, and increased heart and breathing rates as the body tries to supply the body with more oxygen. Death can occur due to a severe lack of oxygen in the cells and tissues of the body.
Diagnosis of Red Maple Poisoning in Horses
Red maple poisoning is diagnosed primarily on the symptoms present, and on a history of red maple leaf ingestion in your horse. It is important to know what your horse ingested so that your veterinarian can properly diagnose your horse and begin treatment immediately. If in doubt, bring a sample or picture of the material to your veterinarian so that a proper diagnosis can be given. Results from blood work can also help a diagnosis. A diagnosis can be made post-mortem through examining intestinal and stomach contents for maple leaves.
Treatment of Red Maple Poisoning in Horses
Treatment is mainly through the administration of activated charcoal through a nasogastric tube to absorb the red maple leaf toxins within the first few hours after ingestion. Mineral oil can be given after the charcoal to decrease your horse’s absorption of the red maple leaves. Other treatments are supportive, and can include the administration of intravenous fluid therapy to flush the kidneys, Vitamin C, corticosteroids, non-steroidal anti-inflammatory drugs, oxygen therapy, and whole blood transfusions if needed.
Recovery of Red Maple Poisoning in Horses
Recovery of your horse depends entirely on how much of the red maple leaves were ingested and how quickly treatment can be administered. As such, your horse’s recovery is dependent on your horse’s case. For the best chance of recovery, seek immediate veterinary care if you suspect your horse has ingested red maple leaves. Prevent this potentially fatal poisoning through maintenance of your horse’s exposure to red maple leaves. Ways you can do this include:
- Remove any red maples from pastures, paddocks or areas where they can contaminate your horse’s areas or feed
- Refrain from planting red maples on your property, near or in horse pastures, or near barns
- If red maple is in your horse’s pasture and you cannot remove the trees, move your horse to a different pasture
- Remove any fallen branches or leaves from red maple trees, particularly after a storm
- Ensure that branches or leaves from overhanging trees cannot fall into the horse’s paddock
- Be sure that bales of hay are not contaminated with red maple leaves
- Know what a red maple tree and leaf look like to be able to identify this possible toxin
- Monitor your horse when browsing to keep him from ingesting red maple leaves
- Seek medical attention immediately if ingestion of red maple is suspected
- Be aware of the cycle of toxicity in red maple (leaves wilted after September 15 are the most toxic, leaves remain toxic for up to 4 weeks in the fall and winter months)
Red Maple Poisoning Questions and Advice from Veterinary Professionals
I moved my horse to a stable February 18 of this year. They have red maples on property. My horse does not typically eat leaves but in the grassy spring may have ingested a few over many days. He seems off, lightly colicy yesterday, stiff and not wanting to move. Can the toxicity of these leaves last months? These leaves would have fallen last Fall before I arrived. Thanks a bunch, Liz
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