Red Maple Toxicosis in Horses

Red maple toxicosis is rare, but there are some occurrences in eastern North America where red maple trees are common. It is important to contact the local extension office for information about red maple growth and ingestion risk in the local area.

Fresh leaves do not carry the same risk, however a horse should never be kept in an area where red maple leaves are accessible.

Symptoms of red maple toxicity do not vary in severity significantly. Symptoms arise within 12-48 hours after leaf consumption. Horses who have ingested a large number of leaves may display symptoms sooner.

Red maple toxicosis has a very high mortality rate. If a horse may have eaten dried or wilted red maple leaves, immediate veterinary assistance is required.

Red maple toxicosis is caused by eating a toxic dose of wilted or dried red maple leaves. Red maple leaves contain a toxin that destroys red blood cells, causing anemia.

Diagnosis is aimed at verifying the cause of red blood cell destruction. Knowing the horse’s recent history, including whether it may have had access to red maple leaves, can save critical time.

Diagnostic tests include:

• Physical examination
• Blood work
• Urinalysis
• Stomach lavage to recover leaves for identification

Treatment for red maple toxicosis is supportive. Administration of activated charcoal by nasogastric intubation can help bind the toxin and prevent absorption. Only a veterinarian should administer activated charcoal. There is no safe way to intubate a horse at home.

Other treatments include:

• Fluid therapy
• Blood transfusions
• Supplemental oxygen

Even with aggressive and timely veterinary care, the prognosis for this condition is poor, and largely dependent on how many leaves the horse ate. Mortality rates are around 60-65%, and horses may have long-term side effects from development of kidney disease or laminitis.

The best way to prevent this toxicosis is to avoid situations where a horse may eat dried or wilted red maple leaves. Fencing off red maple trees in horse pastures and thorough cleaning of fallen branches and leaves after storms may help prevent toxicosis.

Only dried and wilted leaves are toxic. Keeping up with details of where there are maple trees near the horse’s living environment and avoiding them helps to restrict access. As well, leaves falling in autumn create an elevated risk of this condition.

This toxicosis is not common, though it is more common in eastern North America due to a higher concentration of red maple trees.

• Supportive care
• Nasogastric intubation of activated charcoal
• Blood transfusion
• Fluid therapy