Red Maple Toxicosis in Horses

Key Takeaways

Eating dry or wilted red maple leaves is poisonous for horses, leading to life threatening toxicosis. 

• Storms, high winds, and autumn all result in more leaves on the ground, and it is important to not allow a horse to graze in any place where red maple leaves may fall

Red maple toxicosis leads to destruction of red blood cells and is a life threatening emergency

• Symptoms of red maple toxicosis include yellow gums, colic, bloody or brown urine, and fever

• Diagnosis of red maple toxicosis relies on physical examination, blood work, and urinalysis

• The prognosis for red maple toxicosis is poor

• Treatment is predominately supportive, consisting of fluid therapy, blood transfusions, and administration of activated charcoal, which may reduce toxin absorption

A Closer Look: What is 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.

Risk Factors

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.

Possible Causes

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.

Main Symptoms

Symptoms include

• Yellow gums/whites of the eyes (jaundice) • Colic • Shallow/rapid breathing (tachypnea) 

• Difficulty breathing (dyspnea) • Fever • Bloody/brown urine • ‘Muddy’/brown gums

• Lack of appetite • Lethargy • Uncoordinated movement (ataxia)

Testing and Diagnosis

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

Steps to Recovery

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.

Prevention

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.

Is Red Maple Toxicity Common in Horses?

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

Typical Treatment

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

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