• October 5, 2009 -

EEE Update:  As of Wednesday September 16th there have been 11 confirmed EEE positive horses in Maine.  Positive cases were confirmed in the following towns:  Troy, Thorndike, Stetson, Unity, Gorham, Newport, Berwick, Windsor, Jackson & Acton.        



Red Maple (Acer rubrum) Leaf Toxicity
                
It's that time of year when Red Maple Leaves can be extremely toxic to our horses.  Here is some information about Red Maple Leaves, and the Toxicity that comes from them:

Red Maple Toxicity is seasonal, it occurs mainly in the summer and fall months.  Fresh Red Maple Leaves, still on trees are safe, though they may cause Colic, just as any other strange food might.  Also, the leaves that have naturally dropped from trees are not as toxic.

Toxicity occurs only when Red Maple Leaves have wilted, this is when a limb is broken or cut from a green tree and the leaves wilt.  These dried-wilted or fresh-wilted leaves are deadly.

The poisonous toxin in Red Maple Leaves is Gallic Acid (Cornell University).  "The clinical disease produced is that of an acute hemolytic anemia - the abnormal break-down of Red Blood Cells with ultimate destruction of Red Blood Cells. (David Marshall VDM, University of Delaware)"

Signs of Red Maple Leaf Toxicity can occur 1-2 days after ingestion and may include:
Acutely Lethargic, not eating, weak & depressed, breathing with exaggerated effort, heart rate greatly increased.  Fever is not included in the signs of Red Maple Leaf Toxicity.

It is extremely important to contact your Veterinarian if you believe your horse has ingested Red Maple Leaves, as this Toxicity is deadly in more than 60% of cases.

Identifying Red Maple Leaves (http://www.omafra.gov.on.ca/english/livestock/horses/facts/06-109.htm):

"The leaves of red maples are palmate (like the palm of your hand), 5-15 cm long and about as wide, with 3 to 5 lobes. The two sides of the centre lobe are almost parallel to the midvein (5). Between the lobes, the leaf edge or leaf margin is serrated or jagged, while the leaf margin of sugar maple and Norway maple is smooth with no serrations. The underside of the red maple leaf is silver grey and the keys are red. Red maple can hybridize with silver maple, creating crosses of intermediate forms that should also be avoided near horse pastures. Silver maple is a soft maple with heavily indented lobes compared to red maple or sugar maple."

Prevention is key.  Here are some steps to follow:

1. Be sure to remove broken Red Maple Tree branches after a wind storm or cutting
2. Avoid piling cut or broken branches near horse paddocks and in Manure pits
3. Provide enough forage (hay or grass) to keep your horse busy, as they are much less likely to eat leaves.

References: 

1. University Of Delaware Cooperative Extension, David Marshall, VMD Delaware Equine Extension Veterinarian.   
2. Ontario Ministry Agriculture, Food & Rural Affairs  http://www.omafra.gov.on.ca/english/livestock/horses/facts/06-109.htm#general
3. Cornell.edu