Red Maple Leaf Poisoning Scare

The wilted, poisoned leaves from a fallen red maple tree limb prove irresistible to an easygoing mare, and she nearly pays with her life. Written by Susan Owen for EQUUS magazine.
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While wilted red maple leaves are toxic, fresh growing leaves do not appear to cause any harm. |

While wilted red maple leaves are toxic, fresh growing leaves do not appear to cause any harm. |

My 9-year-old Racking horse mare, Brandi, and our Clydesdale/Thoroughbred yearling were safely in the barn when a ferocious thunderstorm passed through our area in southeastern Virginia on May 13, 2002.

When I inspected the farm for damage the next day, I was relieved to find only one problem: a large limb had fallen from a mature tree that stands in the horses' pasture.

Since the fences were all intact, I turned the Brandi and the yearling back out that morning, and in the evening my fiancé, Darren Owens, arrived to help me cut the limb into manageable pieces. We piled as much as we could in the farm pickup truck, but it was so late by the time we returned from disposing of the load that I decided to finish the job in the morning. The next day I cleaned up the rest of the small branches and leaves and thought nothing more of it.

But the incident was far from over. When I went out to feed the horses the next morning, Thursday, May 16, Brandi was lethargic and refused her grain. This was unusual so I immediately called my veterinarian. Like our other horses, Brandi had had all of her vaccinations but I didn't want to take any chances.

The veterinarian suggested I take Brandi's temperature and call back. The mare's temperature was a perfectly normal 101 degrees Fahrenheit, and since she was showing no other signs of illness, the veterinarian suggested that I continue to monitor her behavior and temperature. I had not told the veterinarian about the fallen limb; frankly, I didn't even think of it.

On Friday I went out to care for the horses around 7:30 a.m. and was encouraged when Brandi ate some of her feed. But when I went back out at 9:30, Brandi had developed muscle twitches in her hips. I called my friend Cyndi Raiford, who arrived a few minutes later. When Cyndi picked up Brandi's hooves, she noticed they were icy cold. Together we got out our books to research this mystery illness and while we were watching her, Brandi urinated. The stream was black--the color of strong coffee.

That was when it dawned on me that the fallen limb might have something to do with this. I knew that certain leaves were dangerous, but trees had never been an issue in all my years with horses. Further, the tree that lost the limb had never caused any trouble before. But nothing else in Brandi's routine had changed over the past week--the fallen limb was the only suspect.

Cyndi and I immediately trailered Brandi to my veterinarian's office. An examination revealed classic early signs of red maple poisoning: yellow scleras indicative of jaundice; pale, almost white gums; and dark-colored, almost black urine. In addition, bloodwork showed that Brandi had a low packed cell volume--an indication that the toxins from the leaves were causing her red blood cells to break down.

Brandi needed to be transported to a veterinary hospital immediately. Arrangements were made to admit her to North Carolina State (NCS) Teaching Hospital in Raleigh, more than three hours away. Our veterinarian felt that Brandi was stable enough to withstand the trip, so Cyndi and I drove her down that afternoon.

The NCS staff was ready and waiting for us when we arrived. Brandi went straight to the examination room, where a complete history was taken, including details of her past health, the illness and our treatment to date. The staff immediately put Brandi on intravenous (IV) saline solution as they conducted their examination. The staff veterinarian, Malcolm Roberts, BVSc, PhD, told us that he also suspected red maple poisoning.

It was devastating news. Red maple poisoning is often fatal; in fact, many horses succumb within hours of eating as little as a pound or two of leaves. The toxins in wilted red maple leaves disable the red blood cells, rendering them incapable of carrying oxygen and eventually causing them to disintegrate. In addition, the toxins cause devastating damage to the kidneys, liver and other internal organs.

There is no known antidote for red maple poisoning. All that can be done is to provide the horse with supportive care in the form of fluids to dilute the toxins and assist vital functions throughout the body. Roberts was frank--even if Brandi survived the next 24 to 48 hours, he said, she would still face a long road for recovery.

However, we did have some cause for optimism. The severity of red maple poisoning depends largely on how many of the leaves were eaten, and we were told that a severely ill horse can be entirely oblivious to his surroundings. Brandi, however, despite her jaundice and dark urine, was relatively alert and her heart rate was in the normal range. Although her blood tests still showed a low packed cell volume, as well as high levels of creatinine and other indicators of the red cell breakdown, Roberts was reasonably optimistic that Brandi had a good chance to pull through.

For the next three days in the hospital, she received large amounts of IV fluids to help flush the toxins and the byproducts of cell destruction from her system. The veterinary staff inserted a catheter into her bladder so they could monitor her urine output both for quantity, which is essential for ensuring her kidneys are functioning, and for color.

We received daily telephone updates. Brandi's urine output was low at first, and blood tests showed that her red cells were continuing to break down. Then she hit a plateau--the deterioration slowed to a stop. Gradually, over the next 24 hours, her jaundice began to disappear and her urine began to return to a normal color. Finally, on May 21, after about 80 hours of continuous treatment, Brandi had improved enough so that she no longer needed the IV fluids.

But her ordeal wasn't over yet. As with many illnesses that affect the circulation, red maple poisoning often leads to laminitis, and soon I got the troubling call from Roberts: Brandi had begun to develop laminitis in all four feet. The staff had been monitoring the mare's digital pulse for indications of laminitis and when signs of trouble appeared they sprang into action with wraps and bute. However, the mare was in obvious pain and spent much of her time lying down. Her heart rate also spiked due to the pain.

My fiancé and I made the trip down to visit, and I cried when I saw her. My bright, easygoing horse was in obvious distress. When she wasn't down, she would just shift her weight from foot to foot. She hovered in the back of her stall, as if to say, "Leave me alone, I hurt!"

We were told that the red maple reaction was slowly diminishing, but it was too early to tell if Brandi had permanent injuries to her kidneys or other internal organs and now the laminitis could possibly be causing long-term damage to her feet. Brandi was a fighter, but with two serious problems to contend with, I wasn't sure how much she could withstand.

More days passed, and we continued to receive daily updates on Brandi's progress. Her urine remained clear and slowly her laminitis began to respond to continued treatment. Finally, on May 25, nine days after Brandi was admitted to the hospital, the NCS staff felt it was safe to send her home.

We were to keep administering bute for several more days, but Roberts said Brandi should require no other treatment. However, we were told that it would take more than three weeks for her red blood cell counts to return to normal, so she would fatigue easily for a while.

Brandi still seemed somewhat distant when we picked her up that day, but she perked up and acted a little happier once we got her home. For the first few days we kept her separate from her youthful pasturemate, because he tends to want to play. Brandi was brought in each night, and she seemed grateful to have a place to lie down undisturbed. Her appetite continued to improve and a week later we turned her back out with the yearling.

Brandi was the only horse to develop signs of poisoning; apparently the yearling didn't like the taste of the wilted leaves from the fallen limb. We decided not to cut down the tree, but we did close off that pasture to horses. Then last fall, after Darren and I married, we moved to a new farm--one with no trees in the horse pasture.

Despite her lengthy bout of laminitis Brandi never foundered--her coffin bones didn't rotate. Still, I ended up giving her a year-long sabbatical to let her recover from the ordeal. She now gallops around her new paddock as if nothing had ever happened. I plan on riding her again this fall.

This article originally appeared in the September 2003 issue of EQUUS magazine.