What is Laurel Poisoning?
Laurel plants are a small genus of flowering shrub known scientifically as the kalmia genus that belongs in the heather family. They have clusters of white, pink, or purple flowers with lanceolate leaves that resemble the blooms on the Rhododendron plant and all parts of these shrubs contain the potent neurotoxins called grayanotoxins. These poisons work by disrupting the ability of the cells of the body to return to their normal state after excitation. Ingested grayanotoxins can interfere with typical skeletal and nerve functionality as well as interfering with the action of the cardiac muscle. If your horse has eaten any part of a laurel shrub, contact your equine vet immediately.
Laurel plants contain powerful neurotoxins known as grayanotoxins which disturb the proper function of the body’s cell membranes. Poisoning from laurel plants should be treated as an emergency.
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Symptoms of Laurel Poisoning in Horses
Symptoms of laurel poisoning can begin within just a few hours after ingestion. A relatively small amount of most varieties of laurel plant is required for toxicity:
- Abdominal pain
- Abnormal heart rate
- Abnormal heart rhythms
- Excessive salivation
- Loss of appetite
- Low blood pressure
- Muscle weakness
- Poor performance
- Rapid, shallow breathing
- Temporary blindness
- Kalmia angustifolia - Also known as lambkill and sheep laurel, this wild shrub produces bright pink clusters of flowers in the summer throughout the eastern portion of North America
- Kalmia Carolina - Also referred to as the Carolina laurel and the Carolina wicky, this variety of laurel is found in the warmer southern regions and has pink blooms
- Kalmia cuneata - An endangered variety of laurel known as white wicky, this shrub has attractive cream colored flowers with a red band
- Kalmia latifolia - This variety goes by the names mountain laurel, calico-bush, and spoonwood; due to its method of pollen dispersal, the kalmia latifolia flower is capable of throwing its pollen up to 15 centimeters away
- Kalmia microphylla - The bog laurel is a shorter shrub, generally keeping under eight inches tall and is found in wet and boggy environments throughout the western half of North America
Causes of Laurel Poisoning in Horses
The toxicity of this shrub is contained in the neurotoxins that it produces, called grayanotoxins. The grayanotoxins, which are located in the leaves, petals and even pollen of the laurel plant, have chemical properties that resemble turpentine, which can cause burning in the oral area when chewed. This organic compound binds to the sodium channels in the horse’s cell membranes once it is inside the body, and disrupts the natural electrical current present in the host’s cells preventing them from returning to their normal state which leaves the cells in a permanently excited state.
Diagnosis of Laurel Poisoning in Horses
If you see your horse grazing on any part of a Laurel shrub, identification is often sufficient information for a primary diagnosis for the origin of your horse’s distress. A sample of the plant that your horse ingested will help to identify the plant correctly, and your horse’s doctor will take samples to evaluate standard tests like a biochemistry profile, urinalysis, and complete blood count, as well as perform a full physical examination at this time.
If the consumption of the plant was not witnessed, your veterinarian would take particular note of any plants that are growing within reach the pasture and stable area in addition to information regarding any other supplements or prescriptions that are being administered to your horse. This will help to reveal any drug interactions or toxins that could induce the same symptoms as laurel toxicity. A sample of the patient’s feces will also be evaluated, and plant material found in the feces may assist the examiner in determining an accurate diagnosis. Due to the severity of the symptoms, supportive treatment typically starts before a definitive diagnosis is made.
Treatment of Laurel Poisoning in Horses
No specific antidote is available for the grayanotoxins in the laurel plant, so preliminary treatments will be focused on removing as much of the toxin from the horse’s system as possible and easing the symptoms. As equines are unable to vomit, the veterinarian will need to fully irrigate the stomach using a nasogastric tube to prevent the absorption of the toxins into the bloodstream.
A slurry of activated charcoal will also be will be dispensed to the patient in an attempt to soak up as much of the grayanotoxin as possible, followed immediately by a laxative. Many equine vets recommend magnesium sulfate (Epsom salts) or sodium sulfate (Glauber’s salt) as a laxative, and mineral oil may be utilized as an intestinal protectant. Supportive treatments will also be administered, including large volumes of IV fluids to prevent dehydration, treat shock, and protect the kidneys, and possibly corticosteroids to reduce inflammation. Intravenous atropine may also be suggested for horses with an elevated heart rate or tremors.
Recovery of Laurel Poisoning in Horses
Animals that are going to recover from mild laurel poisoning usually do so within about 24-48 hours after treatment. Circumstances like excessive doses, extreme reactions to the toxin, or an extended time before diagnosis may increase the recovery time. Plenty of clean, fresh water should be available for the recovering patient, and care should be taken when the patient is recovering from anesthesia. It is critical that horses not be urged to stand before they are ready as they may be unsteady when they first awaken, and padded recovery stalls will often be utilized to prevent injuries upon regaining their faculties.