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What is Black Laurel Poisoning?

The black laurel is one of approximately 50 species of blooming plants that are native to Madagascar, America, and Asia. These shrub like plants grow to about three to nine feet tall and have leathery dark green alternate leaves with groups of bell-shaped flowers in white or pink. The black laurel is commonly found along streams and rivers, or in natural areas in wet woodlands. Some varieties have been cultivated to adapt to cooler weather and there are those that are made to be smaller than the average laurel, up to about 18 inches tall. The dangerous toxins are still just as lethal with these varieties as well, but harder to recognize. Therefore, if you have horses, you should become familiar with all of the poisonous plants that may be in your area and check your fields regularly.

Black laurel is one of the most dangerous plants in North America and the effects can be life threatening if the plant is consumed by your horse. The toxic substances in the black laurel are grayanotoxins and andromedotoxin, which can cause severe cardiovascular, gastrointestinal, and central nervous system irritation. These toxins have the ability to attach to channel receptors and interrupt the electrical currents, which produces constant excitation. This allows too much calcium into the bloodstream and will lead to heart irregularities, central nervous system changes, drooling, coma, and will eventually be fatal without treatment.

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Symptoms of Black Laurel Poisoning in Horses

The signs of black laurel poisoning may not be noticed until it is too late. Often, once the symptoms are evident, the condition may be further along than hoped. However, sometimes you can obtain immediate help and prevent any worse side effects.

  • Appetite loss
  • Dizziness
  • Excessive drooling
  • Depression
  • Abdominal pain
  • Diarrhea
  • Weakness
  • Muscle tremors
  • Cardiovascular trouble (low blood pressure, irregular heartbeat, palpitations, extreme fatigue)
  • Convulsions
  • Coma
  • Death

 Types

The scientific name of Black Laurel is Leucothoe davisiae from the Ericaceae family. It is also commonly known as:

  • Sierra Laurel
  • Fetter Bush
  • Dog Laurel
  • Dog Hobble
  • Coastal Dog Hobble
  • Black Laurel
  • Sweet Bells

Causes of Black Laurel Poisoning in Horses

  • Grayanotoxins, which are cardiac glycosides that stimulate the heart and cause your horse’s cardiac system to become overexcited
  • It only takes two pounds of black laurel shrub to make your horse seriously ill

Diagnosis of Black Laurel Poisoning in Horses

Obtain a sample of the plant you believe your horse has been snacking on to help the veterinarian identify the toxins that are affecting him. A complete and thorough physical evaluation will be done, which will include taking your horse’s vital signs, performing palpation and auscultation on all large muscles and organs, giving a behavioral and performance assessment, and performing a lameness examination.

The most common clinical signs of black laurel poisoning in horses include low blood pressure, slow breathing, and a weak, irregular heart rate. In addition, the veterinarian will most likely perform an electrocardiogram (EKG) to evaluate the function of your horse’s heart. This procedure is simple and painless and can tell your veterinarian how well the electrical signals in the heart are working. An endoscopy may also be done to check the esophagus and upper airway to look for plant particles, inflammation, and blockages.

Treatment of Black Laurel Poisoning in Horses

Because your horse is not able to vomit like other animals, your veterinarian will need to decontaminate the stomach before doing any other treatments. Some other steps may include oxygen and fluid therapy, medications, and hospitalization.

Decontamination

This step requires the administration of activated charcoal to absorb as much of the toxins as possible. It will be given by mouth or feeding tube directly into the stomach, depending on your horse’s condition. Afterward, a gastric lavage is performed by pumping in warm saline solution with a tube placed in the gastrointestinal tract through the nose or mouth. Your horse will likely be sedated during this procedure.

Oxygen and Fluid Therapy

In many cases of black laurel poisoning, the horse’s breathing may be irregular so the veterinarian will provide oxygen by face mask or nasal cannula. Fluids and electrolytes are given by intravenous (IV) line to promote good circulation and prevent dehydration.

Medications

To help strengthen the heart rate, atropine is usually added to the IV line and medication for abdominal pain may also be given. Stomach protectants will be provided to soothe the gastric irritation.

Hospitalization

The veterinarian will probably want to keep your horse overnight for observation and to provide treatment as needed.

Recovery of Black Laurel Poisoning in Horses

Your horse’s prognosis is guarded for the first 24-48 hours. If your horse makes it past 48 hours, a full recovery is expected with no further complications. Your veterinarian will advise you on the expected rate of return to normal activity. Stall rest and limited exercise may be suggested until the follow up examination has been done.