What is Western Yew Poisoning?
Western yew, or Taxus brevifolia Nutt, is a member of the yew family, and is also known as Pacific yew, yew brush, and mountain mahogany. Western yew is often used as an ornamental shrub, a hedge plant, and in Christmas wreaths. This dark green shrub has needlelike leaves that are 1 to 2.5 cm long, with bright red, ovoid shaped fruit surrounding a brown seed. Though eaten by some birds and moose, Western yew is toxic to dogs and many other mammals, especially when cut and left out to rot.
Western yew is an evergreen tree and shrub that grows along the Pacific coast of North America, including California, Alaska, and British Columbia. It is also found in the Rocky Mountains, in parts of Montana, Idaho, Washington and Oregon. Related to English yew, Western yew when ingested can cause gastrointestinal and nervous system issues, decreases in heart rate and blood pressure, hypotension, and often leads to cardiac arrest. Depending on the level of toxicity, this can happen anywhere from 1 to 48 hours from ingestion.
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Symptoms of Western Yew Poisoning in Dogs
Signs of poisoning can appear within minutes to days from ingestion. It often causes acute gastroenteritis, or inflammation of the intestines, as well as severe cardiac issues. Symptoms can include:
- Abdominal pain
- Dilated pupils
- Increased aggressiveness
- Abnormal heart rhythm
- Bradycardia, or abnormally slow heart action
- Loss of bodily control
- Low blood pressure
- Difficulty breathing, or breathing failure
- Sudden death
There are two recognized syndromes recognized in western yew poisoning.
Acute syndrome – This is a rapid toxicity that creates an abnormal heart rhythm, or cardiac arrhythmia. Death from cardiac arrest generally occurs in 1 to 3 hours after the plant is ingested. Treatment is generally ineffective.
Subacute syndrome – This is a longer process, with symptoms such as digestive issues, hypotension, weakness, coma, and seizures. Death occurs in 24 to 48 hours after yew ingestion. Survival is possible with treatment.
Causes of Western Yew Poisoning in Dogs
There are many components in yew plants, but the parts responsible for most of its toxicity are taxines. Found in all parts of the yew plant except for the aril, or the bright red seed covering, taxine A and taxine B are cardiotoxins that inhibit sodium and calcium currents, block the heart’s signals, suppress heart contractibility, cause increased blood flow and hypotension, and can result in cardiac arrest.
The amount of plant needed for your dog to become poisoned is small, about 2.3 grams of leaves, or 11.5 mg of taxine. Your dog can get a lethal dose while playing with yew branches or sticks. Though the taxines remain in the yew plant throughout the year, the concentrations are highest in winter.
Diagnosis of Western Yew Poisoning in Dogs
Whether or not your dog is showing symptoms, seek medical help immediately if any part of the yew plant has been ingested. This is a time sensitive toxicity that is often diagnosed post mortem. If possible, bring a sample of the plant to the veterinary clinic, as this will help to make a possible identification. Diagnosis will depend on what was ingested, any symptoms present, and the detection of yew leaves or taxines in vomit or blood. The severity of poisoning depends on the amount of yew consumed, and the health and age of your dog. Your veterinarian will determine if it is an acute or subacute syndrome.
Often, your veterinarian will induce vomiting. If successful, the gastric contents are examined for yew leaves, twigs, and pieces. Blood can also be tested through gas or liquid chromatography, and mass spectroscopy.
Treatment of Western Yew Poisoning in Dogs
If diagnosis is an acute syndrome, there is no treatment available and death can occur quickly. For a subacute syndrome, treatment is as follows.
Gastric lavage, or stomach pumping, is performed as soon as possible, and is best within 30 minutes to 1 hour of ingestion. This involves the careful placement of a tube down into the stomach, which both administers warm water or saline into the stomach, and siphons it back out. A purgative drug may also be administered. The gastric contents are then carefully examined. This may not be recommended if a significant amount of taxine has been absorbed, as it can trigger nervous system and cardiac complications.
Aggressive decontamination of the stomach may continue with activated charcoal, which can stop further absorption of the toxin.
Atropine sulfate may be administered to counteract any cardiotoxic effects, such as bradycardia. This treatment is more successful if administered early. Unfortunately, this treatment can slow the elimination of the yew plant, and must be done carefully.
Fluid therapy helps to support blood pressure, maintain hydration and renal function, and to flush out the toxin. Anti-emetics may also be prescribed subcutaneously, orally, or intravenously. Nervous system issues like seizures and aggressiveness can be controlled by medications, such as diazepam.
Your dog may be kept hospitalized for the next several days so that your veterinarian can watch for cardiac arrhythmias and heartbeat intervals using EKG monitoring.
Recovery of Western Yew Poisoning in Dogs
Once your dog is released to come home, make sure to avoid any cardiac stress, such as exercise, transportation, or any excitement. To prevent Western yew poisoning, do not play with yew branches with your dog, and dispose of any yew trimmings in your yard, or areas available to your dog.