What is Yew Poisoning?
There are several different species of the Yew plant, and this evergreen can be found in many parts of the world. The Yew is of the Taxus species, or Taxus spp., and is commonly used as an ornamental plant in landscapes and gardens. All species of the Yew are poisonous to horses, as well as other animals and humans.
These evergreen shrubs have flat, pointed, and soft leaves with a darker tone on the upper side. The lighter green tone underneath gives the leaves a striking effect. The seeds of the plant are dark in color, hard, and almost resemble a nut. A reddish, soft fruit surrounds each seed, and this fruit can be quite enticing to animals, including horses. The fruit and seeds are found underneath new, soft twig growth.
The yew plant may be native to specific countries, but has been widely cultivated and is common in the United States. It is important to be able to recognize this plant so it can be completely avoided if you have horses or other pets.
Yew poisoning in horses is the result of the ingestion of the toxic yew plant. There are several different varieties of this plant, and each of them are highly poisonous and can be fatal if not immediately treated.
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Symptoms of Yew Poisoning in Horses
Typically, once horses have ingested yew, they succumb to the poisoning within a few hours or less. Common symptoms of yew poisoning may include:
- Loss of muscle control
- Problems with breathing
- A slower heart rate
Taxus, the genus of the yew plant consists of three common types of shrubs. Each type is toxic to horses and should be kept off your property if you are a horse owner. Yew is also toxic to cattle, sheep, goats, and other animals. The three common types of yew shrubs are:
- English yew
- Canada yew
- Japenese yew
- Hybrids of the yew plant
Causes of Yew Poisoning in Horses
The causes of yew poisoning are directly related to the containment of toxic alkaloids. Areas of property that contain this plant can put your horse at risk. Causes of yew poisoning are:
- Yew contains toxic alkaloids, namely taxine A and B
- These taxines cause heart damage
- These toxic alkaloids impede calcium and sodium exchange across the cells of the heart muscle
- These toxic alkaloids inhibit electrical conduction through the heart
Diagnosis of Yew Poisoning in Horses
A very small amount of the yew plant can cause great danger to your horse. If your horse is showing any symptoms, contact your veterinarian immediately. Your veterinarian will ask questions about the time and amount of yew he ingested, his health history, and any other questions he feels he needs to know in order to properly diagnose and treat your horse.
He will begin with bloodwork, a serum chemistry panel, and with testing his gastric content for any plant material or toxic alkaloids. Your veterinarian may also perform a liquid chromatography as well as a mass spectroscopy.
Your veterinarian will be looking for dimethoxyphenol within the gastric contents or the bloodstream, which is a sign of yew poisoning. Gastroenteritis is also a clinical sign. The veterinarian will continuously test the contents of the gastrointestinal system. The veterinarian will also depend on the electrocardiogram, as poisoned horses suffer from bradycardia, or slowed heart rate.
Yew poisoning is very rapid, and often the tests conducted above take time. It is important that you are able to communicate with your veterinarian if your horse ate the plant and, if possible, to take a sample of the shrub in with you. The veterinarian must act quickly in order to try to help your horse survive.
Treatment of Yew Poisoning in Horses
There is not an antidote for yew poisoning; treatment methods are dependent upon supportive care and symptomatic care. Treatment methods may include:
Your veterinarian may administer specific medications, especially if your horse is asymptomatic. Atropine may be given in order to aid cardiac conduction, and the veterinarian will use this carefully in order to avoid the known side-effects of colic and gut stasis. Lidocaine may be given; however, the horse must continuously be monitored. If your horse is suffering from seizures, diazepam may be given to minimize this nervous system disruption.
The veterinarian may perform gastric lavage on your horse in order to attempt to decontaminate the stomach and system of your horse. This is followed up with activated charcoal to further assist in absorbing the toxins.
Your medical professional will continue to monitor your horse’s electrocardiogram and observe any arrhythmias. Your horse will also be carefully monitored and treated for any symptoms that arise from this toxicity. Your horse will receive fluid therapy to stabilize his blood pressure, keep hydrated, and promote proper kidney function.
Symptomatic care is very difficult in horses with yew toxicity. Unfortunately, horses showing signs of this poisoning are often at a stage where it is too late for any treatments to be successful. Activated charcoal may be useful in horses that are showing symptoms; however, this depends on the horse and the level of toxicity he is suffering. Yew toxicosis typically is diagnosed too late, and horses that have ingested this plant suffer fatal results.
Recovery of Yew Poisoning in Horses
Yew toxicity is generally fatal; recovery from this poisoning is dependent upon your horse’s unique situation and how much he ingested. If you have other horses, or if your horse does recover, it is very important to prevent the exposure to the plant.
The removal of yew from the property or anywhere your horse may be exposed is very important. All parts of the plant are toxic, and must be removed by the root. The plant must be properly disposed of so your horse will not come into contact once it is removed.
When your horse is at pasture, be sure to know the specific plants that are in the pasture at all times so your horse does not come into contact with other toxic greenery. Walking through the pasture on a regular basis and being proactive and knowledgeable of the types of plants that are present is a key element in preventing plant toxicity and protecting your companion.