American Mistletoe Poisoning in Dogs

American mistletoe is (as the name implies) native to America and can be found growing as a small shrub or as a parasite plant on trees and other plants. It has the unique ability to attach itself to the foliage, branches, or trunk of trees and is able to grow there without roots. American mistletoe looks like a bunch of evergreen leaves with woody branches wrapped around the host plant or tree. Small flowers grow in spikes and turn into white berries.

American mistletoe poisoning is caused by the consumption of any part of the American mistletoe plant, especially the berries and leaves. In many cases, the side effects are not life-threatening unless a large amount of leaves or berries were ingested, but there are exceptions if your dog is small, elderly, or sick. There are several toxic properties in American mistletoe which are toxalbumin, lectins, phoratoxins, and tyramine. These substances can all be dangerous to your pet and cause severe toxic reactions in the cardiovascular system, digestive tract, and central nervous system. The damage they can do to your dog’s cells and DNA may be serious if your dog eats more than just a few berries or leaves.

The signs that your dog may have eaten American mistletoe may vary depending on what part and how much was eaten. Some of the most common signs are:

• Dilation of the eyes
• Abdominal pain
• Drooling
• Diarrhea
• Vomiting
• Weakness
• Drowsiness
• Depression
• Walking as if drunk
• Difficulty breathing
• Erratic behavior from hallucinations
• Slow heart rate
• Low blood pressure
• Seizures
• Cardiovascular collapse (fainting, no pulse, not breathing)
• Death

 Types

The scientific Name of American mistletoe is Phoradendron flavescens from the Viscaceae family. Some of other names that American mistletoe is known by are:

• Eastern mistletoe
• Oak mistletoe
• Hairy mistletoe
• Viscum serotinum
• Viscum villosum
• Viscum tomentosum
• Viscum leucarpum
• Phoradendron villosum
• Phoradendron serotinum
• Phoradendron tomentosum
• Phoradendron leucarpum

• Phoratoxins are proteins that damage the membranes of the cells in your dog’s body.
• Lectins are carbohydrates that bind to proteins, making them unavailable to the body’s systems when needed.
• Toxalbumin is a protein that stops the ribosomes from doing their job in making more protein cells
• Tyramine is an amino acid that can raise blood pressure and increase the heart rate

When you get to the veterinarian’s office or clinic, some of the things you need to tell the veterinarian is your dog’s age, weight, overall health condition, the part and amount of plant that was swallowed, and what side effects you have noticed. If you are able to bring a picture or a piece of the plant, that can be very helpful in diagnosis and treatment. The veterinarian will give your pet a thorough physical examination, which includes checking body temperature, weight, height, reflexes, heart rate, blood pressure, breath sounds, respiration rate, coat and skin condition. An electrocardiogram (EKG) will be done right away to measure the heart’s electrical activity and muscle functioning. In addition, an endoscopy will be performed by feeding an endoscope tube into the throat and upper airway to make sure there are no plant particles or blockages. The veterinarian is also able to take photographs and remove foreign material by inserting microscopic tools through the hollow flexible tube. 

A certain amount of laboratory testing is usually completed during the examination, which may include urinalysis, liver enzyme panel, blood chemistry profile, complete blood count (CBC), and glucose levels. The veterinarian will be looking for the amounts of albumin, protein, phosphorous, creatinine, sodium, chloride, potassium, and bilirubin in your dog’s body. Also, she may want to get the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALKP). Digital radiographs (x-rays) and ultrasound of the abdomen will also be performed to check for obstructions and inflammation.

Treating American mistletoe poisoning is similar to other poisonings, but may be altered by your dog’s symptoms, test results, and the amount of berries or leaves eaten. However, the most common treatment includes evacuation, detoxification, medications, and observation.

Evacuation

Removing the toxins is the most important step, done by giving a hydrogen peroxide solution or ipecac fluid to instigate vomiting. The veterinarian will also give your pet activated charcoal to absorb any undigested toxins.

Detoxification

Intravenous (IV) fluids will be given to flush the kidneys and prevent dehydration. In addition, gastric lavage may be done to cleanse the digestive system.

Medication

The medications your veterinarian gives your dog depends on the symptoms and may be atropine to regulate heartbeat, phenobarbital to control seizures, omeprazole to ease gastric distress, and in addition, antiemetics if your dog is still vomiting.

Observation

Hospitalization will probably be suggested for at least 24 hours for observation. The veterinarian will also provide additional medications, fluids, and oxygen therapy if necessary.

Your dog’s chances of recovery are good as long as treatment is given within a few hours of ingestion. After about four hours, the toxins are already digested and released into the bloodstream so the only treatment that will be available after that would be supportive.