Pieris Poisoning in Dogs

Pieris japonica, better known as lily of the valley, is an eye-catching evergreen shrub with clusters of small bell-shaped flowers. This is a fall blooming member of the Heather family that grows wild in the mountain thickets of Asia. Pieris is a rather beautiful shrub that is often used for its ornamental value.  The lily of the valley also contains a potent neurotoxin known as grayanotoxin. Grayanotoxin is sometimes used as a pesticide and causes severe health conditions when ingested, including heart arrhythmias, seizures, and coma.

The flowering bush Pieris japonica contains a neurotoxin called Grayanotoxin which disturbs the proper function of the cell membranes. Pieris plant poisoning should be treated as an emergency.

Symptoms generally begin within just a few hours after consumption. Just a few leaves of the pieris japonica plant can prompt the symptoms of poisoning:

• Abdominal pain
• Abnormal heart rate  
• Abnormal heart rhythms
• Coma
• Depression
• Diarrhea
• Excessive drooling
• Lethargy
• Loss of appetite
• Low blood pressure
• Muscle weakness
• Perspiration
• Rapid, shallow breathing
• Seizures
• Shaking
• Temporary blindness
• Tremors        
• Vomiting
• Weakness

Types 

Pieris is a small genus of plant, with just a few species of shrub. The other types of Pieris plant in this genus includes:

• Pieris floribunda - A North American species within this genus, this bush is also known as the mountain fetterbush or the mountain andromeda
• Pieris cubensis - A species found only in and around Pinar del Rio in western Cuba
• Pieris formosa - Also known as they Himalayan Pieris, this variety is found in thickets and open slopes in northeast India
• Pieris nana - The shortest variety of Pieris at 3 or 4 inches in height, this hardy little shrub is native to north Japan, Kamchatka peninsula, and Bering island
• Pieris phillyreifolia - Found throughout the southeastern states of the United States, this type has shorter, smaller flowers and is known as a climbing fetterbush
• Pieris swinhoei - This species is found throughout China

The toxicity of the pieris plant lies in the neurotoxin that it contains, called grayanotoxin. The toxin is located in the leaves, petals and even pollen of the pieris plant. The grayanotoxin produced in the pieris japonica has turpentine-like chemical properties which can cause painful burning in the mouth when it is chewed. Once this plant has been ingested the organic compound binds to the sodium channels in the host’s cell membranes which disrupts the natural electrical current present in the cells. This prevents them from returning to their normal state, leaving the cells in a permanently excited state.

Identification is often adequate information for a primary diagnosis if you see your pet consuming any part of the pieris plant bush. A sample of the shrub that your dog consumed will help to positively identity of the flower that was eaten, and your veterinarian will likely order diagnostic blood tests, including a biochemistry profile, (CBC) complete blood count, and urinalysis at this time as well, before performing a full physical examination. These tests will help to reveal the drug interaction or the toxins that are at the root of the symptoms. Plant material found in the stools or in the vomit of your pet will assist in an accurate diagnosis. Supportive treatment will often start before a definitive diagnosis is made due to the severity of the symptoms.

Preliminary treatment will be dependent on the length of time since the flower was consumed and if any symptoms have already become apparent. In most cases of pieris plant poisoning, your dog will be admitted to the veterinary hospital for treatment right away. If the pieris plant was ingested very recently and if no symptoms are showing as of yet, vomiting will be induced as soon as possible to prevent the absorption of the toxins into the bloodstream. In some cases, your veterinarian will give you instructions on how to induce vomiting on your own, so this can take place before the animal’s transfer to the clinic. Activated charcoal will also be dispensed to the patient in an attempt to soak up as much of the grayanotoxin as possible. 

If the exposure was more than an hour or so before treatment, the attending veterinarian might choose to perform a gastric irrigation under general anesthetic to remove as much toxin from the patient’s digestive system as possible. Once the toxins have been eliminated from the gastrointestinal system, supportive treatments can begin. Supportive measures that may occur include IV fluids to prevent dehydration and electrolytes and sugar imbalances. Respiratory support may be required, and atropine may also be needed if the canine’s heart rate drops below 40 - 50 beats per minute.

Recovery from mild pieris plant poisoning usually takes place within about 24 hours. Larger doses and extended times before diagnosis may lengthen the recovery time, as will extreme reactions to the toxin. Plenty of fresh water should be available for the recovering patient, and extra bathroom breaks should be planned for as both the toxins and the medications make their way through the dog’s digestive system. Patients recovering from anesthesia for gastric irrigation may have coordination difficulties when they arrive home, and they are often confused and disoriented as well. Isolation from other children and even from other pets is generally advised until the medication has a chance to fully clear from your companion’s system. Your veterinarian may recommend more frequent monitoring of your pet’s blood chemistry levels in the future, particularly in relation to kidney and liver functionality or impairment.