Rosebay Poisoning in Dogs

The rosebay shrub (Rhododendron maximum) is a variety of rhododendron that can grow to between thirteen and thirty-three feet high. Also known as great laurel, great rhododendron, and American rhododendron, this beautiful plant also contains powerful neurotoxins known as grayanotoxins. If you see your dog eating any part of this plant it is crucial to get treatment as soon as possible. Grayanotoxins can be fatal in relatively small doses, particularly if supportive measures are delayed.

The rosebay shrub contains potent neurotoxins called grayanotoxins which disturb the proper functioning of the cell membranes in the body. Rosebay poisoning should be treated as an emergency.

Symptoms of Rosebay poisoning can start within just a few minutes, or be delayed for a few hours after ingestion. Very little of the plant is needed to instigate the symptoms of poisoning, sometimes just a few leaves:

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

Types 

Grayanotoxins can be encountered from several natural sources. Plant groups that contain these dangerous neurotoxins include:

• Azaleas
• Laurel 
• Pieris 
• Rhododendrons

Grayanotoxins are also in the nectar of these plants. Bees that used the nectar from these toxic plants transfer that poison to their honey as well. The toxins are diluted in the honey, however, there can still be enough to cause mild to moderate clinical symptoms in people or pets. Accidental poisonings are rare, but this toxic treat is sometimes taken intentionally by people as it is rumored to improve sexual performance. Commercial honey usually is a combination of honey from several hives, which helps to further reduce the risk factors. Although honey is safe for adult dogs, it should never be given to puppies or babies as it can contain botulism spores that the immature immune system of the very young is unable to counteract.

The toxicity of the rosebay rhododendron lies in the potent neurotoxin that it contains. The neurotoxin, grayanotoxin, is located in the leaves, petals and even pollen of the rosebay. The grayanotoxin produced in the rosebay shrub has chemical properties that closely resemble turpentine, and this can lead to burning sensations in and around the mouth when it is chewed. Once processed by the body this organic compound binds to the sodium channels in the host’s cell membranes, disrupting the natural electrical current present in the cells. This prevents them from returning to their normal state and leaves the cells in a permanently excited state.

In order to ensure the plant is correctly identified you can bring a sample of the rosebay that your dog consumed into the clinic with you. Based on the symptoms, your veterinarian will likely perform a full physical examination as well as ordering some general tests, including a biochemistry profile, complete blood count, and a urinalysis at this time.

If the consumption of the plant was not observed, your dog’s doctor will be sure to note any opportunistic eating that was seen or suspected (such as foraging in garbage or gluttonous behavior), as well as any information regarding prescriptions or dietary supplements that are being given to your pet. This information may reveal toxins or drug interactions that are instigating the symptoms. The vomit and stools of the dog and any plant material that is found will assist in an accurate diagnosis as well. Due to the severity of the symptoms supportive treatment will often start before a definitive diagnosis is determined.

Initial treatment will be dependent on the length of time since the flower was ingested and if any symptoms have already become apparent. In most cases of grayanotoxin poisoning, your dog will be admitted to the veterinary hospital for treatment right away. If no symptoms are yet showing and the rosebay rhododendron was consumed recently, vomiting will be induced as soon as possible in order to prevent the further absorption of the toxic compounds into the bloodstream. If you have not yet transported your dog to the clinic, you may be given instructions to induce vomiting before coming to the clinic.

Activated charcoal will also be will be dispensed to the patient in an effort to soak up the remaining grayanotoxins. If the exposure was more than an hour or so before treatment, your veterinarian might choose to perform a gastric lavage to more efficiently remove the toxic substance from the patient’s digestive system. Once the poison has been evacuated from the digestive system more supportive treatments will be started. IV fluid therapy will help to prevent dehydration and combinations of electrolytes and sugars will assist in adjusting any imbalances. Atropine will need to be included if your canine’s heart rate drops below 40-50 beats per minute, and respiratory support may also be required.

Recovery from mild rosebay poisoning usually occurs within about 24 hours. A protracted time frame before diagnosis and treatment can cause the recovery time to increase, as can extreme reactions to the toxin. If your pet ingested a large amount of the plant or suffered a severe reaction to the grayanotoxins, he may need to be in the hospital for a few days until the veterinarian feels he is well enough to go home.

Patients that are recovering from the anesthesia from gastric lavage may have some coordination difficulties when they first arrive home, and they are often confused and disoriented as well. Fresh water should be close by during the patient’s recovery, and extra bathroom breaks should be expected as both the toxins and the medications make their way through the dog’s digestive system. Your veterinarian may also suggest that you bring your pet in for more frequent monitoring of their blood chemistry levels, particularly in relation to kidney and liver functionality or impairment.