What is Seven Bark Poisoning?

Seven bark plants get their toxic abilities, not from inherited lethal chemicals, but the environmental factors the plant developed in. The seven bark contains cyanogenic glycosides, nitrates and oxalates, which do not generally cause harm in low quantities. Plants naturally possess these chemicals as regular functioning elements and levels remain low under normal growing conditions. An animal can eat these plants of low chemical value and, in most cases, their bodies will naturally separate the chemicals into waste products. However, in plants which grow into harsh environments, like in times of drought or desert-like conditions, the chemical levels raise to lethal amounts.

Seven bark poisoning in cats is a form of plant toxicity caused by the direct or indirect ingestion of the seven bark plant. The seven bark plant is part of the Hydrangeaceae family and can be identified by its scientific name; Hydrangea arborescens. The seven bark may be known by its other names: hortensia, hydrangea or hills of snow. The seven bark is highly toxic to felines, humans, dogs and ruminants, such as sheep or cattle. 

Symptoms of Seven Bark Poisoning in Cats

Seven bark poisoning symptoms may include: 

  • Irritation to the skin around and inside the mouth
  • Gastrointestinal upset (nausea, vomiting, diarrhea) 
  • Depression
  • Rapid breathing 
  • Labored breathing 
  • Dark colored mucous membranes
  • Weakness 
  • Sleepiness 
  • Tremors
  • Ataxia
  • Staggering gait 
  • Dark or brown colored blood 
  • Seizures 
  • Cardiac irregularities 
  • Hypocalcemia 
  • Coma 
  • Death 

Causes of Seven Bark Poisoning in Cats

Seven bark poisoning in cats is caused by consuming the leaves, stems, flower or pollen of the seven bark plant. A feline can consume the plant directly by chewing on the leaves or indirectly by grooming or ingesting soil containing the seven bark pollen. The toxic components of the seven bark plant are cyanogenic glycosides, oxalates and nitrates, which transforms to nitrite. The end result is a nitrite poisoning as the lethal chemicals from the plant are absorbed into the bloodstream. 

Diagnosis of Seven Bark Poisoning in Cats

The best way to diagnose seven bark poisoning in a cat is to witness the feline consuming the plant. If you do witness your cat licking, chewing or eating a seven bark plant, take the plant with you to your cat’s veterinary appointment. If you have not witnessed plant consumption, the veterinarian will base his or her diagnosis off your cat’s presenting clinical signs. The diagnostic process will begin with a physical examination, review of the feline’s medical history and a consultation with the pet owner. Unfortunately, seven bark nitrite poisoning symptoms mimic the symptoms of cyanide poisoning, so your veterinarian will need to conduct a diagnostic differential. The easiest way for a veterinarian to rule out cyanide poisoning is to take a sample of your cat’s blood. When a feline is suffering a cyanide toxicity, her/his blood will be a bright red, cherry color, whereas a nitrite toxicity will cause the feline’s blood to turn a dark brown, chocolate color. 

Diagnostic tests the veterinarian will likely request include: 

  • CBC (complete blood cell count) 
  • Biochemical profile (blood work) 
  • Blood smear test 
  • Urinalysis (examination of urine) 
  • Fecal floatation test
  • Fecal examination 
  • Radiographs 
  • Ultrasound 

Treatment of Seven Bark Poisoning in Cats

Seven bark poisoning is generally treated with methylene blue administered intravenously. Methylene blue works by reducing the ferric iron in hemoglobin (red blood cells) to the ferrous state. Therefore, this therapeutic agent converts methemoglobin cells that don’t carry oxygen into hemoglobin cells that will once again be receptive to oxygen transport. The veterinarian may pair the use of Methylene blue with mineral oil. Used as a cathartic, mineral oil can aid in a faster defecation and speed up the removal of toxic material from the feline’s gastrointestinal tract. 

Recovery of Seven Bark Poisoning in Cats

The prognosis of a seven bark poisoning in cats depends on how quickly veterinary medical attention was sought out. If the feline was taken immediately to seek veterinary care and received treatment before experiencing seizures, the prognosis is generally good.