Mushrooms Poisonous to Pets

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Dr. Charlotte Means, D.V.M., ASPCA National Animal Poison Control Center

They pop up everywhere – in yards, in the woods, in parks, alongside roads . . . and in salad bars. Some dogs, like some people, like to eat them. They can be a gourmet delicacy . . . or deadly poisonous. They are mushrooms.

Mushrooms Poisonous to Pets

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Mushrooms are hard to identify. They can’t be differentiated by studying pictures in a text or on the Internet. Many species, both poisonous and nonpoisonous, look very much alike, and they frequently grow side by side. When a mushroom is obtained for identification, it must be identified as quickly as possible before it begins to deteriorate. Accurate identification of a mushroom usually requires a mycologist (a fungus specialist) or someone who has been hunting wild mushrooms for years. Mycologists may be found at universities and botanical gardens. Local mushroom clubs may be helpful in identifying mushrooms, as well. But if all attempts fail, what do you do?

Presumed Poisonous

Although most mushrooms are known as LBMs (little brown mushrooms) and are generally nontoxic, when I receive a call that a dog has just eaten a mushroom, I always advise decontamination for safety. This means that vomiting is induced, and unless the entire mushroom is seen in the vomitus, activated charcoal is given to adsorb remaining toxins. Once decontaminated, each dog is treated individually, based on clinical signs that develop. Poisonous mushrooms can cause four distinct clinical syndromes.

  • Gastrointestinal irritation. This is the most common syndrome and is rarely fatal. Vomiting and diarrhea generally develop within six hours of ingestion. The upset stomach lasts about 24 hours and requires minimal veterinary care.
  • Gastrointestinal upset plus muscarinic signs. Muscarinic effects – similar to those caused by organophosphate and carbamate insecticide poisoning – include excessive salivation and tear production. Pupils are often very small and constricted. The most serious clinical sign is bradycardia – a very slow heartbeat. In most cases, this clinical syndrome will develop within six hours post-ingestion and almost always requires veterinary care. The two most common species of mushrooms that cause this syndrome are Inocybe spp. and Clitocybe spp.
  • Gastrointestinal upset, muscarinic signs, plus depression and lethargy. Severe abdominal pains and signs of colic occur, as do severe bouts of vomiting. The mushrooms destroy the liver, causing the dog to develop jaundice (the whites of the eyes and mucous membranes turn yellow.) Because the liver produces blood-clotting factors, bleeding disorders can develop. Seizures occur due to the liver damage. The most deadly syndrome has a delayed onset of greater than six hours and up to 20 hours post-ingestion. Without prompt, aggressive treatment, this syndrome is often fatal. Humans may be given liver transplants, but this is not an option for dogs. The death cap (Amanita phalloides) is the mushroom most likely to cause this syndrome, although the false morel (Gyromitra esulenta) and Galerina spp. also cause it and may be found in areas that dogs frequent. To add to the confusion, some species of Amanita and Gyromitra are considered nontoxic.
  • Hallucinogenic syndrome. Mushrooms that cause this syndrome are known as magic mushrooms, blue legs or liberty caps, and are considered illicit drugs in many places. “Street” mushrooms are generally edible mushrooms, like those found in supermarkets, laced with LSD or other illicit drugs. Whereas dogs ingest other poisonous mushrooms in woods or the back yard, they pull hallucinogenic mushrooms out of backpacks or other hiding places. Behavior changes include restlessness and hallucinations. Dogs who are hallucinating frequently snap at invisible flies, may be extremely depressed, stagger when walking and become comatose. Muscle tremors and seizures also occur. Dogs who ingest hallucinogenic mushrooms always require rapid decontamination and monitoring by a veterinarian.

Bon Appetit!

Mushrooms in yards should be removed promptly before the dog notices them. If your dog becomes ill, and you suspect mushroom ingestion, place the vomitus and any bowel movements in a plastic bag for identification, and refrigerate the bag. Try to have the contents identified within 24 hours. Notify your veterinarian that your dog may have ingested a mushroom, so that he or she can be alert to clinical signs that may require treatment. Finally, go ahead and enjoy your salads and quiches and sauces – as long as the mushroom’s origin is known!

Dr. Means, a veterinary toxicologist, is a member of the staff at the ASPCA National Animal Poison Control Center in Urbana, IL.

© 2000 ASPCA
ASPCA Animal Watch Fall 2000

Courtesy of
ASPCA National Shelter Outreach
424 East 92nd Street
New York, NY 10128-6804
212-876-7700

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