Mushroom Poisoning in Dogs and Cats

Laurie Anne Walden, DVM

Galerina species. Photo by Bernard Spragg.

Most wild mushrooms aren’t dangerous, but some are fatal if eaten. Keep your pets safe by removing wild mushrooms from their environment.
 
Because it’s not easy to know if a wild mushroom is poisonous, treat any wild mushroom ingestion as a medical emergency. If your dog or cat eats wild mushrooms, call an emergency animal clinic, your veterinary clinic, or a pet poison hotline right away. Don’t wait until your pet gets sick before you call. Some of the most toxic mushrooms don’t cause symptoms until hours after they’re swallowed.
 
Pet poison hotlines (fees might apply):
ASPCA Animal Poison Control: 888-426-4435
Pet Poison Helpline: 855-764-7661
 
Photos of toxic mushrooms in North Carolina:
NC State Extension Gardener Plant Toolbox: mushrooms
 
Symptoms
Symptoms of mushroom poisoning depend on the type of mushroom and the amount eaten. Toxic mushrooms can be categorized by the type of problem they cause: liver and kidney failure, central nervous system effects, muscarinic reactions, hallucinations, or gastrointestinal irritation.[1]
 
Liver and Kidney Failure
The mushrooms responsible for the most deaths are in the Amanita, Galerina, and Lepiota genera.[2] Examples are Amanita phalloides (death cap), Amanita bisporigera (destroying angel), and Galerina autumnalis (autumn skullcap).
 
The toxic compounds in these mushrooms are amatoxins, phallotoxins, or virotoxins. These toxins damage cells of the liver, kidneys, and intestines. The symptoms progress through stages:

• Latent phase: no symptoms for 6 to 24 hours
• Gastrointestinal phase: vomiting, bloody diarrhea, and abdominal pain for about 24 hours
• Apparent remission: improvement in gastrointestinal symptoms for 12 to 24 hours; damage to the liver and kidneys continues but does not yet cause new symptoms
• Liver and kidney failure: jaundice, vomiting, increased urine production, loss of appetite, and coma a few days after ingestion
• Death in more than half of patients[3]

 
Central Nervous System Effects
Mushrooms containing the compounds ibotenic acid and muscimol affect the central nervous system. The mushrooms most often involved in this type of poisoning are Amanita muscaria (fly agaric) and Amanita pantherina. Symptoms usually begin 30 minutes to 2 hours after ingestion (possibly earlier in cats) and include the following:

• Loss of coordination
• Lethargy
• Panting
• Labored breathing
• Vomiting
• Paddling or chewing motions
• Tremors
• Seizures
• Death

 
Muscarinic Reactions
Muscarine is a substance that affects a specific metabolic pathway in cells of the body. Ingestion of muscarine-containing mushrooms—usually Clitocybe and Inocybe species—causes clinical signs related to part of the nervous system that regulates routine (not conscious) body functions. Symptoms appear a few minutes to a couple of hours after ingestion:

• Salivation
• Increased tear production
• Urination
• Diarrhea
• Vomiting
• Pinpoint pupils
• Wheezing
• Slow heart rate
• Shock

 
Hallucinations
Hallucinogenic mushrooms include those in the genera Psilocybe, Conocybe, Panaeolus, Copelandia, Pluteus, and Gymnopilus. The toxic components are psilocybin and psilocin, which are similar to the drug lysergic acid diethylamide (LSD). Symptoms usually begin within an hour or two after ingestion:

• Vocalization
• Aggression
• Stumbling
• Vomiting
• Rapid heart rate
• Urinary incontinence
• Labored breathing
• Large pupils
• Hallucinations (for example, biting at imaginary flies)
• Coma
• Death from trauma caused by abnormal behavior[3]

 
Gastrointestinal Irritation
Many mushrooms cause gastrointestinal (digestive tract) problems. The exact toxin in most of these mushrooms is not known. Some of the mushroom genera that cause this type of problem are Chlorophyllum (which often forms fairy rings on lawns), Omphalotus, and Scleroderma. Symptoms usually begin soon after ingestion and improve on their own within a few hours. Most symptoms are mild:

• Abdominal discomfort
• Vomiting
• Diarrhea

 
Diagnosis
Diagnosing mushroom poisoning is difficult unless the animal is seen eating the mushroom or vomits up pieces of mushroom. Known access to wild mushrooms, compatible symptoms, and physical examination findings can put mushroom poisoning on the list of possibilities. Blood and urine tests are used to assess organ function in dogs with symptoms.
 
Treatment
Treatment depends on the symptoms and type of mushroom (if known). Animals exposed to the most toxic mushrooms need early and aggressive treatment to survive. Unfortunately, early treatment isn’t possible if the ingestion was not witnessed and symptoms don’t begin until several hours later.
 
No antidote is available for mushroom poisoning. The best way to manage the risk is to prevent pets from eating wild mushrooms.
 
References
1. Hovda LR. Unfriendly fungi: five groups of mushrooms toxic to pets. DVM 360. Published October 20, 2015. Accessed July 23, 2020. https://www.dvm360.com/view/unfriendly-fungi-five-types-mushrooms-toxic-pets
2. Brownie CF. Poisonous mushrooms. Merck Veterinary Manual. Updated August 2014. Accessed July 23, 2020. https://www.merckvetmanual.com/toxicology/poisonous-mushrooms
3. Cope RB. Toxicology brief: mushroom poisoning in dogs. DVM 360. Published February 1, 2007. Accessed July 23, 2020. https://www.dvm360.com/view/toxicology-brief-mushroom-poisoning-dogs
 
Photo of Galerina species by Bernard Spragg

---