Mushroom toxins are challenging to deal with. They can be hard to properly identify, their range of toxicity goes from minor to deadly, they appear suddenly — generally in wet, warm weather like spring and fall — and many animals can get to them easily.
The ASPCA Animal Poison Control Center provides this overview to help with diagnosis and treatment of mushroom toxicities.
Mushroom Types
Many species of mushrooms exist, but knowing the specific name is not always the most important aspect. Mushrooms can be lumped into four categories to help you remember them: hepatotoxic, neurotoxic, gastrointestinal and nephrotoxic.
Hepatotoxic
With common names like death cap or death angel (Amanita phalloides) it’s easy to remember these.
Amanitins are responsible for the acute liver failure associated with these mushrooms. Onset of signs can be delayed six to 12 hours, giving owners a false sense of security. Once pets start showing signs of gastrointestinal distress, liver failure can quickly follow. Death may occur one to two days after exposure in severe cases.
These mushrooms can be found in North America and are commonly found in the Pacific Northwest, parts of California and the northeastern part of the United States.
Neurotoxic
Three main groups of mushrooms will cause neurological signs: psilocybin or “magic” mushrooms, hydrazines and isoxazole mushrooms. Onset of signs with these mushrooms is going to be more rapid; as soon as 30 to 90 minutes is common and less than six hours is likely.
Exposure to psilocybin mushrooms occurs more often inside the house instead of outside, since typically the pet has gotten into the owner’s supply.
Gyromitrin is the primary compound of concern with hydrazine mushrooms. While neurological signs can be seen such as weakness, ataxia, tremors and seizures, gastrointestinal signs are more common. These mushrooms may also be associated with a hemolysis, methemoglobinemia and, rarely, renal and hepatic involvement.
Isoxazole mushrooms will cause gastrointestinal signs along with ataxia, disorientation, hallucinations, vocalization, alternating lethargy and agitation as well as tremors and seizures.
Gastrointestinal
The group of mushrooms causing gastrointestinal signs is relatively large, with signs that may be mild to severe. The onset of signs will be on the rapid side, as soon as 15 minutes and typically less than six hours after exposure.
One type of mushroom to note in this group is the muscarinic mushroom. In addition to potentially significant vomiting and diarrhea leading to hypovolemia, these mushrooms will also cause bradycardia, bronchial secretions and classic SLUDDE signs.
Nephrotoxic
Nephrotoxic mushrooms, Cortinarius spp, are more elusive. While reports of toxicity exist in humans, and most of those in Europe, there are no reports of unintentional poisonings in dogs or cats.
Like hepatotoxic mushrooms, onset of signs can be delayed (typically 12 hours but can be eight days or longer). Signs would be expected to include polydipsia and polyuria, vomiting, nausea and dehydration.
Treatment
Due to the potential seriousness of a mushroom exposure in a pet or rapid onset of signs, worrying about identification of the mushroom will take a back seat to decontamination or symptomatic care.
Once the pet is stable — and if mushrooms are available for identification — consider contacting a mycologist at a local college or university or the North American Mycological Association. The website is a good source of information and also provides a list of volunteers across the country who may aid in mushroom identification.