‘Death Cap’ Mushrooms Pose Threat to Dogs

While enjoying the warm weather of summer, pet parents should take precautions to protect their dogs from dangerous variations of mushrooms along paths, trails and yards.

“Death cap” mushrooms, in particular – a member of the amanita genus of mushrooms – are a poisonous species found in Wisconsin and, more broadly, in the U.S. Ingesting even a single mushroom can be fatal to an adult human. Because pets typically have smaller body weights, doses can be lethal in less quantity.

Amanita phalloides mushrooms CC BY-SA 3.0 via Wikimedia Commons
Amanita phalloides or “death cap” mushrooms. (Credit: CC BY-SA 3.0 via Wikimedia Commons)

These large mushrooms, known scientifically as Amanita phalloides, have a broad, off-white cap. When mature, they measure several inches tall and across; immature death cap mushrooms have a rounded cap. They grow readily in moist and warm conditions and are often found in late summer and fall, particularly during heavy rainfall, growing under trees or in forests.

Death caps look fairly bland and have no reported distinctive taste, notes Megan Climans, a veterinary pathology resident with the University of Wisconsin–Madison School of Veterinary Medicine. For pets, unfortunately, that means there isn’t much deterrent to eating them.

If ingested, toxins within death cap mushrooms damage the body’s cells. They target the liver and kidney specifically and can become deadly when the exposure leads to liver failure.

According to Climans, an animal will not typically experience noticeable signs in the first six to 24 hours after ingestion. However, a period of gastrointestinal upset follows, with the affected pet experiencing abdominal cramping and vomiting.

“After the abdominal pain passes, patients can seem to fully recover, but damage to the liver and kidney is ongoing, and organ failure can result,” Climans explains. This progression of signs and symptoms can vary depending on the size of the patient and the toxic dose consumed.

In Wisconsin, fatal cases of death cap poisoning have occurred in dogs. Organ transplants aren’t typically an accessible treatment option for dogs, so taking preventative steps remains vital.

“Monitor your pets when they go outside, particularly if they tend to be indiscriminate eaters,” Climans advises. “It’s very important to catch a case of mushroom poisoning as early as possible.”

“If you see your pet eating a wild mushroom, contact a veterinarian or poison control immediately,” she adds. “Save a sample of the mushroom that was eaten or others growing next to it if possible, for later identification.”

If there is suspicion of intoxication, the UW School of Veterinary Medicine can diagnose mushroom poisoning through mushroom identification or laboratory urine tests. Several UW Veterinary Care hospital services are also currently partnering to potentially begin carrying a patient-side urine test to detect toxins.

Alisyn Amant


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