Potentially fatal 'death cap' mushroom spreading along B.C. coast, doctor warns

Amanita phalloides, also known as the death cap mushroom, has been spotted in the Vancouver area again. Sept. 1, 2016. (BayAreaMushrooms.org)

VANCOUVER - A critical care doctor is warning British Columbians about a “sinister” deadly mushroom and the importance of health-care providers recognizing signs of poisoning from a variety that is spreading along the Pacific coast.

Dr. Omar Ahmad, head of critical care and emergency medicine for Island Health, said the so-called death cap mushroom can easily be mistaken for edible varieties and is responsible for 90 per cent of the world's mushroom-related fatalities.

A three-year-old boy died in 2016 after consuming a mushroom foraged from a residential street in Victoria. In 2008, a 63-year-old woman who ate a death cap in Vancouver recovered in hospital, and five years earlier, a 43-year-old man was hospitalized in Victoria.

People who eat death caps can experience abdominal pain, vomiting and diarrhea within six to 12 hours, but a false recovery phase follows up to three days later and can prevent people from seeking medical help as toxins attack the liver and possibly the kidneys in a “sinister manner,” Ahmad said.

“That's really quite a dangerous period with that false reassurance with clinicians as well as patients because that's when things are happening and it really is the time when we should be intervening and try to prevent further damage,” he said, adding a liver transplant may be the only treatment for people who don't reach a critical stage.

While patients may think they've had the flu or food poisoning, liver damage could progress before convulsions occur and lead to coma and death from the mushroom, Ahman said.

The mushroom was first spotted in the Fraser Valley east of Vancouver in 1997 and Victoria the following year but it also grows in Atlantic Canada.

One mushroom cap is enough to kill an adult but just a small amount is toxic for a child, he said, adding the health authority has been educating doctors through seminars and he has co-authored an article in the BC Medical Journal.

Edible mushrooms called puffballs and paddy straws should not be picked if there's a chance they could be growing near death caps, which can be abundant between June and November, Ahmad said.

Death caps were first discovered in B.C. on beech trees imported from Europe and they spread to native Garry oaks, Ahmad said, adding California has also had a public education campaign after several deaths.

There is no antidote for poisoning from a death cap but people should not pick mushrooms if they have any concerns about whether they are safe, he said.

Last year, the Canadian Forest Service and the Parks, Recreation and Culture Department in the Victoria municipality of Oak Bay reported death caps sprouted earlier and in greater number than in previous years.

Chris Hyde-Lay, manager of park services for Oak Bay, a suburb of Victoria, said the mushrooms were found last year on irrigated boulevards and crews were sent to get rid of them.