Death cap mushrooms: why are they so toxic and how can poisoning be treated?
The Guardian: Three people are dead and one is in a critical condition in a Melbourne hospital from suspected mushroom poisoning after eating a beef wellington pie in the Victorian town of Leongatha.
Police have said their symptoms were consistent with having eaten death cap mushrooms, although the official cause of death has not yet been confirmed.
The death cap, Amanita phalloides, is responsible for about 90% of mushroom-related deaths globally. It can be mistaken for edible mushroom varieties such as the field mushroom or the straw mushroom.
“It’s quite upright, it’s very bright white … it’s eye-catching,” says Dr Michael Taylor, a mycology expert at Flinders University.
The cap of a typical Amanita phalloides mushroom may measure about 10cm across, Taylor says. “Half of that would be toxic, probably enough to kill a person. That might be, once it’s cooked down, a mouthful – maybe two or three mouthfuls of actual mushroom … at absolute most.”The toxicity of individual mushrooms may vary depending on geographical location, Taylor says. Death caps are not native to Australia and are usually only found in Victoria and the Australian Capital Territory.
What are the effects of eating a death cap mushroom?
“Death cap mushrooms contain three broad classes of toxins: the amatoxins, the phallotoxins and the virotoxins,” says Dr Ian Musgrave, a molecular pharmacologist at the University of Adelaide.
The most toxic of these is an amatoxin known as α-Amanitin. Amatoxins inhibit an enzyme called RNA polymerase II, preventing cells from carrying out essential functions such as creating proteins. The toxin cannot be destroyed by cooking or drying.
Once a death cap is eaten, people are often asymptomatic for several hours before its effects become apparent. Nausea, diarrhoea and other symptoms of gastrointestinal upset develop from about six to 12 hours after ingestion, though this may occur sooner if a high dose is ingested, Taylor says.