New Zealanders are not generally inclined to harvest the bodies of fungi (such as mushrooms or puff balls) from the wild, so there have been few cases of serious poisoning from eating toxic mushrooms. The majority of mushroom-forming fungi in New Zealand are not poisonous, but it is difficult to identify some species, and unknown fungi should not be eaten.
Death cap mushroom
Worldwide, most fatal fungal poisonings occur when people mistake death cap mushrooms (Amanita phalloides) for an edible species. Toxins in the mushroom act on the liver and kidneys. In June 2005 a recent Vietnamese immigrant became critically ill after eating some cooked death caps. Symptoms do not develop for some hours, by which time it is usually too late to save the victim’s liver.
Fly agaric and magic mushrooms
Two other types of toxic mushroom are fly agaric (Amanita muscaria), and several species of magic mushroom (Psilocybe species). Both types contain hallucinogenic chemicals, and some people deliberately risk the toxic effects to achieve a psychedelic high.
Fly agaric poison may cause severe stomach pain, vomiting and diarrhoea. Magic mushroom poisoning is unlikely to be fatal, but small, brown magic mushrooms are easily mistaken for other toxic species such as Clitocybe, Entoloma and Cortinarius.
Fungal poisoning of livestock
The most significant forms of fungal poisoning in New Zealand are those that cause facial eczema and grass staggers in livestock. Losses from facial eczema cost the New Zealand meat industry $80–$400 million annually.
The microscopic fungus Pithomyces chartarum grows on dead leaves at the base of pasture grasses. It produces toxic spores that cause liver damage in grazing animals, and facial eczema develops as a result.
The fungus that causes grass staggers (tremors, stumbling and muscle spasms) in stock animals is an endophyte – it grows within the grass without harming it. Perennial ryegrass (Lolium perenne) endophytes produce several toxins: one affects the nerves and muscles of grazing stock, and one causes heat stress. Tall fescue (Schedonorus phoenix) endophytes cause fescue foot (lameness) and ill-thrift (slow growth) in cattle and sheep.