Mushroom poisoning

Overview
Mushroom poisoning, also known as mycetism, refers to deleterious effects from ingestion of toxic substances present in a mushroom. These symptoms can vary from slight gastrointestinal discomfort to death. The toxins present are secondary metabolites produced in specific biochemical pathways in the fungal cells. Mushroom poisoning is usually the result of ingestion of wild mushrooms after misidentification of a toxic mushroom as an edible species. The most common reason for this misidentification is close resemblance in terms of colour and general morphology of the toxic mushrooms species with edible species. Even very experienced wild mushroom gatherers are sometimes poisoned by eating toxic species, despite being well aware of the risks.

To prevent mushroom poisoning, mushroom gatherers need to be very intimately familiar with the mushrooms they intend to collect, including knowledge of the toxic species that look similar to these edible species. Other considerations regard methods of preparation and toxicity of some fungal species that appears to vary with geographic location, raising the potential of mushroom poisoning due to local toxicity of a correctly identified species.

Folk traditions
There are many folk traditions concerning the defining features of poisonous mushrooms. Unfortunately there are no general identifiers for poisonous mushrooms, and so such traditions are unreliable guides. For example, while some highly coloured mushrooms such as fly agaric are indeed poisonous, other strongly coloured mushrooms are harmless. Other highly toxic mushrooms, such as the appropriately named destroying angel, are of unremarkable white colour. Lack of snail or insect infestation is also an unreliable identifier, since fungi that are harmless to invertebrates can still be toxic to humans; the death cap, for instance, is often infested by insect larvae. Likewise, poisonous mushrooms neither blacken silverware during cooking, nor necessarily smell or taste unpleasant. Importantly, many fungal toxins are not particularly sensitive to heat and so are not broken down during cooking.

Guidelines
Persons who gather wild mushrooms should follow some practical guidelines. In particular, they should not eat any mushroom they cannot positively identify; not allow small children to gather mushrooms for consumption; or mix known edibles with questionable species while gathering, since mushroom parts could break off and be confused with edible species.

Cooking mushrooms before eating is a safer practice, as only very few species can be eaten raw. Alcohol consumption should be limited when eating wild mushrooms positively identified as edible, but not consumed before. Some species, most notably certain ink caps (Coprinopsis atramentaria) can cause an adverse reaction when eaten with alcohol. Portions of species that a person has not eaten before should be kept small (no more than 150 grams per person at one meal).

In some regions in Europe, mushrooms are not eaten at all; in other regions, such as Finland, Scandinavia and Russia, which traditionally have suffered from food shortage in winters, strong local knowledge on edible mushrooms exists and mushrooms form a remarkable part of cuisine. Yet many mushroom enthusiasts limit their pickings to only easily recognizable mushrooms, such as chanterelles and boletes, and leave agarics unpicked. False morel (Gyromitra esculenta) is often called the "fugu of the Finnish cuisine", since it is deadly poisonous when raw, but rarely causes poisoning if properly prepared (although its edibility is still a matter of dispute).

Specimens that look similar to edibles at one geographic location may be deadly in another region and should not be collected without good knowledge of the local biota. For instance, Cantharellus is often picked in Scandinavia where no risk of confusing this mushroom with toxic species exists. However, in North America, this ground-dwelling mushroom has been known to be mistaken for the wood-decaying Jack O'Lantern mushroom (Omphalotus olearius), which may grow from the ground if there is buried wood present. Note also recent reports of confusion between Volvariella speciosa, a popular edible species in Asia, and Amanita phalloides, a deadly poisonous species in North America and Europe.

Very young fruiting bodies of destroying angel (Amanita virosa) mushrooms resemble the well-known champignon, or button mushroom, a mushroom widely sold in markets. Similarities between these two species lead to a few deaths every decade in Scandinavia alone.

Cases of fatal mushroom poisoning are relatively common in Europe, but less so in North America; this may be related to the use of folklore rather than detailed knowledge in Europe, whereas North American mushroom collectors tend to refer often to authoritative reference works.

Symptoms
Symptoms may vary from gastric upset to life-threatening organ failure. Serious symptoms do not always occur immediately after eating; often not until the toxin attacks the kidney, from minutes to hours later, or, as is the case for alpha-amanitin poisoning, not until days after consumption.

Symptoms typically include: If treated promptly, death can usually be avoided. Otherwise, with some toxins, death could result within a week or a few days. More detail on the exact symptoms associated with different toxins can be found below.
 * Fatigue
 * Headache
 * Dizziness
 * Cold sweat
 * Hallucinations
 * Vomiting
 * Sharp abdominal pains
 * Jaundice
 * Severe diarrhea
 * Blurred vision

Toxins
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 * alpha-amanitin (deadly) – principal toxin in genus Amanita
 * bolesatine (found in Boletus satanas)
 * coprine (only poisonous with alcohol)
 * orellanine (deadly) – principal toxin in genus Cortinarius
 * gyromitrin (deadly)
 * muscarine (sometimes deadly)
 * arabitol (causes gastrointestinal irritation in some people)

Poisonous species
Three of the most lethal mushrooms belong to the genus Amanita: the death cap (A. phalloides) and destroying angels (A. virosa, and A. bisporiga); and two are from the genus Cortinarius: the deadly webcap (C. rubellus), and the fool's webcap (C. orellanus). These species cause the greatest number of fatalities. Poisoning by Amanita phalloides is characterized by a delay of between 6 and 24 hours from the time of ingestion to the onset of symptoms. During this time, the cells of the kidneys and liver are attacked. There is no antidote for poisoning and mortality is between 10 and 15 percent. There have been some recorded studies suggesting that Silybum marianum or blessed milk thistle protect the liver from aminita toxins and promote regrowth of damaged cells, including a study in which 60 patients exposed to death cap poison were given 20 mg/kg of milk thistle seeds per day within 48 hours of consuming the deadly mushrooms. None of the patients died. Many species of Galerina, Lepiota, and Conocybe contain also lethal amounts of amatoxins.

The following species may cause great discomfort, but are less often lethal.
 * Amanita muscaria (fly agaric) – poisonings rare, possibly because its unique and obvious appearance make it easily identifiable; it is known for its use as an entheogen, and it is now known that the toxins convert to psychoactives upon drying.
 * Amanita pantherina (panther mushroom) – contains similar toxins as A. muscaria, but in higher quantities.
 * Amanita muscaria var. regalis – symptoms generally mild.
 * Chlorophyllum molybdites (greengills) – causes intense gastointestinal upset.
 * Entoloma (pinkgills) – highly poisonous, such as livid entoloma (Entoloma sinuatum), Entoloma rhodopolium, and Entoloma nidorosum. First symptoms appear after 20 minutes to 4 hours.
 * Galerina – some species contain alpha-amanitin.
 * Many Inocybe species such as Inocybe fastigiata and Inocybe geophylla contain muscarine, while Inocybe erubescens is the only one known to have caused death.
 * Some white Clitocybe, including C. rivulosa and C. dealbata – first symptoms after 15 to 20 minutes
 * Tiger Tricholoma  (Tricholoma tigrinum) – no lasting effect after 2 to 6 hours of great pain.
 * Man-on-horseback Tricholoma equestre – until recently thought edible and good, can lead to rhabdomyolysis after repeated consumption.
 * Sulfur tuft (Hypholoma fasciculare) – poisoning may be serious
 * Omphalotus olearius – severe
 * False morel (Gyromitra esculenta) – deadly poisonous when raw; usually OK cooked, and delicious if correctly prepared.
 * Brown roll-rim (Paxillus involutus) – once thought edible, but now found to destroy red blood cells with regular or long-term consumption.
 * Devil's bolete (Boletus satanas)
 * Purple bolete (B. rhodoxanthus)
 * Conocybe filaris – contains amatoxins, sometimes mistaken for Psilocybe.
 * Some species of Agrocybe contain a deadly amount of toxins.
 * Hebeloma crustuliniforme (known as Poison pie or Fairy cakes) – can cause gastrointestinal symptoms such as nausea and vomiting.

Other causes of poisoning
Mushrooms may be rendered poisonous by insecticides or herbicides sprayed on lawns or reserves. At least one author recommends never picking them in non-natural landscapes for this reason.

Also, mushrooms are sometimes contaminated by concentrating pollutants, such as heavy metals or radioactive material (see Chernobyl disaster effects).

Famous poisonings

 * Roman Emperor Claudius is said to have been murdered by being fed the death cap mushroom. However this story appears some two centuries after the events, and it is even debatable whether Claudius was murdered at all.
 * Holy Roman Emperor Charles VI, Pope Clement VII, and Tsaritsa Natalia Naryshkina are believed to have died from eating the death cap mushroom.