Amanita virosa

Taxobox
name=Destroying Angel
status= secure


image_width=250px
regnum=Fungi
divisio=Basidiomycota
classis=Agaricomycetes
subclassis=Hymenomycetes
ordo=Agaricales
familia=Amanitaceae
genus="Amanita"
species="A. virosa"
binomial="Amanita virosa"
binomial_authority=(Fr.) Bertillonmycomorphbox
name=Amanita virosa
whichGills=free
capShape=convex
capShape2=flat
hymeniumType=gills
stipeCharacter=ring and volva
ecologicalType=mycorrhizal
sporePrintColor=white
howEdible=deadly

"Amanita virosa", commonly known as the destroying angel or more precisely as European destroying angel, is a poisonous basidiomycete fungus, one of many in the genus "Amanita". Occurring in Europe, "A. virosa" associates with various deciduous and coniferous trees. The large fruiting bodies ("i.e.", the mushrooms) appear in summer and autumn; the caps, stipes and gills are all white in colour.

Immature specimens of "A. virosa" resemble several edible species commonly consumed by humans, increasing the risk of accidental poisoning. Along with its geographical namesakes, "A. virosa" is one of the most poisonous of all known toadstools; its principal toxic constituent α-amanitin damages the liver and kidneys, often fatally. No antidote is known.

Taxonomy and naming

The common name of "destroying angel" is applied to several all-white species of poisonous "Amanita", to this species in Europe and to "Amanita bisporiga" in eastern North America, and "A. ocreata" in the west. "A. virosa" was first collected and described by Elias Magnus Fries in Sweden. Its specific epithet "virosa" derived from the Latin adjective "virōsus" 'toxic' [cite book | last = Simpson | first = D.P. | title = Cassell's Latin Dictionary | publisher = Cassell Ltd. | date = 1979 | edition = 5 | location = London | pages = 883 | id = ISBN 0-304-52257-0] [cite book | last = Nilson|first= Sven |coauthors= Olle Persson | year = 1977 | title = Fungi of Northern Europe 2: Gill-Fungi | publisher = Penguin|isbn=0-14-063006-6|pages=p. 54] (compare virus).

"Amanita virosa" is very similar to several other species of all-white amanitas known as destroying angels, which has led to confusion over which occurs where. This specific name has been applied to all-white destroying angels occurring in North America, though others propose these all belong to "A. bisporiga" and other rarer species instead. There has been some question over whether "Amanita verna" is a valid species.

Description

"A. virosa" first appears as a white egg-shaped object covered with a universal veil. As it grows, the mushroom breaks free, though there may be ragged patches of veil at the cap edges. The cap is initially conical with inturned edges, before becoming hemispherical and flattening with a diameter up to 12 cm (4½ in). The cap often has a distinctive boss; it is able to be peeled and white, though the centre may be ivory in colour. The crowded free gills are white, as is the stipe and volva. The thin stipe is up to 15 cm (6 in) tall, with a hanging grooved ring. The spore print is white and the spores egg-shaped conical and 7-10 μm long. They stain blue with iodine. The flesh is white, with a taste reminiscent of radishes, and turns bright yellow with sodium hydroxide.cite book|last=Zeitlmayr|first= Linus|year=1976|title=Wild Mushrooms:An Illustrated Handbook|pages=p. 62-63|publisher=Garden City Press|location=Hertfordshire|isbn= 0-584-10324-7]

This fungus highlights the danger of picking immature fungi as it resembles the edible mushrooms "Agaricus arvensis" and "A. campestris", and the puffballs ("Lycoperdon" spp. ) before the caps have opened and the gills have become visible.

The ability to be peeled has been taken as a sign of edibility in mushrooming, which is a potentially lethal mistake in this species. It is unclear why this fungus which more closely resembles edible species has been implicated in fewer deaths than the death cap, though its rarity may contribute to this.cite book | author = Ramsbottom J | year = 1953 | title = Mushrooms & Toadstools |pages=p. 39 | publisher = Collins | id = ISBN 1870630092]

Distribution and habitat

"A. virosa" is found in mixed woodland, especially in association with beech, on mossy ground in summer and autumn. All "Amanita" species form ectomycorrhizal relationships with the roots of certain trees.

Toxicity

"Amanita virosa" is highly toxic, and has been responsible for severe mushroom poisonings.Benjamin.p200] Like the closely related death cap ("A. phalloides"), it contains the highly toxic amatoxins, as well as phallotoxins. Some authorities strongly advise against putting these fungi in the same basket with those collected for the table and to avoid touching them.Jordan & Wheeler. p99] [cite book | author = Carluccio A | year = 2003 | title = The Complete Mushroom Book | publisher = Quadrille | location = London|pages = 224| id = ISBN 1-84400-040-0]

Amatoxins consist of at least eight compounds with a similar structure, that of eight amino-acid rings; they were isolated in 1941 by Heinrich O. Wieland and Rudolf Hallermayer of the University of Munich.cite journal |last=Litten|first= W. |year=1975|month=March |title=The most poisonous mushrooms |journal=Scientific American |volume=232 |issue=3 |pages=90–101 |pmid=1114308] Of the amatoxins, α-amanitin is the chief component and along with β-amanitin is likely responsible for the toxic effects.cite journal |author=Köppel C |title=Clinical symptomatology and management of mushroom poisoning |journal=Toxicon |volume=31 |issue=12 |pages=1513–40 |year=1993 |pmid=8146866 |doi=10.1016/0041-0101(93)90337-I] cite book |last=Dart| first= RC |chapter=Mushrooms |title=Medical toxicology |publisher=Williams & Wilkins| location=Philadelphia |year=2004|pages=1719–35| isbn=0-7817-2845-2] Their major toxic mechanism is the inhibition of RNA polymerase II, a vital enzyme in the synthesis of messenger RNA (mRNA), microRNA, and small nuclear RNA (snRNA). Without mRNA essential protein synthesis and hence cell metabolism grind to a halt and the cell dies.cite journal |author=Karlson-Stiber C, Persson H |title=Cytotoxic fungi - an overview |journal=Toxicon |volume=42 |issue=4 |pages=339–49 |year=2003 |pmid=14505933|doi=10.1016/S0041-0101(03)00238-1] The liver is the principal organ affected, as it is the organ which is first encountered after absorption in the gastrointestinal tract, though other organs, especially the kidneys, are susceptible.Benjamin.p217]

The phallotoxins consist of at least seven compounds, all of which have seven similar peptide rings. Phalloidin was isolated in 1937 by Feodor Lynen, Heinrich Wieland's student and son-in-law, and Ulrich Wieland of the University of Munich. Though phallotoxins are highly toxic to liver cells, [cite journal |author=Wieland T, Govindan VM |title=Phallotoxins bind to actins |journal=FEBS Lett. |volume=46 |issue=1 |pages=351–3 |year=1974 |pmid=4429639|doi=10.1016/0014-5793(74)80404-7] they have since been found to have little input into the destroying angel's toxicity as they are not absorbed through the gut. Furthermore, phalloidin is also found in the edible (and sought-after) Blusher ("Amanita rubescens"). Another group of minor active peptides are the virotoxins, which consist of six similar monocyclic heptapeptides.cite journal|first=János| last=Vetter|year=1998| month=January| title=Toxins of "Amanita phalloides"| journal=Toxicon| volume=36| issue=1 |pages=13–24|pmid=9604278| doi=10.1016/S0041-0101(97)00074-3] Like the phallotoxins they do not exert any acute toxicity after ingestion in humans.

Treatment

Consumption of "Amanita virosa" is a medical emergency requiring hospitalization. There are four main categories of therapy for poisoning: preliminary medical care, supportive measures, specific treatments, and liver transplantation.cite journal |author=Enjalbert F, Rapior S, Nouguier-Soulé J, Guillon S, Amouroux N, Cabot C |title=Treatment of amatoxin poisoning: 20-year retrospective analysis |journal=Journal of Toxicology - Clinical Toxicology |volume=40 |issue=6 |pages=715–57 |year=2002 |pmid=12475187]

Preliminary care consists of gastric decontamination with either activated carbon or gastric lavage. However, due to the delay between ingestion and the first symptoms of poisoning, it is commonplace for patients to arrive for treatment many hours after ingestion, potentially reducing the efficacy of these interventions.cite journal |author=Vesconi S, Langer M, Iapichino G, Costantino D, Busi C, Fiume L |title=Therapy of cytotoxic mushroom intoxication |journal=Critical care medicine |volume=13 |issue=5 |pages=402–6 |year=1985 |pmid=3987318 |doi=10.1097/00003246-198505000-00007] Supportive measures are directed towards treating the dehydration which results from fluid loss during the gastrointestinal phase of intoxication and correction of metabolic acidosis, hypoglycemia, electrolyte imbalances, and impaired coagulation.

No definitive antidote for amatoxin poisoning is available, but some specific treatments have been shown to improve survivability. High-dose continuous intravenous penicillin G has been reported to be of benefit, though the exact mechanism is unknown,de iconcite journal| last=Floerscheim| first=G.L.| coauthors=O. Weber, P. Tschumi & M. Ulbrich|year=1982|month=August|title=Die klinische knollenblatterpilzvergiftung ("Amanita Phalloides"): prognostische faktoren und therapeutische massnahmen (Clinical death-cap (Amanita phalloides) poisoning: prognostic factors and therapeutic measures.)| journal=Schweizerische medizinische Wochenschrift |volume=112 |issue=34 |pages=1164–1177 |pmid=6291147] and trials with cephalosporins show promise.Benjamin.p227] [de iconcite journal|author=Neftel, K. "et al."| year=1988| month=January|title=(Are cephalosporins more active than penicillin G in poisoning with the deadly "Amanita"?)|journal=Schweizerische medizinische Wochenschrift|volume=118| issue=2|pages=49–51|pmid=3278370] There is some evidence that intravenous silibinin, an extract from the blessed milk thistle ("Silybum marianum"), may be beneficial in reducing the effects of death cap poisoning. Silibinin prevents the uptake of amatoxins by hepatocytes, thereby protecting undamaged hepatic tissue; it also stimulates DNA-dependent RNA polymerases, leading to an increase in RNA synthesis. [cite journal |author=Hruby K, Csomos G, Fuhrmann M, Thaler H |title=Chemotherapy of Amanita phalloides poisoning with intravenous silibinin |journal=Human toxicology |volume=2 |issue=2 |pages=183–95 |year=1983 |pmid=6862461] [it icon cite journal|author=Carducci, R. "et al."| year=1996| month=May| title=Silibinin and acute poisoning with "Amanita phalloides"|journal=Minerva Anestesiologica|volume=62 |issue=5 |pages=187–93|pmid=8937042] [cite book| last=Jahn| first=W.| coauthors=|year=1980|chapter=Pharmacokinetics of {3H}-methyl-dehydroxymethyl-amanitin in the isolated perfused rat liver, and the influence of several drugs| editor=Helmuth Faulstich, B. Kommerell & Theodore Wieland| title=Amanita toxins and poisoning|publisher=Witzstrock| location=Baden-Baden|pages=80–85|isbn=3-87921-132-9] N-acetylcysteine has shown promise in combination with other therapies. [cite journal |author=Montanini S, Sinardi D, Praticò C, Sinardi A, Trimarchi G |title=Use of acetylcysteine as the life-saving antidote in Amanita phalloides (death cap) poisoning. Case report on 11 patients |journal=Arzneimittel-Forschung |volume=49 |issue=12 |pages=1044–7 |year=1999 |pmid=10635453] Animal studies indicate the amatoxins deplete hepatic glutathione; [cite journal |author=Kawaji A, Sone T, Natsuki R, Isobe M, Takabatake E, Yamaura Y |title=In vitro toxicity test of poisonous mushroom extracts with isolated rat hepatocytes |journal=The Journal of toxicological sciences |volume=15 |issue=3 |pages=145–56 |year=1990 |pmid=2243367] N-acetylcysteine serves as a glutathione precursor and may therefore prevent reduced glutathione levels and subsequent liver damage. [cite journal |author=Chyka P, Butler A, Holliman B, Herman M |title=Utility of acetylcysteine in treating poisonings and adverse drug reactions |journal=Drug safety |volume=22 |issue=2 |pages=123–48 |year=2000 |pmid=10672895 |doi=10.2165/00002018-200022020-00005] None of the antidotes used have undergone prospective, randomized clinical trials, and only anecdotal support is available. Silibinin and N-acetylcysteine appear to be the therapies with the most potential benefit. Repeated doses of activated carbon may be helpful by absorbing any toxins that are returned to the gastrointestinal tract following enterohepatic circulation. [ cite journal |author=Busi C, Fiume L, Costantino D, Langer M, Vesconi F |title=Amanita toxins in gastroduodenal fluid of patients poisoned by the mushroom, Amanita phalloides |journal=New England Journal of Medicine |volume=300 |issue=14 |pages=800 |year=1979 |pmid=423916] Other methods of enhancing the elimination of the toxins have been trialed; techniques such as hemodialysis, [ cite journal |author=Sabeel AI, Kurkus J, Lindholm T |title=Intensive hemodialysis and hemoperfusion treatment of Amanita mushroom poisoning |journal=Mycopathologia |volume=131 |issue=2 |pages=107–14 |year=1995 |pmid=8532053 |doi=10.1007/BF01102888] hemoperfusion, [cite journal |author=Wauters JP, Rossel C, Farquet JJ |title=Amanita phalloides poisoning treated by early charcoal haemoperfusion |journal=British medical journal |volume=2 |issue=6150 |pages=1465 |year=1978 |pmid=719466] plasmapheresis, [ cite journal |author=Jander S, Bischoff J, Woodcock BG |title=Plasmapheresis in the treatment of Amanita phalloides poisoning: II. A review and recommendations |journal=Therapeutic apheresis |volume=4 |issue=4 |pages=308–12 |year=2000 |pmid=10975479| doi=10.1046/j.1526-0968.2000.004004303.x] and peritoneal dialysis [ cite journal |author=Langer M, Vesconi S, Iapichino G, Costantino D, Radrizzani D |title=The early removal of amatoxins in the treatment of amanita phalloides poisoning |language=German |journal=Klinische Wochenschrift |volume=58 |issue=3 |pages=117–23 |year=1980 |pmid=7366125 |doi=10.1007/BF01477268] have occasionally yielded success but overall do not appear to improve outcome.

In patients developing liver failure, a liver transplant is often the only option to prevent death. Liver transplants have become a well-established option in amatoxin poisoning.cite journal|author= Klein AS, Hart J, Brems JJ, Goldstein L, Lewin K, Busuttil RW |year=1989| month=February|title= "Amanita" poisoning: treatment and the role of liver transplantation|journal=American Journal of Medicine| volume=86| issue=2| pages=187–93|pmid=2643869|doi=10.1016/0002-9343(89)90267-2] cite journal|author=Pinson CW, Daya MR, Benner KG, Norton RL, Deveney KE, Ascher NL, Roberts JP, Lake JR, Kurkchubasche AG, Ragsdale JW |year=1990|month=May| title=Liver transplantation for severe "Amanita phalloides" mushroom poisoning| journal=American Journal of Surgery|volume=159|issue=5|pages=493–9|pmid=2334013|doi=10.1016/S0002-9610(05)81254-1] [cite journal |author=Ganzert M, Felgenhauer N, Zilker T |title=Indication of liver transplantation following amatoxin intoxication |journal=Journal of Hepatology |volume=42 |issue=2 |pages=202–9 |year=2005 |pmid=15664245|doi=10.1016/j.jhep.2004.10.023] This is a complicated issue, however, as transplants themselves may have significant complications and mortality; patients require long-term immunosuppression to maintain the transplant. That being the case, there has been a reassessment of criteria such as onset of symptoms, prothrombin time (PTT), serum bilirubin, and presence of encephalopathy for determining at what point a transplant becomes necessary for survival. [cite journal|last=O'grady| first=John G.| coauthors=Graeme J.M. Alexander, Karen M. Hayllar & Roger Williams|title=Early indicators of prognosis in fulminant hepatic failure| month=august| year=1989| journal=Gastroenterology|volume=97| issue=2| pages=439–445|pmid=2490426] [cite journal| last=Panaro| first=Fabrizio| coauthors=Enzo Andorno, Nicola Morelli, Marco Casaccia, Giuliano Bottino, Ferruccio Ravazzoni, Monica Centanaro, Sara Ornis & Umberto Valente|year=2006| month=April| title=Letter to the editor: Liver transplantation represents the optimal treatment for fulminant hepatic failure from "Amanita phalloides" poisoning| journal= Transplant International|volume=19 |issue=4 |pages=344–5| pmid=16573553|doi=10.1111/j.1432-2277.2006.00275.x] [cite journal |author=Escudié L, Francoz C, Vinel JP, Moucari R, Cournot M, Paradis V, Sauvanet A, Belghiti J, Valla D, Bernuau J, Durand F |title=Amanita phalloides poisoning: reassessment of prognostic factors and indications for emergency liver transplantation |journal=J. Hepatol. |volume=46 |issue=3 |pages=466–73 |year=2007 |pmid=17188393 |doi=10.1016/j.jhep.2006.10.013] Evidence suggests that, although survival rates have improved with modern medical treatment, in patients with moderate to severe poisoning up to half of those who did recover suffered permanent liver damage.Benjamin.p231–232] However, a follow-up study has shown that most survivors recover completely without any sequelae if treated within 36 hours of mushroom ingestion. [cite journal |author=Giannini L, Vannacci A, Missanelli A, Mastroianni R, Mannaioni PF, Moroni F, Masini E |title=Amatoxin poisoning: A 15-year retrospective analysis and follow-up evaluation of 105 patients |journal=Clinical toxicology (Philadelphia, Pa.) |volume=45 |issue=5 |pages=539–42 |year=2007 |pmid=17503263 |doi=10.1080/15563650701365834]

References

ources

*cite book |last=Benjamin| first= Denis R. |title=Mushrooms: poisons and panaceas — a handbook for naturalists, mycologists and physicians |publisher=WH Freeman and Company| location=New York |year=1995| isbn=0-7167-2600-9
*cite book | author=Jordan Peter, Wheeler Steven. | year=2001 | title=The Ultimate Mushroom Book | location=London | publisher=Hermes House | isbn = 1-85967-092-X