Editing Anthrax (section)

== Cause ==
=== Bacteria ===
[[Image:Bacillus anthracis Gram.jpg|thumb|[[Photomicrograph]] of a [[Gram stain]] of the bacterium ''Bacillus anthracis'', the cause of the anthrax disease]]
{{Main|Bacillus anthracis}}
''Bacillus anthracis'' is a rod-shaped, [[Gram-positive]], facultative anaerobe<ref>{{cite journal | vauthors = Koehler TM | title = Bacillus anthracis physiology and genetics | journal = Molecular Aspects of Medicine | volume = 30 | issue = 6 | pages = 386–396 | date = December 2009 | pmid = 19654018 | pmc = 2784286 | doi = 10.1016/j.mam.2009.07.004 }}</ref> bacterium about 1 by 9&nbsp;μm in size.<ref name=CDC2015Bas /> It was shown to cause disease by [[Robert Koch]] in 1876 when he took a blood sample from an infected cow, isolated the bacteria, and put them into a mouse.<ref name="pages 277-310">{{cite journal | vauthors = Koch R |title=Untersuchungen über Bakterien: V. Die Ätiologie der Milzbrand-Krankheit, begründet auf die Entwicklungsgeschichte des ''Bacillus anthracis'' |journal=Beiträge zur Biologie der Pflanzen |volume=2 |issue=2 |pages=277–310 |year=1876 |url=http://edoc.rki.de/documents/rk/508-5-26/PDF/5-26.pdf |url-status=live |archive-url=https://web.archive.org/web/20110718171133/http://edoc.rki.de/documents/rk/508-5-26/PDF/5-26.pdf |archive-date=18 July 2011 }} [Investigations into bacteria: V. The etiology of anthrax, based on the ontogenesis of ''Bacillus anthracis''], Cohns</ref> The bacterium normally rests in spore form in the soil, and can survive for decades in this state. Herbivores are often infected while grazing, especially when eating rough, irritant, or spiky vegetation; the vegetation has been hypothesized to cause wounds within the gastrointestinal tract, permitting entry of the bacterial spores into the tissues. Once ingested or placed in an open wound, the bacteria begin multiplying inside the animal or human and typically kill the host within a few days or weeks. The spores germinate at the site of entry into the tissues and then spread by the circulation to the lymphatics, where the bacteria multiply.<ref name="Widdicombe">{{cite journal | vauthors = Hughes R, May AJ, Widdicombe JG | title = The role of the lymphatic system in the pathogenesis of anthrax | journal = British Journal of Experimental Pathology | volume = 37 | issue = 4 | pages = 343–49 | date = August 1956 | pmid = 13364144 | pmc = 2082573 }}</ref>

The production of two powerful exotoxins and lethal toxin by the bacteria causes death. Veterinarians can often tell a possible anthrax-induced death by its sudden occurrence and the dark, nonclotting blood that oozes from the body orifices. Most anthrax bacteria inside the body after death are outcompeted and destroyed by anaerobic bacteria within minutes to hours ''post mortem'', but anthrax vegetative bacteria that escape the body via oozing blood or opening the carcass may form hardy spores. These vegetative bacteria are not contagious.<ref name=Liu>{{cite journal | vauthors = Liu H, Bergman NH, Thomason B, Shallom S, Hazen A, Crossno J, Rasko DA, Ravel J, Read TD, Peterson SN, Yates J, Hanna PC | title = Formation and composition of the Bacillus anthracis endospore | journal = Journal of Bacteriology | volume = 186 | issue = 1 | pages = 164–78 | date = January 2004 | pmid = 14679236 | pmc = 303457 | doi = 10.1128/JB.186.1.164-178.2004 }}</ref> One spore forms per vegetative bacterium. The triggers for spore formation are not known, but oxygen tension and lack of nutrients may play roles. Once formed, these spores are very hard to eradicate.<ref>{{Citation |title=Disinfection, decontamination, fumigation, incineration |date=2008 |work=Anthrax in Humans and Animals. | edition = 4th |url= https://www.ncbi.nlm.nih.gov/books/NBK310477/ |access-date=2025-03-05 |publisher=World Health Organization |language=en}}</ref>

The infection of herbivores (and occasionally humans) by inhalation normally begins with inhaled spores being transported through the air passages into the tiny air sacs (alveoli) in the lungs. The spores are then picked up by scavenger cells ([[macrophage]]s) in the lungs and transported through small vessels ([[lymphatic system|lymphatics]]) to the [[lymph nodes]] in the central chest cavity ([[mediastinum]]). Damage caused by the anthrax spores and bacilli to the central chest cavity can cause chest pain and difficulty breathing. Once in the lymph nodes, the spores germinate into active bacilli that multiply and eventually burst the macrophages, releasing many more bacilli into the bloodstream to be transferred to the entire body. Once in the bloodstream, these bacilli release three proteins: [[Anthrax lethal factor endopeptidase|lethal factor]], edema factor, and protective antigen. The three are not toxic by themselves, but their combination is incredibly lethal to humans.<ref name=Pimental04>{{cite journal | vauthors = Pimental RA, Christensen KA, Krantz BA, Collier RJ | title = Anthrax toxin complexes: heptameric protective antigen can bind lethal factor and edema factor simultaneously | journal = Biochemical and Biophysical Research Communications | volume = 322 | issue = 1 | pages = 258–62 | date = September 2004 | pmid = 15313199 | doi = 10.1016/j.bbrc.2004.07.105 }}</ref> Protective antigen combines with these other two factors to form lethal toxin and edema toxin, respectively. These toxins are the primary agents of tissue destruction, bleeding, and death of the host. If antibiotics are administered too late, even if the antibiotics eradicate the bacteria, some hosts still die of toxemia because the toxins produced by the bacilli remain in their systems at lethal dose levels.<ref name="Sweeney">{{cite journal | vauthors = Sweeney DA, Hicks CW, Cui X, Li Y, Eichacker PQ | title = Anthrax infection | journal = American Journal of Respiratory and Critical Care Medicine | volume = 184 | issue = 12 | pages = 1333–41 | date = December 2011 | pmid = 21852539 | pmc = 3361358 | doi = 10.1164/rccm.201102-0209CI }}</ref>

<gallery>
File:Bacillus Anthracis.png|''Bacillus anthracis''
File:Anthrax color enhanced micrograph.JPG|Color-enhanced [[Scanning electron microscope|scanning electron micrograph]] shows [[spleen|splenic tissue]] from a [[monkey]] with inhalational anthrax; featured are rod-shaped [[bacilli]] (yellow) and an [[red blood cell|erythrocyte]] (red)
File:Gram Stain Anthrax.jpg|Gram-positive anthrax bacteria (purple rods) in [[cerebrospinal fluid]]: If present, a Gram-negative bacterial species would appear pink. (The other cells are [[white blood cell]]s.)
</gallery>

=== Exposure and transmission ===
Anthrax can enter the human body through the intestines (gastrointestinal), lungs (pulmonary), or skin (cutaneous), and causes distinct clinical symptoms based on its site of entry.<ref name=":5" /> Anthrax does not usually spread from an infected human to an uninfected human.<ref name=":5" /> If the disease is fatal to the person's body, its mass of anthrax bacilli becomes a potential source of infection to others and special precautions should be used to prevent further contamination.<ref name=":5" /> Pulmonary anthrax, if left untreated, is almost always fatal.<ref name=":5" /> Historically, pulmonary anthrax was called woolsorters' disease because it was an occupational hazard for [[Wool classing|people who sorted wool]].<ref name=":6">{{cite journal | vauthors = Metcalfe N | title = The history of woolsorters' disease: a Yorkshire beginning with an international future? | journal = Occupational Medicine | volume = 54 | issue = 7 | pages = 489–93 | date = October 2004 | pmid = 15486181 | doi = 10.1093/occmed/kqh115 }}</ref> Today, this form of infection is extremely rare in industrialized nations.<ref name=":6" /> Cutaneous anthrax is the most common form of transmission but also the least dangerous of the three transmissions.<ref name=":4" /> Gastrointestinal anthrax is likely fatal if left untreated, but very rare.<ref name=":4" />[[File:Anthrax - inhalational.jpg|thumb|Inhalational anthrax, [[mediastinum|mediastinal]] widening]]The spores of anthrax are able to survive in harsh conditions for decades or even centuries.<ref>{{Cite web | vauthors = Bloomfield R |date=2012-04-12 |title=Crossrail work stopped after human bones found on site |url=https://www.standard.co.uk/hp/front/crossrail-work-stopped-after-human-bones-found-on-site-6759649.html |access-date=2023-11-02 |website=Evening Standard |language=en |archive-date=25 October 2023 |archive-url=https://web.archive.org/web/20231025123650/https://www.standard.co.uk/hp/front/crossrail-work-stopped-after-human-bones-found-on-site-6759649.html |url-status=live }}</ref> Such spores can be found on all continents, including Antarctica.<ref>{{Cite journal | vauthors = Hudson JA, Daniel RM, Morgan HW |title=Acidophilic and thermophilic Bacillus strains from geothermally heated antarctic soil |journal=FEMS Microbiology Letters |volume=60 |issue=3 |date=August 1989 |pages=279–82 |doi=10.1111/j.1574-6968.1989.tb03486.x |doi-access=free }}</ref> Disturbed grave sites of infected animals have been known to cause infection after 70 years.<ref>{{Cite book | vauthors = Guillemin J |url=http://archive.org/details/anthraxinvestiga0000guil |title=Anthrax : the investigation of a deadly outbreak |date=1999 |publisher=Berkeley : University of California Press |others=Internet Archive |isbn=978-0-520-22204-5}}</ref> In one such event, a young boy died from gastrointestinal anthrax due to the thawing of reindeer corpses from 75 years before contact.<ref name=":7">{{Cite magazine | vauthors = Luhn A |date=August 8, 2016 |title=Siberian Child Dies After Climate Change Thaws an Anthrax-Infected Reindeer |url=https://www.wired.com/2016/08/child-dead-climate-change-thawed-anthrax-infected-reindeer/ |access-date=2023-11-02 |magazine=Wired |language=en-US |issn=1059-1028 |archive-date=17 August 2016 |archive-url=https://web.archive.org/web/20160817043745/http://www.wired.com/2016/08/child-dead-climate-change-thawed-anthrax-infected-reindeer/ |url-status=live }}</ref> Anthrax spores traveled though groundwater used for drinking and caused tens of people to be hospitalized, largely children.<ref name=":7" /> Occupational exposure to infected animals or their products (such as skin, wool, and meat) is the usual pathway of exposure for humans.<ref name=":8">{{Citation |title=Anthrax in humans |date=2008 |url=https://www.ncbi.nlm.nih.gov/books/NBK310487/ |work=Anthrax in Humans and Animals|edition=4th |access-date=2023-11-02 |publisher=World Health Organization |language=en |archive-date=18 June 2022 |archive-url=https://web.archive.org/web/20220618172116/https://www.ncbi.nlm.nih.gov/books/NBK310487/ |url-status=live }}</ref> Workers exposed to dead animals and animal products are at the highest risk, especially in countries where anthrax is more common.<ref name=":8" /> Anthrax in [[livestock]] grazing on open range where they mix with wild animals still occasionally occurs in the U.S. and elsewhere.<ref name=":8" />

Many workers who deal with wool and animal hides are routinely exposed to low levels of anthrax spores, but most exposure levels are not sufficient to produce infection.<ref name=":9">{{cite book |vauthors=Chambers J, Yarrarapu SN, Mathai JK |chapter=Anthrax Infection |date=2023 |chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK535379/ |title=StatPearls |access-date=2023-11-02 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=30571000 |archive-date=28 April 2022 |archive-url=https://web.archive.org/web/20220428091329/https://www.ncbi.nlm.nih.gov/books/NBK535379/ |url-status=live }}</ref> A lethal infection is reported to result from inhalation of about 10,000–20,000 spores, though this dose varies among host species.<ref name=":9" />