Anthrax spores, which can survive for decades, are found in the soil, and animals typically contract the disease while grazing. Transmission to humans normally occurs through contact with infected animals but can also occur through eating meat from an infected animal or breathing air laden with the spores of the bacilli. The disease is almost entirely occupational, i.e., restricted to individuals who handle hides of animals (e.g., farmers, butchers, and veterinarians) or sort wool.
In the cutaneous, or skin, form of the disease, which is not usually fatal to humans, the bacillus enters the skin through a scratch, cut, or sore. Pustules occur on the hands, face, and neck; if the disease is not treated with antibiotics, the bacteria can migrate to the blood vessels, causing septicemia (blood poisoning) and death. Gastrointestinal anthrax is more likely to be fatal. Nausea, vomiting, and fever can be followed by abdominal bleeding, tissue death, and septicemia. Pulmonary, or inhalation, anthrax begins with flulike symptoms and ultimately causes lesions in the lungs and brain. It is rarer, but is usually fatal if not treated early. Because of this, individuals without symptoms who have been exposed to inhaled anthrax are treated with antibiotics for 60 days.
Anthrax is a well-known, ancient disease; the fifth plague visited upon the Egyptians in Genesis (see plagues of Egypt) resembles the disease. Pure cultures of the anthrax bacillus were obtained in 1876 by Robert Koch, who demonstrated the relationship of the microbe to the disease. Confirmation of the bacillus as the cause of anthrax was provided by Louis Pasteur, who also developed a method of vaccinating sheep and cattle against the disease. Anthrax is now uncommon in the United States because of widespread vaccination of animals and disinfection of animal products such as hides and wool.
Anthrax spores have been used experimentally by various nations as a biological warfare agent, but effective delivery of anthrax to a population is difficult, and such use is now banned by international convention. Because anthrax has been tested as a biological weapon, the United States has developed a vaccine for military use, but it requires several injections and annual boosters. An accidental release of anthrax from a military laboratory near Sverdlovsk (now Yekaterinburg) in the Soviet Union resulted in 68 deaths from pulmonary anthrax in 1979. In 2001 a number of people in the United States were exposed to spores that were sent through the mails and contracted anthrax; several persons died. Although these bioterror attacks occurred shortly after the terrorist attacks on the World Trade Center and the Pentagon, it did not appear to be linked to them.
Infectious disease of warm-blooded animals, caused by Bacillus anthracis, a bacterium that, in spore form, can retain its virulence in contaminated soil or other material for many years. A disease chiefly of herbivores, the infection may be acquired by persons handling the wool, hair, hides, bones, or carcasses of affected animals. Infection may lead to death from respiratory or cardiac complications (within 1–2 days if acute), or the animal may recover. In humans, anthrax occurs as a cutaneous, pulmonary, or intestinal infection. The most common type, which occurs as an infection of the skin, may lead to fatal septicemia (blood poisoning). The pulmonary form of the disease is usually fatal. Sanitary working environments for susceptible workers are critical to preventing anthrax; early diagnosis and treatment are also of great importance. In recent decades, various countries have attempted to develop anthrax as a weapon of biological warfare; many factors, including its extreme potency (vastly greater than any chemical-warfare agent), make it the preferred biological-warfare agent. Concerns about anthrax mounted in 2001 after it was found in letters mailed to members of the U.S. government and news agencies.
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The anthrax bacillus is one of only a few that can form long-lived spores: in a hostile environment, caused perhaps by the death of an infected host or extremes of temperature, the bacteria become inactive dormant spores which can remain viable for many decades and perhaps centuries. Spores are found on all continents except Antarctica. When spores are inhaled, ingested, or come into contact with a skin lesion on a host they reactivate and multiply rapidly.
Anthrax most commonly infects wild and domesticated herbivorous mammals which ingest or inhale the spores while eating grass or browsing. Ingestion is assumed to be the most common route by which herbivores contract anthrax, but this is as yet unproven. Carnivores living in the same environment may ingest infected animals and become infected themselves. Anthrax can also infect humans when they are exposed to blood and other tissues from infected animals (via inhalation or direct inoculation through broken skin), eat tissue from infected animals, or are exposed to a high density of anthrax spores from an animal's fur, hide, or wool.
Anthrax spores can be grown in vitro and used as a biological weapon. Anthrax does not spread directly from one infected animal or person to another, but spores can be transported by clothing, shoes etc.; and the body of a mammal that died of anthrax can be a very dangerous source of anthrax spores.
Anthrax is one of the oldest recorded diseases of grazing animals such as sheep and cattle and is believed to be the 8_-_9:12.29_.D7.A9.D6.B0.D7.81.D7.97.D6.B4.D7.99.D7.9F Plague mentioned in the Book of Exodus in the Bible. Anthrax is also mentioned by Greek and Roman authors such as Homer (in The Iliad), Virgil (Georgics), and Hippocrates. Anthrax can also infect humans, usually as the result of coming into contact with infected animal hides, fur, wool ("Woolsorter's disease"), leather or contaminated soil. Anthrax ("siberian ulcer" ) is now fairly rare in humans, although it still regularly occurs in ruminants, such as cattle, sheep, goats, camels, wild buffalo, and antelopes, in hind-gut fermenters such as zebras and rhinos, and in other wildlife such as elephants and lions in certain endemic areas of the world.
Bacillus anthracis bacteria spores are soil-borne and because of their long lifetime, they are still present globally and at animal burial sites of anthrax-killed animals for many decades; spores have been known to have reinfected animals over 70 years after burial sites of anthrax-infected animals were disturbed.
Until the twentieth century, anthrax infections killed many thousands of animals and thousands of people each year in Europe, Asia and North America. French scientist Louis Pasteur developed the first effective vaccine for anthrax in 1881. Thanks to over a century of animal vaccination programs, sterilization of raw animal waste materials and anthrax eradication programs in North America, Australia, New Zealand, Russia, Europe and parts of Africa and Asia, anthrax infection is now relatively rare in domestic animals with normally only a few dozen cases reported every year. Anthrax is even rarer in dogs and cats: there had only ever been one documented case in dogs in the USA by 2001, although the disease affects livestock. Anthrax typically does not cause disease in carnivores and scavengers, even when these animals consume anthrax-infected carcasses. Anthrax outbreaks do occur in some wild animal populations with some regularity. The disease is more common in developing countries without widespread veterinary or human public health programs.
There are 89 known strains of anthrax, the most widely recognized being the virulent Ames strain used in the 2001 anthrax attacks in the United States, when people were sent anthrax in the mail. The Ames strain is extremely dangerous, though not quite as virulent as the Vollum strain which was successfully developed as a biological weapon during the Second World War, but never used. The Vollum (also incorrectly referred to as Vellum) strain was isolated in 1935 from a cow in Oxfordshire, UK. This is the same strain that was used during the Gruinard bioweapons trials. A variation of Vollum known as "Vollum 1B" was used during the 1960s in the US and UK bioweapon programs. Vollum 1B was isolated from William A. Boyles, a 46-year-old USAMRIID scientist who died in 1951 after being accidentally infected with the Vollum strain. The Sterne strain, named after a South African researcher, is an attenuated strain used as a vaccine.
The infection of herbivores (and occasionally humans) via the inhalational route normally proceeds as follows: once the spores are inhaled, they are transported through the air passages into the tiny air sacs (alveoli) in the lungs. The spores are then picked up by scavenger cells (macrophages) in the lungs and are transported through small vessels (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 which multiply and eventually burst the macrophages, releasing many more bacilli into the bloodstream to be transferred to the entire body. Once in the blood stream these bacilli release three substances: lethal factor, oedema factor and protective antigen. Protective antigen combines with these other two factors to form lethal toxin and oedema 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 will still die. This is because the toxins produced by the bacilli remain in their system at lethal dose levels.
In order to enter the cells, the edema and lethal factors use another protein produced by B. anthracis, protective antigen. Oedema factor inactivates neutrophils (a type of phagocytic cell) so that they cannot phagocytose bacteria. Historically, it was believed that lethal factor caused macrophages to make TNF-alpha and interleukin 1, beta (IL1B), both normal components of the immune system used to induce an inflammatory reaction, ultimately leading to septic shock and death. However, recent evidence indicates that anthrax also targets endothelial cells (cells that lines serous cavities, lymph vessels, and blood vessels), causing vascular leakage of fluid and cells, and ultimately hypovolemic shock (low blood volume), and septic shock.
The virulence of a strain of anthrax is dependent on multiple factors, primarily the poly-D-glutamic acid capsule that protects the bacterium from phagocytosis by host neutrophils and its toxins, edema toxin and lethal toxin.
In July 2006 an artist who worked with untreated animal skins became the first person in more than 30 years to die in the United Kingdom from anthrax.
Anthrax can enter the human body through the intestines (ingestion), lungs (inhalation), or skin (cutaneous) and causes distinct clinical symptoms based on its site of entry. An infected human will generally be quarantined. However, anthrax does not usually spread from an infected human to a noninfected human. But if the disease is fatal the person’s body and its mass of anthrax bacilli becomes a potential source of infection to others and special precautions should be used to prevent further contamination. Inhalational anthrax, if left untreated until obvious symptoms occur, will usually result in death, as treatment will have started too late.
Anthrax can be contracted in laboratory accidents or by handling infected animals or their wool or hides. It has also been used in biological warfare agents and by terrorists to intentionally infect humans.
Respiratory infection in humans initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse. This disease can rarely be treated, even if caught in early stages of infection; mortality is nearly 100%. A lethal infection is reported to result from inhalation of about 10,000–20,000 spores, though this dose varies amongst host species. Like all diseases there is probably a wide variation to susceptibility with evidence that some people may die from much lower exposures; there is little documented evidence to verify the exact or average number of spores needed for infection. Inhalational anthrax is also known as woolsorters' or ragpickers' disease as these professions were more susceptible to the disease due to their exposure to infected animal products. Other practices associated with exposure include the slicing up of animal horns for the manufacture of buttons, the handling of hair bristles used for the manufacturing of brushes, and the handling of animal skins. Whether these animal skins came from animals that died of the disease or from animals that had simply laid on ground that had spores on it is unknown. This mode of infection is used as a bioweapon.
Cutaneous (on the skin) anthrax infection in humans shows up as a boil-like skin lesion that eventually forms an ulcer with a black centre (eschar). The black eschar often shows up as a large, painless necrotic ulcer (beginning as an irritating and itchy skin lesion or blister that is dark and usually concentrated as a black dot, somewhat resembling bread mold) at the site of infection. Cutaneous infections generally form within the site of spore penetration within 2 to 5 days after exposure. Unlike bruises or most other lesions, cutaneous anthrax infections normally do not cause pain.
Cutaneous anthrax is rarely fatal if treated, but without treatment about 20% of cutaneous skin infection cases progress to toxemia and death.
If a person is suspected as having died from anthrax, every precaution should be taken to avoid skin contact with the potentially contaminated body and fluids exuded through natural body openings. The body should be put in strict quarantine. A blood sample taken in a sealed container and analyzed in an approved lab should be used to ascertain if anthrax is the cause of death. Microscopic visualization of the encapsulated bacilli, usually in very large numbers, in a blood smear stained with polychrome methylene blue (McFadyean stain) is fully diagnostic, though culture of the organism is still the gold standard for diagnosis. Full isolation of the body is important to prevent possible contamination of others. Protective, impermeable clothing and equipment such as rubber gloves, rubber apron, and rubber boots with no perforations should be used when handling the body. No skin, especially if it has any wounds or scratches, should be exposed. Disposable personal protective equipment is preferable, but if not available, decontamination can be achieved by autoclaving. Disposable personal protective equipment and filters should be autoclaved, and/or burned and buried. Bacillus anthracis bacillii range from 0.5-5.0 μm in size. Anyone working with anthrax in a suspected or confirmed victim should wear respiratory equipment capable of filtering this size of particle or smaller. The US National Institute for Occupational Safety and Health (NIOSH) and Mine Safety and Health Administration (MSHA) approved high efficiency-respirator, such as a half-face disposable respirator with a high-efficiency particulate air (HEPA) filter, is recommended. All possibly contaminated bedding or clothing should be isolated in double plastic bags and treated as possible bio-hazard waste. The victim should be sealed in an airtight body bag. Dead victims that are opened and not burned provide an ideal source of anthrax spores. Cremating victims is the preferred way of handling body disposal. No embalming or autopsy should be attempted without a fully equipped biohazard lab and trained and knowledgable personnel.
Delays of only a few days may make the disease untreatable and treatment should be started even without symptoms if possible contamination or exposure is suspected. Animals with anthrax often just die without any apparent symptoms. Initial symptoms may resemble a common cold – sore throat, mild fever, muscle aches and malaise. After a few days, the symptoms may progress to severe breathing problems and shock and ultimately death. Death can occur from about two days to a month after exposure with deaths apparently peaking at about 8 days after exposure. Antibiotic-resistant strains of anthrax are known.
Aerial spores can be trapped by a simple HEPA or P100 filter. Inhalation of anthrax spores can be prevented with a full-face mask using appropriate filtration. Unbroken skin can be decontaminated by washing with simple soap and water. These procedures do not actually kill the spores, which are very hardy and can only be destroyed by extensive treatment. Filters, clothes, etc. exposed to possible anthrax-contaminated environments should be treated with chemicals or destroyed by fire to minimize the possibility of spreading the contamination.
In recent years there have been many attempts to develop new drugs against anthrax, but existing drugs are effective if treatment is started soon enough.
Early detection of sources of anthrax infection can allow preventative measures to be taken. In response to the anthrax attacks of October, 2001 the United States Postal Service (USPS) installed BioDetection Systems (BDS) in their large scale mail cancellation facilities. BDS response plans were formulated by the USPS in conjunction with local responders including fire, police, hospitals and public health. Employees of these facilities have been educated about anthrax, response actions and prophylactic medication. Because of the time delay inherent in getting final verification that anthrax has been used, prophylactic antibiotic treatment of possibly exposed personnel must be started as soon as possible.
The most effective form of prevention is vaccination against infection but this must be done well in advance of exposure to the bacillus, and does not protect indefinitely.
Components of tea, such as polyphenols, have the ability to inhibit the activity both of bacillus anthracis and its toxin considerably; spores, however, are not affected. The addition of milk to the tea completely inhibits its antibacterial activity against anthrax. Activity against the anthrax bacillum in the laboratory does not prove that drinking tea affects the course of an infection.
Unlike the West, the Soviets developed and used a live spore anthrax vaccine, known as the STI vaccine, produced in Tbilisi, Georgia. Its serious side effects restrict use to healthy adults.
Chlorine dioxide has emerged as the preferred biocide against anthrax-contaminated sites, having been employed in the treatment of numerous government buildings over the past decade. Its chief drawback is the need for in situ processes to have the reactant on demand.
To speed the process, trace amounts of a non-toxic catalyst composed of iron and tetro-amido macrocyclic ligands are combined with sodium carbonate and bicarbonate and converted into a spray. The spray formula is applied to an infested area and is followed by another spray containing tertiary-butyl hydroperoxide.
Using the catalyst method, a complete destruction of all anthrax spores takes 30 minutes. A standard catalyst-free spray destroys fewer than half the spores in the same amount of time. They can be heated, exposed to the harshest chemicals, and they do not easily die.
Cleanups at a Senate office building, several contaminated postal facilities and other U.S. government and private office buildings showed that decontamination is possible, but it is time-consuming and costly. Clearing the Senate office building of anthrax spores cost $27 million, according to the Government Accountability Office. Cleaning the Brentwood postal facility outside Washington cost $130 million and took 26 months. Since then newer and less costly methods have been developed.
Clean up of anthrax-contaminated areas on ranches and in the wild is much more problematic. Carcasses may be burned, though it often takes up to three days to burn a large carcass and this is not feasible in areas with little wood. Carcasses may be buried, though the burying of large animals deeply enough to prevent resurfacing of spores requires much manpower and expensive tools. Carcasses have been soaked in formaldehyde to kill spores, though this has obvious environmental contamination issues. Block burning of vegetation in large areas enclosing an anthrax outbreak has been tried; this, while environmentally destructive, causes healthy animals to move away from an area with carcasses in search of fresh graze and browse. Some wildlife workers have experimented with covering fresh anthrax carcasses with shadecloth and heavy objects. This prevents some scavengers from opening the carcasses, thus allowing the putrefactive bacteria within the carcass to kill the vegetative B. anthracis cells and preventing sporulation. This method also has drawbacks, as scavengers such as hyenas are capable of infiltrating almost any exclosure. The occurrence of previously dormant anthrax, stirred up from below the ground surface by wind movement in a drought-stricken region with depleted grazing and browsing, may be seen as a form of natural culling and a first step in rehabilitation of the area.
The human vaccine for anthrax became available in 1954. This was a cell-free vaccine instead of the live-cell Pasteur-style vaccine used for veterinary purposes. An improved cell-free vaccine became available in 1970.
Anthrax spores can and have been used as a biological warfare weapon. Its first modern incidence occurred when Scandinavian freedom fighters supplied by the German General Staff used anthrax with unknown results against the Imperial Russian Army in Finland in 1916. There is a long history of practical bioweapons research in this area. For example, in 1942 British bioweapons trials severely contaminated Gruinard Island in Scotland with anthrax spores of the Vollum-14578 strain, making it a no-go area until it was decontaminated by 1990. The Gruinard trials involved testing the effectiveness of a submunition of an "N-bomb"—a biological weapon. Additionally, five million "cattle cakes" impregnated with anthrax were prepared and stored at Porton Down in 'Operation Vegetarian'—an anti-livestock weapon intended for attacks on Germany by the Royal Air Force The infected cattle cakes were to be dropped on Germany in 1944. However neither the cakes nor the bomb were used; the cattle cakes were incinerated in late 1945.
More recently the Rhodesian government used anthrax against cattle and humans in the period 1978–1979 during its war with black nationalists.
American military and British Army personnel are routinely vaccinated against anthrax prior to active service in places where biological attacks are considered a threat. The anthrax vaccine, produced by BioPort Corporation, contains non-living bacteria, and is approximately 93% effective in preventing infection.
Weaponized stocks of anthrax in the US were destroyed in 1971–72 after President Nixon ordered the dismantling of US biowarfare programs in 1969 and the destruction of all existing stockpiles of bioweapons. Research is known to continue in the United States on ways to counteract bioweapons attacks.
The Soviet Union created and stored 100 to 200 tons of anthrax spores on Vozrozhdeniya Island. They were abandoned in 1992 and destroyed in 2002.
Despite signing the 1972 agreement to end bioweapon production the government of the Soviet Union had an active bioweapons program that included the production of hundreds of tons of weapons-grade anthrax after this period. On April 2, 1979 some of the over one million people living in Sverdlovsk (now called Ekaterinburg, Russia), about 850 miles east of Moscow, were exposed to an accidental release of anthrax from a biological weapons complex located near there. At least 94 people were infected, of whom at least 68 died. One victim died four days after the release, ten over an eight-day period at the peak of the deaths, and the last six weeks later. Extensive cleanup, vaccinations and medical interventions managed to save about 30 of the victims. Extensive cover-ups and destruction of records by the KGB continued from 1979 until Russian President Boris Yeltsin admitted this anthrax accident in 1992. Jeanne Guillemin reported in 1999 that a combined Russian and United States team investigated the accident in 1992.
Nearly all of the night shift workers of a ceramics plant directly across the street from the biological facility (compound 19) became infected, and most died. Since most were men, there were suspicions by Western governments that the Soviet Union had developed a sex-specific weapon. The government blamed the outbreak on the consumption of anthrax-tainted meat and ordered the confiscation of all uninspected meat that entered the city. They also ordered that all stray dogs be shot and that people not have contact with sick animals. There was also a voluntary evacuation and anthrax vaccination program established for people from 18–55.
To support the cover-up story Soviet medical and legal journals published articles about an outbreak in livestock that caused GI anthrax in people who consumed infected meat, and cutaneous anthrax in people who came into contact with the animals. All medical and public health records were confiscated by the KGB. In addition to the medical problems that the outbreak caused, it also prompted Western countries to be (justifiably) more suspicious of a covert Soviet Bioweapons program and to increase their surveillance of suspected sites. In 1986 the US government was allowed to investigate the incident, and concluded that the exposure was from aerosol anthrax from a military weapons facility. In 1992, President Yeltsin admitted that he was "absolutely certain" that "rumors" about the Soviet Union violating the 1972 Bioweapons Treaty were true. The Soviet Union, like the US and UK, had agreed to submit information to the UN about their bioweapons programs but omitted known facilities and never acknowledged their weapons program.
Theoretically anthrax spores can be cultivated with minimal special equipment and a first-year collegiate microbiological education, but in practice the procedure is difficult and dangerous. To make large amounts of an aerosol form of anthrax suitable for biological warfare, extensive practical knowledge, training and highly advanced equipment are required.
Concentrated anthrax spores were used for bioterrorism in the 2001 anthrax attacks in the United States, delivered by mailing postal letters containing the spores. Only a few grams of material were used in these attacks and in August 2008 the US Department of Justice announced they believed that Dr. Bruce Ivins, a senior biodefense researcher, was responsible. These events also spawned many anthrax hoaxes.
A scientific experiment performed by a high school student, later published in The Journal of Medical Toxicology, suggested that a domestic electric iron at its hottest setting (at least ) used for at least 5 minutes should destroy all anthrax spores in a common postal envelope.