Anthrax is a life-threatening infectious disease that normally affects animals, especially ruminants (such as goats, cattle, sheep, and horses). Anthrax can be transmitted to humans by contact with infected animals or their products.
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Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal. There are effective vaccines against anthrax, and some forms of the disease respond well to antibiotic treatment.
Like many other members of the genus Bacillus, Bacillus anthracis can form dormant endospores (often referred to as “spores” for short, but not to be cnfused with fungal spores) that are able to survive in harsh conditions for decades or even centuries. Such spores can be found on all continents, even Antarctica. When spores are inhaled, ingested, or come into contact with a skin lesion on a host they may reactivate and multiply rapidly.
Anthrax spores can be produced in vitro and used as a biological weapon. Anthrax does not spread directly from one infected animal or person to another; it is spread by spores. These spores can be transported by clothing or shoes. The dead body of an animal that died of anthrax can also be a source of anthrax spores.
In recent years, anthrax has received a great deal of attention as it has become clear that the infection can also be spread by a bioterrorist attack or by biological warfare.
There are three different types of anthrax.
1.Cutaneous anthrax ,2.Inhalational anthrax and 3.Intestinal anthrax
1.Cutaneous anthrax – this type accounts for about 95 per cent of cases. People handling dead animals – such as abattoir workers and tanners – are at most risk. Infection occurs when the bacterium comes into direct contact with a cut or abrasion in the skin.
At first the skin itches. This is soon followed by the appearance of a small, raised itchy bump that looks like an insect bite. This skin lesion is commonly located on the head, forearms or hands.
Within one to two days the skin lesion develops into a vesicle and becomes a painless ulcer, usually about 1cm to 3cm in diameter. After two to six days the black dying central area of the ulcer that’s characteristic of cutaneous anthrax is apparent.
If left untreated, cutaneous anthrax infection can spread and cause blood poisoning, which is fatal in up to 20 per cent of cases, but with effective antibiotic treatment few deaths occur.
2.Inhalational anthrax – when inhaled, the larger spores lodge in the windpipe or throat, while smaller ones lodge further down the respiratory tract in the lungs. The anthrax bacteria produce toxins that enter the bloodstream and cause haemorrhaging and tissue decay.
Initial symptoms of inhalational anthrax, which is rare, are mild and non-specific, similar to the symptoms of a flu-like infection. These include tiredness, weakness, fever, mild non-productive cough and chest pain.
If left untreated, over the next two to six days this mild phase becomes severe, causing breathing problems, sepsis and bleeding. By the time the infection has reached this stage it’s usually fatal.
3.Intestinal anthrax – a very rare form of food poisoning that may follow the ingestion of contaminated meat.
Initial symptoms are nausea, vomiting, loss of appetite and fever. As the infection becomes more severe, abdominal pain, vomiting of blood and severe diarrhoea occur.
Intestinal anthrax is often fatal.
Bacillus anthracis is a rod-shaped, Gram-positive, aerobic bacterium about 1 by 9 micrometers in length. It was shown to cause disease by Robert Koch in 1876. The bacterium normally rests in endospore form in the soil, and can survive for decades in this state. Herbivores are often infected whilst grazing or browsing, 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 endo-spores into the tissues, though this has not been proven. Once ingested or placed in an open cut, the bacterium begins multiplying inside the animal or human and typically kills the host within a few days or weeks. The endo-spores germinate at the site of entry into the tissues and then spread via the circulation to the lymphatics, where the bacteria multiply.
Occupational exposure to infected animals or their products (such as skin, wool, and meat) is the usual pathway of exposure for humans. Workers who are exposed to dead animals and animal products are at the highest risk, especially in countries where anthrax is more common. Anthrax in livestock grazing on open range where they mix with wild animals still occasionally occurs in the United States and elsewhere. Many workers who deal with wool and animal hides are routinely exposed to low levels of anthrax spores but most exposures are not sufficient to develop anthrax infections. It is presumed that the body’s natural defenses can destroy low levels of exposure. These people usually contract cutaneous anthrax if they catch anything. Throughout history, the most dangerous form of inhalational anthrax was called Woolsorters’ disease because it was an occupational hazard for people who sorted wool. Today this form of infection is extremely rare, as almost no infected animals remain. The last fatal case of natural inhalational anthrax in the United States occurred in California in 1976, when a home weaver died after working with infected wool imported from Pakistan. The autopsy was done at UCLA hospital. To minimize the chance of spreading the disease, the deceased was transported to UCLA in a sealed plastic body bag within a sealed metal container.
Respiratory infection in humans initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse. Historical mortality was 92%, but, when treated early (seen in the 2001 anthrax attacks), observed mortality was 45%. Distinguishing pulmonary anthrax from more common causes of respiratory illness is essential to avoiding delays in diagnosis and thereby improving outcomes. An algorithm for this purpose has been developed. Illness progressing to the fulminant phase has a 97% mortality regardless of treatment.
Gastrointestinal infection in humans is most often caused by eating anthrax-infected meat and is characterized by serious gastrointestinal difficulty, vomiting of blood, severe diarrhea, acute inflammation of the intestinal tract, and loss of appetite. Some lesions have been found in the intestines and in the mouth and throat. After the bacterium invades the bowel system, it spreads through the bloodstream throughout the body, making even more toxins on the way. Gastrointestinal infections can be treated but usually result in fatality rates of 25% to 60%, depending upon how soon treatment commences. This form of anthrax is the rarest form. In the United States, there is only one official case reported in 1942 by the CDC.
Anthrax skin lesionCutaneous (on the skin) anthrax infection in humans shows up as a boil-like skin lesion that eventually forms an ulcer with a black center (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. In general, cutaneous infections form within the site of spore penetration between 2 and 5 days after exposure. Unlike bruises or most other lesions, cutaneous anthrax infections normally do not cause pain.
Mode of infection :-
Inhalational anthrax, mediastinal wideningAnthrax 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. In general, an infected human will be quarantined. However, anthrax does not usually spread from an infected human to a noninfected human. But, 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. Inhalational anthrax, if left untreated until obvious symptoms occur, may be fatal.
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 as exemplified by the 2001 anthrax attacks.
Other than Gram Stain of specimens, there are no specific direct identification techniques for identification of Bacillus species in clinical material. These organisms are Gram-positive but with age can be Gram-variable to Gram-negative. A specific feature of Bacillus species that makes it unique from other aerobic microorganisms is its ability to produce spores. Although spores are not always evident on a Gram stain of this organism, the presence of spores confirms that the organism is of the genus Bacillus.
All Bacillus species grow well on 5% Sheep blood agar and other routine culture media. PLET (polymyxin-lysozyme-EDTA-thallous acetate) can be used to isolate B.anthracis from contaminated specimens, and bicarbonate agar is used as an identification method to induce capsule formation.
Bacillus sp. will usually grow within 24 hours of incubation at 35 degrees C, in ambient air (room temperature) or in 5% CO2. If bicarbonate agar is used for identification then the media must be incubated in 5% CO2.
B.anthracis appears as medium-large, gray, flat, irregular with swirling projections, often referred to as “medusa head” appearance, and is non-hemolytic on 5% sheep blood agar. It is non-motile, is susceptible to penicillin and produces a wide zone of lecithinase on egg yolk agar. Confirmatory testing to identify B.anthracis includes gamma bacteriophage testing, indirect hemagglutination and enzyme linked immunosorbent assay to detect antibodies.
Anthrax cannot be spread directly from person to person, but a patient’s clothing and body may be contaminated with anthrax spores. Effective decontamination of people can be accomplished by a thorough wash-down with antimicrobial effective soap and water. Waste water should be treated with bleach or other anti-microbial agent. Effective decontamination of articles can be accomplished by boiling contaminated articles in water for 30 minutes or longer. Chlorine bleach is ineffective in destroying spores and vegetative cells on surfaces, though formaldehyde is effective. Burning clothing is very effective in destroying spores. After decontamination, there is no need to immunize, treat or isolate contacts of persons ill with anthrax unless they were also exposed to the same source of infection. Early antibiotic treatment of anthrax is essential—delay significantly lessens chances for survival. Treatment for anthrax infection and other bacterial infections includes large doses of intravenous and oral antibiotics, such as fluoroquinolones, like ciprofloxacin (cipro), doxycycline, erythromycin, vancomycin or penicillin. In possible cases of inhalation anthrax, early antibiotic prophylaxis treatment is crucial to prevent possible death. In May 2009, Human Genome Sciences submitted a Biologic License Application (BLA, permission to market) for its new drug, raxibacumab (brand name ABthrax) intended for emergency treatment of inhaled anthrax. If death occurs from anthrax the body should be isolated to prevent possible spread of anthrax germs. Burial does not kill anthrax spores.
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 laboratory 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 ?m 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 laboratory and trained and knowledgeable 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.
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 preventive 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.
When treated with antibiotics, cutaneous anthrax is likely to get better. However, up to 20% of people who do not get treatment may die due to anthrax-related blood infections.
People with second-stage inhalation anthrax have a poor outlook, even with antibiotic therapy. Up to 90% of cases in the second stage are fatal.
Gastrointestinal anthrax infection can spread to the bloodstream, and may result in death.
•Spread of infection into the bloodstream
•Swelling of lymph nodes in the chest (mediastinal adenopathy)
•Fluid buildup in the chest (pleural effusion)
•Severe bleeding (hemorrhage)
There are two main ways to prevent anthrax.
For people who have been exposed to anthrax (but have no symptoms of the disease), doctors may prescribe preventive antibiotics, such as ciprofloxacin, penicillin, or doxycycline, depending on the strain of anthrax.
An anthrax vaccine is available to certain military personnel, but not to the general public. It is given in a series of six doses over 18 months. There is no known way to spread cutaneous anthrax from person to person. People who live with someone who has cutaneous anthrax do not need antibiotics unless they have also been exposed to the same source of anthrax.
An anthrax vaccine licensed by the U.S. Food and Drug Administration (FDA) and produced from one non-virulent strain of the anthrax bacterium, is manufactured by BioPort Corporation, subsidiary of Emergent BioSolutions. The trade name is BioThrax, although it is commonly called Anthrax Vaccine Adsorbed (AVA). It was formerly administered in a six-dose primary series at 0, 2, 4 weeks and 6, 12, 18 months, with annual boosters to maintain immunity. On December 11, 2008, the FDA approved the removal of the 2-week dose, resulting in the currently recommended five-dose series.
Unlike NATO countries, 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.
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.
- Anthrax – All Information (umm.edu)
- Cutaneous anthrax – All Information (umm.edu)
- Threat of Bioterrorism in Today’s World (socyberty.com)
- Inhalation anthrax – All Information (umm.edu)
- Anthrax (socyberty.com)
- ‘Bacillus anthracis and Anthrax’: The past, present and future of anthrax research (physorg.com)
- New Sensor Detects Anthrax Spores Better Than Current Methods (medgadget.com)
- How anthrax bacteria impair immune response (sciencedaily.com)
- Anthrax Linked to Hippies [Dance Of Death] (gawker.com)
- Scientists show how anthrax bacteria impair immune response (physorg.com)
- NIH scientists show how anthrax bacteria impair immune response (eurekalert.org)