(Redirected from Anthrax
- Alternate meanings in Anthrax (disambiguation)
Anthrax is an acute infectious disease caused by the bacteria Bacillus anthracis and is highly lethal in its most virulent form. Anthrax most commonly occurs in wild and domestic herbivores, but it can also occur in humans when they are exposed to infected animals, tissue from infected animals, or high concentrations of anthrax spores. Still there are no cases of people who got sick through contact with a diseased person. Anthrax means "coal" in Greek, and is used because victims develop black skin lesions.
Anthrax infection is rare but not remarkably so in herbivores such as cattle, sheep, goats, camels, and antelopes. Anthrax can be found globally. It is more common in developing countries or countries without veterinary public health programs. Certain regions of the world (South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East) report more anthrax in animals than others.
When anthrax affects humans, it is usually due to an occupational exposure to infected animals or their products (such as skin and meat). Workers who are exposed to dead animals and animal products from countries where anthrax is more common may become infected with B. anthracis, and anthrax in wild livestock has occurred in the United States. Although many such workers are routinely exposed to significant levels of anthrax spores, most are not sufficiently exposed to develop symptoms.
Means of infection
Anthrax can enter the human body through the intestines, lungs (inhalation), or skin (cutaneous). Anthrax is non-contagious, and is unlikely to spread from person to person.
Pulmonary (pneumonic, respiratory, inhalation) anthrax infection initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory problems. If not treated soon after exposure, before symptoms appear, inhalation infection is the most deadly, with a nearly 100% mortality rate. A lethal case of anthrax is reported to result from inhaling 10,000-20,000 spores. This form of the disease has also been known as Woolsorters' disease. Other routes have included the slicing up of animal horns for the manufacture of buttons, and handling bristles used for the manufacturing of brushes.
Gastrointestinal (gastroenteric) anthrax infection often presents with serious gastrointestinal difficulty, vomiting of blood, and severe diarrhea. Untreated, intestinal infection results in a 25-60% death rate.
Cutaneous (skin) anthrax infection presents with a large, painless necrotic ulcer (beginning as an irritating and itchy skin lesion or blister which is dark in color, usually concentrated as a black dot, somewhat resembling bread mold) at the site of infection, forming about a week or two after exposure. Unlike bruises or most other lesions, cutaneous anthrax does not cause pain. Cutaneous infection is the least deadly; without treatment, approximately 20% of all skin infection cases are fatal. Treated cutaneous anthrax is rarely fatal.
Treatment and prevention
Treatment for anthrax infections includes large doses of intravenous and oral antibiotics, such as penicillin, ciprofloxacin, doxycycline, erythromycin, and vancomycin. For inhalation cases, antibiotic treatment is not very effective unless initiated within a day of exposure, before any symptoms appear. Antibiotic prophylaxis is crucial in cases of pulmonary anthrax to save lives. Some antibiotic-resistant strains are known.
A vaccine, produced from one component of the toxin of a non-virulent strand, is also available. The vaccine must be given at least four weeks before exposure to anthrax; annual booster injections are required to maintain immunity.
The spores can be trapped with a simple HEPA or P100 filter. Anthrax as an airborne threat can be prevented with a full-face mask. Unbroken skin is decontaminated simply with soap and water.
Description of the bacterium
Bacillus anthracis is a rod-shaped Gram-positive bacterium of size about 1 by 6 micrometres. It was the first bacterium ever to be shown to cause disease, by Robert Koch in 1877. The bacteria normally rest in spore form in the soil, and can survive for decades in this state. Once taken in by an herbivore, the bacteria start multiplying inside the animal and eventually kill it, then continue to reproduce in the carcass. Once they run out of nutrients there, they revert back to the dormant spore state.
The infection of herbivores (and humans) proceeds as follows: the spore is located and engulfed by scavenger cells of the immune system specialized to deal with invaders. Inside the scavenger cell, the spore turns into a bacillus, multiplies, and eventually bursts the cell, releasing bacilli into the bloodstream. There they release a protein toxin which has macrophages as its principal target. The toxin has two components: edema factor and lethal factor. Edema factor inactivates macrophages such that they cannot phagocytose bacteria. Historically, it was believed that lethal factor caused the macrophage to make TNF-alpha and interleukin-1-beta , both normal components of the immune system used to induce an inflammatory reaction, and ultimately leads to septic shock and death.
However, recent evidence indicates that anthrax also targets endothelial cells, causing vascular leakage (similar to hemorrhagic bleeding), and ultimately hypovalemic shock, not spetic shock.
The virulence of a strain of anthrax is dependent on multiple factors, primarily which include its poly-D-glutamic acid capsule which protects the bacterium from phagocytocis by host macrophages, and its toxins, Edema Toxin and Lethal Toxin
Spores of this bacteria can be used in biological warfare. US Army personnel are now routinely vaccinated prior to active service in places where biological attacks are considered a threat. The anthrax vaccine , produced by BioPort Corporation , contains no live bacteria, and is approximately 93% effective in preventing infection. Anthrax vaccination is one of many factors suspected of causing Gulf War syndrome.
British tests in 1942 contaminated Gruinard Island in Scotland with anthrax spores, and rendered it unusable for the following 48 years. An accidental release of anthrax in a research lab at Fort Detrick in Frederick, Maryland in the United States led to the permanent sealing of a building with plastics and glues.
The simplest method of obtaining an anthrax sample would be to get it from an animal killed by anthrax; this source is rare in developed countries but common in underdeveloped countries.
Cultivating anthrax spores can take minimal equipment and about a first-year collegiate microbiological education. However, to make an aerosol form of anthrax suitable for biological warfare requires extensive training and highly developed equipment.
In May 1881, Louis Pasteur performed a public experiment to demonstrate his concept of vaccination. He prepared two lots of 25 sheep. The sheep of one lot were all injected with a self-prepared antianthrax vaccine twice, with an interval of 15 days. The sheep of the other lot were left alone. 30 days after the first injection, both lots were injected with a culture of living anthrax bacteria. Each one of the sheep in the non-vaccinated pen died shortly after, whilst all of the sheep in the vaccinated lot survived.
Last updated: 10-24-2005 03:54:43