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What is Anthrax?

Anthrax is caused by exposure to the spores of the bacteria Bacillus anthracis that become entrenched in the host body and produce lethal poisons. It is primarily a disease of grazing animals such as cattle, sheep, goats, and horses. Pigs are more resistant, as are dogs and cats. Birds usually are naturally resistant to anthrax. Buzzards and vultures are naturally resistant to anthrax but may transmit the spores on their talons and beaks.

The bacteria that cause anthrax are able to go into a dormant phase, in which they form spores. Spores can exist in the environment for decades. Under the right conditions, the dormant spores can germinate and multiply.

The U.S. Centers for Disease Control and Prevention classifies anthrax as a Category A agent with serious bioterrorism potential. If terrorists were to use the anthrax spores, they would most likely want to disperse it into the air for mass effect. As seen in October 2001, terrorists could also deliver anthrax by other means, such as placing spores in letters or packages to be opened, inhaled, and handled by unsuspecting recipients.

People of any age may be affected. Most cases are mild and go away with treatment. Anthrax, however, can be lethal. There are several ways anthrax can cause illness. These are the three main ways anthrax affects humans:

  • Cutaneous (skin) anthrax causes a characteristic sore on the skin and results from exposure to the spores after handling sick animals or contaminated animal wool, hair, hides, or bone meal products. It is an occupational hazard for veterinarians, farmers, and people who handle animal products. Where the bacteria are common, human infection remains uncommon. Humans are relatively resistant, but the spores may gain access through even tiny breaks in the skin. Cutaneous anthrax is easy to cure if it is treated early with appropriate antibiotics.
  • Inhalational anthrax results from breathing anthrax spores into the lungs. People who handle animal hides infested with spores may develop inhalational anthrax, known as woolsorter's disease. Earliest symptoms resemble those of a respiratory infection such as mild fever and sore throat. Once established, the organisms multiply and may spread their toxins to the bloodstream and many other organs. Infection may spread from the liver, spleen, and kidneys back into the bloodstream, thus causing an overwhelming infection and death. This type of infection (known as septicemic anthrax) most commonly follows inhalational anthrax.
  • Gastrointestinal anthrax results from eating meat products that contain anthrax. Gastrointestinal anthrax is difficult to diagnose. It can produce sores in the mouth and throat. A person who has eaten contaminated products may feel throat pain or have difficulty swallowing. Other symptoms can include nausea, loss of appetite, bloody diarrhea, and fever. This form of anthrax has a very high death rate.

Anthrax is described in the early literature of the Greeks, Romans, and Hindus. The fifth plague, described in the book of Genesis, may be among the earliest descriptions of anthrax.

What Causes Anthrax?

Anthrax is caused by the bacteria B. anthracis. These are rod-shaped bacteria that can change from "normal" bacteria into spores (or single-celled seeds that can reproduce the bacteria).

Microscopic picture of anthrax. Image courtesy of AVIP agency, Office of the Army Surgeon General, U.S.
Microscopic picture of anthrax. Image courtesy of AVIP agency, Office of the Army Surgeon General, U.S.

Last Reviewed 11/20/2017

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Anthrax and Other Potential Biological Weapons

Biological weapons include any organism (such as bacteria, viruses, or fungi) or toxin found in nature that can be used to kill or injure people. Types of biological agents include:

  • anthrax,
  • plague,
  • cholera,
  • tularemia,
  • brucellosis,
  • Q fever,
  • smallpox,
  • monkeypox,
  • arboviral encephalitides,
  • viral hemorrhagic fevers (like Marburg and Ebola virus),
  • staphylococcoal enterotoxin B,
  • ricin,
  • botulinum toxin,
  • mycotoxins,
  • glanders,
  • typhus, and
  • anti-crop biological agents.

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Anthrax was described in the early literature of the Greeks, Romans, and Hindus.

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