Above: Anthrax lesion on the neck (CDC, Wikimedia Commons)

I first heard about anthrax in a news story about a dangerous white powder being sent through the mail. To me, it sounded like a deadly toxic chemical. But anthrax is not a chemical substance. Anthrax is alive!

What is anthrax?

Anthrax is a disease caused by a bacterium—a tiny living thing sometimes called a germ—named Bacillus anthracis. Famous microbiologist Robert Koch was the first person to link the disease with this tiny rod-shaped organism. Bacillus anthracis lives naturally in the soil. It is commonly found on and around grazing animals like cows and sheep.

Bacillus anthracis is special because it is one of only a few bacteria that can form spores. Spores are a dormant form of a bacterium that can survive without food or water. They can even survive being frozen or boiled! In spore form, anthrax can survive for decades, waiting for the right conditions to regenerate as a pathogenic (disease-causing) bacterium.

Did you know? The word anthrax is derived from the Greek word anthrakos, which means coal, because anthrax infections cause coal-black lesions in the skin.

How is anthrax spread?

Because Bacillus anthracis is naturally found in soil, grazing mammals like cows and sheep are much more likely to get infected than people. Anthrax infection usually begins when animals eat or breathe in spores while grazing, or when carnivores eat infected animals.

The most common way for humans to become infected is by working with animal skins or sheep’s wool containing spores. Anthrax infections are caused only by exposure to spores. The disease is not spread from person to person.

Did you know? Anthrax used to be called “woolsorters’ disease” because people who worked with wool were more likely to become infected.

What are the symptoms of an anthrax infection?

There are three main kinds of anthrax infection: in the skin, in the digestive tract, and in the lungs. The type of infection depends on how anthrax enters the body. For example, it can enter through cuts or minor abrasions in the skin. This kind of infection produces small red bumps that develop into large black skin sores, usually on the head, neck, forearms, and hands. When the disease is treated, death from anthrax skin infections is rare. Even without treatment, 80 per cent of people infected survive.

Bacillus anthracis, the bacterium that causes anthrax (CDC, Wikimedia Commons)

Anthrax infections of the digestive tract are rare, but they can happen if you eat meat contaminated with spores. There’s no conclusive evidence that cooking the meat will help, so it’s best to avoid possibly contaminated food altogether! Symptoms of anthrax digestive tract infection include fever, nausea, bloody vomiting, abdominal swelling, pain, and bloody diarrhea. With treatment, 60 per cent of those infected in this way survive the disease.

Anthrax infection in the lungs, caused by breathing in spores, is the least common kind of infection. But it is also the most deadly. After spores are inhaled, they become trapped in tiny air sacks in the lungs called alveoli. The immune system then carries the spores to lymph nodes in the chest cavity. There, the spores germinate into active pathogenic bacteria that multiply and infect the bloodstream. In the blood, anthrax travels throughout the body and produces very lethal toxins.

Anthrax spores (CDC, Wikimedia Commons)

This whole process takes time. There is a lag phase between exposure to anthrax and the onset of symptoms, which include fever, confusion and dizziness, sweats, nausea and vomiting, and coughing. Without treatment, 85 to 90 per cent of whose lungs are infected with anthrax eventually die from the disease. With aggressive treatment, the death rate drops to 45 per cent.

How is anthrax treated?

People with anthrax infections can be treated with antibiotics. Anthrax vaccines also exist. But because most people are at very low risk of contracting the disease, these vaccines aren’t normally given to the general public. They are mainly given to military personnel (who might encounter anthrax as a biological weapon) and to lab personnel who work with anthrax spores.

Did you know? Louis Pasteur invented the anthrax vaccine in 1881. But the US Food and Drug Administration didn’t approve it until 1970!

Researchers study anthrax to understand what makes it so good at infecting mammals, and what can be done about treating anthrax infections in the future. Some scientists also study how anthrax can be used as a weapon. This research helps organizations and countries protect themselves against this kind of attack.

Learn More!

General information on anthrax:

Anthrax (2015)
US Centers for Disease Control and Prevention

Anthrax - Effects of Heat, Cleaning Compounds and Chemical Disinfectants (2016)
Minnesota Department of Agriculture

B. Rauner, Illinois Department of Public Health

News article on anthrax attacks:

Examples of scientific articles on anthrax:

Anthrax toxin complexes: heptameric protective antigen can bind lethal factor and edema factor simultaneously (2004)
R. A. Pimental, K. A. Christensen, B. A. Krantz, R. J. Collier, Biochemical and Biophysical Research 322
Link to summary. Registration or subscription required to view full text.

Bacillus anthracis (2003)
R. C. Spencer, Journal of Clinical Pathology 56

Technology Challenges in Responding to Biological or Chemical Attacks in the Civilian Sector (2003)
J.P. Fitch, E. Raber, D.R. Imbro, Science 302
Link to summary. Registration or subscription required to view full text.

Mira Okshevsky

Mira has a Master of Science in Marine Microbiology and a PhD in Nanoscience. She is currently a postdoctoral research fellow at McGill University, where she studies how bacteria stick together is communities called biofilms. In her free time, Mira enjoys exploring the coves and beaches of her home province of Newfoundland.

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