Anthrax

Anthrax is a serious infectious disease caused by specific bacteria. These bacteria are known as Bacillus anthracis or Bacillus cereus biovar anthracis.

The name "anthrax" comes from the Greek word for coal. This refers to the black skin lesions that the infection often creates. The disease is caused by rod-shaped, Gram-positive bacteria. These bacteria are unique because they can form hardy spores. Spores are protective shells that allow the bacteria to survive in soil for many decades. While the disease is rare in many places, it remains a significant concern for global health.

The mechanism of infection begins when spores enter a host. These spores can enter through the skin, the lungs, or the digestive tract. Once inside the body, the spores undergo germination. This means they transform from hard shells into active, multiplying bacteria called bacilli. These bacilli then spread through the lymphatic system and into the bloodstream. As they multiply, the bacteria produce three specific proteins: lethal factor, edema factor, and protective antigen. While these proteins are not toxic alone, they combine to form lethal toxin and edema toxin. These toxins are the primary agents that cause tissue destruction and death in the host.

There are three distinct clinical forms of anthrax based on how the bacteria enter the body. Cutaneous anthrax is the most common form, representing more than 95% of all cases.

It occurs when spores enter through a cut or break in the skin. This form usually results in a painless ulcer with a black center called an eschar.

The second form is inhalation anthrax, which occurs when spores are breathed into the lungs. This form is very dangerous and can lead to respiratory failure. The third form is gastrointestinal anthrax. This happens when a person eats meat contaminated with the bacteria. It causes abdominal pain, nausea, and diarrhea that may contain blood.

History shows that humans have struggled with anthrax for centuries. Before the 20th century, the disease killed hundreds of thousands of people and animals every year. Early clinical descriptions of skin anthrax were provided by Maret in 1752 and Fournier in 1769. However, a major breakthrough occurred in 1876. The German scientist Robert Koch identified Bacillus anthracis as the specific cause of the disease. He proved this by isolating the bacteria from an infected cow and using it to infect a mouse.

This discovery helped scientists understand how to fight the infection.

The significance of anthrax is seen in its varying mortality rates. While skin infections are common, they have a 23.7% death rate if left untreated.

Gastrointestinal infections are much more severe, with death rates between 25% and 75%. Inhalation anthrax is the most lethal, with a mortality rate of 50% to 80%, even when medical treatment is provided.

Globally, at least 2,000 cases occur every year. Most cases are found in Africa and central or southern Asia. In the United States, the disease is much rarer, with about two cases occurring annually.

Anthrax has also played a role in history through warfare. Because the spores are so tough, several countries and groups developed anthrax as a biological weapon. It has been used in biowarfare and bioterrorism since 1916. During World War II, the Empire of Japan's Unit 731 used it against China. Other nations, including the Soviet Union, the United States, and Iraq, also developed weaponized strains. In 1975, the Biological Weapons Convention was created to prohibit the development and stockpiling of such weapons. Despite this, it was used in bioterrorism during the 2001 attacks in the United States.

Today, we manage anthrax through vaccination and medical treatment. Doctors use antibiotics like ciprofloxacin, levofloxacin, or doxycycline to fight the bacteria.

If the infection is widespread, doctors may also use an antitoxin. Vaccines are recommended for people at high risk, such as military personnel or those working with animals. It is also important to vaccinate livestock in areas where the disease has appeared before. This helps prevent the bacteria from moving from animals to humans through contact or food.