Anthrax

I

Introduction

Anthrax, disease of warm-blooded animals, including humans, caused by the bacterium Bacillus anthracis. Anthrax most commonly occurs in cattle and other plant-eating mammals, but it can also affect humans who come in contact with infected animals. The disease is not considered contagious, however, and person-to-person spread of the disease is highly unlikely. Vaccines can protect against anthrax, and antibiotics can treat the disease in its early stages.

Anthrax is a spore-forming bacterium. The spores have protective coats and can withstand extreme heat, drought, and other harsh conditions. They can live for centuries in soil. Anthrax spores also have the potential for use in biological warfare because of their ability to survive and because they spread easily in air and can be inhaled. Once the spores are inside the lungs, the bacteria develop and begin to multiply (see Chemical and Biological Warfare).

II

Anthrax in Animals

Animals can acquire anthrax from drinking water that has drained from soil contaminated with the bacteria, from eating infected carcasses and feedstuffs, and from the bites of bloodsucking insects. The disease, sometimes manifested by staggering, bloody discharge, convulsions, and suffocation, may be fatal almost immediately. Death is caused by toxemia (poisoning). The disease can be prevented by immunization, and in animals that have not been vaccinated, it can be treated with antibiotics. Anthrax is more common in agricultural regions of Africa, Asia, the Middle East, and Central and South America than in the United States, Canada, and western Europe.

III

Anthrax in Humans

In humans, the disease can appear in three forms: cutaneous, inhalation, and gastrointestinal. The cutaneous, or external form, primarily involves the skin and is contracted mainly by those who handle contaminated hides, wool, or carcasses. The bacteria enter through a cut or other opening in the skin, and a dark, itchy bump that resembles an insect bite appears. The bump then develops into an open sore with a black area in the center. The cutaneous form of anthrax can be treated with antimicrobial drugs. Death results in about 20 percent of untreated cases. Veterinarians, mill workers, laboratory researchers, and other people at risk of exposure to anthrax are generally vaccinated against the disease.

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Humans contract internal forms of anthrax by inhaling anthrax spores or by eating contaminated meat. People who work with animal hair and wool are most likely to inhale the spores, especially in areas where anthrax occurs in animals. Symptoms of inhaled anthrax initially resemble those of a cold or the flu—general aches and pains, fever, fatigue, cough, and mild chest pain. Inhaled anthrax is fatal unless the infected person has been vaccinated or antibiotics are administered soon after inhalation. Ciprofloxacin, penicillin, and other antibiotics are effective treatments, except in rapidly progressing cases.

The gastrointestinal form of anthrax results from eating contaminated meat. Its symptoms are nausea, vomiting, abdominal pain, and severe diarrhea. The disease can be fatal in 20 percent to 60 percent of cases.

IV

History

One of the oldest known diseases, anthrax was once epidemic and still appears in many areas of the world. It was the first infectious disease for which scientists isolated the causative organism. French parasitologist C. J. Davaine first saw the rod-shaped organisms under a microscope in the blood of infected sheep in 1850. German bacteriologist Robert Koch demonstrated in 1876 that the disease occurred when spores of Bacillus anthracis were injected into mice. French biologist Louis Pasteur also demonstrated that the bacteria caused the disease and in 1881 developed an effective vaccine against anthrax in animals.

The worst outbreak of anthrax occurred in 1979, when a biological weapons plant in Sverdlovsk, Russia (present-day Yekaterinburg), accidentally released airborne anthrax spores, killing 66 people. In 1998 American scientists at Los Alamos National Laboratory used newly developed techniques to determine that the spores released in the accident contained at least four different strains of anthrax. This raised concerns that Russia, and possibly other countries, were working on a vaccine-resistant form of anthrax for use as a biological weapon.

During the 1991 Persian Gulf War, about 150,000 members of the armed services were vaccinated against anthrax because of fears that Iraq had been developing biological weapons. The United States Department of Defense later approved a program to vaccinate members of the armed forces stationed in the Middle East. Cases of inhaled anthrax were reported in several states in the United States in 2001. The U.S. Federal Bureau of Investigation quickly became involved in investigating the cause of these cases because they followed closely after terrorist attacks on the World Trade Center in New York City and the Pentagon in Arlington, Virginia.

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