Anthrax

Anthrax is a sometimes deadly infection caused by the bacterium Bacillus anthracis. This bacterium is housed in a spore — a cell that's dormant, but may become active in the right conditions. Anthrax usually affects livestock, but it also infects humans. Humans can become infected when handling products of infected animals, or if exposed to anthrax that's used as a biological weapon — such as when anthrax spores were deliberately spread in powder-containing envelopes through the U.S. postal system in 2001.

Anthrax infection can occur through a wound in the skin, by ingesting it or by inhaling it. Symptoms depend on which way you're infected and range from a sore on the skin to nausea and vomiting to shock. Early treatment with antibiotics can cure most anthrax infections spread through the skin and many of those spread by ingestion. Inhaled anthrax is the most difficult to treat and is often fatal.

There are three major anthrax syndromes: cutaneous, inhalational, and gastrointestinal anthrax. Cutaneous anthrax, which makes up 95% of naturally occurring infections, begins as a painless, pruritic papule that develops into a vesicle within 2 days.

As the vesicle enlarges, striking edema may form around it, and there is regional lymphadenopathy. After the vesicle ruptures, the remaining ulcer becomes covered with a characteristic black eschar, which dries and falls off as the patient recovers. Bacteremia is rare with cutaneous anthrax.

Inhalational anthrax occurs when spores are inhaled. The organism grows and is carried to lymph nodes by phagocytes where the spores germinate, and the release of toxins causes hemorrhagic mediastinitis.

After a prodromal illness of 1 to 6 days characterized by fever, cough, and chest or abdominal pain, there is abrupt onset of increased fever, hypoxia, and sweating. Frequently, anthrax meningitis develops due to bacteremia. Inhalational anthrax rapidly leads to shock and frequently death within 1 to 2 days.

Gastrointestinal anthrax is an uncommon form of this infection that is usually contracted by eating undercooked meat contaminated with B. anthracis. Initially, the patient has nausea, abdominal pain, and vomiting. Severe, bloody diarrhea rapidly develops, and mortality is over 50%.

Prevention

In addition to treating anthrax, antibiotics are recommended to prevent infection in anyone exposed to anthrax. Ciprofloxacin and doxycycline are FDA-approved for post-exposure prevention of anthrax in adults and children. Levofloxacin is approved for adults who've been exposed.

Anthrax vaccine
The FDA approved a human vaccine in 1970, which has mostly been used by military personnel. Vaccination consists of three shots given two weeks apart followed by three additional shots given at six, 12, and 18 months. Annual booster shots are recommended to maintain immunity.

The human anthrax vaccine doesn't contain live anthrax bacteria, so it can't cause the infection. Side effects may include soreness at the injection site, a flu-like reaction and possibly more-serious allergic reactions. The anthrax vaccine isn't recommended for children, pregnant women or older adults. It's an effective, but not a 100 percent protective vaccine.

The vaccine isn't available to the public. Instead, the vaccine is reserved for:

• Active-duty U.S. military personnel who are deployed to areas with high risk of exposure to anthrax
• People who work with anthrax in a laboratory setting
• People who handle potentially infected animal products in areas of the world where anthrax is a threat to livestock
• People who work with imported animal hides or furs from areas with a high incidence of anthrax

Scientists are working to produce a new anthrax vaccine. The new vaccine may require fewer doses and be available in large quantities.

Avoiding contact with infected animals
In countries where anthrax is common and vaccination levels of animal herds are low, it's wise to avoid contact with livestock and animal products and to avoid eating meat that hasn't been properly slaughtered and cooked.

Other preventive measures include carefully handling dead animals suspected of having the disease and providing good protection when processing hides, fur, wool or hair.

Risks

Anthrax isn't contagious. People who get inhalation anthrax don't exhale spores. There are no reports of the disease spreading from one person to another.

To contract anthrax, you must come in direct contact with anthrax spores. However, you can be exposed to anthrax spores and not become infected.

Treatment

Treatment for all three forms of anthrax depends on oral or intravenous (IV) antibiotics. Treatment is most effective when started as early as possible.

Some strains of anthrax may be more responsive to one type of antibiotic than to another. Ciprofloxacin (Cipro), doxycycline and penicillin are approved by the Food and Drug Administration (FDA) for treatment of anthrax in adults and children. However, your doctor may prescribe other antibiotics or a combination of antibiotics.

These medications work by killing the anthrax bacteria. However, antibiotics may fail in inhalation anthrax once symptoms become severe because the bacteria may already have released large amounts of toxin that aren't affected by antibiotics. Scientists are working to develop an anthrax antitoxin that could neutralize the toxin produced by anthrax bacteria.

If you've been exposed to anthrax, your doctor will likely prescribe a long course — 60 days or more — of antibiotics. If you have inhalation anthrax, you'll likely be hospitalized and treated with intravenous antibiotics.

Anthrax isn't spread person to person. So a person with anthrax doesn't have to be quarantined or isolated. If you were in contact with someone with anthrax, you'll need to be treated only if you were exposed to a source of anthrax infection.