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Anthrax (Bacillus anthracis)
What is anthrax?
Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. Although anthrax can be found globally, it is most common in the animals of agricultural regions where there are less standardized and effective public health programs. These include South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East.
Who can get it?
When anthrax affects humans, it is usually due to an occupational exposure to infected animals or their products. Workers who are exposed to dead animals and animal products (industrial anthrax) from other countries where anthrax is more common may become infected with B. anthracis.
Anthrax in animals rarely occurs in the United States. Of those cases in the U.S., most have been animal infection reports received from Texas, Louisiana, Mississippi, Oklahoma, and South Dakota.
How is anthrax transmitted?
Anthrax infection can occur in three forms:
- cutaneous (skin)
- inhalation
- gastrointestinal
B. anthracis spores can live in the soil for many years and humans can become infected with anthrax by handling animal products from infected animals or by inhaling anthrax spores from contaminated animal products. Anthrax can also be spread by eating undercooked meat from infected animals. There is no human to human transmission from any of the forms. Animals infected with B. anthracis are rare in the U.S.
Symptoms
Symptoms vary depending on how the disease was contracted, but usually occur within seven days.
Cutaneous: Most anthrax infections occur when the bacterium enters a cut or abrasion on the skin, such as when handling contaminated wool, hides, leather or hair products (especially goat hair) of infected animals. Skin infection begins as a raised itchy bump that resembles an insect bite but within 1-2 days develops into a vesicle and then a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20% of untreated cases of cutaneous anthrax will result in death. Deaths are rare with appropriate antimicrobial therapy.
Inhalation: Initial symptoms may resemble a common cold. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax usually results in death in 1-2 days after onset of the acute symptoms.
Intestinal: The intestinal disease form of anthrax may follow the consumption of contaminated meat and is characterized by an acute inflammation of the intestinal tract. Initial signs of nausea, loss of appetite, vomiting, and fever are followed by abdominal pain, vomiting of blood, and severe diarrhea. Intestinal anthrax results in death in 25% to 60% of cases.
Precautions and Decontamination
Standard precautions and standard hospital infection control are recommended to prevent additional exposure to anthrax spores. All three forms of anthrax are not spread from person to person.
How is anthrax diagnosed?
Anthrax is diagnosed by isolating B. anthracis from the blood, skin lesions, or respiratory secretions, or by measuring specific antibodies in the blood of suspected cases.
What is the treatment for anthrax?
Doctors can prescribe effective antibiotics. Penicillin is usually preferred, but erythromycin, tetracycline, or chloramphenicol can also be used. To be effective, treatment should be initiated early. If left untreated, the disease can be fatal.
Is there an anthrax vaccine for humans?
The anthrax vaccine for humans licensed for use in the United States is a cell-free filtrate vaccine, which means it uses dead bacteria as opposed to live bacteria. Anthrax vaccine is indicated for individuals who come in contact in the workplace with imported animal hides, furs, bonemeal, wool, animal hair (especially goat hair), and bristles; and for individuals engaged in diagnostic or investigational activities which may bring them into contact with anthrax spores. The vaccine is reported to be 93% effective in protecting against cutaneous anthrax.
Who should be vaccinated against anthrax?
Because anthrax is considered to be a potential agent for use in biologic warfare, the Department of Defense has a systematic vaccination of U.S. military personnel.
Among civilians, the Advisory Committee for Immunization Practices (ACIP), recommends anthrax vaccine be given to individuals who come in contact in the workplace with imported animal hides, furs, bonemeal, wool, animal hair (especially goat hair), and bristles; and for individuals engaged in diagnostic or investigational activities which may bring them into contact with anthrax spores. The vaccine should only be administered to healthy men and women from 18 to 65 years of age since investigations to date have been conducted exclusively in that population. Because it is not known whether the anthrax vaccine can cause fetal harm, pregnant women should not be vaccinated.
What is the protocol for anthrax vaccination?
The immunization consists of three subcutaneous injections given two weeks apart followed by three additional subcutaneous injections given at 6, 12, and 18 months. Annual booster injections of the vaccine are required to maintain immunity.
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