Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. It is usually a disease of wild and domestic animals, including cattle, sheep, and goats. However, human infection, while rare, does occur. Human infection usually results from contact with infected animals or their products. However, anthrax has become of interest because of the possibility that a nation or terrorist group might attempt to use it as a weapon of warfare or terrorism. There are three types of anthrax: cutaneous (through the skin), gastrointestinal, and inhalational.
Symptoms usually appear within seven days of exposure, although in some cases the incubation period has been significantly longer than this.
Cutaneous anthrax begins with a raised area on the skin that itches (pruritic papule). Usually, this occurs on exposed areas, most often on the arms and hands followed by the face and neck. It resembles an insect bite. This area becomes larger and, within one or two days, develops into an ulcer, surrounded by small blisters containing fluid. A characteristic black, crusty spot develops on the affected skin area later and, after a few weeks, begins to loosen and ultimately falls off, leaving a scar. The course of these events is so characteristic that the diagnosis is not often missed by physicians familiar with the disease, even though it is rare.
Gastrointestinal anthrax can present as either intestinal or throat and pharynx (oropharyngeal) disease. The symptoms for intestinal infection include fever, nausea, abdominal pain, vomiting, and anorexia. As the disease progresses, there may also be vomiting of blood, bloody diarrhea, toxemia, shock and a bluish tinge to the skin and mucous membranes (cyanosis). Symptoms for oropharyngeal illness may include fever, sore throat, difficulty in swallowing (dysphagia), collection of fluid (edema) in the tissues of the throat, and swelling of the lymph nodes.
Inhalational anthrax typically begins with one to three days of fatigue, low-grade fever, and dry cough. These symptoms, typical of a mild upper respiratory tract infection, may be accompanied by an ache of feeling of heaviness in the chest and the area just below the chest. Following this relatively mild onset, there will be a period of more intense illness characterized by high fever, elevation of the pulse and respiratory rate, heavy perspiration (profuse diaphoresis), and difficult or labored breathing (dyspnea).
Anthrax is primarily a disease of animals, specifically herbivores such as cattle, goats, and sheep. They contract the disease after coming into contact with B. anthracis spores, which are present in the soil around the world. The rare cases when humans are infected typically occur when people come into contact through their occupations with infected animals or when people eat undercooked meat or other products from infected animals. Its occurrence is most likely in developing countries, although animal products imported from those countries may pose a risk.
Human infection sometimes results from contact in an industrial setting. In the United States, there have been occasional episodes in industrial settings resulting from, for instance, processing contaminated animal fibers such as goat hair.
Infection may also occur among those who work in agricultural jobs. These infections typically occur among people who have had direct contact with animals sick with anthrax or those who have died with the disease.
Cutaneous anthrax occurs after spores come into contact with skin that is broken as a result of a wound or lesion. Gastrointestinal anthrax occurs as a result of eating poorly cooked or raw meat from animals that are infected with the disease. Inhalational anthrax occurs as a result of breathing in (inhaling) the spores.
There have been no confirmed cases of person-to-person transmission of cutaneous, gastrointestinal, or inhalational anthrax. For this reason, it is believed unnecessary to immunize or treat the family members, friends, or co-workers of those who become ill with anthrax unless it is possible that they have been exposed to the same original source of the infection.
Anthrax is most common in developing countries. It can be found globally, although the regions of the world with the greatest incidence of agricultural anthrax are South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East.
The largest reported agricultural outbreak occurred in Zimbabwe, with more than 10,000 cases reported between 1979 and 1985.
In 1979, 79 cases of inhalational anthrax were reported in the area of Sverdlovsk, Russia. Sixty-eight of those cases ultimately were fatal. It is believed that this outbreak was caused by the accidental release of aerosolized anthrax spores from a military laboratory.
Cutaneous anthrax may be diagnosed by the characteristic signs, such as the raised area on the skin and detection of the presence of the anthrax bacilli in the area of the lesion. A history of exposure to livestock or other possible animal sources also is important. Gastrointestinal anthrax is more difficult to diagnose. In the first, mild phase of inhalational anthrax, symptoms resemble a common cold or upper respiratory infection. With the sudden onset of the more severe symptoms of the second phase, radiographic examination of the chest may show characteristic changes.
Antibiotics, such as penicillin, are used to treat all forms of anthrax. However, to be effective, treatment must be started as soon as possible after exposure. Once symptoms begin, there is a significant decline in the likelihood that treatment will be successful.
An antibiotic known as ciprofloxacin (Cipro) was approved in Augustl 2000 by the U.S. Food and Drug Administration for treating people who have been exposed to inhalational anthrax. However, Cipro, too, needs to be taken soon after exposure, and before symptoms begin, to be effective. Taking this or other antibiotics before exposure, as a preventive measure, is not recommended and may cause harm. Before being approved for this purpose, Cipro had been used for several years to treat a variety of infections, including cutaneous anthrax.
Once symptoms have begun, antibiotic therapy is rarely successful against the gastrointestinal or inhalational forms of the disease.
There is a vaccine for anthrax, but it is not generally available at the present time. It is produced by the BioPort Corporation in Michigan, and contains no dead or live bacteria. It is believed to be 93 percent effective in preventing infection, and it has been used in recent years to protect military personnel and people whose jobs put them at high risk of exposure to infected animals.
However, production capacity of the company that makes the vaccine is modest, and the vaccine is not currently available in quantities that would allow its use among civilians.
For more information about antibiotic treatments used for anthrax, you may access the following government web sites:
Cipro (Ciprofloxacin): Use by Pregnant and Lactating Women (10/31/2001); http://www.fda.gov/cder/drug/infopage/cipro/cipropreg.htm
Doxycycline: Questions and Answers for Consumers (10/31/2001); http://www.fda.gov/cder/drug/infopage/penG_doxy/QA_doxy.htm
Doxycycline (Vibramycin, Monodox, Doryx, Doxy, Atridox, Periodox, Vibra_Tabs): Use by Pregnant and Lactating Women (10/31/2001); http://www.fda.gov/cder/drug/infopage/penG_doxy/doxypreg.htm
Drug Preparedness and Response to Bioterrorism (10/31/2001); http://www.fda.gov/cder/drugprepare/default.htm
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
Research is underway on vaccines to prevent anthrax.
Healthy volunteers are being recruited for a phase II study of a recombinant anthrax vaccine, rPA102, being developed by VaxGen, Inc., under a contract with the U.S. government through the National Institute of Allergy and Infectious Diseases (NIAID). The study is being conducted at 12 centers throughout the U.S. by the Center for Vaccine Development in collaboration with SoLUtions, a clinical research organization, both of Saint Louis University School of Medicine. Healthy individuals between the ages of 18 and 55, who have not served in the Armed Forces, active or reserve, since 1990, may be eligible to participate. For information, contact:
Saint Louis University
Salus Center, 2nd Floor
3545 Lafayette Avenue
St. Louis, MO 63104-1314
Telephone: (314) 977-7520
NIAID is also sponsoring a study of the natural history of anthrax, focusing on infected or exposed individuals to learn more about the disease symptoms, prevention, and response to treatment. People who have been exposed to anthrax but have no clinical symptoms, people with confirmed or suspected anthrax, and healthy people who have been vaccinated with AVA (Anthrax Vaccine Adsorbed) may be eligible to participate in this study. For information, contact the NIH Patient Recruitment Office listed above or visit www.clinicaltrials.gov.
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