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Microbiology => Procaryotes => Anthrax
Anthrax
Anthrax, contagious disease of warm-blooded animals, including humans, caused by the bacterium Bacillus anthracis. One of the oldest known diseases, it was once epidemic and still appears in many world areas, but only sporadically in the western and southern United States. It was the first disease for which the causative organism was isolated, by C. J. Davaine in 1863, for which a pure culture was obtained, by Robert Koch in 1876, and for which an effective vaccine was developed, by Louis Pasteur in 1881.
Animals acquire the disease from drinking water draining from contaminated soil, in which the infectious bacteria may live for years; 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 in acute cases and within three to five days in subacute cases. Death is caused by toxemia. The disease can be prevented by immunization, and in animals that have not been vaccinated, it can be treated with antibiotics.
In humans, the disease appears in both external and internal forms, with a death rate of about 20 percent. The external or cutaneous form is contracted through cuts or abrasions in the skin by those who handle infected hides and carcasses and may be self-limiting, but often disseminates into the bloodstream, with fever and prostration. The external form is characterized by malignant pustules on exposed skin areas. The internal type is acquired by inhaling anthrax spores, as from animal hair and wool, which invade the lungs and sometimes the intestinal tract to cause hemorrhage. A particularly virulent form of inhaled anthrax, sometimes called battlefield anthrax, has been developed as a biological weapon. This anthrax strain is fatal unless the infected person has been vaccinated or antibiotics are administered within 12 hours. It is speculated that an intestinal variety may be caused by consuming contaminated meat or milk. Workers exposed to animal products, especially wool, are protected by vaccination. Penicillin and tetracyclines are effective in treatment except in rapidly progressing cases.
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, may be working on a vaccine-resistant form of anthrax for use as a biological weapon. The United States government had previously planned to vaccinate all American personnel against anthrax; however, the possibility of genetically engineered new forms of the disease currently has scientists divided as to the effectiveness of such a vaccine.
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