Anthrax
Anthrax
is a 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 (see
Chemical and Biological Warfare). 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.