Anthrax Information
What is anthrax?
Anthrax is an acute infectious
animal disease caused by the spore-forming bacterium
Bacillus anthracis. Anthrax most commonly occurs in
wild and domestic lower vertebrates (cattle, sheep, goats,
camels, antelopes, and other herbivores), but it can also
occur in humans when they are exposed to infected animals,
or, tissue or products from infected animals. While it is
rare to find infected animals in the United States, it is
common in agricultural regions worldwide.
Historically, anthrax was first
identified when people who handled the wool of infected sheep
came down with the disease, hence the original name of “woolsorter’s
disease.” In fact, in 1876 German scientist Robert Koch first
formulated the famous "Koch’s Postulates," which proved that
a specific disease is caused by a specific bacteria, using
Bacillus anthracis.
What does "spore-forming" mean?
Bacilli, like many organisms,
have evolved mechanisms to enhance their survival. The formation
of spores, or more correctly for this bacterium, endospores,
allow these bacteria, which normally live in the soil, to
survive long periods of time in harsh environmental conditions,
such as heat, cold or drought. To create the endospore, bacteria
form a tough outside coating that protects the cell's nuclear
material. Think of a bacteria with a suit of heat-, rust-,
chemical-resistant armor… Endospores have been known to exist
for many years in this dormant state. Then, when conditions
are favorable, the outside spore coat breaks down and the
bacteria begin to grow.
How is anthrax transmitted?
In humans anthrax infections
occur by exposure to the bacteria to the skin (cutaneous),
lungs (inhalation), and/or gastrointestinal tract. Skin infections
can only occur when the bacteria enter the body through break
in the skin. Since the bacteria are very small, a very small
break in the skin could allow infection. The spores must
be inhaled (at least several hundred of them) to affect the
lungs. Gastrointestinal anthrax is the result of ingesting the
meat from an infected animal.
What are the symptoms of anthrax?
Symptoms of disease vary depending
on how the disease was contracted, but symptoms usually occur
within 7 days, although some sources say anywhere from 12
hours to several days.
Cutaneous: Most (about
95%) 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 is usually fatal.
Gastrointestinal: 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, fever are followed by abdominal pain, vomiting of
blood, and severe diarrhea. Intestinal anthrax results in
death in 25% to 60% of cases.
Can anthrax be spread from person-to-person?
Direct person-to-person spread
of anthrax is extremely unlikely to occur. Communicability
is not a concern in managing or visiting with patients with
inhalation anthrax.
Is there a way to prevent infection?
In countries where anthrax
is common and vaccination levels of animal herds are low,
humans should avoid contact with livestock and animal products
and avoid eating meat that has not been properly slaughtered
and cooked. Also, an anthrax vaccine has been licensed for
use in humans. The vaccine is reported to be 93% effective
in protecting against anthrax.
The anthrax vaccine is manufactured
and distributed by BioPort Corporation, Lansing, Michigan.
The vaccine is a cell-free filtrate vaccine, which means it
contains no dead or live bacteria in the preparation. The
final product contains no more than 2.4 mg of aluminum hydroxide
as adjuvant. Anthrax vaccines intended for animals should
not be used in humans.
Pregnant women should be vaccinated
only if absolutely necessary.
What is the protocol for anthrax vaccination?
The immunization consists of
three subcutaneous injections given 2 weeks apart followed
by three additional subcutaneous injections given at 6, 12,
and 18 months. Annual booster injections of the vaccine are
recommended thereafter.
Are there adverse reactions to the anthrax vaccine?
Mild local reactions occur
in 30% of recipients and consist of slight tenderness and
redness at the injection site. Severe local reactions are
infrequent and consist of extensive swelling of the forearm
in addition to the local reaction. Systemic reactions occur
in fewer than 0.2% of recipients.
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 persons with suspected cases.
Is there a treatment for anthrax?
Doctors can prescribe effective
antibiotics. To be effective, treatment should be initiated
early. If left untreated, the disease can be fatal.
This information
was obtained from the Centers for Disease Control in Atlanta,
Georgia;
Microbiology, 2nd Edition by L.M. Prescott,
et al, 1990;
and Biology of Microbiology, Fifth Edition,
T.D. Brock and M.T. Madigan, 1988.
Revised: 7/22/2008 SB