|
 Anthrax is an acute infectious disease caused
by a spore-forming bacterium called Bacillus
anthracis. It is generally acquired following contact with
anthrax-infected animals or anthrax-contaminated animal products.
Anthrax has received heightened attention recently because of its
use as a biological warfare agent.
| What
is Bacillus anthracis? |
-
 Bacillus anthracis, the
etiologic agent of anthrax, is a large, gram-positive,
non-motile, spore-forming bacterial rod. The three
virulence factors of Bacillus
anthracis are edema toxin, lethal toxin, and a
capsular antigen. Human anthrax has three major clinical
forms: cutaneous, inhalation, and gastrointestinal.
- Bacillus anthracis spores do
not have a characteristic appearance such as color, smell,
or taste. Spores themselves are too small to be seen by
the naked eye, but have been mixed with powder to
transport them.
|
| How
can I be exposed to Bacillus anthracis? |
-
 Anthrax infection can occur in three forms:
- Cutaneous (skin)
- Inhalation
- Gastrointestinal
- Bacillus anthracis spores
can live in soil for many years. Humans can become
infected with anthrax by handling 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. It is rare to find infected animals in the
United States.
- Direct person-to-person spread of anthrax is extremely
unlikely to occur. Communicability is not a concern in managing
or visiting with patients with inhalational anthrax.
|
| What
are the symptoms of anthrax? |
Symptoms
of disease vary depending on how the disease was contracted, but
symptoms usually occur within 7 days.
- Cutaneous: Most (about 95 percent)
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 centimeters in
diameter, with a characteristic black necrotic (dying) area in
the center. Lymph glands in the adjacent area may swell. About
20 percent 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 often fatal.
- 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
percent to 60 percent of cases. [Source:
Questions and Answers about Anthrax. Centers for Disease Control and Prevention (CDC).]
|
| What
are the incidence rates of anthrax? |
As
of December 5, 2001, a total of 22 cases of anthrax have been
identified in the United States -- 11 were confirmed as inhalational
anthrax and 11 (seven confirmed and four suspected) were cutaneous.
Of the 11 cases of inhalational anthrax, direct exposure to Bacillus
anthracis-containing envelopes was confirmed or likely in the
first nine cases.
Before 2001, the incidence rates of anthrax were:
- From January 1955 to December 1999, there were 236 reported
cases of anthrax, most of them cutaneous, in 30 states and the
District of Columbia.
- The last case of inhalational anthrax in the United States,
before 2001, was in 1976 in California. A home craftsman died of
the disease. He was exposed through his work with yarn; Bacillus
anthracis was isolated from some of the imported yarns
used by the patient.
- The last case of cutaneous anthrax, before 2001, occurred in
North Dakota, in 2000. It was the only case since
1992.
The case fatality rates for the various forms
of anthrax are:
- Cutaneous: Early treatment of
cutaneous anthrax is usually curative, and early treatment of
all forms is important for recovery. Patients with cutaneous
anthrax have reported case fatality rates of 20 percent without
antibiotic treatment and less than 1 percent with it.
- Inhalational: Although
case-fatality estimates for inhalational anthrax are based on
incomplete information, the rate is extremely high,
approximately 75 percent, even with all possible supportive care
including appropriate antibiotics. Estimates of the impact of
the delay in post-exposure prophylaxis or treatment on survival
are not known.
- Gastrointestinal: For
gastrointestinal anthrax, the case-fatality rate is estimated to
be 25 percent to 60 percent. The effect of early antibiotic
treatment on the case-fatality rate is not defined.
|
| How
is anthrax diagnosed and treated? |
 Diagnosis:
Anthrax is diagnosed by isolating Bacillus
anthracis from the blood, skin lesions, or respiratory
secretions or by measuring specific antibodies in the blood of
persons with suspected cases.
Treatment: Doctors can prescribe effective antibiotics.
Bacillus anthracis usually
responds effectively to several antibiotics including
penicillin, doxycycline, and fluoroquinolones (such as
ciprofloxacin). To be effective, treatment should be initiated
early. If left untreated, the disease can be fatal.
Further information on antimicrobial
treatment of anthrax can be found on the following websites:
|
| 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
percent effective in protecting against anthrax.
The anthrax 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 milligrams of
aluminum hydroxide as an additive. Anthrax vaccines intended
for animals should not be used in humans.
The
Advisory
Committee on Immunization Practices [PDF - 226 KB] has recommend anthrax
vaccination for the following groups:
- People who work directly with the organism in the laboratory,
- People who work with imported animal hides or furs in areas
where standards are insufficient to prevent exposure to anthrax
spores,
- People who handle potentially infected animal products in
high-incidence areas (Incidence is low in the United States, but
veterinarians who travel to work in other countries where
incidence is higher should consider being vaccinated.), and
- Military personnel deployed to areas with high risk for
exposure to the organism (as when it is used as a biological
warfare weapon).
- First responders and workers involved in anthrax
decontamination.
Pregnant women should be vaccinated only if
absolutely necessary.
Further information on anthrax vaccination can be found on the
following websites:
- The anthrax
Vaccine
Immunization Program in the U.S. Army Surgeon General's
Office can be reached at (877)GETVACC (877)438-8222.
-
Use of Anthrax Vaccine in the United States. Centers
for Disease Control (CDC), Morbidity and
Mortality Weekly Report (MMWR), 49;RR-15, (2000, December 15), 226 KB PDF.
|
| Links
to additional information on Bacillus anthracis
and anthrax |
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Accessibility Assistance: Contact the OSHA Directorate of Technical Support and Emergency Management at 202-693-2300 for assistance accessing PDF materials.
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