Anthrax
Submitted by John N. Goldman, M.D., chief,
division of Infectious Diseases, Penn State
Hershey Medical Center
What is it?
Anthrax is a disease caused by Bacillus
anthracis, bacteria that lives in the soil.
Animals such as cattle, sheep and goats are the
usual hosts for anthrax and contact with infected
animals or animal products infect humans
secondarily. It can infect the skin, lungs, and
gastrointestinal tract. In the year 2001,
terrorists spread anthrax by sending spores
through the mail in the United States. A spore is
a dormant (inactive) form of bacteria that can
survive under poor conditions, such as high
temperatures and dryness. When the conditions are
right, these spores can then become active again.
Who gets it?
Outbreaks of anthrax among cattle or people are
rare in the United States because most animals are
vaccinated against the disease. It occurs most
often in agricultural regions outside the United
States, such as the Caribbean, southern and
eastern Europe, South and Central America, Asia,
Africa, and the Middle East. People who handle the
contaminated animals, such as farmers,
veterinarians, or butchers, are more likely to get
the disease. However, anthrax spores can be grown
in a laboratory, and we have seen that people can
contract anthrax when it is used as a weapon in
biological warfare.
What are the forms of
anthrax and what are the symptoms of each form?
There are three forms of
anthrax in humans:
- Cutaneous
– or skin anthrax
- Pulmonary
– or inhalation anthrax
- Gastrointestinal
– or ingested anthrax
The cutaneous, or skin,
anthrax results from spores getting on the skin
and then getting into a break in the skin. There
is a 1-7 day incubation period. In this environment, the spores begin to
grow and cause a small raised area – known as a
papule – a person may have localized itching that may then form a small blister that
then develops into an ulcerated area that becomes
covered with a black scab – or eschar in about
2-6 days. The area is commonly seen on the head,
forearm and hands. There may be fever, local redness and
swollen lymph glands in the area.
Even if untreated, skin anthrax has a
relatively low mortality and, if treated with
antibiotics, is rarely ever fatal.
This is the most common form of anthrax.
Pulmonary, or inhalation,
anthrax results from inhalation of the spores into
the lungs. The incubation period can be from 2-60
days for the symptoms to occur. The
spores then grow and get into the local lymph
nodes and lymphatic vessels and cause an
aggressive inflammation in the tissues of the
chest – known as the mediastinum.
There may be hemorrhage locally as well as
spread of the bacteria to the brain resulting in
meningitis in as many as 50% of affected
individuals.
The earliest symptoms of pulmonary, or
inhalation, anthrax are very nonspecific and may
resemble the early phases of the flu – with
fever, muscle aches and pains, and mild
respiratory complaints. If untreated and
these symptoms progress, it may lead to death. Pulmonary
anthrax has been quite rare in this country with
only 18 cases reported prior to the events of
September 11th.
The gastrointestinal form of
anthrax results from eating meat from infected
animals. The incubation period is typcially 1-7
days and includes symptoms such as abdominal pain,
nausea, vomiting and fever following ingestion of
contaminated food or water bloody diarrhea, and
vomiting blood. This results in infected areas of the intestines with
death of tissues and is almost always fatal.
Gastrointestinal anthrax has never been
seen in this country.
Is anthrax contagious?
Anthrax is not contagious,
that is, it cannot be spread from person to
person. The
reason it cannot be spread is because infected
persons have only the actively growing bacteria
and do not have the infectious spores.
How many spores does it
take to get infected?
The best evidence on this
suggests that it takes between 8,000 and 40,000
spores to be inhaled, perhaps fewer to cause the
cutaneous form of anthrax.
One would guess that it takes many more
organisms to cause the gastrointestinal form,
since it is so rare and since infected meat may
contain millions of organisms.
What is the difference
between “exposed to” and “infected with”
anthrax?
One can be exposed to anthrax
without getting infected with the bacteria, and,
in fact, this is probably the most common
occurrence. One
becomes infected only when the spores grow
successfully and multiply in tissues.
The spores may not grow or the body’s
natural defenses may kill the bacteria before they
cause disease.
Having the spores recovered from the nose
or skin indicates exposure only – but unless the
bacteria successfully grow in the skin, lungs or
gastrointestinal tract, there is no infection.
How is it diagnosed?
To diagnose anthrax, your doctor will evaluate
your symptoms, taking into consideration any
possibility that you could have had contact with
the Bacillus anthracis bacterium. He or she may
take samples of any skin infections, or
respiratory secretions, called sputum.
However, there are no tests that can be used to
reliably detect the presence of anthrax in exposed
persons. This is because the bacteria are present
in only small numbers on the skin or on mucous
membranes of the nose or pharynx before an
infection is established. Without the locus of
infection on the skin or in the lungs, the usual
tests are just not sensitive enough to find the
organism in a high percentage of those exposed.
Some of these tests are used for epidemiological
studies to see if any persons within a group that
may have been exposed are positive. If any are
positive, then one may consider that all of those
exposed have been put at risk and treatment of the
entire group with prophylactic antibiotics may be
considered.
How quickly must a
possible exposure be treated?
The usual incubation period
of anthrax is from several days to as many as 60
days from a single discrete exposure.
This gives several days to assess the risks
involved. Assessment
by a physician or other person knowledgeable in
this area should be undertaken sooner rather than
later. No
preventative measure needs to be given in these
first few days, even for true exposure.
This is especially true since all
antibiotics, as well as other drugs, have the
potential to cause serious side effects in some
people.
What is the treatment ?
While anthrax usually kills infected animals,
it can be successfully treated in humans if caught
in the early stages. Penicillin has been the drug
of choice for years and remains effective, even
for the infections we have all read about
recently. Other
drugs from the penicillin family such as
amoxicillin should be equally effective.
Doxycycline, one of the tetracycline family
of antibiotics – and most recently listed as the
CDC’s drug of choice in treating anthrax, is
also effective.
Ciprofloxacin – more commonly known as
Cipro – is one of the quinolone antibiotics and
is also effective.
Cipro has made news since the September 11th
terrorist attack and is recommended as the first drug to use
until the sensitivities of the organisms are known
because the Soviet Union was known to produce
anthrax bacilli that were resistant to penicillin
and tetracycline in their germ warfare program.
The anthrax used in the most recent
incidents, however, has all been sensitive to all
antibiotics listed above. Lung infections
may be treated with intravenous antibiotics. It is
important to take the full course of prescribed
antibiotics to prevent complications. If
untreated, cutaneous anthrax may result in death.
Untreated inhalation anthrax always results in
death.
According to the American Medical Association
and other authorities, physicians should not
prescribe antibiotics for patients as a preventive
measure against anthrax. This may lead patients to
initiate unnecessary treatment and could
contribute to the development of antibiotic
resistant organisms.
Is there an anthrax
vaccine?
The vaccine is a cell-free
filtrate vaccine, which means it contains no dead
or live bacteria in the preparation.
Anthrax vaccines intended for animals should not be used on
humans. The
vaccine is reported to be 93 percent effective in
protecting against anthrax and is not
recommended for the general public.
Self-care tips
People who work in professions that involve
frequent contact with animals or animal products
that could be infected with anthrax can get an
anthrax vaccine that is highly effective against
the disease. People who will be visiting countries
where there is poor control of the disease should
not eat meat that has not been properly prepared
or cooked, and should avoid contact with animals
or animal products that could be contaminated.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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