Anthrax

Definition

Anthrax is a disease caused by a rod-shaped bacterium called

anthracis

organism) that can live for decades in the soil. Robert Koch (1843

Bacillus. The bacterium forms spores (tough dormant forms of the–

1910), the German doctor who is considered the father of microbiology,

identified the bacteria as the cause of anthrax in 1877.

Anthrax is primarily a disease of grazing animals such as sheep, goats,

camels, and cattle. It rarely affects household pets like cats and dogs. It is

one of the oldest animal diseases known to humans and is probably one

of the ten plagues of Egypt described in the Book of Exodus in the Old

Testament of the Bible. Animals can become infected by anthrax through

eating grass coated with anthrax spores or getting the spores into open

wounds on their hides. Thousands of cattle in Europe and North

America died each year from anthrax until French scientist Louis Pasteur

(1822

–1895) developed an effective vaccine against the bacteria in 1881.

Description

Anthrax can take three different forms in humans. The most common

form, accounting for 95 percent of cases, is cutaneous (skin-related)

anthrax. It occurs when anthrax spores enter the body through a cut or

break in the skin, producing a painless sore with a black center. Cutaneous

anthrax is easily treated with antibiotics and is rarely fatal unless

the infection spreads into the bloodstream.

The second form is gastrointestinal anthrax. Humans can get it by

eating raw or undercooked meat from an infected animal. In this form

of anthrax, the bacteria cause inflammation of the intestines leading to

ulcers in the tissues lining the digestive tract. The infected person experiences

nausea, vomiting, and bloody diarrhea. Between 25 and 60 percent

of people with this form of anthrax die.

Inhalation anthrax is the third form, caused when anthrax spores enter

a person

lymphatic system and the lymph nodes in the central chest cavity. There,

the spores germinate into active bacteria. The bacteria enter the bloodstream

and are carried throughout the body. The bacteria

then produce toxins that cause bleeding,

tissue destruction, and eventual death.

Inhalation anthrax is fatal in about 75 percent

of cases even when treated. This form of

anthrax used to be called woolsorter

disease because it was most likely to

affect weavers and other people who worked with

wool or hair taken from infected animals. Inhalation

anthrax is the form most feared today

because it is the form that develops when anthrax

spores are used as a method of bioterrorism.

’s or ragpicker’s

Demographics

Anthrax is a relatively rare disease in humans in

developed countries since the introduction of

Pasteur

animals from the disease. Other safety measures

include the sterilization of animal waste

materials.

Prior to the 2001 anthrax mailings, the last

case of inhalation anthrax in the United States

took place in 1976, when a weaver in California

died after using wool imported from

Pakistan. In 2006 an artist in the United

Kingdom died from inhalation anthrax linked

to working with untreated animal skins. The

last known case of gastrointestinal anthrax in

the United States occurred in 2000, when several

people in Minnesota fell ill after eating

meat from an infected steer.

People of all races and ages are equally likely to get inhalation anthrax

when the bacillus is used as a weapon of bioterrorism. Cutaneous and gastrointestinal

anthrax are rare in the United States. Young adults are the

age group most commonly affected due to occupational exposure. People

in the following occupations are at some risk of cutaneous anthrax:

’s vaccine made it possible to protect

•

Veterinarians•

•

Forest rangers, field biologists, and others who study wildlife

•

products

People who work with wool, animal hides, hair, or bone meal

Causes and Symptoms

The cause of anthrax is a bacterium,

organ destruction and internal bleeding in animals and humans through

the release of toxins that target the tissues lining blood vessels, lymph vessels,

and the intestines. One of the toxins causes fluid to build up in the

tissues and damages the body

kills infected cells directly.

It is important to understand that humans cannot transmit anthrax

directly to one another, although a person

be contaminated by anthrax spores. People can be decontaminated after

exposure to anthrax spores by showering in hot water and using an antimicrobial

soap. Suspected articles of clothing should be boiled in water

for a minimum of thirty minutes or else burned. It is not necessary to isolate

or quarantine a living patient diagnosed with anthrax after he or she

has been decontaminated.

The symptoms of anthrax depend on the type:

B. anthracis. The bacteria cause’s immune system, while the other toxin’s skin, hair, or clothing can

•

the spores get into a cut or break in the skin. An itchy papule (raised

skin lesion) appears, followed by a blackish painless ulcer about an

inch across with a round, swollen edge. Nearby lymph nodes may

be swollen. The ulcer lasts for about two weeks before separating

from the skin and leaving a permanent scar. The infection spreads

into the bloodstream in about 5 to 10 percent of untreated patients.

Cutaneous: The incubation period is between two and five days after

•

eating infected meat. The patient experiences nausea, vomiting,

painful abdominal cramps, loss of appetite, vomiting blood, and

bloody diarrhea.

Gastrointestinal: Symptoms appear between two and five days after

•

three days after exposure. However, in some cases it may take as long

as forty-two days after exposure (and perhaps longer) for the person

to feel sick. The person first notices coughing and mild discomfort

around the breastbone, quickly followed by high fever, severe shortness

of breath, coughing or vomiting blood, heavy sweating, and

chest pain severe enough to be mistaken for a heart attack.

Diagnosis

There is no screening test for anthrax. Diagnostic tests for the various

forms of anthrax are ordered according to the patient

’s history—

including his or her occupational history

—and specific symptoms:

•

skin ulcer caused by cutaneous anthrax can be stained and

viewed under a microscope for evidence of the anthrax bacteria.

Skin scraping or biopsy: A sample of tissue fluid from the characteristic

•

inhalation anthrax can also be examined under a microscope.

Sputum culture. The secretions from the lungs of a patient with

•

suspected gastrointestinal anthrax.

Stool sample. Stool can be tested for anthrax bacteria in cases of

•

inserted into the throat or the intestines to look for the characteristic

ulcers caused by the anthrax bacteria.

Endoscopy. An endoscope is a lighted flexible tube that can be

•

studies can be done to look for signs of inhalation anthrax.

Chest x ray or computed tomography (CT) scan. These imaging

•

for any of the three forms of anthrax. The sample is cultured on

a material called blood agar, which is made from animal blood

combined with a gelatin-like substance derived from seaweed. If

Blood test and laboratory culture. This test can be done to check

B. anthracis

the bacterial colony will be destroyed.

is present, the red blood cells in the gelatin surrounding

Treatment

All three forms of anthrax are treated with oral or intravenous antibiotics.

Penicillin is usually effective for cutaneous anthrax. However, ciprofloxacin

and doxycycline are usually recommended for the other forms of the disease.

Inhalation anthrax requires hospitalization and treatment with intravenous

antibiotics. People who may have been exposed to anthrax may

be given antibiotics for as long as sixty days to prevent inhalation anthrax.

Prognosis

Cutaneous anthrax has the best prognosis; most people recover

without complications except for a scar where the ulcer appeared. Gastrointestinal

anthrax has a mortality rate of 25 to 60 percent, while

inhalation anthrax has a death rate between 45 and 75 percent even

when treated.

Prevention

Anthrax can be prevented in several ways. One preventive measure is

to give a sixty-day course of antibiotics to anyone exposed to the disease.

Another preventive measure is to avoid eating raw or undercooked

meat.

There is a vaccine against anthrax that was approved by the Food and

Drug Administration (FDA) in 1970, but it is not given to the general

public. Those who are eligible to receive the vaccine include:

•

exposure to anthrax.

Active-duty military personnel in areas that carry a high risk of

•

Researchers and laboratory assistants who work with anthrax.

•

world where livestock are not routinely vaccinated against

anthrax.

People who must work with animal products in parts of the

•

countries.

People or animals who die from anthrax must be buried or otherwise

disposed of carefully in order to prevent contaminating others. The body

of a person who is known to have died from anthrax is considered a biohazard

because the skin and any body fluids can contaminate healthcare

workers. The body must be placed in an airtight bag and preferably cremated,

as burial will not kill anthrax spores.

People who work with animal hides or wool imported from these

The Future

Anthrax is a major concern to public health officials because of its potential

as an agent of bioterrorism. The Centers for Disease Control and Prevention

(CDC) classifies anthrax as a Category A agent, the highest of

three levels. Category A agents are defined as disease organisms that pose

the greatest possible threat to public health; can be easily spread over a

large geographic area; and require a high level of planning in order to

protect the public. In addition, the fact that anthrax spores can survive

in the environment for years makes the disease even more dangerous. In

1942, during World War II, the British deliberately tested anthrax as a

bioweapon on a small island off the coast of Scotland. It took until

1990 for the island to be completely decontaminated.

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