Anthrax
What is Anthrax?
Anthrax is an acute infectious disease caused by a spore-forming gram-positive, rod-shaped bacteria known as
Bacillus anthracis. Anthrax is a rare and fatal zoonotic disease (animal to human transmission) that can be found
naturally in soil and usually affects wild and domestic animals around the world.
● The term anthrakis means coal in Greek, and the disease is named after the black appearance of its
cutaneous form.
● Contact with anthrax can cause severe illness in both humans and animals.
Pathophysiology
Anthrax is primarily a disease of herbivores (eg, cattle, sheep, goats, horses).
● Bacillus anthracis is a large, spore-forming, gram-positive rod.
● Persistence of spores is aided by nitrogen and organic soil content, environmental pH greater than 6,
and ambient temperature greater than 15°C.
● Spores can exist indefinitely in the environment; optimal growth conditions result in a vegetative
phase and bacterial multiplication.
● Drought or rainfall can trigger anthrax spore germination, while flies and vultures spread the spores.
● Anthrax toxins are composed of 3 entities: a protective antigen, a lethal factor, and an edema factor.
● The protective antigen is an 83-kd protein that binds to cell receptors within a target tissue.
● The binding of edema factor at this site results in the formation of edema toxin; the binding of lethal
factor results in the formation of lethal toxin.
● Humans are relatively resistant to cutaneous invasion by B anthracis, but the organisms may gain
access through microscopic or gross breaks in the skin.
● The organisms multiply locally and may spread to the bloodstream or other organs (eg, spleen) via
the efferent lymphatics.
● Primary intestinal anthrax predominantly affects the cecum and produces a local lesion similar to the
lesion produced in the cutaneous form.
● Inhaled spores are ingested by pulmonary macrophages and then carried to hilar and mediastinal
lymph nodes.
● Anthrax in the lungs does not cause pneumonia, but it does cause hemorrhagic mediastinitis and
pulmonary edema.
Causes
Anthrax is caused by Bacillus anthracis, a gram-positive bacillus.
● Working with infected animals or animal products. Most people who get sick from anthrax are
exposed while working with infected animals or animal products such as wool, hides, or hair.
, ● Eating raw or undercooked meat from infected animals. People who eat raw or undercooked
meat from infected animals may get infected with gastrointestinal anthrax; this usually occurs in
countries where livestock are not routinely vaccinated against anthrax and food animals are not
inspected prior to slaughter.
● Injecting heroin. A newly discovered type of anthrax is injection anthrax; this type of anthrax has
been seen in northern Europe in people injecting heroin.
Types
The type of illness a person develops depends on how anthrax enters the body; typically, anthrax gets into the
body through the skin, lungs, or gastrointestinal system.
● Cutaneous anthrax. Cutaneous anthrax is the most common form of anthrax infection, and it is also
considered to be the least dangerous; cutaneous anthrax is most common on the head, neck,
forearms, and hands; infection usually develops from 1 to 7 days after exposure.
● Inhalation anthrax. Inhalation anthrax is considered to be the most deadly form of anthrax; infection
usually develops within a week after exposure, but it can take up to 2 months; without treatment,
only about 10-15% of patients with inhalation anthrax survive.
● Gastrointestinal anthrax. Gastrointestinal anthrax has rarely been reported in the United States;
infection usually develops from 1 to 7 days after exposure; once ingested, anthrax spores can affect
the upper gastrointestinal tract, stomach, and intestines.
● Injection anthrax. Injection anthrax can spread throughout the body faster and be harder to
recognize and treat; symptoms may be similar to those of cutaneous anthrax, but there may be
infection deep under the skin or in the muscle where the drug was injected.
Statistics and Incidences
Natural incidence is rare, but infection is an occupational hazard among veterinarians, farmers, and individuals
who handle animal wool, hair, hides, or bone meal products.
● From 1955–1994, US cases totaled 235, with 224 cases of cutaneous anthrax, 11 cases of
inhalational anthrax, and 20 fatalities.
● In October 2001, 22 confirmed or suspected cases of anthrax infection were identified.
● Cases were reported from Florida, New York, New Jersey, the District of Columbia, and Connecticut.
● There were 11 confirmed cases of inhalational anthrax (5 deaths) and 7 confirmed and 4 suspected
cases of cutaneous anthrax (no deaths).
● Anthrax is uncommon in Western Europe, but the disease is not uncommon in the Middle East, the
Indian subcontinent, Africa, Asia, and Latin America.
● Anthrax is endemic in Africa and Asia despite vaccination programs.
Clinical Manifestations
What is Anthrax?
Anthrax is an acute infectious disease caused by a spore-forming gram-positive, rod-shaped bacteria known as
Bacillus anthracis. Anthrax is a rare and fatal zoonotic disease (animal to human transmission) that can be found
naturally in soil and usually affects wild and domestic animals around the world.
● The term anthrakis means coal in Greek, and the disease is named after the black appearance of its
cutaneous form.
● Contact with anthrax can cause severe illness in both humans and animals.
Pathophysiology
Anthrax is primarily a disease of herbivores (eg, cattle, sheep, goats, horses).
● Bacillus anthracis is a large, spore-forming, gram-positive rod.
● Persistence of spores is aided by nitrogen and organic soil content, environmental pH greater than 6,
and ambient temperature greater than 15°C.
● Spores can exist indefinitely in the environment; optimal growth conditions result in a vegetative
phase and bacterial multiplication.
● Drought or rainfall can trigger anthrax spore germination, while flies and vultures spread the spores.
● Anthrax toxins are composed of 3 entities: a protective antigen, a lethal factor, and an edema factor.
● The protective antigen is an 83-kd protein that binds to cell receptors within a target tissue.
● The binding of edema factor at this site results in the formation of edema toxin; the binding of lethal
factor results in the formation of lethal toxin.
● Humans are relatively resistant to cutaneous invasion by B anthracis, but the organisms may gain
access through microscopic or gross breaks in the skin.
● The organisms multiply locally and may spread to the bloodstream or other organs (eg, spleen) via
the efferent lymphatics.
● Primary intestinal anthrax predominantly affects the cecum and produces a local lesion similar to the
lesion produced in the cutaneous form.
● Inhaled spores are ingested by pulmonary macrophages and then carried to hilar and mediastinal
lymph nodes.
● Anthrax in the lungs does not cause pneumonia, but it does cause hemorrhagic mediastinitis and
pulmonary edema.
Causes
Anthrax is caused by Bacillus anthracis, a gram-positive bacillus.
● Working with infected animals or animal products. Most people who get sick from anthrax are
exposed while working with infected animals or animal products such as wool, hides, or hair.
, ● Eating raw or undercooked meat from infected animals. People who eat raw or undercooked
meat from infected animals may get infected with gastrointestinal anthrax; this usually occurs in
countries where livestock are not routinely vaccinated against anthrax and food animals are not
inspected prior to slaughter.
● Injecting heroin. A newly discovered type of anthrax is injection anthrax; this type of anthrax has
been seen in northern Europe in people injecting heroin.
Types
The type of illness a person develops depends on how anthrax enters the body; typically, anthrax gets into the
body through the skin, lungs, or gastrointestinal system.
● Cutaneous anthrax. Cutaneous anthrax is the most common form of anthrax infection, and it is also
considered to be the least dangerous; cutaneous anthrax is most common on the head, neck,
forearms, and hands; infection usually develops from 1 to 7 days after exposure.
● Inhalation anthrax. Inhalation anthrax is considered to be the most deadly form of anthrax; infection
usually develops within a week after exposure, but it can take up to 2 months; without treatment,
only about 10-15% of patients with inhalation anthrax survive.
● Gastrointestinal anthrax. Gastrointestinal anthrax has rarely been reported in the United States;
infection usually develops from 1 to 7 days after exposure; once ingested, anthrax spores can affect
the upper gastrointestinal tract, stomach, and intestines.
● Injection anthrax. Injection anthrax can spread throughout the body faster and be harder to
recognize and treat; symptoms may be similar to those of cutaneous anthrax, but there may be
infection deep under the skin or in the muscle where the drug was injected.
Statistics and Incidences
Natural incidence is rare, but infection is an occupational hazard among veterinarians, farmers, and individuals
who handle animal wool, hair, hides, or bone meal products.
● From 1955–1994, US cases totaled 235, with 224 cases of cutaneous anthrax, 11 cases of
inhalational anthrax, and 20 fatalities.
● In October 2001, 22 confirmed or suspected cases of anthrax infection were identified.
● Cases were reported from Florida, New York, New Jersey, the District of Columbia, and Connecticut.
● There were 11 confirmed cases of inhalational anthrax (5 deaths) and 7 confirmed and 4 suspected
cases of cutaneous anthrax (no deaths).
● Anthrax is uncommon in Western Europe, but the disease is not uncommon in the Middle East, the
Indian subcontinent, Africa, Asia, and Latin America.
● Anthrax is endemic in Africa and Asia despite vaccination programs.
Clinical Manifestations
