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Anthrax
Anthrax, caused by the organism bacillus anthracis, is an
ancient disease affecting herbivores that can also cause
severe illness in humans. Perhaps somewhat fancifully said
to be the cause of the 5th plague in the book of Genesis,
Anthrax was nevertheless known to both the Greeks and
Romans. In fact the characteristic black mark, or eschar,
which can develop at the site of infection on the skin, gives
rise to the disease’s name that is derived from the word
anthrakis – the Greek for coal.
Most human cases are caused by the handling of infected
animals or animal products, such as hair, hides or wool; the
industrial illness, Woolpacker’s disease, was actually
correctly attributed to Anthrax as long ago as the mid 1800s. Following improvements in industrial hygiene
and ventilation, as well as the development of effective immunization for both animals and workers, the
incidence of the illness has decreased in the West. In the Far East, India, Africa and Latin America, such
practices are not widespread, however, resulting in 2,000 cases globally each year.
Cattle, horses, goats or sheep can become infected
following the ingestion of anthrax spores in the soil, as
they graze. Spores are the dormant form of the
bacteria, persisting for many decades in the
environment. Other animals such as pigs, or cats and
dogs are relatively resistant. Humans are similarly
resistant but infection can occur when the spores
enter the body through broken skin, following
inhalation, or by eating under-cooked meat infected
with the organism.
Anthrax has received recent attention as a
possible agent for bioterrorism. Although
human to human transmission of Anthrax
does not occur, its potential is seen when the
long-lived spores are inhaled: the resulting
disease is extremely severe, leading to death
in up to 100% of cases if untreated. Following
the 9/11 atrocity, anthrax spores were
intentionally spread in contaminated post in
the US, producing 22 cases – 11 cutaneous
and 11 inhalational.
Types of Anthrax
As the vast majority of anthrax cases are caused by direct contact with infected animal products, skin
infection typically occurs. This cutaneous form is responsible for 95% of all cases of the disease. If
untreated, a fatality rate of 20% can occur but following the early diagnosis and appropriate use of
antibiotics, this can be reduced to 1%.
If the anthrax spores are eaten or inhaled, far rarer forms of the disease can be produced, resulting in
illnesses which are often considerably more severe: gastro-intestinal Anthrax can have a mortality rate of
60% and inhalational Anthrax, up to 100%.
Symptoms
The symptoms produced vary with the site of infection. If infected on the skin: a painless, itchy spot can
occur 2-6 days after infection, which may be associated with painful, swollen lymph glands (under the
shoulder, if infected on the arms; in the groin, if the spot is on the legs). The spot is likely to ulcerate and
after several days, the black eschar may appear.
Ingested Anthrax may produce such severe swelling around the back of the mouth and throat, that the airpassages become completely blocked, stopping breathing. If the infection is lower in the gastro-intestinal
tract, haemorrhage can occur as can abdominal pain and bloody diarrhoea.
Inhaled anthrax spores cause a bloody infection of the lungs as well as pleural effusions (water on the
lungs), producing shortness of breath. Fever and chest pain can also occur.
Diagnosis and Treatment
The initial symptoms of disease can often be difficult to
attribute to anthrax, causing a delay in treatment.
Diagnostic tests are available: the skin lesions usually
have abundant bacilli present making microscopic
identification possible after the organisms are stained.
Antibiotics, either used singly or in combination, are an
effective treatment if used early in the disease progression.
Following the establishment of complications, however,
effective
treatment
becomes
problematic,
often
necessitating advanced life-support techniques in the
Intensive Care Unit.
Shortly after entering the body, the
anthrax spores develop into fully
functioning bacteria. Two toxins are
produced which mediate the principal
effects of the disease at the cellular
level.
Together the lethal and edema toxins
are able to reduce the immune system’s
ability to kill the anthrax infection, as well
as produce an inflammatory response
that makes our circulatory system
collapse; blood capillaries become
profoundly leaky, causing shock to
occur.
Specific interventions to counter the effects of the anthrax toxins are currently being trialled, as is the use
of a therapeutic vaccine that aims to augment the immune response at an early stage of the disease. Preexposure immunization with a vaccine is licensed at present but is only available for high-risk groups;
such as some animal workers, laboratory technicians and the military.
Precautions
Key Points
Cook meat thoroughly
Avoid contact with wool, hair and hide in
developing countries.
Wash hands thoroughly after inadvertent
exposure to animal products.
Increase use of industrial precautions globally:
o Vaccinate high-risk employees
o Improve industrial hygiene and ventilation
o Wear personal protective equipment.
 Anthrax is a serious bacterial infection.
 Exposure to animals or animal products
can transmit the disease.
 Improvements in industrial practices have
reduced incidence in the West.
 Usually infects the skin.
 Early prompt treatment is successful.
 Some threat of use as a bio-weapon.
Further Reading
Concise Clinical Review: Anthrax Infection. D,Sweeny et al. American Journal of respiratory Critical Care Medicine.
2011. 184. 1333-1341.
____________________________________________________________________________________________________________
Written by Dr Simon Worrell BSc MBBS MRCP
Head of Medical Communications, Healix International
E: [email protected]
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