Microbiology

What is Anthrax



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Anthrax, in recent years even the name of this disease has inspired fear. The disease has a long history of causing the occasional illness in man and more frequent illness in hoofed animals such as cattle, horses and deer. Anthrax infection has been known since antiquity. It is possible that the sixth plague of Egypt, mentioned in the book of Exodus in the Bible, was caused by anthrax.

The organism causing anthrax, Bacillus anthracis, is an aerobic, gram-positive spore-bearing bacillus. On an agar based culture medium, the organism produces a characteristic “medusa head” shaped colony.

It was one of the first bacterial species to be studied in depth within the field of medical microbiology.  Casimir-Joseph Davaine identified the bacterium in 1863. In 1876, at the University of Breslau, the now famous microbiologist Robert Koch presented his findings on the bacterium, which showed it could produce spores. Koch demonstrated that these hardy spores allowed the bacterium to persist in the environment. Louis Pasteur made the first effective vaccine against anthrax in 1882.

While rarely seen naturally in the United States, it is a common infection in both domesticated and wild animals in parts of Eastern Europe, Asia, South America and Africa. Exposure to infected skins, fur or to the spores contaminating the ground causes occasional human infections.

There are three types of human disease caused by Bacillus anthracis.

The first and most common form is cutaneous anthrax. The introduction of the organism into the skin, by a small cut or puncture wound, causes this form of anthrax. The area where the bacterium has entered then starts to itch. A boil forms at the site of infection, which ulcerates before producing a black scab. This black scab is the reason the illness is known as anthrax, as the Greek word for coal is “anthrakis”. Untreated cutaneous anthrax can occasionally spread through the body to cause fatal septicemia. This form of anthrax was common among workers in the leather tanning industry who handled untreated hides. Cutaneous anthrax responds well to antibiotic treatment.

Pulmonary anthrax is a serious, frequently fatal, condition caused when a person inhales spores of Bacillus anthracis into the lungs. It starts as a flu-like illness before progressing into pneumonia and respiratory collapse. Even with treatment starting as soon as the early symptoms are apparent, the outcome is frequently fatal. Commonly known as “wool sorter’s disease” or “rag picker’s disease”, pulmonary anthrax is also known as inhalation anthrax or pneumonic anthrax. Wool sorters were particularly prone to the illness as the pulling apart of the wool could encourage spores into the air allowing their inhalation. Lethal infections can occur from inhaling 10,000 to 20,000 spores.

The rarest form of anthrax is gastrointestinal anthrax. Caused by the ingestion of raw or undercooked meat from an infected animal, this form sometimes occurs in endemic areas during times of famine. During famines people are more likely to eat sick animals and there may be a shortage of fuel for cooking of foods. Lesions of this from of anthrax develop in the mouth, throat and intestines. Spread into the rest of the body from these lesions is common. Symptoms of gastrointestinal anthrax include loss of appetite, diarrhea, abdominal pain and vomiting blood. Depending on when treatment starts, this form of anthrax has a fatality rate of 20-80%.

Human to human infections occur very rarely with cutaneous anthrax and not at all with pulmonary or gastrointestinal anthrax. A patient with anthrax is not contagious and does not require special isolation facilities for their care. However, samples taken from them, such as blood or material from a suspect anthrax lesion, require handling with caution. The bodies of fatalities are a source of infectious spores and post-mortem examinations of both human and animal cases require specialized facilities.

A rapid diagnosis using PCR to analyze samples from skin lesions, blood or sputum allows the prompt start of suitable antibiotic therapy. Culture of such samples is slower but provides a confirmed diagnosis if PCR is unavailable. A blood test for antibodies is of use to look for prior exposure to anthrax.

The last, naturally occurring, death from anthrax in the United States was a Californian home weaver who, in 1976, caught the infection from contaminated wool imported from Pakistan. In the United Kingdom, the most recent deaths from this infection were in 2008 when a drum maker died, having caught anthrax from untreated hides and in 2009 when IV drug users, possibly injecting a contaminated batch of heroin, died in Glasgow, Scotland. By February 2010, there were 19 cases and 9 deaths among drug users in the Glasgow area

The fatal pneumonia produced by anthrax has brought the organism to the attention of military scientists looking at the production of biological weapons. For anthrax to be of use as a weapon of mass destruction the spores have to be “weaponized” allowing their dispersal in the environment.

During World War One, the German General Staff supplied Scandinavian freedom fighters with spores of anthrax to use against the Imperial Russian Army in Finland in 1916. The results of this early use of an anthrax bio-weapon are unknown.

The Japanese tested biological weapons containing anthrax on prisoners of war in Manchuria during the 1930’s. Thousands of prisoners died as a result of these experiments.

The allies in World War Two also looked at anthrax as a potential weapon. Designated as agent “N”, the British Military tested a biological bomb on an island of the Scottish coast. Gruinard Island was uninhabited except for a flock of sheep at the time. All the sheep died and the island remained heavily contaminated. Access to the island to all but a few scientists was forbidden until the 1990’s when a special clean up and disinfection process was undertaken. Cattle cakes impregnated with anthrax spores were also prepared for dropping by the RAF on Germany. The planned drop was to have taken place in 1944 and five million of these cattle cakes were readied for the attack. This attack, known as “Operation Vegetarian”, would have severely damaged the already short food supply of the German people. The deadly cattle cakes were never used and were destroyed in 1945, after the war was over.

The most recent instance of a government actually using anthrax as a weapon was in 1979. The Rhodesian government deployed the bacteria against cattle and people in its war against the black nationalists. This led to 10,738 infections and 182 deaths.

The United States ceased production and destroyed all stocks of biological weapons after the signing of the bio-weapons treaty in 1972. According to this treaty, Russia should have also done the same but an accident in Sverdlovsk in April 1979 led to the exposure of over one million people to anthrax from a bio-weapons laboratory. At least 94 people contracted the illness and 68 of those died. Most of the cases came from the night shift at a ceramics factory situated immediately opposite the laboratory complex. It was not until 2002 that all the weaponized anthrax stocks held by Russia were finally destroyed. Research into the defense against bio-weapons, such as anthrax, continues worldwide.

More recently, there have been concerns that such weapons would fall into the hands of terrorist groups. This nightmare scenario became a reality in 2001 when small amounts of a powder containing anthrax spores were sent to addresses in the United States, via the US mail service. This attack killed five people and caused the infection in a further 22 people.

Growing anthrax is comparatively simple, requiring only a bacterial source, suitable media and an incubator. However, the preparation of weaponized spores requires specialized knowledge and equipment. Much of the fight against bio-terrorism involves tracking people with this knowledge and monitoring the sale of suitable equipment.

The fear of anthrax can be justified because of the fatal illness it can cause. However, it is not an easy illness to catch. For example, the Russian laboratory accident exposed over a million people to the disease but less than one hundred became symptomatic. Following the limited use of anthrax as a terrorist bioweapon, disruption of important government and financial institutions occurred with the delivery of envelopes containing innocuous powders, such as talc, to offices around the world. These hoaxes were feeding on the fear of another anthrax attack.

Since the 2001 attacks, a number of recommendations have been made for people who may be the target of a bioterrorism attack using anthrax. Where someone believes he or she has been exposed to Anthrax, then prompt prophylactic treatment with a suitable antibiotic, such as doxycycline or ciprofloxacin, will prevent infection in most cases. Scientists recommend immediate washing of hands, if contaminated by a suspect powder. A shower will remove spores from skin surfaces and hair.

There are a number of disinfectant solutions suitable for treating surfaces contaminated with anthrax. The EPA recommends diluting one part household bleach with eight parts water and then adding one part white vinegar. To keep the contaminated surface moist and ensure disinfection, this solution requires reapplication over a period of an hour. Vinegar should never be added to concentrated bleach as it can produce toxic chlorine gas. Normal washing by machine will remove spores from contaminated clothes.

A vaccine, which is 93% effective, is available to protect people against anthrax infection. Usually the vaccine is available for personnel working in high-risk areas, such as veterinarians and laboratory workers. Military personnel from the United States, Great Britain and some other countries also receive regular vaccinations against anthrax.

Reference sources:

CDC Centers for Disease Control and Prevention

Medline Plus US National Library of Medicine

HPA UK Health Protection Agency

BBC News (Scotland)

South African News

NHS Glasgow

CDC blogs

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