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Anthrax
Written by Dr Dan Rutherford, GP
What is anthrax?
Anthrax is a bacterial disease caused by an organism called Bacillus anthracis. This organism is capable of producing spores - essentially a protective casing - which allows it to survive for decades in soil and other similar environments.
Anthrax is primarily a disease of grass-eating animals such as sheep, goats, cattle and horses. Human infection requires direct contact with either infected animals or animal products such as hides containing spores of the bacteria. There is considerable present anxiety that distribution of anthrax spores could be used as a method of biological warfare or terrorist attack.
Generally anthrax is confined to parts of Asia, Africa and the Middle East where exposure to infected animals or animal products is more likely. Within the UK, anthrax is a rare condition and when it occurs it is usually linked to contaminated imported hides, wool, goat hair, bristles, bone meal in fertilizers, etc.
The spread of anthrax depends on exposure to the bacteria. It is not a contagious disease, ie it is very unusual for it to spread from person to person.
What are the features of anthrax?
Anthrax bacteria can enter the body by the skin, by the soft lining of the mouth and digestive tract (mucous membranes) or by the lungs. The incubation period, ie the time between exposure to the organism and the development of the illness, is between 12 hours to five days, but is usually three to five days.
At first there is an itchy, red-brown lump that enlarges and becomes surrounded by tissues swollen with fluid. This lump then ulcerates, leaving a central black scab, which gives rise to the infection's name - anthrax is the Greek word for coal.
The local lymph nodes are usually swollen and the affected person may have other symptoms such as tiredness, muscle aches, fever, nausea and headaches.
Digestive system
Lung
Generally there is also another condition present, such as a cold perhaps, which has weakened the defences of the lung and airways and upon which the invading anthrax bacteria can settle.
Within the lymph nodes of the central chest (the mediastinum) the bacteria multiply and cause tissue destruction which spreads rapidly to other parts of the body.
The initial symptoms of pulmonary anthrax are very similar to those of the 'flu', but within a few days the picture changes and the infected person develops trouble breathing and then can develop shock, with usually a fatal outcome.
How is anthrax diagnosed?
The exposure history of the patient is therefore very important.
Pulmonary anthrax, for example, is also called 'wool-sorters disease', which relates to an occupational risk which is virtually gone in the UK, but still relevant in some parts of the world.
The skin form of anthrax causes lumps with a characteristic appearance. It also develops fairly slowly, and the affected person is not usually seriously ill.
In such circumstances the diagnosis is usually suspected in time, and examination of swabs from the skin will reveal the anthrax bacteria.
In digestive system anthrax the diagnosis is much harder. The initial symptoms of nausea, vomiting and fever are common to many illnesses, most of them much more likely than anthrax.
If the patient then goes on to develop the full picture of intestinal anthrax they are likely to become very ill rapidly, and the diagnosis may be made only after death has occurred.
Pulmonary anthrax starts like the 'flu' with fever, muscle aches and cough. Influenza is usually a troublesome illness but not serious for most people who get it but it can be associated with complications including pneumonia.
With pulmonary anthrax it is much more likely that lung complications will develop, necessitating prompt admission of the patient to hospital, where the diagnosis will usually be confirmed rapidly from investigations such as the chest X-ray and lab tests looking for the bacteria in body secretions and blood.
How is anthrax treated?
What about vaccination?
Rarely, anthrax can be caught by eating contaminated meat, particularly if there is also a break in the lining of the mouth or gut. Spread of the infection to the lymph nodes within the abdomen can then lead to a severe or possibly fatal illness.
The inhalation of anthrax spores is potentially the most serious route of infection. This is called pulmonary anthrax.
Anthrax is a rare disease, and as with any such condition the first hurdle in diagnosis is to be aware of it as a possibility. Only the skin form of the disease can be caught (rarely) from direct contact with an infected person - there have been no instances of the lung form being transmitted from person to person.
Several antibiotics are effective in cutaneous anthrax, notably doxycycline (and some other antibiotics of the tetracycline class), erythromycin, penicillin and ciprofloxacin. Pulmonary anthrax is much more difficult to treat, and unless caught in the very early stages has a high mortality. Intestinal anthrax is even more difficult to recognise and is equally if not more dangerous.
A vaccine is produced non-commercially within the UK for use by individuals at high risk of exposure (eg vets, abattoir workers, etc.) but the vaccine is not recommended for the general public. It is not possible to purchase the vaccine.
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