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Communicable disease factsheets

Anthrax fact sheet

Anthrax is a disease normally associated with plant-eating animals (sheep, goats, cattle, and to a lesser extent swine). This fact sheet covers: background; anthrax in Australia; how anthrax is spread; anthrax vaccine; State/Territory and Commonwealth roles.

In this section:

Background

Anthrax is a disease normally associated with plant-eating animals (sheep, goats, cattle, and to a lesser extent swine). It is caused by the bacterium Bacillus anthracis and has been recognised as an illness for centuries. Once common where livestock were raised, it is now controlled through animal vaccination programs. Anthrax occurs mainly in countries where animals are not vaccinated. In many countries (such as Australia) it occurs infrequently, due to effective compulsory control measures.

Anthrax in Australia

The Communicable Diseases Network Australia (CDNA) is a Commonwealth body with representatives from the Commonwealth, State/Territory health agencies and other Government and research bodies. CDNA meets on a regular basis and keeps track of disease outbreaks within Australia, New Zealand and the South Pacific region. It is within this forum that a case of anthrax would be reported. An anthrax outbreak would most likely be first recognised in animals, and immediate control measures would involve quarantine and notifying relevant health authorities to look for symptoms in humans.

Human cases of anthrax are rare in Australia. In the 10 years to the end of March 2007, only three cases (all cutaneous) were reported, one in each of 1998, 2006 and 2007. All had plausible natural exposure to anthrax spores. No case of either inhalational or gastrointestinal anthrax has ever been reported in this country.

How Anthrax is spread?

Human infection with anthrax usually results from direct contact with infected animals, or animal products such as wool, meat or hides. The spores can survive for long periods of time in certain soils, in animal products such as hair, hides and wool, and in feeds and fertilisers prepared from animals that died of anthrax.

Human anthrax occurs in four forms: cutaneous (skin infection); inhalational, which is caused by the inhalation of spores of the bacterium; gastrointestinal, which is caused by eating contaminated foods; and meningeal (inflammation of the membranes around the brain), which may be a complication of any of the other three forms. There is no evidence of spread of any of these forms on infection from person to person.

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Symptoms and treatment of anthrax

Cutaneous anthrax occurs when infection takes place through the skin. Sores (papules) develop, usually between 2 to 5 days after infection. These begin as small red swellings which later develop into black depressions (eschars). The case fatality rate of untreated cutaneous anthrax is between 10 and 20 per cent.

Inhalation of infective material causes inhalational anthrax, which may be rapidly fatal. Initial flu-like symptoms progress rapidly to difficulty with breathing, nausea, vomiting, prostration and shock. If untreated, death is almost certain, and even with treatment, the case fatality rate exceeds 40 per cent.

Gastrointestinal anthrax is caused by the consumption of contaminated foods. The most common initial symptoms are mild fever, discomfort, and gastrointestinal disturbance, including abdominal pain, with constipation or diarrhoea. Later, nausea, vomiting and shock may occur, and the case fatality rate is high, ranging from about 6 to 50 per cent.

Anthrax meningitis is a complication of any of the other three forms of anthrax, and is almost invariably fatal, even with antibiotic treatment.

Suspected human cases of anthrax are treated immediately with appropriate antibiotics. Likewise, people who may have been exposed to anthrax are treated with antibiotics at the earliest possible stage to prevent the onset of symptoms and disease.

Anthrax vaccine

The USA manufactures a vaccine for anthrax, but this is not registered in Australia. The vaccine may only be recommended for those at high risk of exposure. The vaccine can, however, be imported by special arrangements when it is needed. The vaccination itself involves six doses, three given two weeks apart followed by three additional injections given at 6, 12, and 18 months, after the first dose. An annual booster is required to maintain ongoing immunity.

How is Australia preparing for a deliberate release of anthrax?

Preparation measures include: