Anthrax is an acute, rapidly fatal disease caused by the bacterium Bacillus anthracis.  It can affect all classes and ages of livestock including cattle, sheep, goats, pigs and horses and can result in significant losses during an outbreak situation.

Disease Epidemiology

The bacteria are present world-wide. The disease was first seen in Australia in 1847 and spread widely soon after introduction due to the absence of appropriate controls. In Australia, a recognised zone known as the “Anthrax Belt” runs through central NSW and into northern Victoria. Most cases of anthrax occur within this region because the soils are favourable for long term survival of spores and the area has become infected with spores due to previous outbreaks of anthrax. Occasionally outbreaks occur outside this area within NSW and isolated cases have occurred in Queensland and Western Australia with no known links to the anthrax endemic area. Anthrax spores are able to exist in deep alkaline soil for many years, but if the spores are close to the surface and are exposed to wind, rain, sunlight and acidic conditions, their survival time will be reduced to around 18 months.

Anthrax is not spread directly from animal to animal. The most common route of infection of livestock is by ingestion of spores that have been present in the soil on a property. Anthrax was often spread from one place to another by animals picking up the disease at one location and then being moved to another area while incubating the infection and subsequently dying of anthrax at that location. Livestock can be infected by contact with the carcass and its discharges. Prior to control programs being in place for anthrax in Australia, spores were often spread via contaminated stockfeed or blood and bone used as fertilizer, that had been made from animals that died of anthrax.

Anthrax bacteria are present in fluids that ooze from a carcase, and when exposed to the environment, these bacteria produce the highly resistant spores which can exist deep in soil for many years. When spores are brought to the surface, usually through soil disruption (for example, after heavy rainfall, erosion or earthworks), livestock may ingest them while grazing. Once inside the animal, they develop into the vegetative organism and multiply rapidly releasing lethal toxins, which cause oedema and tissue damage, resulting in death from shock and organ failure. The most common sign of anthrax is a dead animal without signs of a struggle prior to death. Blood which has failed to clot may be seen to be oozing from body orifices, however this may not always occur. There is usually an absence of rigor mortis (stiffness) in the infected carcass.

In dairy cattle, early signs of infection, such as a fever, milk drop and depression, may be seen prior to death, but progression of signs is invariably rapid.

Anthrax in Humans

Humans can also be infected by Bacillus anthracis. The most common type of human anthrax seen in Australia is cutaneous anthrax, otherwise known as “Woolsorter’s Disease”. This disease can occur when handling stock or carcasses infected with anthrax, with the spores entering the skin through cuts and abrasions.Although not recently recorded in Australia, it is also possible to ingest or inhale spores, resulting in a potentially fatal infection.

Diagnosis and Treatment of Anthrax

Anthrax is a notifiable disease. Anthrax should be a suspected cause of the sudden death of an animal, particularly if unclotted blood is seen oozing from orifices. If suspected, it is important not to touch or move the carcase, and to contact a government veterinary officer or district veterinarian as soon as possible, who will advise on appropriate steps to reach a diagnosis. Diagnosis can be conducted by examining blood smears to confirm the presence of B. anthracis bacteria. Other confirmatory tests are also available.

Treatment of the disease in live animals is usually futile due to the rapid onset of clinical signs and death. Some antibiotics are useful in treating infected animals if diagnosed and treated in the early stages of the disease.

Anthrax Vaccination

A highly effective vaccine is available which contains a live, avirulent (ie does not cause disease) strain of anthrax. Use of the vaccine is highly regulated and permission from the Chief Veterinary Officer in each state is required to obtain this vaccine. In order to purchase the vaccine, contact your government veterinary officer or district veterinarian.

It is important that antibiotics are not used at the same time as the vaccine, as this may interfere with the development of protective immunity within the animal.

Disposing of Carcasses

Extreme care must be taken when disposing of infected carcasses to, firstly, prevent human disease and secondly, to minimise the risk of spores from the infected carcass contaminating the environment. Any direct contact with the carcass must be avoided and appropriate personal protective equipment must be worn.

Please contact your local government veterinary officer or district veterinarian for information on carcass disposal and decontaminating affected areas.

Further information on anthrax and its control within Australia is available from the following web sites:

For NSW click here

For Victoria click here

National control strategy: click here

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