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Anthrax

About the disease

By Dr Andrew Turner

Anthrax is caused by Bacillus anthracis, a rod shape bacterium with a characteristic polychromatic capsule easily demonstrated in infected animals.

Anthrax is an infection of essentially herbivore animals and is characterised in these animals as an acute infection involving massive proliferation of anthrax organisms and toxins in the lymphatic system and their sudden release into the bloodstream causing sudden death. With the sudden death and breakage of blood vessels, vegetative organisms are released from the body to sporulate in the air and reseed infection back into the environment. The incubation period is short being five to ten days and infection is acquired by ingestion of contaminated plants/soil sites or meat and/or bone meals.

It is important not to open the carcasses of anthrax affected herbivores as this prevents a great majority of vegetative bacteria from sporulating. The vegetative bacteria die in the unopened carcass due to lack of oxygen to allow sporulation. Disinfection of the outside of carcasses and death sites with 5% formaldehyde destroys the environmental contamination with spores. The preferred method of disposal of infected carcasses is burning as this eliminates environmental contamination. Burying carcasses in subsoils that are calcareous and pH 9 ensures the probability of infection remaining.

Pigs and dogs acquire infection through eating infected carcasses. Infection in these animals is usually restricted to the throat area and death takes longer than in herbivores and usually after clinical signs have been observed for days; some animals recover. Anthrax organisms are not as readily demonstrated in the lesions of pigs and dogs.

Vegetative organisms are very fragile and easily destroyed by disinfectants. Spores were originally thought to last for centuries on the soil. It is now known that surface spore infections are short-lived and for up to three years; spores in the subsoil deeper than 15 cm in calcareous soils of pH 9 can survive and re-emerge after decades or centuries.

Anthrax now occurs rarely in Australia and is confined to parts of New South Wales and northern Victoria. In New South Wales, the disease occurs mainly in summer while the disease occurs throughout the year in Victoria. In different areas, the disease is either predominantly seen in sheep or cattle.

Anthrax can be readily prevented by the use of a vaccine using the Sterne 34F2 mutant spore forming bacterium. Vaccination with more than 2 million viable spores induces immunity for about 6 to 12 months; a second vaccination 6 to 12 months after the first dose induces a long-term immunity.

Humans acquire infection through the skin (cutaneous form), ingestion (gastrointestinal form) or inhalation (pulmonary form; Woolsorters disease). Only the cutaneous form has occurred in Australia and has resulted from the infection of cuts or abrasions when handling infected carcasses. Such infections are readily treated with antibiotics if recognised as a skin infection caused by B anthracis.

Australasian Resources

Agriculture Notes - Anthrax in Animals
Agriculture Note produced by the Victorian Department of Primary Industries. Provides brief information about anthrax in animals.

Anthrax Farmnote No 55/94
Published by Agriculture Western Australia, this Farmnote provides information about an occurrence of anthrax in Western Australia. It also includes brief information about the disease, cause and diagnosis.

Anthrax
Published by the Population Health Division of the Department of Health, Western Australia, this website provides a range of anthrax information. All pages are in .pdf format. Information provided includes:

• Questions and answers about anthrax
• How to handle potential anthrax exposures
• Handling of mail and packages
• Questions and answers about possible anthrax exposures

Anthrax in livestock
An information sheet from the Staff of Animal and Plant Health Service, DPI and Queensland Health Department.

Overseas Resources

ProMED-mail
ProMED-mail is a program for monitoring emerging diseases produced by the International Society for Infectious Diseases. Check the alphabetic index for recent reports of anthrax - in both animals and humans.

Anthrax & Bioterrorism - News & Resources
Hosted by Pighealth.com, this website is a collection of links to articles and news reports on the subject of anthrax and bioterrorism.

Anthrax
Published by the United States Department of Agriculture's (USDA's) Veterinary Services (VS) division, this document provides a brief outline of the disease. It includes a description of anthrax, where it occurs, epidemiology, clinical signs, diagnosis, human health risks, prevention, treatment and control measures.

Anthrax
Authored by John Kirk, DVM, and Heidi Hamlen, DVM, of the University of California Davis' Veterinary Medical Extension programme, this page contains a brief fact sheet about anthrax.

Nature - Focus on anthrax
This special topics website from Nature contains two pre-publication research papers and a collection of articles, news stories, and commentary from Nature's archive. The two research papers are in .pdf format and are: Bradley et al.'s "Identification of the cellular receptor for anthrax toxin" and "Crystal structure of the anthrax lethal factor" by Pannifer et al. Two other feature articles are provided, "Designing a polyvalent inhibitor of anthrax toxin" by Mourez et al. and "Genomics and future biological weapons: the need for preventive action by the biomedical community," by Fraser et al. Links to a range of related Nature news stories are also included.

Anthrax
Produced by the Division of Bacterial and Mycotic Disease at the Centers for Disease Control and Prevention, this site answers a number of frequently asked questions about anthrax, including symptoms and epidemiology. The site also provides technical information and links to further resources.

Bacteriology 330 Lecture Topics: Anthrax
This site consist of lecture notes authored by Kenneth Todar of the University of Wisconsin Department of Bacteriology. The lecture is about the anthrax bacillus and discusses both pathogenicity and determinants of virulence of the bacterium. Colour images illustrate the notes.

Anthrax as a Biological Weapon: Medical and Public Health Management
Authored by Thomas V. Inglesby, MD et al, this article, published in the Journal of the American Medical Association in 1999, outlines some of the findings from the Working Group on Civilian Biodefence. The Group was established to develop recommendations for measures to be taken by medical and public health professionals following the use of anthrax as a biological weapon against a civilian population.

USA Department of Defense Anthrax Vaccine Immunization Program
This website is the home page for the USA Department of Defense anthrax vaccine programme. It provides information about the disease, the vaccine, as well as links to related information.

From Mutation to Medication? Faulty Toxin Sabotages Anthrax Infection
This article by Heather Ettinger appeared in the Microbiology section of Focus, published by Harvard Medical, Dental and Public Health Schools, May 4 2001. The article reports on the development of a new potential anthrax therapy and can be read in summary or in full.

Occupational Health and Safety Considerations

Material Safety Data Sheet - Anthrax
Produced by the Office of Laboratory Security, Canada, this site is a safety data sheet for laboratory workers.

Handling of Mail and Packages
Issued by the Attorney-General's Department, this fact sheet provides some guidelines for handling mail and packages in light of the recent anthrax scares in Australia.

Guidelines and Policies

Guidelines for the Surveillance and Control of Anthrax in Humans and Animals
Produced by the World Health Organisation, this lengthy document is available in both .html and .pdf format. It provides some unofficial guidelines for the surveillance and control of anthrax. According to Agriculture, Fisheries and Forestry, Australia (ABA), the measures used in an unusual outbreak of anthrax in Victoria, Australia in 1997 have been incorporated into these Guidelines.

Search PubMed for Anthrax related articles

Search PubMed for:

• All articles on anthrax in relation to animals
• Articles on anthrax in relation to animals published in the last year
• Review articles on anthrax, in both animals and humans.

Research databases and indexes

Recommended research databases and indexes for this area of study are: CAB Abstracts, MEDLINE, AGRICOLA, TOXLINE, BIOSIS Previews and Web of Science.