Occupational Health & Safety

Anthrax

Anthrax (PDF) is primarily a disease of herbivores. Humans and carnivores are incidental hosts.

Anthrax is an infrequent and sporadic human infection in most industrialized countries. It is an occupational hazard primarily of workers who process hides, hair, (especially from goats), bone and bone products and wool; and of veterinarians and agricultural and wildlife workers who handle infected animals. Human anthrax is endemic in those agricultural regions of the world where anthrax in animals is common. These countries include South and Central America, southern and eastern Europe, Asia and Africa. New areas of infection in livestock may develop through the introduction of animal feed containing contaminated bone meal. Environmental events, such as a dry period, followed by heavy rains and/or flooding, may provoke epizootics.

Anthrax is considered a leading potential agent in bioterrorism or biowarfare and, as such, could present in epidemiologically unusual circumstances.

Animals (normally herbivores, both livestock and wildlife) shed the bacilli in terminal hemorrhages or spilt blood at death. On exposure to the air, the vegetative forms sporulate, and the spores of Bacillus anthracis, which are very resistant to adverse environmental conditions and disinfection, may remain viable in contaminated soil for many years.

Bacillus  anthracis is a soil commensal in many parts of the world. Bacterial growth and spore density in soil are enhanced by flooding or other ecological conditions. Soil can also be contaminated by vultures, gulls,or ravens, which spread the organism from one area to another after feeding on anthrax infected carcasses. Note - Most birds, except ratites, are naturally resistant. Dried or otherwise processed skins and hides of infected animals may harbor the spores for years and are the fomites by which the disease is spread worldwide.

Cutaneous infection is by contact with tissues of animals dying of the disease. Biting flies that had partially fed on infected animals have also been implicated as a source of infection. Contact with contaminated hair, wool, hides, or products made from them, or by contact with soil associated with infected animals or contaminated bone meal used in gardening, have been documented as sources of infection.

Inhalation anthrax results from inhalation of spores in risky industrial processes, such as tanning hides and processing wool or bone, where aerosols Bacillus anthracis may be produced. Intestinal and oropharyngeal anthrax arise from ingestion of contaminated undercooked meat. There is no evidence that milk from infected animals transmits anthrax.

The disease spreads among grazing animals through contaminated soil and feed. The spread among omnivorous and carnivorous animals is through contaminated meat, bone meal, or other feed, while the spread in the wildlife population is from feeding on carcasses infected with anthrax.