Epidemiology Anthrax is a disease of herbivores, infecting sheep, goats cattle and swine. It is caused by B anthracis, a gram positive, sporulating bacillus. The reservoir of B anthracis is the soil and the organism is distributed worldwide. It exists in the infected host as the bacillus and in the environment as a spore. The spore is very durable and can survive adverse environmental conditions and remain dormant for decades.
Animals contract the spores while grazing.
Humans contract anthrax via innoculation of minor skin lesions with spores, from ingestion of contaminated meat or inhalation of the spores. Another mechanism that has been described is biting flies. The spores can be found in live animals as well as their hides, wool or other products. Triggers of spore germination and environmental spread include drought, heavy rain as well as dissemination via biting flies and vultures. B. anthracis is endemic in Africa and Asia.