Bacillus anthracis spores as viewed in SEM (left) and TEM (right). Bacillus anthracis is a species of bacillus that causes anthrax in humans and in animals (cattle and swine and sheep and rabbits and mice and guinea pigs); can be used a bioweapon. Anthrax is an infectious, usually fatal disease of mammals. The disease is transmitted to humans through cutaneous contact, ingestion, or inhalation. Cutaneous anthrax is marked by the formation of a necrotic skin ulcer, high fever, and toxemia. Inhalation anthrax leads to severe pneumonia that is usually fatal.