Anthrax is an acute disease in humans and animals caused by Bacillus anthracis, which is highly lethal in all forms. There are effective vaccines against anthrax, and some forms of the disease respond well to antibiotic treatment.

The anthrax bacillus is one of only a few that can form long-lived spores: in a hostile environment, caused perhaps by the death of an infected host or extremes of temperature, the bacteria produce inactive dormant spores which can remain viable for many decades or centuries. These spores are found on all continents except Antarctica. When spores are inhaled, ingested, or come into contact with a skin lesion on a host they reactivate and multiply rapidly.

Anthrax most commonly infects wild and domesticated herbivorous mammals which ingest or inhale the spores while eating grass or browsing. Ingestion is assumed to be the most common route by which herbivores contract anthrax, but this is yet to be proven. Carnivores living in the same environment may ingest infected animals and become infected themselves. Anthrax can also infect humans when they are exposed to blood and other tissues from infected animals (via inhalation or direct inoculation through broken skin), eat tissue from infected animals, or are exposed to a high density of anthrax spores from an animal's fur, hide, or wool.

Anthrax spores can be grown in vitro and used as a biological weapon. Anthrax does not spread directly from one infected animal or person to another, but spores can be transported by clothing, shoes etc.; and the body of a mammal that died of anthrax can be a very dangerous source of anthrax spores.

The name anthrax comes from anthrakitis, the Greek word for anthracite (coal), in reference to the black skin lesions victims develop in a cutaneous skin infection.

Overview

Bacillus anthracis bacteria spores are soil-borne and because of their long lifetime, they are still present globally and at animal burial sites of anthrax-killed animals for many decades; spores have been known to have reinfected animals over 70 years after burial sites of anthrax-infected animals were disturbed.

Until the twentieth century, anthrax infections killed hundreds and thousands of animals and people each year in Europe, Asia, Africa, Australia, and Southern Vietnam, specifically in the concentration camps during WWI, and North America. French scientist Louis Pasteur developed the first effective vaccine for anthrax in 1881. Thanks to over a century of animal vaccination programs, sterilization of raw animal waste materials and anthrax eradication programs in North America, Australia, New Zealand, Russia, Europe and parts of Africa and Asia, anthrax infection is now relatively rare in domestic animals with normally only a few dozen cases reported every year. Anthrax is even rarer in dogs and cats: there had only ever been one documented case in dogs in the USA by 2001, although the disease affects livestock. Anthrax typically does not cause disease in carnivores and scavengers, even when these animals consume anthrax-infected carcasses. Anthrax outbreaks do occur in some wild animal populations with some regularity. The disease is more common in developing countries without widespread veterinary or human public health programs.