Anthrax is primarily a disease of grazing domestic animals. It is an acute disease caused by the spore-forming, gram-positive, nonmotile, toxin-producing aerobic rod Bacillus anthracis. It is the oldest known zoonosis with worldwide distribution: rare and sporadic and almost dis-appearing in the United States and in central and northern Europe, moderately common in southern Europe, and common in the former Soviet Union, in tropical and subtropical Africa, Asia, the Caribbean, and South America. The most affected countries are Turkey, Afghanistan, Iran, Pakistan, the Central Asian republics of the former Soviet Union, and sub-Saharan and South Africa. The incidence of human anthrax has decreased considerably in all countries since the introduction of an effective vaccine for use in animals. The frequency of infections in humans depends on the prevalence of the disease in livestock, which increases in years of drought.

EPIDEMIOLOGY

The ability to form spores permits the organism to survive environmental and disinfective measures that destroy most other bacteria. Public health problems largely arise from its long persistence in the soil (up to 90 years). In the Anglo-American biologic warfare experiments conducted in 1942 to 1943 on the uninhabited island of Gruinard off the western coast of Scotland, an estimated 4 × 1014 spores were exploded over the surface. Animal tests for more than 20 years demonstrated the persistence of virulent spores, eventually eliminated by disinfection of the area with a mixture of formaldehyde and sea water.