Animal Models for the Pathogenesis, Treatment, and Prevention of Infection by Bacillus anthracis

Anthrax is primarily a zoonotic disease caused by the Gram-positive spore-forming bacterium Bacillus anthracis, which occurs in domesticated and wild animals, primarily herbivores. B. anthracis is found throughout the world and exists in the soil as the dormant, highly resistant spore form. Animals become infected when they ingest spores while grazing on contaminated land or ingesting spore-laden feed, although mechanical spreading by flies or vultures from one animal environmental locus to another could be possible ( 1 – 3 ). Humans are incidental and relatively rare hosts that, in natural settings, become infected by contact with infected animals or contaminated animal products ( 3 – 7 ). These infections occur most often in agricultural settings and lesser-developed countries. Before the development of effective vaccines and disinfection practices, industrial exposures were also common in European and North American countries. The latter were associated with the processing of animal materials (hides, hair, wool, and bones), as illustrated by the highly lethal illness known as woolsorter’s disease. This disease occurred after inhalation of spore-laden dust and aerosols in wool and textile mills in England and the industrialized regions of the northeastern United States ( 4 , 6 , 8 ).