Effects of Experimental Exclusion of Scavengers from Carcasses of Anthrax-Infected Herbivores on Bacillus anthracis Sporulation, Survival, and Distribution

Abstract

ABSTRACTScavenging of anthrax carcasses has long been hypothesized to play a critical role in the production of the infectious spore stage ofBacillus anthracisafter host death, though empirical studies assessing this are lacking. We comparedB. anthracisspore production, distribution, and survival at naturally occurring anthrax herbivore carcasses that were either experimentally caged to exclude vertebrate scavengers or left unmanipulated. We found no significant effect of scavengers on soil spore density (P> 0.05). Soil stained with terminally hemorrhaged blood and with nonhemorrhagic fluids exhibited high levels ofB. anthracisspore contamination (ranging from 103to 108spores/g), even in the absence of vertebrate scavengers. At most of the carcass sites, we also found that spore density in samples taken from hemorrhagic-fluid-stained soil continued to increase for >4 days after host death. We conclude that scavenging by vertebrates is not a critical factor in the life cycle ofB. anthracisand that anthrax control measures relying on deterrence or exclusion of vertebrate scavengers to prevent sporulation are unlikely to be effective.