Anthrax spores are highly persistent and resist adverse environmental elements and remain viable for hundreds of years in soil and in dried or processed hides. Spores are Resistant to drying, heat, and sunlight.They have been known to survive in milk for up to 10 years, on dried filter paper for 41 years, on dried silk threads for up to 71 years, and in pond water for 2 years. Anthrax is a disease that is present in the soil and occurs naturally in livestock, including pigs, horses, goats, cattle, and sheep. Farmers who work with these animals have been known to contract anthrax. Human-to-human contact has not been documented and is thought to be unlikely. Infection occurs from skin contact with infected animal tissue and possibly from biting fleas feeding on the animals. The bacterium enters a cut or abrasion on the skin while handling contaminated products from infected animals. Most commonly, the disease appears on the hands and forearms of people working with infected animals (Figure 8.43).