Etiology and Epidemiology

Because B. anthracis produces resistant spores in suitable soils, the disease has long been endemic in many areas throughout the world, with a majority of the outbreaks occurring in Europe and Asia. The Americas, Africa, and Australasia are less affected. Once contaminated with anthrax spores, an area can be extremely difficult to clear, as has been demonstrated on the island of Gruinard off the west coast of Scotland, which was experimentally contaminated during World War II. This is of prime importance for the eipdemiology of the disease because it is rarely spread directly from animal to animal, but almost always through ingestion of contaminated food, either by grazing or, in cooler climates, through imported winter foodstuffs. Humans are accidentally infected either by contact with infected animals or by contaminated animal products. The infectivity of the anthrax bacillus for people is low, and therefore, even where large numbers of spores and bacilli are found in an industrial environment, only relatively few cases occur.

The nonindustrial type of anthrax in humans affects those in professions such as veterinary surgery, pathology, farming, butchery, and the like and takes the form of malignant pustule - a lesion due to contamination of the skin with material from infected animals. The industrial type may present as either malignant pustule or pulmonary disease and is acquired in the woolen industries especially through contaminated air. The disease approached an epidemic situation in the late eighteenth and nineteenth centuries in France and in England in factories processing imported horsehair and sheep's wool.

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