Bacillus anthracis on Gruinard Island

Abstract

During the Second World War, trials of Bacillus anthracis as a potential agent of biological warfare (BW) were carried out on Gruinard Island off the west coast of Scotland (57°56′N, 5°35′W). Small bombs containing a slurry of spores of B. anthracis were detonated: most were suspended, about 6 feet above ground, from a gantry but one was dropped from an aircraft. The resulting aerosol clouds of spores were observed to pass through lines of sheep tethered at various distances down-wind of the detonation site and after a few days several sheep died of anthrax. The lethal nature of BW weapons used in the open had, therefore, been shown; the unfortunate legacy was an island heavily contaminated with the persistent spores of a virulent microorganism. Soil samples were tested annually from 1948 to 1968 and again in 1972 by Ministry of Defence staff and were found to contain viable spores of B. anthracis (unpublished work), although accurate counts were not made. We report here the results of the first full survey of the extent of the contaminated area and the numbers of viable spores of B. anthracis present. The survey, carried out in 1979, shows that areas around the gantry remain contaminated to a detectable level but a much wider surrounding zone of undetectable contamination, possibly containing localized high concentrations of spores, could also constitute a hazard.