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Anthrax can be used as a weapon for bioterrorism. In the First World War an attempt was made in Scandinavia to infect horses and reindeer with sugar lumps containing anthrax spores. The animals were used for transporting the allies’ supplies. Baron Otto Karl von Rosen was arrested in 1917, suspected of sabotage and spying for Germany. It was only 80 years later that it was discovered that the sugar lumps in his bag contained anthrax. So many years after the incident, the bacterial spores were still alive. In World War II the American forces prepared thousands of small hay balls impregnated with anthrax spores. These were shipped to England with the intention of dropping them over cattle-breeding areas of the Axis countries in order to disrupt meat supplies in Germany. The weapon was never used however. Before the first Gulf War, Iraq made large quantities of anthrax. Here too the weapon was not used.
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In 1993, members of the Japanese Aum Shinrikyo sect repeatedly spread anthrax in Kameido, Tokyo. There were however no cases of disease, because the sect had used a non-virulent strain (vaccine strain without capsule), low spore concentration, ineffective dispersal, a clogged spray device and probably also because of inactivation by sunlight
(on a bright summer day, B. anthracis spores have an estimated survival time of less than 150 minutes). The toxicogenic bacteria can be cultured in vitro. To obtain a weapon that can be used in aerosol form, the formation of spores from the cultures has to be promoted. The mass that is obtained is then freeze-dried and ground to a fine powder. Weapons-grade powder would be characterized by high spore concentration, uniform small particle size, particles with a certain electrostatic charge to promote mutual repulsion and an agent to prevent clumping. The spores display a tendency to stick together (due to certain surface glycoproteins and Van der Waals forces) so that quite large particles are formed. Large particles do not stay airborne for a long time. Because the greatest danger comes from spores between 1 and 5 µm, which can reach the alveoli quickly, the spore powder has to be treated in order to prevent its forming larger particles. Bentonite (a clay that contains a high percentage of fine-particulate silica) and silica itself can be used for stabilisation. Coupling agents such as certain silanes and siloxanes, e.g. Cab-O-Sil and Aerosil, promote the bond between silica and spores. Details about this are classified. In this way, after they have been dispersed or whirled up, the pathogens can reach the pulmonary alveoli by inhalation, without being exhaled again immediately or being removed by mucociliary clearing. The inoculation dose for inhalational anthrax for a person is estimated at 10,000 (2,500-55,000) spores. This is quite high and explains why formerly "woolsorters’ disease", even among furriers who used goat’s wool, was rare. These figures were obtained by extrapolation from tests with primates. Nonlethal Bacillus globigii spores were used by the military as an anthrax simulant.*
The fear that anthrax would be used in bioterrorism became reality after the attacks of September 11, 2001 on the World Trade Center, New York and the Pentagon, Washington DC, USA. In October 2001, anthrax spores were sent by mail to various people, government departments, news agencies and caused multiple cases of cutaneous and pulmonary anthrax, including people working in mail sorting centres. The powder in the envelopes contained high concentrations of finely dispersed anthrax spores. The government has to be informed of any incident where release of anthrax is suspected. Samples are taken for bacteriological examination from the area in which the spores are released. Afterwards, decontamination is carried out with a strong hypochlorite solution. For the people involved, who may still be asymptomatic, nasal swabs are taken and potential victims are advised to immediately wash thoroughly with soap in a shower, and then to take ciprofloxacin 500 mg bid (adults) until the full result of the laboratory examination is known. The accuracy of a nasal swab culture in predicting exposure is not known. The value of nasal swabs is greatly disputed. There is really no good method for determining whether someone has or has not been exposed to an aerosol that contains B. anthracis. If the infection is confirmed and there are still no symptoms, ciprofloxacin PO is taken for two months. Vaccination can be considered, but has never been used in these cases. The vaccine is not routinely available. Anthrax is not spread from person to person and medical personnel do not need to use additional protective equipment apart from the usual standard hygiene precautions, an important difference compared with plague pneumonia.
