Microbe of the Month: Warfare waged by a gadfly: Bernard Dixon looks at a would-be weapon now adding to the woes of what was Yugoslavia

ANY MILITARY action inevitably opens up channels through which dangerous microbes can spread far and wide, producing debilitating and fatal epidemics. For disease-causing organisms able to exploit these new opportunities, prolonged civil disturbances are at least as helpful as conflicts confined to so-called 'theatres of war'. Interruptions to water distribution and sewage disposal, perhaps accompanied by scarcity of food (causing malnutrition and, thus, increased vulnerability to infection) lead almost inevitably to outbreaks of water-borne conditions such as typhoid fever, cholera and dysentery.

Two doctors working in Split, Croatia, have now written to the Lancet to highlight the threat posed by a very different type of infection, one not usually associated with the breakdown of sanitary, medical and other infrastructure during war. The disease is anthrax. And the doctors' concern has been triggered by the experience of treating a patient who apparently acquired the microbe, Bacillus anthracis, when she was bitten by a gadfly. In turn, the gadfly almost certainly received it from a cow that had died of the disease. Because of the chaos of war, the animal's carcass had not been destroyed and thus rendered safe.

Although long considered a potential weapon of biological warfare, B. anthracis is primarily responsible for disease in herbivores, especially cattle and sheep. Infected through the soil, they develop a type of anthrax with a mortality rate of about 80 per cent. B. anthracis can also enter the human body, usually through contact with animal products.

This is reflected in two earlier names for human anthrax. 'Hide porter's disease' was the vernacular for cutaneous anthrax, which begins when the microbe passes into the body through small cuts or abrasions. 'Wool sorter's disease' was pulmonary anthrax, caused by breathing B. anthracis into the lungs. The more serious of the two human conditions, this causes haemorrhaging of the lungs and severe breathing difficulties, and is fatal if not treated.

Insects, too, can transmit the microbe, which is what happened recently to a 38-year-old woman in rural south-western Bosnia-Herzegovina. Bitten on the neck, probably by a gadfly, she developed a painful swelling and was initially diagnosed as suffering from an allergic reaction to the bite, and treated accordingly. But her condition deteriorated rapidly and she had to be admitted to hospital, where she was soon taken into intensive care. There, Dr Nikola Bradaric and Dr Volga Punda-Polic realised that the pustule on her neck, associated with very low blood pressure and general distress, could be attributable to cutaneous anthrax.

Although the patient did not respond to penicillin, which is normally an effective treatment for anthrax, examination of a smear from the pustule confirmed that she had indeed been infected by B. anthracis. Antibiotic tests then showed that the microbe was resistant to penicillin but sensitive to tetracycline. Treatment was switched accordingly and the woman recovered, returning home after spending about a month in hospital.

The evidence is circumstantial, but it is highly likely that the original source of the microbe, transmitted by a gadfly or other biting insect, was the carcass of a cow that had died of anthrax a few weeks earlier and had simply been left in a pit near the woman's home. Drawing attention to the disruption of veterinary and medical services during the conflict in Croatia and Bosnia-Herzegovina, Dr Bradaric and Dr Punda-Polic argue that this incident raises the possibility of entire outbreaks of anthrax - which would be doubly dangerous if caused by the penicillin-resistant B. anthracis.

It's an ironic coincidence that such a prospect arises on the 50th anniversary of experiments conducted in Great Britain that were designed to clarify the suitability of B. anthracis as an agent of biological warfare. Following a pilot experiment the previous year, it was in the autumn and winter of 1942 that scientists from a Ministry of Defence laboratory at Porton Down in Wiltshire paid three visits to Gruinard Island off Scotland's north-west coast. There they exploded six 'bomblets' containing billions of anthrax spores. The bomblets were detonated on a gantry, with sheep tethered in concentric circles below. Finally, an aeroplane came in low over the island and dropped another anthrax bomb into the experimental area.

The purpose of these manoeuvres remains controversial even today. In addition to assessing the implications of a form of warfare thought to be under development in Germany and Japan, there have been claims that the British government was also giving serious consideration to the idea of using biological weapons. Possible, though ambiguous, support for that proposition comes from Churchill's statement that he was 'prepared to do anything to hit the enemy in a murderous place'. What is certain (though eminently predictable at the time) is that the Gruinard sheep began to die within days of being exposed to B. anthracis. Moreover, when Porton's bacteriologists left their Hebridean testing ground, the soil was to remain heavily contaminated for more than four decades until it was finally disinfected in 1986 and 1987. Confirmation that this deadly microbe can survive almost indefinitely in the environment remains grimly relevant to warfare today.

(Photograph omitted)