The Plague As A Weapon?

Main Category: Bio-terrorism / Terrorism
Article Date: 11 Apr 2007 - 7:00 PDT

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The possibility of bubonic plague and pneumonic plague being used as bioterrorism agents is discussed in an article published in The Lancet.

Professor Mike Prentice, of University College, Cork, Ireland, and Dr Lila Rahalison, of Institut Pasteur, Madagascar, did a comprehensive review of the genetic makeup of the plague, its transmission vectors, and potential use as a biological weapon. They also look at a number of historical outbreaks of the disease, including the Black Death.

Plague is caused by the bacterium Yersinia Pestis, which multiplies in the gut fleas which have fed on blood from infected aminals. This causes a blockage in the proventriculus - the tube which connects the gut and the oesophagus of the flea. This blockage causes the flea to continually regurgitate and feed again, introducing Y. Pestis into the bloodstream of whatever it is biting - rodent or human.

The onset of bubonic plague is sudden, and causes malaise, dizziness, high fever and swellings near the lymph nodes called "buboes", after two to six days incubation.

Patients who develop secondary plague pneumonia after fleabite can transmit pneumonic plague directly to others. This form of plague generally has a shorter incubation time (two to three days) and is characterised by sudden onset, high fever, pleuritic chest pain and a cough containing bloody sputum.

It is now possible to harness the ability of the plague to spread by respiratory droplets, and make aerosol-based weapons capable of causing widespread pneumonic plague outbreak. This and many other factors could combine to make Y. Pestis an attractive agent for bioterrorism - its wide distribution, simple culture techniques, the high mortality rate of the associated pulmonary disease, availability of expert advice from former weapons scientists, or perhaps only the knowledge that many countries have investigated its use as a weapon.

Untreated bubonic plague has mortality of 50 to 90 per cent; and associated untreated meningitis, pneumonia or septicaemia is fatal in most cases. Diagnosis and appropriate therapy reduces bubonic plague mortality to five to 15 per cent, but delays in diagnosis and treatment can also be fatal.

Standard antibiotic therapy (originally Strepotmycin, later tetracycline or gentamicin) is successful in treating the disease, but there are concerns about a Y. pestis strain in Madagascar showing multiple antimicrobial resistance. Due to bioterrorism concerns, a number of vaccines are currently in development, one of which has reached phase II trials (an intermediate stage in the clinical trials process).

Plague control aims to reduce the likelihood of people being bitten by infected fleas or being exposed to infected droplets from people or animals with plague pneumonia. Thus monitoring and controlling local plague hosts (i.e. rodent populations) is vital in plague-endemic regions.

But the authors add: "However, removal of the fleas' normal food supply by poisoning their usual hosts can increase human contact with starving fleas, so flea control by application of insecticides in plague outbreak areas is also important."

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Contact: Professor Mike Prentice
Lancet

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