Chapter 23: Plague   [open pdf - 266KB]

Plague is a zoonotic infection caused by the Gram-negative bacillus Yersinia pestis. Three great human pandemics have been responsible for more deaths than any other infectious agent in history. Plague is maintained in nature, predominantly in urban and sylvatic rodents, by a flea vector. Humans are not necessary for persistence of the organism, and we acquire the disease from animal fleas, contact with infected animals, or, rarely, from other humans, via aerosol or direct contact with infected secretions. To be able to differentiate endemic disease from plague used in biological warfare, medical officers must understand the typical way in which humans contract plague in nature. First, a dieoff of animals in the mammalian reservoir that harbors bacteria-infected fleas will occur. Second, troops who have been in close proximity to such infected mammals will become infected. By contrast, in the most likely biological warfare scenario, plague would be spread via aerosol. A rapid, person-to-person spread of fulminant pneumonia, characterized by blood-tinged sputum, would then ensue. If, on the other hand, an enemy force were to release fleas infected with Y pestis, then soldiers would present with classic bubonic plague before a die-off in the local mammalian reservoir occurred. The most common form of the disease is bubonic plague, characterized by painful lymphadenopathy and severe constitutional symptoms of fever, chills, and headache. Septicemic plague without localized lymphadenopathy occurs less commonly and is difficult to diagnose. Secondary pneumonia may follow either the bubonic or the septicemic form. Primary pneumonic plague is spread by airborne transmission, when aerosols from an infected human or animal are inhaled. Diagnosis is established by isolating the organism from blood or other tissues. Rapid diagnosis may be made with fluorescent antibody stains of sputum or tissue specimens. Patients should be isolated and treated with aminoglycosides, preferably streptomycin, plus chloramphenicol when meningitis is suspected or shock is present. A licensed, killed, whole-cell vaccine is available to protect humans against bubonic, but not against primary pneumonic, plague.

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Textbook of Military Medicine: Medical Aspects of Chemical and Biological Warfare, p. 479-502
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