Agents of Bioterrorism: Pathogens and Their Weaponization

James Hudspeth

Francisella tularensis, the bacterium causing the disease tularemia, has been a subject of biological weapons research since World War II, and was developed into a deployable weapon by both sides during the Cold War. It occurs infrequently in nature, infecting humans through contact with infected animals, bites from infected insects, inhalation of aerosolized substances such as rodent droppings, and the consumption of contaminated food and water. Although the disease can be readily treated with basic antibiotics, reducing the frequency of fatalities to around 2.5% from the preantibiotic mortality rate of 50%, its extreme infectivity and virulence mean that it remains a considerable threat. Because of these reasons, the U.S. Centers for Disease Control and Prevention rates F. tularensis as one of six Category A biological agents, agents with “potential for major public health impact.”

Francisella tularensis, the causative agent of the zoonosis tularemia, was first described in the English-language literature as a bacterium infecting rodents in 1911 in Tulare County, California. Shortly thereafter, Lamb and Wherry identified the first case of human tularemia. Dr. Edward Francis, one of the premier researchers on tularemia, wrote several reviews on the disease after its discovery in humans, developing the hypothesis that the disease spread from rodents to humans through bloodsucking insects. In later commemoration of his work the bacterium was given its present name, Francis-ella tulare-nsis.

Reported cases of tularemia rose to high levels throughout the United States and world during the first half of the twentieth century, peaking in the United

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