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Chapter 20

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The agents in this section are typically diseases of animals; with the exception of psittacosis, the animals are usually livestock, although other animals may be carriers. Psittacosis is commonly viewed as an avian disease (it is also known as ornithosis). Typhus fever is the only one of the group carried and passed by an invertebrate. As is characteristic of Category B diseases, these agents do not carry a high mortality rate. In fact, many infections with Category B agents will resolve without medical intervention. Typhus fever has the highest mortality rate of the group, roughly 50% if untreated, but death is rare with treatment. With Category B agents the health concerns are more with debility and psychological consequences, rather than with death or permanent or serious injury. Clinicians and public health officials are likely to be familiar with many of these agents in their natural or sporadic form, but they have potential as low-tech biological weapons and are therefore included in the Sourcebook.

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Background

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The “Q” in Q fever stands for “query” because investigators looking into one of the earliest documented outbreaks of the disease in the 1930s could not identify the causative agent. Later it was determined that the etiologic agent of Q fever was Coxiella burnetii, a rickettsial bacterium. Livestock, such as cattle and sheep, as well as other animals (e.g., cats and dogs) serve as natural reservoirs for the disease. Infected animals are typically asymptomatic.

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There are reports that in the past the Soviet Union attempted to weaponize C. burnetii; whether this was successful is unknown. As a biological weapon, C. burnetii is most likely to be aerosolized, but it has potential as a food or waterborne contaminant. Q-fever is a self-limited illness, its primary impact as a bioterror weapon is to cause morbidity and spread fear.

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Properties

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C. burnetii has a hardy spore form that is capable of surviving for long periods outside the host, even with exposure to heat or dehydration. The spore form also tolerates many ordinary disinfectants. This agent is not highly pathogenic, is rarely fatal, and usually resolves even without treatment of any kind. It is highly infective, however. Indeed, some experts believe that even a single organism is sufficient to cause the illness. With infection, C. burnetii is found in higher concentrations in the products of gestation including placenta, amniotic fluid, as well as in the animal’s waste products.

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Sources

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C. burnetii is found throughout the globe and is considered a potential bioweapon primarily because of its impressive infectivity. Livestock and other animals are the primary hosts and therefore the source for cross-infection of humans living in close proximity to these animals, or having direct contact with the animals.

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Epidemiology

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Although Q fever is found worldwide, its exact incidence is difficult to establish because so many ...

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