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