Characteristics.
Plague is a zoonotic disease caused by Yersinia
pestis. Under natural conditions,
humans become infected as a result of
contact with rodents and their fleas.
Transmission of this gram-negative
coccobacillus is by the bite of an
infected flea. Under natural conditions.
three syndromes are recognized: bubonic,
primary septicemic, or pneumonic plague.
In a biological attack scenario, the
plague bacillus could be delivered via
contaminated vectors (fleas) causing the
bubonic type or, more likely, via aerosol
causing the pneumonic type. In bubonic
plague, the incubation period ranges from
2 to 10 days.
Clinical
Features. The onset is acute and
often fuliminant with malaise, high
fever, and one or more tender lymph
nodes. Inguinal lymphadenitis (bubo)
predominates, but cervical and axillary
lymph nodes can also be involved. The
involved nodes are tender, fluctuant, and
necrotic.
Bubonic plague may progress
spontaneously to the septicemic form with
organisms spreading to the central
nervous system, lungs (producing
pneumonic disease), and elsewhere.
Mortality is 50 percent in untreated
patients with the terminal event being
circulatory collapse, hemorrhage, and
peripheral thrombosis. In primary pneumonic
plague, the incubation period is 2 to 3
days. The onset is acute and fulminant
with malaise, high fever, chills,
headache, myalgia, cough with production
of a bloody sputum, and toxemia. The
pneumonia progresses rapidly, resulting
in dyspnea, stridor, and cyanosis. In
untreated patients, the morality is 100
percent with the terminal event being
respiratory failure, circulatory
collapse, and a bleeding diatheses.
Vaccine.
A formalin-inactivated (licensed). Y.
pestis vaccine is produced in the
United States and has been extensively
used. Live-attenuated vaccines are
available elsewhere, but are highly
reactogenic and without proven efficacy
against aerosol challenge. The current
plague vaccine does not reliably protect
laboratory animals from aerosol challenge
and would not be an effective biological
attack countermeasures versus aerosol
attack. Chemoprophylaxis is recommended
for contacts of pneumonic plague
patients. Post-exposure prophylaxis with
either doxycycline or tetracycline has
been recommended in known exposures. The
addition of ceftraxone is recommended for
plague meningitis.
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Medical
Management of Biological Agent Patients
