Environmental Engineering Reference
In-Depth Information
nature of
Y. pestis
, the organism has a relatively short-lived existence in the free
state, disfavoring its use as a terror agent for causing widespread panic.
Tularemia
Like
Y. pestis
, the etiologic agent of tularemia,
Franciscella tularensis
,isa
gram negative, nonendospore-forming, coccobacillus. It is a strict aerobe and
nonmotile, having many natural arthropod and animal reservoirs and not limited
to a particular group of related species. Transmission of the infectious bacterium
may occur by several routes:
Insect bite
•
Contaminated aerosols
•
Contact with infected animal carcasses, hides, or fluids
•
Contaminated water, food, or soil
•
It is not contagious; person-to-person transmission has not been demonstrated.
Virulence of the organism varies among the subspecies, and type A, the North
American variety, is the most virulent. There are six clinical manifestations of
the disease, of which three are described here: ulceroglandular, pneumonic, and
typhoidal. Ulceroglandular infection results from the bite of an insect, often a
tick, or a scratch from an animal. The infectious bacteria initiate ulcer formation
at the point of entry to the body and in various organs accessed through travel in
the bloodstream. The pneumonic form of the disease results from inhalation of
the infectious bacteria during handling of infected animals. Advanced symptoms
include fatigue, malaise, atypical pneumonia signs, and, possibly respiratory fail-
ure. Pneumonic tularemia can develop in any of the other forms of tularemia.
Typhoidal tularemia results from ingestion of the infectious bacteria and the
symptoms resemble gastroenteritis-type diseases (i.e., vomiting, diarrhea, and
abdominal pain). Typhoidal tularemia usually follows in pneumonic cases and is
the most fatal form of the disease, with fatality rates as high as 35 percent in
untreated cases.
The attractiveness of
F. tularensis
as a bioterror agent is its high rate of
infectivity, high virulence, low infectious dose (25 to 50 percent rate of infection
in exposed individuals when 10 organisms are presented by the respiratory route),
and ease of dissemination by aerosolization. Incubation periods vary from 3 to 15
days, however, clinical symptoms typically appear in 3 to 5 days. There is ample
evidence of the interest in
F. tularensis
as a bioweapon, having been studied by
both the Japanese and United States during World War II and the Soviet Union
into the 1990s.
29
Glanders
Glanders is a disease occurring mostly in horses and rarely encountered in the
United States. The disease in humans is very rare; however, one case was reported
