Facts about the PLAGUE!
- From: "Peter Jason" <td@xxxxxxxxxx>
- Date: Sat, 26 Aug 2006 09:01:01 +1000
I post, again, a scan from the Merck Manual
concerning the Bubonic Plague, so that clever
readers might arrange prophylaxis & antidotes
BEFORE it's too late:
****
PLAGUE (Bubonic Plague; Pestis; Black Death)
An acute, severe infection appearing most
commonly in a bubonic or pneumonic form,
caused by the bacillus Yersinia pestis.
*Etiology and Epidemiology*
Yersiniapestis (formerlyPasteurellapestis) is
a short bacillus that often shows bipolar
staining (especially with Giemsa stain) and
may resemble safety pins.
Plague occurs primarily in wild rodents (eg,
rats, mice, squirrels, prairie dogs); it may
be acute, subacute, or chronic, and urban
(mainly murine) or sylvatic. Massive human
epidemics have occurred (eg, the Black Death
of the Middle Ages); more recently, plague
has occurred sporadically or in limited
outbreaks. In the USA, > 90 % of human plague
occurs in the southwestern states, especially
New Mexico, Arizona, California, and
Colorado. Bubonic plague is the most common
form.
Plague is transmitted from rodent to humans
by the bite of an infected flea vector.
Human-to-human transmission occurs by
inhaling droplet nuclei through the cough of
patients with bubonic or septicemic plague
who have pulmonary lesions (primary pneumonic
plague). In endemic areas in the USA, a
number of cases have been associated with
household pets, especially cats. Transmission
from cats can be by bite, or, if the cat has
pneumonic plague, by inhalation of infected
droplets.
*Symptoms and Signs*
In bubonic plague, the incubation period is
usually 2 to 5 days but varies from a few
hours to 12 days. Onset is abrupt and often
associated with chills; the temperature rises
to 39.5 to 41° C (103 to 106° F). The pulse
may be rapid and thready; hypotension may
occur. Enlarged lymph nodes (buboes) appear
with or shortly before the fever. The femoral
or inguinal lymph nodes are most commonly
involved (50%), followed by axillary (22%),
cervical (10%), or multiple (13%) nodes.
Typically, the nodes are extremely tender and
firm, surrounded by considerable edema; they
may suppurate in the 2nd wk. The overlying
skin is smooth and reddened but often not
warm. A primary cutaneous lesion, varying
from a small vesicle with slight local
lymphangitis to an eschar, occasionally
appears at the bite. The patient may be
restless, delirious, confused, and
uncoordinated. The liver and spleen may be
palpable. The-WBC count is usually 10,000 to
20,000/p.L with a predominance of immature
and mature neutrophils. The nodes may
suppurate in the 2nd wk.
Primary PNEUNOMIC PLAGUE has a 2- to 3day
incubation period
incubation period, followed by abrupt onset
of high fever, chills, tachycardia, and
headache, often severe. Cough, not prominent
initially, develops within 20 to 24 h; sputum
is mucoid at first, rapidly shows blood
specks, and then becomes uniformly pink or
bright red (resembling raspberry syrup) and
foamy. Tachypnea and dyspnea are present, but
pleurisy is not. Signs of consolidation are
rare, and rales may be absent. Chest x-rays
show a rapidly progressing pneumonia.
Septicemic plague usually occurs with the
bubonic form as an acute, fulminant illness.
Abdominal pain, presumably due to mesenteric
lymphadenopathy, occurs in 40% of patients.
Pharyngeal plague and plague meningitis are
less common forms. Pestis minor, a benign
form of bubonic plague, usually occurs only
in endemic areas. Lymphadenitis, fever,
headache, and prostration subside within a
week.
*Diagnosis and Prognosis*
Diagnosis is based on recovery of the
organism, which may be cultured from blood,
sputum, or lymph node aspirate. Because
surgical drainage may disseminate the
organism, needle aspiration of a bubo is
preferred. Y. pestis can grow on ordinary
culture media or be isolated by animal
(especially guinea pig) inoculation.
Serologic tests include complement fixation,
passive hemagglutination, and
immunofluorescent staining of a node or
tissue biopsy or secretions. Prior
vaccination does not exclude plague in the
differential diagnosis, since clinical
illness may occur in vaccinated persons.
The mortality rate for untreated patients
with bubonic plague is about 60%, with most
deaths occurring from sepsis in 3 to 5 days.
Most untreated patients with pneumonic plague
die within 48 h of symptom onset. Septicemic
plague may be fatal before bubonic or
pulmonary manifestations predominate.
*Prophylaxis and Treatment*
Rodents should be controlled and repellents
used to minimize fleabites. Although
immunization with standard killed plague
vaccine gives protection, vaccination is not
indicated for most travellers to countries
reporting cases of plague. Travellers should
consider prophylaxis with tetracycline 500 mg
po q 6 h during exposure periods.
Immediate treatment reduces mortality to <
5%. In septicemic or pneumonic plague,
treatment must begin within 24 h with
streptomycin 30 mg/kg/day IM in 4 divided
doses q 6 h for 7 to 10 days. Many physicians
give higher initial dosages, up to 0.5 g IM q
3 h for
48 h. Tetracycline 30 mg/kg IV or po in 4
divided doses is an alternative.
Gentarrticit, is probably also effective,
although no controlled clinical trials have
been conducted. For plague meningitis,
chloramphenicol should be given in a loading
dose of 25 mg/ kg IV, followed by 50
mg/kg/day in 4 divided doses IV or po. A
multidrug-resistant strain has been reported
from Madagascar.
Routine aseptic precautions are adequate for
patients with bubonic plague. Those with
primary or secondary pneumonic plague require
strict (airborne agent) isolation. All
pneumonic plague contacts should be under
medical surveillance; their temperatures
should be taken q 4 h for 6 days. If this is
not possible, tetracycline 1 g/day po for 6
days can be given; however, this can produce
drug-resistant strains.
.
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