Download The Plague

By Kayla Frick
History of Plague
Arguably the ultimate scourge of
mankind (and over 100 species of
animals) was the so-called Black
Death. The generic "plague" (with
a lower case p) has entered the
language as a descriptor for any
deadly epidemic disease. Plague
(with an upper case P) is caused
by Yersinia pestis, a rod-shaped,
Gram negative bacterium. As few
as one bacterium is an infective
dose!
Facts
Plague is caused by the bacteria
Yersinia pestis. Rodents, such as
rats, carry the disease. It is
spread by their fleas.
People can get the plague when
they are bitten by a flea that
carries the plague bacteria from
an infected rodent.
A plague lung infection called
pneumonic plague can spread
from human to human. An
epidemic may be started this
way.
In the Middle Ages in Europe,
massive plague epidemics killed
millions of people. Plague can
still be found in Africa, Asia, and
South America.
Today, plague is rare in the
United States, but it has been
known to occur in parts of
California, Arizona, Colorado, and
New Mexico.
Facts
There three most common forms
of plague are:
Bubonic plague -- an infection
of the lymph nodes
Pneumonic plague -- an
infection of the lungs
Septicemic plague -- an
infection of the blood
The time between being infected
and developing symptoms is
typically 2 to 7 days, but may be
as short as 1 day for pneumonic
plague.
Risk factors for plague include a
recent flea bite and exposure to
rodents, especially rabbits,
squirrels, or prairie dogs, or
scratches or bites from infected
domestic cats.
History of Plague
Simple children's rhymes illustrate
some profundities associated with
the times, e.g.
”Ring around the rosies,
A pocket full of posies,
Ashes, ashes!
We all fall down.”
The Black Death
Also known as the Great
Plague originated in China in
1334 and spread along the
great trade routes to
Constantinople and then to
Europe, where it claimed an
estimated 60% of the
European population. Entire
towns were wiped out. It
has even been considered a
factor in the emergence of
the Renaissance in the late
14th century.
The Black Death
It is estimated that The
Black Death was
responsible for 200
million deaths in
Europe between 13281351, with outbreaks
occurring well into the
1400’s
The 1328 outbreak in
China caused the
population to drop
from 125 million to 90
million in just fifty
years
7500 victims of the
disease were dying
every day
Case Study
A 25-year-old New Mexico rancher was admitted
to an El Paso Hospital on February 12
because of a two-day history of headache,
chills, and fever. The day before admission,
he began vomiting. The day of admission, an
orange-sized swelling in the left axilla was
noted.
A lymph-node aspirate and a smear of peripheral
blood were reported to contain gram-positive
cocci, often in pairs. Under the assumption
that a gram-positive organism had caused the
patient's illness, he was given cefoxitin.
Case Study cont.
The man was acutely ill. Within a few hours of
admission, he had a cardiopulmonary arrest.
During resuscitation efforts, he vomited and
aspirated his vomitus; a chest X-ray showed
bilateral infiltrate.
Additionally, the patient bled from several body
sites. The patient died within 6 hours of
admission. In the 2 weeks prior to becoming
ill, the patient had trapped, killed, and skinned
3 kit foxes, 4 coyotes, and 1 bobcat. The
patient had cut his left hand shortly before
skinning the bobcat on February 7
Pathogenesis
Yersinia pestis is primarily a rodent pathogen, with
humans being an accidental host when bitten by an
infected rat flea. The flea draws viable Y. pestis
organisms into its intestinal tract. These organisms
multiply in the flea and block the flea's
proventriculus.
Some Y. pestis in the flea are then regurgitated when the
flea gets its next blood meal thus transferring the
infection to a new host. While growing in the flea, Y.
pestis loses its capsular layer. Most of the organisms
are phagocytosed and killed by the
polymorphonuclear leukocytes in the human host. A
few bacilli are taken up by tissue macrophages. The
macrophages are unable to kill Y. pestis and provide a
protected environment for the organisms to
synthesize their virulence factors.
Pathogenesis
The organisms then kill the macrophage and are released
into the extracellular environment, where they resist
phagocytosis by the polymorphs. The Y. pestis quickly
spread to the draining lymph nodes, which become
hot, swollen, tender, and hemorrhagic. This gives rise
to the characteristic black buboes responsible for the
name of this disease.
Within hours of the initial flea bite, the infection spills
out into the bloodstream, leading to involvement of
the liver, spleen, and lungs. The patient develops a
severe bacterial pneumonia, exhaling large numbers
of viable organisms into the air during coughing fits.
As the epidemic of bubonic plague develops, it
eventually shifts into a predominately pneumonic
form, which is far more difficult to control and which
has 100 percent mortality.
Transmission
Flea bites. Plague bacteria are most often
transmitted by the bite of an infected flea.
Contact with contaminated
fluid or tissue. Humans can become
infected when handling tissue or body fluids of a
plague-infected animal.
Infectious droplets. When a person
has plague pneumonia, they may cough droplets
containing the plague bacteria into air.
Transmission
Symptoms
Bubonic plague symptoms appear suddenly,
usually after 2 - 5 days of exposure to the
bacteria. Symptoms include:
•Chills
•Fever
•General ill feeling (malaise)
•Headache
•Muscle pain
•Seizures
• Smooth, painful lymph gland swelling
called a bubo
• Commonly found in the groin, but
may occur in the armpits or neck,
most often at the site of the
infection (bite or scratch)
• Pain may occur in the area before
the swelling appears
Treatment
People with the plague need
immediate treatment. If treatment
is not received within 24 hours of
when the first symptoms occur,
death may occur.
Antibiotics such as streptomycin,
gentamicin, doxycycline, or
ciprofloxacin are used to treat
plague. Oxygen, intravenous fluids,
and respiratory support usually are
also needed.
Plague in the U.S.
This bar graph shows the number of plague cases by year, but can
be interpreted in two separate time frames.
Plague cases in the United States, 1900–2010. In 1907,
an outbreak of plague followed in the aftermath of the
San Francisco earthquake. Since the mid–20th
Plague Worldwide
Plague epidemics have occurred in Africa,
Asia, and South America but most human
cases since the 1990s have occurred in
Africa.
Sources
Medicine Plus
http://www.nlm.nih.gov/medlineplus/ency/article/000596.htm
Hartford University
http://uhavax.hartford.edu/bugl/histepi.htm#plague
Science Illustrated
scienceillustrated.com.au
University of Maryland
http://www.life.umd.edu/classroom/bsci424/BSCI223WebSiteFiles/Pla
gueCaseStudy.htm
Centers for disease control
http://www.cdc.gov/plague
Middle Ages History
http://www.middle-ages.org.uk/black-death.htm
A.T. Still University
http://www.atsu.edu/faculty/chamberlain/Website/lectures/lecture/pl
ague.htm
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