Transcript Slide 1

Microbe of the day: Yersinia pestis
Plague in Humans: A Bubo Formed in the Groin
Plague is an infectious disease caused by Yersinia pestis, a naturally occurring bacterium found primarily in wild
rodents. Plague has been the cause of three of the great pandemics of the modern era—in the mid-6th century, the mid14th century (known as the Black Death), and the early 20th century.
Three forms of naturally-occurring plague infection exist:
• Pneumonic plague is the result of Y. pestis infection of the lungs. Primary pneumonic plague would be the
expected form of disease following an aerosol attack with Y. pestis. Secondary pneumonic plague may occur if
bubonic or septicemic plague goes untreated and the plague bacteria are allowed to spread to the lungs.
• Bubonic plague is the most common form of naturally occurring plague, typically acquired through the bite of
an infected flea. Bubonic plague is characterized primarily by swollen, tender lymph nodes (called buboes).
• Septicemic plague is the result of plague bacteria multiplying in the blood and disseminating throughout the
body. Septicemic plague usually occurs as a result of untreated bubuonic or pneumonic plague.
Microbe of the day: Yersinia pestis
Plague
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Pandemic plague has caused more human deaths than any other
infectious disease except for malaria and tuberculosis
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Caused by Yersinia pestis, a gram-negative facultatively aerobic rod-shaped bacterium
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Disease of domestic and wild rodents
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Humans are accidental hosts and are not critical for maintenance of the disease
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Fleas are intermediate hosts and vectors that spread plague between mammalian hosts
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Y. pestis produces virulence factors that contribute to the disease process
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Plague is also called bubonic plague because of the development of
buboes in the infected individual
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Plague can be successfully treated if it is rapidly diagnosed
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Treatment with gentamycin or streptomycin
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It treatment is started promptly, mortality is only 1-5% of those infected
Microbe of the day: Yersinia pestis
The causative organism, the bacterium Yersinia pestis, has a rodent reservoir.The rodents' fleas,
such as the oriental rat flea, Xenopsylla cheopis, acquire Y. pestis from a meal of infected blood,
and transmit the bacterium primarily to other rodents or to humans, causing bubonic plague in
people. Human-to-human transmission can also take place, through the human flea Pulex
irritans. Pneumonic plague is less frequent but even more severe; it is transmitted from person
to person through respiratory droplets, or even by artificially generated aerosols, containing Y.
pestis.
Microbe of the day: Yersinia pestis
The Epidemiology of Plague Due to Yersinia pestis
Flea, Vector of Yersinia pestis (Plague).
Microbe of the day: Yersinia pestis
Causative Agent of Plague in Humans
Antoine Jean Gros, "Pest House at Jaffa”, 1804. Napoleon Visits Soldiers Dying of Plague
Peter Bruegel (the elder) "Triumph of Death" (Black Plague