2The Darkest Ages Justinian’s Plague Great Pestilence/Black Death A.D. 541, Egypt70,000 dead within 2 yearsGreat Pestilence/Black Death1346, Europe30+ million deadMost recent pandemic1890, China12.5 million dead
3The Cause of The PlagueThe bacterium which causes plague was first isolated:Time: 1894Place: Hong KongBy: Andre Yersin, a French bacteriologistThe bacteria was later named after him, Yersinia pestis
4The Cause of The Plague (cont’) Wayson Stain of Yersinia Pestis
5The Cause of The Plague (cont’) Fluorescence antibody positively is seen as bright, intense green staining around the bacterial cell
6How is Plague Transmitted? Plague is transmitted from animal to animal by the bites of infective flea.Both male and female fleas can transmite the infectionPlague is also transmitted from animal to human in the same way.
7How is Plague Transmitted? (cont’) Plague is also transmitted by inhaling infected droplets expelled by coughing, by a person or animal, especially domestic catThe organism may enter through a break in the skin by direct contact with tissue or body fluids of a plague-infected animal.
8How is Plague Transmitted? (cont’) Male Xenopsylla cheopis (oriental rat flea) engorged with blood.This flea is the primary vectore of plague epidemics in Asia, Africa, and South America.
9Yersinia pestisBacteria multiplies, attaches to host cell and injects the following proteins:Invasin: A protein that helps it in attachment and gain entry to the human cells.Plasminogen activator protease: prevents the fibrin clot to form which would trap the bacteria at the site of the flea biteYOPS (Yersinia outer-membrane proteins): it is injected into human cells, it interferes with signaling and prevents phagocytosis by immune system cells.
10Types of plague Bubonic Pneumonic Septicemic The initial symptoms are: headache, nausea, aching joints, and a general feeling of ill health.
11Bubonic PlagueAppearance of buboes, painful inflammations about the size of chicken eggs at lymph nodes in the neck, armpits, and groin.Hemorrhaging under the skin, causing black splotchesLate stage symptoms: very high fever and delirium.About 50-60% of the infected die after 4 days when left untreated.
12Pneumonic Plague When the bacterium enters the lung It usually spreads by sneezingSymptomsCoughing, expulsion of slimy sputum with traces of bloodFree-flowing and bright red sputum appears in advance stages.Untreated, % of cases lead to coma and death in about 2-3 days.
13Septicemic PlagueIs when a large amount of the bacterium is found in the bloodstreamSymptoms:Rashes, gangrene, sudden high fever.During the last hours, victims body turns deep purple due to respiratory failureVictim usually dies the same day. Fatality is 100%. The color that all plague victim have before dying is what gave it the name“Black Death”
15Streptomycin Drug of choice for treatment of plague Aminoglycoside BacteriocidalInhibits protein synthesisDamages cell membranesAminoglycosidecontains amino sugars attached to an aminocyclitol ring (hexose nucleus) by glycosidic bonds
16Plague: Treatment Gentamycin Aminoglycoside Preferred drug in certain cases:Can be used in pregnancySafe for infants
17Plague: Treatment Chloramphenicol Tetracyclines Sulfonamides Useful only in cases of bubonic/septicaemic plagueTetracyclinesSulfonamidesSulfmethoxazole/trimethoprim safe in infants
18Mortality Without treatment, plague kills 50-90% of infected people With treatment, 5-15% will dieA strain of Yersinia pestis demonstrating streptomycin resistance was found in Madagascar, 1995