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Lecture 9

HLTB21H3 Lecture Notes - Lecture 9: Germ Theory Of Disease, Cholera Toxin, Serotype


Department
Health Studies
Course Code
HLTB21H3
Professor
Caroline Barakat
Lecture
9

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Until the 19th Century
Miasmatic:
-Pettenkofer (1818 -1901)
-steadfastly refused to believe in the germ thoery
-drunk a vial of bacteria contaminated water
-disease caused by ‘bad vapour
-Contagionists:
-Believed the ‘germ theory’ announced by Pasteur (1862)
-Koch and Hansen
-Diseases spread from person to person by an infectious agent
Epidemiology
-History of cholera is described as the history of pandemics
-7 pandemics
-1) 1816-1821: originated in India (River Gangs) and was spread by mainly by British troops,
headquaters in Bengal
-2) 1829-1851: more widespread, reaching Europe, Canada, and the US
1831-mortality of 13% in Cairo, Egypt
1832-3: 60,000 deaths in England - disease known as ‘King Cholera’
1849 - called ‘America’s greatest scourge’
-3) 1852-1859: Scientific advances in understanding cholera
-4) 1863-1873
-5) 1881-1896: hygienic measures stopped its spread to N America
-6) 1899-1923: for teh most part missed the western hemisphere
-7) 1961-ongoing
-series of epidemics:
-1961: Celebes Island, Asia, Middle East
-1992: aboard a flight from S America to the US
-1990s: 200,000in SE Asia
-1994: Zaire, killed 50,000 Rwandan refugees in 21 days
-2000: Africa
Etiology
-During the 5th epidemic (1883)
-Koch dispatched to Egypt to isolate the microbe
-Able to see the bacteria in feces of 12 patients
-Vibrio cholerae (due to its vibrating wiggles)
-Incubation period - few hours to 5 days
-139 different serogroups
-V. cholerae must itself be infected w/2 viruses
-One has a gene that codes for the cholera toxin (cause of diarrhea)
-other must have a gene that codes for the receptor that allows the toxin-coding virus to
enter the bacterium
Infection with Cholera
-infected individual excretes a trillion V. cholerae each day
Lecture 9 - Cholera
1
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