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Chapter 8

Chapter 8.docx

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Health Studies
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Rhan- Ju Song

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Chapter 8: King Cholera  Pettenkofer’s theory said that there was a factor in the air, called x, but x could not cause disease itself. They factor was required, which was found in the soil. Y also could not cause disease alone; however, when x got into the soil with y it caused z, a ‘miasma’. This is what caused cholera  Miasmatists: believed that disease arises from “bad vapors” and not contagious agents  The cholera epidemic began in the slums, and the poor suffered the most  Cholera was believed to travel in air, breathed in by all  Max Pettenkofer’s (first scientific hygienist) thought that its causes were filth. Laziness, and neglected hygiene. His solution was not cure but prevention  Koch used his microscope to see bacteria swimming in the feces of 12 cholera patients, he called it Vibrio cause of it vibrating wiggles A Look Back  In ancient times, outbreaks of disease were considered to be caused by divine intervention, a punishment for the wicked. o Later it was believed that there were vapors of “plagues miasmas” that caused disease  It was believed that aromatic materials could ward-off disease, so people burned tar and old shoes  Leeuwenhoek discovered bacteria and the first human parasite  Giardia is a cause of diarrhea  Pasteurization: a method for reducing spoilage by heating then cooling The Disease Cholera  Symptoms were horrible: o Radical dehydration which meant that a victim shrinked within a few hours, ruptured capillaries discoloured the skin turning them black and blue ( called the blue stage of cholera) o Cholera is a disease that causes severe diarrhea, producing “rice water” stools. There is also vomiting, seizures, muscle cramps and little abdominal pain, death may occur within a day  The origin of the word “cholera” meaning the Greek word “gutter of a roof” o Another meaning was “bad illness” from an Arabic word  Cholera is a waste-or food borne- disease that does not manifest itself until the “germ” enters the human digestive tract  The greatest epidemic of diseases of the 19 century was cholera o We are currently in a cholera epidemic that started in 1961 o Cholera was called “Americas’ greatest scourge” Vibrio Discovered  In 1883, when cholera broke out in Egypt, Koch had the intuitive insight to suggest that the disease was caused by a microbe  Koch discovered the gram-negative, comma-shaped bacillus he called Vibrio cholera Cholera and Evolution  The cause of the diarrhea in cholera is a toxin that affects the adenyl cyclase of the gut cells, producing what is called secretory diarrhea- which is of great benefit to an intestinal parasite, since the bacteria are rapidly expelled from the host and move on to infect other host  Before a person can come down with cholera, that individual must be infected by a V. cholera that is itself is infected with two viruses o One of the viruses has a gene that codes for the cholera toxin 1 o The other has a gene that codes for the receptor that allows the toxin-coding virus to enter the bacterium o Only when BOTH viruses are present is the disease-causing toxin produced  People with type O blood are more susceptible to cholera than other blood groups  People living in where cholera is endemic have some acquired immunity Catching Cholera  An infected individual excretes a trillion V.cholerae each day, so water and food can easily be contaminated  By eating vibrio-contaminated food and bathing in contaminated water, one can developed cholera  It has been found that stomach gastric juice is lethal to V.cholerae o Therefore, it takes about a billion bacteria to infect a person with normal acidity, whereas people who have low stomach acidity, only 100,000 bacteria would be needed to establish an infection  Bacteria go dormant and enter a sporelike state when conditions for their reproduction are not favourable o Under the right conditions they come out of dormancy, multiply and spread their misery Cholera Today  Most often, clinical diagnosis is based on the history of the time of appearance of acute symptoms, such as “rice water” diarrhea. Then treatment is begun.  Dr. Thomas Latta carried out the first practical application of intravenous injections of a salt solution, which did save a lot of lives  160 years later, research showed that the cholera toxins act on the absorptive cells of the intestine to shut down one major route of sodium transport which allows sodium into cells together with chloride, but the toxin leaves unaffected the transport system that brings sodium and glucose simultaneously into the cells from the lumen of the intestine o This transport system only works when both sodium and glucose are present, and it remains active during diarrhea  Today, oral rehydration treatment (ORT) involves oral or intravenous administration of a solution containing glucose, sodium chloride, potassium, and lactate, and the cost is $5 per quart
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