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Cholera

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

   CAPTION: Cholera
   Classifications and external resources

   Vibrio cholerae: The bacterium that causes cholera ( SEM image)
     ICD- 10   A 00.
     ICD- 9    001
   DiseasesDB  2546
   MedlinePlus 000303
    eMedicine  med/351  ped/382
   MeSH        C01.252.400.959.347

   Cholera is a water-borne disease caused by the bacterium Vibrio
   cholerae, which is typically ingested by drinking contaminated water,
   or by eating improperly cooked fish, especially shellfish. This
   phenomenon was first described in a scientific manner by the Portuguese
   physician Garcia de Orta in Colóquios dos Simples e Drogas da India (
   1563). Europe witnessed several epidemics in the 19th century, but the
   disease is since mostly seen in Third World countries, due to poor
   water infrastructure
   Cholera Toxin. The delivery region (blue) binds membrane carbohydrates
   to get into cells. The toxic part (red) is activated inside the cell
   (PDB code: 1xtc)
   Enlarge
   Cholera Toxin. The delivery region (blue) binds membrane carbohydrates
   to get into cells. The toxic part (red) is activated inside the cell
   (PDB code: 1xtc)

Susceptibility

   Recent epidemiologic research suggests that a person's susceptibility
   to cholera (and other diarrheas) is affected by their blood type. Those
   with type O blood are the most susceptible . Those with type AB are the
   most resistant, virtually immune. Between these two extremes are the A
   and B blood types, with type A being more resistant than type B .

   About one million V. cholerae bacteria must be ingested to cause
   cholera in normally healthy adults, although increased susceptibility
   may be observed in those with a weakened immune system, individuals
   with decreased gastric acidity (as from the use of antacids), or those
   who are malnourished.

Transmission

   Drawing of Death bringing the cholera, in Le Petit Journal.
   Enlarge
   Drawing of Death bringing the cholera, in Le Petit Journal.

   V. cholerae occurs naturally in the plankton of fresh, brackish, and
   salt water, attached primarily to copepods in the zooplankton. Coastal
   cholera outbreaks typically follow zooplankton blooms. This makes
   cholera a zoonosis. Cholera is then transmitted through ingestion of
   feces contaminated with the bacterium. The contamination usually occurs
   when untreated sewage is released into waterways or into groundwater,
   affecting the water supply, any foods washed in the water, and
   shellfish living in the affected waterway — it is rarely spread
   directly from person to person.

   The resulting diarrhea allows bacteria to spread to other people under
   unsanitary conditions.

Symptoms

   Symptoms include those of general GI tract upset, including profuse
   diarrhea. Symptoms are caused by the enterotoxins that V. cholerae
   produces. The main enterotoxin, known as cholera toxin, interacts with
   G proteins and cyclic AMP in the intestinal lining to open ion
   channels. As ions flow into the intestinal lumen, water follows due to
   osmosis.

Famous cholera victims

   The crying and pathos in the last movement of Tchaikovsky's last
   symphony made people think that Tchaikovsky had a premonition of death.
   "A week after the premiere of his Sixth Symphony, Tchaikovsky was
   dead.... The cause of this indisposition and stomach ache was suspected
   to be his infecting himself with cholera by drinking contaminated
   water. The day before while having lunch with Modest (his brother and
   biographer), he is said to have poured faucet water from a pitcher into
   his glass and drunk a few swallows. Since the water was not boiled and
   cholera was once again rampaging St. Petersburg, such a connection was
   quite plausible ...."

   Other famous people who succumbed to the disease include:
     * James K. Polk
     * Nicolas Léonard Sadi Carnot
     * Georg Wilhelm Friedrich Hegel
     * Samuel Charles Stowe, son of Harriet Beecher Stowe
     * Carl von Clausewitz
     * George Bradshaw
     * Adam Mickiewicz
     * August von Gneisenau
     * William Jenkins Worth
     * John Blake Dillon
     * Daniel Morgan Boone, founder of Kansas City, Missouri, son of
       Daniel Boone
     * James Clarence Mangan
     * Juan de Veramendi, Mexican Governor of Texas, father-in-law of Jim
       Bowie
     * Grand Duke Constantine Pavlovich of Russia
     * William Shelley, son of Mary Shelley
     * William Godwin, brother of Mary Shelley
     * Judge Daniel Stanton Bacon, father-in-law of George Armstrong
       Custer
     * Inessa Armand, mistress of Lenin and the mother of Andre, his son.

   Alexandre Dumas, French author of The Three Musketeers and The Count of
   Monte Cristo, also contracted cholera in the 1832 Paris epidemic and
   almost died, before he wrote these two novels.

Biochemistry of the V. cholerae bacterium

   Most of the Vibrio cholerae bacteria in the water that a potential host
   drinks do not survive the very acidic conditions of the human stomach
   But the few bacteria that manage to survive the stomach's acidity
   conserve their energy and stored nutrients during the perilous passage
   through the stomach by shutting down much protein production. When the
   surviving bacteria manage to exit the stomach and reach the favorable
   conditions of the small intestine, they need to propel themselves
   through the thick mucus that lines the small intestine to get to the
   intestinal wall where they can thrive. So they start up production of
   the hollow cylindrical protein flagellin to make flagella, the curly
   whip-like tails that they rotate to propel themselves through the pasty
   mucus that lines the small intestine.

   But when the cholera bacteria reach the intestinal wall, they do not
   need the flagella propellers to move themselves any more, so they stop
   producing the protein flagellin, thus again conserving energy and
   nutrients by changing the mix of proteins that they manufacture,
   responding to the changed chemical surroundings. And on reaching the
   intestinal wall, they start producing the toxic proteins that give the
   infected person a watery diarrhea which carries the multiplying and
   thriving new generations of V. cholerae bacteria out into the drinking
   water of the next host—if proper sanitation measures are not in place.

   Microbiologists have studied the genetic mechanisms by which the V.
   cholerae bacteria turn off the production of some proteins and turn on
   the production of other proteins as they respond to the series of
   chemical environments they encounter, passing through the stomach,
   through the mucous layer of the small intestine, and on to the
   intestinal wall. Of particular interest have been the genetic
   mechanisms by which cholera bacteria turn on the protein production of
   the toxins that pull chloride ions and accompanying water from the
   host's blood supply into the small intestine to create the sickening
   diarrhea. The host can become rapidly dehydrated if an appropriate
   mixture of dilute salt water and sugar is not taken to replace the
   blood's water and salts lost in the diarrhea.

   By inserting separately successive sections of V. cholerae DNA into the
   DNA of other bacteria such as E. Coli that would not naturally produce
   the protein toxins, researchers could find out the separate pieces of
   the mechanisms by which V. cholerae respond to the changing chemical
   environments of the stomach, mucous layers, and intestinal wall.
   Researchers discovered that there is a complex cascade of regulatory
   proteins that control expression of V. cholerae virulence determinants.
   In responding to the chemical environment at the intestinal wall, the
   V. cholerae bacteria produce the TcpP/TcpH proteins which, together
   with the ToxR/ToxS proteins, activate the expression of the ToxT
   regulatory protein. ToxT then directly activates expression of
   virulence genes that produce the toxins that cause diarrhea in the
   infected person and that permit the bacteria to colonize the intestine.
   Current research aims at discovering "the signal that makes the cholera
   bacteria stop swimming and start to colonize (that is, adhere to the
   cells of) the small intestine."

History

Origin and Spread

   Cholera was originally endemic to the Indian subcontinent, with the
   Ganges River likely serving as a contamination reservoir. It spread by
   trade routes (land and sea) to Russia, then to Western Europe, and from
   Europe to North America. It is now no longer considered an issue in
   Europe and North America, due to filtering and chlorination of the
   water supply.
     * 1816-1826 - First pandemic: Previously restricted, the pandemic
       began in Bengal, then spread across India by 1820. It extended as
       far as China and the Caspian Sea before receding.
     * 1829-1851 - Second pandemic reached Europe, London and Paris in
       1832. In London, it claimed 6536 victims; in Paris, 20,000
       succumbed (out of a population of 650,000) with 100,000 victims in
       all of France . It reached Russia ( Cholera Riots), Quebec, Ontario
       and New York in the same year and the Pacific coast of North
       America by 1834.
     * 1849 - Second outbreak in Paris. In London, it was the worst
       outbreak in the city's history, claiming 14,137 lives. An outbreak
       in North America took the life of former U.S. President James K.
       Polk
     * 1852-1860 - Third pandemic mainly affected Russia, with over a
       million deaths. In 1853-4, London's epidemic claimed 10,738 lives.
     * 1854 - Outbreak of cholera in Chicago took the lives of 5 1/2 per
       cent of the population
     * 1863-1875 - Fourth pandemic spread mostly in Europe and Africa.
     * 1866 - Outbreak in North America. In London, a localised epidemic
       in the East claimed 5,596 lives.
     * 1899-1923 - Sixth pandemic had little effect in Europe because of
       advances in public health, but Russia was badly affected again.
     * 1961-1970s - Seventh pandemic began in Indonesia, called El Tor
       after the strain, and reached Bangladesh in 1963, India in 1964,
       and the USSR in 1966. From North Africa it spread into Italy by
       1973. In the late 1970s there were small outbreaks in Japan and in
       the South Pacific. There were also many reports of a cholera
       outbreak near Baku in 1972, but information of this was suppressed
       in the USSR.
     * January 1991 to September 1994 - Outbreak in South America,
       apparently initiated by discharged ballast water. Beginning in Peru
       there were 1.04 million identified cases and almost 10,000 deaths.
       The causative agent was a non-O1, nonagglutinable vibrio (NAG)
       named O139 Bengal. It was first identified in Tamilnadu, India and
       for a while displaced El Tor in southern Asia before decreasing in
       prevalence from 1995 to around 10% of all cases. It is considered
       to be an intermediate between El Tor and the classic strain and
       occurs in a new serogroup. There is evidence as to the emergence of
       wide-spectrum resistance to drugs such as trimethoprim,
       sulfamethoxazole and streptomycin.

Research

   The scientists with major contributions to fighting cholera were John
   Snow, who found the link between cholera and drinking water in 1854,
   and Robert Koch, who identified V. cholerae as the bacillus causing the
   disease. The bacterium was originally isolated thirty years earlier by
   Italian anatomist Filippo Pacini, but his results were not widely known
   around the world. However John Snow and Robert Koch didn't know of
   Pacini's previous success and so were widely credited for the
   breakthrough.

   Cholera has been a laboratory for the study of evolution of virulence.
   The province of Bengal in British India was partitioned into West
   Bengal (a state in India) and the nation of Bangladesh in 1947. Prior
   to partition, both regions had Cholera pathogens with similar
   characteristics. After 1947, India made more progress on public health
   than Bangladesh. As a consequence, the strains of the pathogen which
   succeeded in India had a greater incentive in the longevity of the
   host, and are less virulent than the strains prevailing in Bangladesh,
   which uninhibitedly draw upon resources of the host thus rapidly
   killing him.

Other historical information

   In the past, people travelling in ships would hang a yellow flag if one
   or more of the crew members suffered from cholera. Boats with a yellow
   flag hung would not be allowed to disembark at any harbour. (See Love
   in the Time of Cholera)

Treatment

   Nurses encouraging this patient to drink an Oral Rehydration Solution
   to improve dehydration he acquired from cholera.Courtesy:Centers for
   Disease Control and Prevention
   Enlarge
   Nurses encouraging this patient to drink an Oral Rehydration Solution
   to improve dehydration he acquired from cholera.
   Courtesy: Centers for Disease Control and Prevention

   Treatment typically consists of aggressive rehydration and replacement
   of electrolytes, since the death rate is generally high due to the
   serious dehydration caused by the illness.

   Tetracycline antibiotics may have a role in reducing the duration and
   severity of cholera, although drug-resistance is occurring, and their
   effects on overall mortality is questioned. Other antibiotics that have
   been used include ciprofloxacin and azithromycin.

Prevention

   Although cholera can be life-threatening, it is easily prevented. In
   the United States and Western Europe, because of advanced water and
   sanitation systems, cholera is not a major threat. The last major
   outbreak of cholera in the United States was in 1911. However,
   everyone, especially travellers, should be aware of how the disease is
   transmitted and what can be done to prevent it.

   Simple sanitation is usually sufficient to stop an epidemic. There are
   several points along the transmission path at which the spread may be
   halted:
     * Sickbed: Proper disposal and treatment of waste produced by cholera
       victims.
     * Sewage: Treatment of general sewage before it enters the waterways.
     * Sources: Warnings about cholera contamination posted around
       contaminated water sources.
     * Sterilization: Boiling, filtering, and chlorination of water before
       use.

   Filtration and boiling is by far the most effective means of halting
   transmission. Cloth filters, though very basic, have greatly reduced
   the occurrence of cholera when used in poor villages in Bangladesh that
   rely on untreated surface water.

   In general, education and sanitation are the limiting factors in
   prevention of cholera epidemics.

Trivia

     * A persistent but false urban legend states that 90,000 people died
       in Chicago of cholera and typhoid fever in 1885. This story has no
       factual basis.

   Retrieved from " http://en.wikipedia.org/wiki/Cholera"
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   with only minor checks and changes (see www.wikipedia.org for details
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