Catherine has taught various college biology courses for 5 years at both 2-year and 4-year institutions. She has a Ph.D. in cell and molecular biology.
The devastating 2010 earthquake in Haiti killed over 300,000 people. The survivors had to deal with the loss of loved ones, rebuilding homes and seeking out a livelihood. Unbeknownst to them, they also had to contend with an invisible microbe that wreaked havoc in the aftermath of the earthquake. In the two years following the earthquake almost a half a million cases of cholera were reported and over 6,600 people died of the disease in Haiti. This was the biggest outbreak of cholera in over a century.
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Cholera is caused by Vibrio cholerae, a gram-negative, rod-shaped bacteria with a small bend in the middle and a long tail-like flagella. V. cholerae looks basically like a bratwurst with a tail! Gram-negative refers to its thin cell wall, which is surrounded by a protective outer membrane. The bacteria swim quickly about in infested water using their flagella in a whip-like manner to propel forward. V. cholerae can survive in warm, basic (pH > 7) and salty water for long periods of time, but it always needs a source of water. It doesn't grow well in cold and dry climates. This is one reason that cholera is endemic (remains without external input) in parts of Asia and Latin America.
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Cholera is contracted by drinking water or eating food contaminated with V. cholerae. The contamination is typically from the feces of an infected person; however, naturally occurring populations of the bacteria are present in areas where the disease is endemic. If a V. cholerae bacterium survives the high acidic environment of the stomach, it will stick to the walls of the small intestine and reproduce. The bacterium will also produce a toxin called cholera toxin (CT), which alters the activity of the cells that line the wall of the small intestine.
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The cells of the intestinal wall have several functions, including produce mucus, and transfer nutrients from the intestine to the blood stream. However, when cells encounter CT, they also start to excrete copious amounts of electrolytes, like sodium and potassium, into the small intestine. Water typically flows towards the highest concentration of electrolytes, so copious amounts of water enter the intestine as well. This results in a very watery diarrhea with flecks of mucus, which is called rice-water stool and is the hallmark of cholera. In very severe cases, a person can lose 1 L of fluid an hour! This intense diarrhea leads to other complications, including
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If left untreated, cholera will cause death in approximately 48 hours in ~55% of cases. Although there are treatments available, the best course of action is preventing the spread of V. cholerae in the first place. Basic water purification systems and effective sewage decontamination will eliminate V. cholera and prevent its transmission. However, in rural, poor areas of the tropics and after natural disasters, basic sanitary conditions are a luxury. This is why cholera remains endemic in these areas and why Haiti experienced a large cholera outbreak after the 2010 earthquake. Vaccines are also available for people traveling to endemic countries, but the protection only lasts a few months.
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Because water and electrolyte loss are the main cause of cholera symptoms, water and electrolytes must be replaced as effectively as possible. Before 1970, the only way to replace water and electrolytes was through an intravenous (IV) needle. These were scarce in the very places that needed them most - poor, rural, tropical areas. In 1970, Oral Replacement Therapy (ORT) was developed and is now the standard treatment for conscious cholera patients. ORT is a low cost, low tech, but highly effective way to treat cholera. It involves drinking a salt-sugar solution that is similar to Gatorade™ but without all the funky food color additives.
If a person is unconscious or has an especially severe case, the sugar-salt solution can be given by IV. To treat a severe infection and limit the transmission of V. cholerae, antibiotics such as tetracycline and trimethoprim-sulfamethoxazole can be used. However, due to the rise of antibiotic-resistant V. cholerae strains (bacteria that cannot be killed by the antibiotic), the World Health Organization only recommends antibiotics in severe cases. ORT is sufficient in milder cases.
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V. cholerae is a gram-negative, bratwurst-shaped bacteria that likes to live in the warm waters of the tropics. If you drink water or eat food contaminated with V. cholerae bacteria, you have a decent chance of developing cholera. In your small intestine, the bacteria will attach to the cells lining the intestinal wall. Here, the bacteria will produce cholera toxin which alters the actions of your intestinal cells. The cells will start to excrete electrolytes and water into the intestine, which leave your body as rice-water stool. Due to this severe diarrhea, you may experience dehydration, muscle cramps, low blood pressure, a fast heart rate and possibly even coma and death if untreated. Luckily, Oral Replacement Therapy is available in nearly every part of the world, which will allow you to drink much needed fluids and electrolytes and save your life!
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.
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