Vibrio cholerae: Symptoms, Treatment and Morphology

Instructor: Catherine Konopka

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 deadly disease cholera is endemic in parts of Asia and Latin America and often follows in the aftermath of natural disasters. In this lesson we will learn more about this horrific disease and the culprit behind the disease.

Cholera and the 2010 Haitian Earthquake

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.

The Culprit

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.

A Vibrio cholerae bacterium is outlined in red
Vibrio cholerae is shaped like a bent hotdog with a tail

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.

Symptoms of Cholera

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

  • Dehydration and severe thirst
  • Muscle cramps due to the loss of potassium
  • Low blood pH (acidosis)
  • Sunken eyes and flaccid skin
  • Loss of blood volume, leading to very low blood pressure (hypotension)
  • Convulsions and coma in young children
  • Very fast heart rate (tachycardia)
  • Shock

An Ounce of Prevention

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.

V. cholerae is transmitted (arrows) by consuming water infested with the bacteria from feces (rice-water stool) of persons with the disease. Transmission can be prevented (dead-ends) by proper water and sewage treatment.
Vibrio cholerae transmission can be prevented by water and sewage treatment

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