Cholera is caused by the Vibrio cholerae bacterium – a curved bacilli (vibrios) each with one flagellum. Because of its shape, it was first given the name of Kommabacillus. The genus Vibrio are members of the family Vibrionaceae, which include Gram-negative, motile, oxidase-positive, facultative anaerobes that utilize glucose as a source of energy. Genera Vibrio, Campylobacter, and Helicobacter were, at one time, thought to be of the same genus. They are closely related biochemically, as well as structurally, and are similar in the diseases that they produce.
Of the more than twenty species and over one hundred serotypes of Vibrio, only eleven are responsible for human diseases. These eleven, though, produce only two kinds of infection – localized and severe disseminated bacteremia. Of these, sero group 01 is the one responsible for classical cholera while the others are capable of producing various forms of gastroenteritis that are nearly always associated with seafood.
V. cholerae 01 biotype El Tor, can jump continents in a matter of days, travelling around the oceans in algae. Ships dumping bilgewater are blamed. When an epidemic in Peru broke out in January 1991, it was because a ship had arrived from the Far East and had dumped bilge water into the harbor at Lima. The bacteria contaminated the shellfish and other fish in the area which were then eaten raw by the locals. From there, the infected people passed it into the sewer system, which spread the disease much farther.
A newer strain is V. cholerae 0139, which swept across India, Bangladesh, and into Thailand in 1993. Raw oysters and undercooked crabs were blamed. Another epidemic struck a refugeee camp along the Rowanda-Zaire border in 1994 where there were no proper toilet facilities or fresh water. It was thought to have started in Samalia in crowded filthy refugee camps. The Rowandan strain proved to be resistant to tetracycline, the standard anticholera drug. However, antibiotic therapy is not as effective as the immediate replacement of the electrolytes and fluids in the body. Cholera was most prevalent on the Indian continent where scientists have counted at least 6 pandemics since 1817 killing tens of thousands of people throughout Europe as well as India.
V.cholerae 0139 produces symptoms that come on rapidly and painlessly, often displaying only profuse watery diarrhea and vomiting. If the diarrhea is bloody, the cause is usually from Shigella, E. coli, or Campylobacter, but not the cholera bacterium. Incubation varies, from a few hours to a few days, after eating infected food. People are infectious until a few days after the diarrhea ceases. Once infected, immunity is developed, but only to that strain.
V. parahemolyticus accounts for the majority of food poisoning from shrimp in Japan and the US. V. alginolyticus and V. vulnificus can infect wounds received in warm salt water environments and can cause blood poisoning, if swallowed. This occurs most often in people with weakened immune systems or liver disease. V. vulnificus has turned up in raw Gulf Coast oysters, causing several deaths. These members of the genus Vibrio cause lesser diarrhea, blood poisoning, and wound infections, and is not nearly as monstrous as the classic cholera strain.
If ingested, the bacteria are quickly killed in the stomach acids. However, if the stomach contents are too alkaline, cholera bacteria have a much better chance of growing. V.cholera produces a powerful enterotoxin which is composed of two proteins – A and B. B binds to intestinal cell receptors, while A enters the cell and activates an enzyme known as adenyl cyclase. This enzyme acts as the messenger, telling the cell to release volumes of water and dissolved salts called electrolytes (sodium, chloride, potassium, and bicarbonate) into the intestine. As much as twenty liters of fluid per day are withdrawn from the body, resulting in acidosis, shock, and death. The sudden stomach cramps, followed quickly by violent diarrhea and vomiting, cause capillaries to rupture, turning the skin black and blue. Only a day or two of this will produce a collapse of the entire circulatory system, resulting in death. If the fluids and electrolytes are replaced in time, the person can recover, and recovery can be just as swift as the onset of the disease. In severe cases, treatment can only be done with IV isotonic electrolyte solutions. For less severe illnesses, oral electrolyte fluids with added glucose is usually sufficient. If they survive, older people (over fifty years of age) often become chronic carriers, intermittently shedding the organism for many years thereafter. Most cases are not treated with an antibiotic for fear of developing a mutant strain. Besides, the cost and availability for underdeveloped countries where this disease occurs most often, is prohibitive.
Cholera is thought to be as effective as a biological warfare agent, with the potential of targeting major drinking water or food supplies. This dispersal would be easy to achieve, says Mangold, and once supplies were infected, an outbreak could be explained as an “act of God,” with the mortality rate being as high as 80%. The reasoning behind this lunacy is this. One person with cholera excretes ten million million bacteria each day, but only 1 million is needed to cause disease in one person. Therefore, one person with the disease can potentially infect as many as ten million others every single day.
