Cholera Infection

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The discovery of the cholera organism is credited to German bacteriologist Robert Koch, who independently identified V cholerae in 1883 during an outbreak in Egypt. The genus name refers to the fact that the organism appears to vibrate when moving.

Cholera is an acute diarrhoeal disease that can kill within hours if left untreated, caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Cholera is transmitted by the fecal-oral route and the bacterium is usually found in water or food sources that have been contaminated by feces from a person infected with cholera. Cholera is most likely to be found and spread in places with inadequate water treatment, poor sanitation, and inadequate hygiene.

Cholera has 2 main reservoirs, humans and water. V cholerae is rarely isolated from animals, and animals do not play a role in transmission of disease. A person can get cholera by drinking water or eating food contaminated with the cholera bacterium. The source of the contamination is usually the feces of an infected person that contaminates water or food. Foods and drinks sold by street vendors, Vegetables grown with water containing human wastes Raw or undercooked fish and seafood caught in waters polluted with sewage. Disease can spread rapidly in areas with inadequate treatment of sewage and drinking water.

The disease is not likely to spread directly from one person to another; therefore, casual contact with an infected person is not a risk for becoming ill. Cholera is an extremely virulent disease. It affects both children and adults and can kill within hours. Researches from Massachusetts General Hospital, Harvard University and the Broad Institute of MIT reported in Science Translational Medicine that people with blood type O are more likely to develop severe cholera.

V cholerae is a comma-shaped, gram-negative aerobic or facultative anaerobic bacillus that varies in size from 1-3 µm in length by 0.5-0.8 µm in diameter.  Its antigenic structure consists of a flagellar H antigen and a somatic O antigen. The differentiation of the latter allows for separation into pathogenic and nonpathogenic strains. Although more than 200 serogroups of V cholerae have been identified, V cholerae O1 and V cholerae O139 are the principal ones associated with epidemic cholera.

Symptoms of cholera can begin as soon as a few hours or as long as five days after infection. Often, symptoms are mild. But sometimes they are very serious. About one in 20 people infected have severe watery diarrhea accompanied by vomiting, which can quickly lead to dehydration. Although many infected people may have minimal or no symptoms, they can still contribute to spread of the infection. Signs and symptoms of dehydration include, rapid heart rate, loss of skin elasticity, dry mucous membranes, including the inside of the mouth, throat, nose, and eyelids, low blood pressure, thirst, and muscle cramps. If not treated, dehydration can lead to shock and death in a matter of hours. It can take anywhere from a few hours to 5 days for symptoms to appear after infection. Symptoms typically appear in 2-3 days.

 Cholera can be simply and successfully treated by immediate replacement of the fluid and salts lost through diarrhea. Patients can be treated with oral rehydration solution, a prepackaged mixture of sugar and salts to be mixed with water and drunk in large amounts. This solution is used throughout the world to treat diarrhea. Severe cases also require intravenous fluid replacement. With prompt rehydration, less than 1% of cholera patients die.

To test for cholera, doctors must take a stool sample or a rectal swab and send it to a laboratory to look for the cholera bacterium. Antibiotics shorten the course and diminish the severity of the illness, but they are not as important as receiving rehydration. Persons who develop severe diarrhea and vomiting should seek medical attention promptly. The disease is not likely to spread directly from one person to another; therefore, casual contact with an infected person is not a risk for becoming ill.

However, you can protect yourself and your family by using only water that has been boiled, water that has been chemically disinfected or bottled water. Be sure to use the bottled, boiled, or chemically disinfected water for the following purposes. Drink only bottled, boiled, or chemically treated water and bottled or canned carbonated beverages. Avoid tap water, fountain drinks, and ice cubes. Wash your hands often with soap and clean water. If no water and soap are available, use an alcohol-based hand cleaner. Clean your hands especially before you eat or prepare food and after using the bathroom. Use bottled, boiled, or chemically treated water to wash dishes, brush your teeth, wash and prepare food, or make ice. Eat foods that are packaged or that are freshly cooked and served hot. Do not eat raw and undercooked meats and seafood or unpeeled fruits and vegetables. Dispose of feces in a sanitary manner to prevent contamination of water and food sources.

The long-term solution for cholera control based in economic development and universal access to safe drinking water and adequate sanitation, which is key in preventing both epidemic and endemic cholera. Actions targeting environmental conditions include the development of piped water systems with water treatment facilities like chlorination, interventions at the household level as water filtration, water chemical or solar disinfection, safe water storage containers as well as the construction of systems for sewage disposal and latrines.

Health education campaigns, adapted to local culture and beliefs, should promote the adoption of appropriate hygiene practices such as hand-washing with soap, safe preparation and storage of food and breastfeeding.

 

 

Dr. Syeda Sadaf Akber

Ph.D (Microbiology)