CHOLERA- What, How, and Where?

Cholera is an intestinal infection caused by a bacteria Vibrio cholerae, which is gram negative comma shaped rod. The Seventh Cholera pandemic began in 1961, started in Indonesia, spreading rapidly elsewhere in eastern Asia, and from there to India and Bangladesh, the USSR, Iran and Iraq. In 1990s it reached Peru and has spread throughout South and Central America. Vibrio cholerae, biotype El Tor, that is responsible for pandemic is more resistant than the classical vibrio. In 1982 the classical vibrio began to reestablish itself in Bangladesh where, in 1992, a new pandemic began, with a new serotype 0139 (Bengal Vibrio cholerae 0139). Many major cholera pandemics have affected countries across the world. An outbreak of Cholera is often linked to contaminated drinking water. Cholera habitats are in the valley of the Ganges and other great rivers of the Far East where the humidity and the increasing population contribute to the disease.

Cholera can spread quickly in areas where there is poor sanitation and where water supplies are tainted. Food contamination by flies or hand, and shellfish also transmit the infection. The bacterium is part of the flora of slightly salty water and when this water somehow mixes into the drinking supply then an outbreak of cholera can start. The bacteria survive for up to 2 weeks in fresh water and 8 weeks in salt water. The development of an infection from the time the pathogen enters the body until signs or symptoms first appear is from a few hours to 5 days.

The main route of transmission is Fecal- oral. It rarely spreads by person-to-person contact. The bacteria are passed in stools or vomit of the patient with cholera which remains in their feces for up to a fortnight and contribute to the illness. The bacteria multiply in the lumen of the small bowel and are non- invasive. They adhere to the mucosal surface and secrete exotoxin, which stimulates the adenylyl cyclase- adenosine monophosphate pathway of the mucosa which results in an outpouring of small bowel fluid. Upto 15 liters of watery diarrhea may be passed each day.

It causes severe diarrhea without pain followed by vomiting suddenly. Once the fecal content of the gut have been evacuated the typical “rice water” material is passed which consists of clear fluid with flecks of mucus. This enormous loss of fluid from the body leads to severe dehydration and muscle cramps. This intense dehydration is the cause of death particularly among children and elderly, as they are vulnerable to the dangerous dehydration. Some symptomatic cases are hard to distinguish from other illnesses that cause diarrhea. Only one in 10 cases shows the severe symptoms such as dehydration.

Diagnosis is made by stool microscopy and culture so that an outbreak can be brought rapidly under control. Stool culture or rectal swab isolates the bacteria and can be viewed under microscope, the bacteria has a characteristic movement. Clinical diagnosis is usually easy during an epidemic.

Treatment of this condition requires strict barrier nursing, replacing the fluid and salt losses. Normally, rehydration salts are the only treatment given, although severely dehydrated patients may need intravenous fluids. Antibiotics like tetracycline is given, which reduces the fluid loss.

A well-organized response to cholera can reduce death from cholera epidemics. However, the clean water and rehydration salts required are often in short supply in areas where they are needed most. There are two types of oral cholera vaccine but is used only for travelers and is not used at a community hit by cholera. Control of an epidemic is difficult in a community unless clean water supplies can be restored.

Alleviating these severe effects requires only simple measures. Drinking boiled or treated water, cooking practices needs to be made safe where possible and practicable, all food needs to be cooked well and eaten while hot, avoid shell fish, peeling all raw fruits and vegetables. Hand washing after going to the toilet is a vital measure to prevent the spread of the disease.

The establishment of proper sanitation system for proper and hygienic disposal of human waste is a must. Control of water sources contamination, and of population movement and public education are most important in an epidemic.