Organism

A bacterial infection (Vibrio cholerae) causing large-scale epidemics of severe dehydrating diarrhoea. The organism does not penetrate the bowel wall, but causes diarrhoea by the production of a potent toxin which results in secretion of water and salts by intestinal cells.

Transmission

It is transmitted via food or water contaminated with faeces or vomitus from infected individuals. A high number of organisms is required to produce diarrhoea and thus person to person transmission is uncommon. The risk of developing disease is higher in individuals who have reduced levels of gastric acid, due to gastric surgery or medications such as antacids or ulcer treatments.

The organism can persist in environmental water for prolonged periods, and can contaminate water supplies. It is associated with poverty and poor sanitation.

Regions affected

There have been recent epidemics of cholera in many parts of the world, in particular South America, central Africa and Southern Asia. Cholera is endemic in these regions and in other poor areas of the world such as the Far East. Cholera is an uncommon cause of travellers' diarrhoea but is becoming increasingly recognised as a possible cause of diarrhoea in travellers, particularly those returning from Latin America.

Prevention

Education of populations in endemic regions about the importance of handwashing, particularly for food handlers and carers, and cleanliness in food preparation is crucial in the prevention of cholera transmission. It is important to provide adequate sanitation, with disposal of human waste far from water supplies. Public water supplies should be protected by purification or chlorination.

Early identification and treatment of infected individuals will reduce transmission. Contacts of infected cases may be given antibiotics to prevent secondary cases in situations where the risk of transmission is high. As discussed below, vaccination does not play a role in the prevention of transmission in the epidemic setting.

Vaccination

The currently available vaccine for cholera takes the form of an intramuscular injection, and is generally not recommended for travellers or individuals living in high risk areas since it gives only partial and short-lived protection. Recently two oral vaccines have been developed which look more promising; these are currently undergoing assessment and are not available for general use. Cholera is uncommon in travellers, and giving advice about prevention of infection is likely to be of much greater benefit than vaccination. Vaccination is rarely of benefit in the prevention of secondary cases during epidemics, since the protective effect of vaccination is too slow compared to the relatively short incubation of the disease, but would be of benefit for protecting individuals living in high risk areas.

Symptoms

After an incubation period of two to three days (range several hours to five days) patients develop abrupt onset profuse watery diarrhoea without blood, and nausea and vomiting. Diarrhoea may be so severe that it results in extreme dehydration and death within hours if fluid is not replaced. Patients rarely have abdominal pain or fever.

Signs

Patients are dehydrated and are passing copious amounts of watery diarrhoea. The degree of dehydration may vary: individuals with mild dehydration will be alert with a dry mouth but normal pulse rate. As the degree of dehydration increases, the pulse will rise and blood pressure fall, the eyes become sunken and the patient will become increasingly restless then drowsy. Children are more likely to be delirious or have fits, and pregnant women and the elderly are at greatest risk of severe illness



Source:www.privatehealth.co.uk
Last Editorial Review: 25/1/2010