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Cholera is an acute diarrhoeal disease caused by "V Cholerae". Cases range from symptomless to severe infections. The majority of infections are mild or asymptomatic. Typical cases are characterised by the sudden onset of profuse, effortless, watery diarrhoea followed by vomiting, rapid dehydration, muscular cramps and suppression of urine. Unless there is rapid replacement of fluid and electrolytes the case fatality may be as high as 30 to 40 per cent.
Agent Factors:
- Agent: the causative agent of cholera is Vibrio cholerae.
- Resistance: the bacteria are killed if heated for 30 minutes at 56ᵒC or few seconds at boiling temperature. Bleaching powder is powerful disinfectant for the bacteria. The organism survives in ice for 4weeks or longer.
- Toxin production: the organism multiplies in the lumen of the small intestine and produce exotoxin, which causes diarrhoea.
- Reservoir of Infection: human being is the only known reservoir of infection; he may be a case or a carrier.
- Source of Infection: immediate sources of infection are the stools and vomit of case and carrier.
- Period of Infectivity: a case of cholera is infective for a period of 7 to 10 days. Convalescent carriers are infective for 2-3 weeks.
Host Factors:
- Age and Sex: Cholera affects all ages and both sexes. The attack rate is highest in children in endemic areas.
- Gastric Acidity: The organism gets destroyed in acidic conditions
- Mobility of Population: Movement of people for pilgrimage, during fairs and festivals results in increased risk of infection.
- Economic Status: The incidence tends to be highest among poor socio-economic status groups, attributable to poor hygiene.
- Immunity: Natural infection offers effective immunity to cholera. Vaccination provides only temporary and partial immunity against cholera for a period of 3-6 months.
Environmental Factors:
The transmission of the organism is possible in poor environmental sanitation. Environmental factors include contaminated water and food. A number of human habits related to water and soil pollution, low standards of personal hygiene, lack of education and poor quality of life lead to the infection. Flies may carry V. cholera.
Mode of Transmission:
Transmission occurs from man to man through-
- Faecally Contaminated water: uncontrolled water sources such as wells, lakes, ponds, streams and rivers pose a threat of infection
- Contaminated food and drinks: ingestion of contaminated food and drink is associated with outbreaks of cholera. Bottle feeding if not hygienic can cause a risk for infants.
- Direct Contact : secondary transmission where in, person to person transmission through fingers, while handling excreta and vomit of patient and infected linen and fomites.
Incubation Features: from few hours to 5 days but commonly 1-2 days
Clinical Features: severity of cholera depends on rapidity and duration of fluid loss. Typical cholera case shows three stages
- Stage of Evaluation: the onset of abrupt with profuse, painless, watery diarrhoea followed by vomiting. A person may pass around 40 stools in a day.
- Stage of Collapse: the patient passes into a stage of collapse due to dehydration. The typical signs are sunken eyes, hollow cheeks, scaphoid abdomen, sub-normal temperature, absent pulse, unrecordable blood pressure, loss of skin elasticity with reduced output of urine. Intense thirst, cramps in legs, and abdomen are frequent complaints.
- Stage of Recovery: if the patient survives, he starts showing the signs of improvement. Blood pressure begins to rise, temperature returns to normal, urine secretion re-establishes
Control:
The best method to control all types of diarrhoeal diseases is to develop and implement a national programme. A programme called ‘The guidelines for ‘Cholera Control’ have been proposed by WHO. The programme is termed as ‘Diarrhoeal Disease Control Programme’. According to this, the means of control involves-
- Verification of the diagnosis
- Notification
- Early case finding
- Establishment of treatment centers
- Rehydration therapy
- Epidemiological investigations
- Sanitation measures
- Vaccination
- Health Education
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