Cholera

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Infectious bacterial gastroenteritis associated with profuse watery diarrhoea caused by Vibrio cholerae, a comma-shaped gram-negative aerobic bacillus.

Original map by John Snow showing cases of cholera in the London epidemic of 1854.
John Snow's 1854 investigation of the Broad Street pump outbreak was one of the earliest documented successes of public health and epidemiology at work.

Contents

Aetiology

Vibrio cholerae is a motile gram negative bacillus which produces an enterotoxin that stimulates secretion of electrolyte-rich fluid from the cells into the lumen. There are actually several Vibrio cholerae toxins[1]. The gene for the classic protein exotoxin is encoded in the genome of a filamentous baceriophage CTXΦ[2]. Spread is classically by the faeco-oral route with an infective dose of from 105 to 108 organisms. While water is the traditional primary means for transmission, outbreaks of cholera have been associated with eating contaminated food (usually due to contaminated water exposure) particularly shellfish and crustaceans, but also fruit and vegetables, meat, cooked grains, etc. The incubation period is typically 2-5 days.

Clinical

Investigations

V. cholerae can be diagnosed in the laboratory by culture of stool. Specific media is required e.g. TCBS media. V. cholerae serotyping is important for epidemiological purposes.

Blood tests

Radiology

Treatment

Medical

LogoKeyPointsBox.pngREHYDRATION - AND FAST as disease kills fast within 12 hours...the rest is small print

Largely supportive - fluid replacement is essential, given that diarrhoea is commonly watery and profuse. This fluid replenishment can be achieved by oral rehydration solution or intravenous fluids. Use IV fluids if vomiting or severe. Typical requirement in severe cholera is 200ml/kg in first 24 hours, but can be up to 350ml/kg. The loss each hour can be 20ml/kg/hour and a cholera cot allowing collection and weighing of the profuse rice water stool is ideal to correctly manage fluid replacement.

Antibiotics

There is differential sensitivity to classic antibiotics which should be reserved therefore for severe disease (WHO recommendation ≥ 10% dehydration). Typical agents are doxycycline, ciprofloxacin or azithromycin. With sensitive strains they will reduce the illness length by about 50% and shorten stool excretion of v. cholerae by 1 or 2 days, and reduce health resource use.

Prevention

Cholera is a notifiable disease. Good public sanitation with clean water and clear separation of drinking water sources from sewage. There is a Cholera vaccine available in the UK, which is a killed, whole cell vaccine combined with recombinant B subunit of Cholera toxin. It is administered orally. Antibiotic prophylaxis is not recommended as a public health control measure.

External links

References

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