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. The gene for the classic protein exotoxin is encoded in the genome of a filamentous baceriophage CTXΦ. 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.
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.
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.
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.
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.
- ↑ Fieldhouse RJ, Turgeon Z, White D, Merrill AR. Cholera- and anthrax-like toxins are among several new ADP-ribosyltransferases. PLoS computational biology. 2010; 6(12):e1001029.(Epub) (Link to article – subscription may be required.)
- ↑ Waldor MK, Mekalanos JJ. Lysogenic conversion by a filamentous phage encoding cholera toxin. Science (New York, N.Y.). 1996 Jun 28; 272(5270):1910-4.
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