Anti-Cholera Vaccine

ANTI-CHOLERA VACCINE

Cholera

Cholera has been known ever since the days of Ancient Greece and it exists all over the planet. In 1995, 78 countries reported more than 200 000 case to the World Health Organization. (WHO). Modern travellers can no longer ignore the risk that cholera presents.

Cholera is caused by Vibria choerae, a bacteria that secretes a toxin irritating the lining of the intestine. Only a small quantity of the cholera toxin is necessary for the appearance of acute diarrhea.

Most infected persons will suffer a benign illness, thinking it is just another case of "tourista". But in about 2% of cases, the amount of water lost through diarrhea and vomiting can cause profound dehydration necessitating emergency medical care.

Transmission

Cholera is transmitted in water. It spreads easily once a water source has been contaminated, given that water is essential for food preparation, washing, cooking, dishwashing.

In general, Vibrio cholerae can infect food substances that do not have an acid pH, in particular vegetables, mollusks, crustaceans, fish. It can survive freezing and refrigeration and even multiply more efficiently under these conditions. It can however be destroyed by boiling; but food must not be exposed again to the bacteria since boiling also destroys competing bacteria thus helping newcomer micro-organisms.

Treatment

Most cases of diarrhea associated with cholera need only replacement of water and lost salts. The World Health Organization suggests an oral rehydration solution: one teaspoon of salt and 2 to 3 teaspoons of sugar in a solution of purified water, or a teaspoon of salt in 200 cc or juice. People afflicted with diarrhea should avoid heavily sweetened drinks (grapejuice, colas, pop, fizzy drinks, sports drinks, unless they are diluted in a good quantity of purified water. Their heavy sugar concentration hastens the elimination of water from the intestine, thus worsening the diarrhea.

Antibiotic treatment (tetracycline, sulfa, ciprofloxacin) cures the intestinal infection.

Prevention

Prevention consists of ensuring the safety of food, water and drinks. Drinks and foods distributed by street vendors are particularly at risk.

Routine immunization against cholera is not recommended in Canada. Travellers who may be exposed to countries with high endemnicity, travelling outside tourist areas, or visiting friends in affected countries may need vaccination however. Vaccination, even incomplete, offers protection when water safety is not assured.

Vaccines

A new oral live attenuated vaccine against cholera is available. One unique dose suffices to induce optimal immunity.

The live attenuated vaccine can be taken at the same time as the administration of other vaccines but it must not be administrated at the same time as antibiotics. In this case, immunization must be postponed at least 48 hours after the last antibiotic dose. Oral accination should also be postponed in the presence of acute illness, fever, diarrhea or vomiting.
For efficiency, the anti-cholera vaccine should be preserved under refrigeration between 2 and 6 °C. It is important that the solution be sealed and that the vaccine be dissolved in cold or lukewarm water at no higher than body temperature (37°C ou 98.6°F). Do not dissolve it in milk or carbonated drinks. It is important that the sealed solution and the vaccine be added simultaneously to 100 cc (4 oz) of fluid and mixed for 5 to 10 seconds. Such reconstituted vaccine should be immediately swallowed an hour before mealtime.
Anti-cholera vaccine and Le vaccin anticholérique oral and Oral anti-typhoid vaccine should be taken at intervals separated by at least 8 hours.

Neither mefloquine nor proquanil impede immune response and so these medications can be used at the same time as the anti-cholera vaccine. Anti-malarial prophylaxis with cholroquine should not be commenced within 7 days of the administration of the vaccine so as not to interfere with immune response.

No study guarantees the innocuacy of anti-cholera vaccine in children less than 2 years old and in pregnant or breastfeeding women.

The protective effect is obtained 8 dans after taking the vaccine. Protection is maintained over 6 months.

In the majority of cases, the vaccine provokes no reaction. Rare side-effects include nausea, abdominal cramping and diarrhea.