Biliary diarrhoea (Greek)Cholera is a severe infectious disease, which mainly causes severe diarrhoea. The disease is triggered by Vibrio cholerae, a gram-negative bacterium that can be transmitted to humans via contaminated drinking water or food. Cholera occurs mainly in countries with inadequate hygienic conditions, especially where food, drinking water and personal hygiene are not guaranteed.
If untreated, cholera can quickly lead to death, as the bacteria quickly infect the small intestine, causing extreme electrolyte and thus water losses. Even the suspicion of cholera must be reported to the World Health Organization (WHO). Populous countries with a lack of separation between drinking water and wastewater systems, such as South America, Africa and parts of South East Asia, are particularly affected.
Occasionally, the pathogens are introduced into Germany, so that cholera cases are rarely reported here either. For tourists from industrialised countries, the risk of infection is quite low, as cholera mainly occurs in people who are already ill and have a poor nutritional status. Every year, there are about 6 million cases worldwide with more than 100 000 deaths.
Cholera has probably been known since the 6th century BC. The disease spread much later, around 1800, from India and spread to Europe. Up to now, there have been 7 cholera pandemics.
In 1883 Robert Koch discovered the cholera pathogen by cultivating it from small intestinal cells of patients who had died of cholera. At present one speaks of the so-called El-Tor pandemic, which has been circulating in Africa and Southeast Asia since 1961 and in Peru, South America, since the 1990s. In 1992 a new subtype (serotype) of the cholera pathogen was described under the name “Bengal”, which led to outbreaks of varying severity, especially in Asia.
Cholera is caused by the gram-negative bacterium Vibrio cholerae, which is found in contaminated drinking water, food or even in seafood contaminated with faeces. In addition, humans can be directly infected with pathogens that are excreted by other carriers via the stool, although this is rather rare. Infection is still possible up to a few weeks after an infection, as pathogens can still be excreted with the stool for that long.
These then end up in the sewage and groundwater. For the disease to break out, a high bacterial count in the small intestine is necessary. Since this number is often not reached, the disease proceeds symptomless in about 85% of cases.
The cholera bacteria produce a toxin, cholera toxin, which activates a certain enzyme in the small intestine. This leads to a reduced activity of certain salt pumps in the small intestine and thus to increased excretion of electrolytes such as sodium, potassium and chloride. Since these electrolytes draw vast amounts of water into the small intestine, the typical severe diarrhoea occurs.
The fear is the rapid drying out (desiccosis) – due to the extreme water loss of up to 20 litres per day – which can lead to death within hours if not treated. A detailed overview of all tropical diseases can be found under the article: Overview of tropical diseasesAfter an infection with cholera, the disease breaks out with an incubation period of only a few hours up to 5 days – if sufficient pathogens are found in the small intestine. A distinction is made between a mild and a severe form.
While the light form – also called cholera – often cannot be distinguished from other mild diarrhoea diseases, the severe form is life-threatening and requires immediate treatment. Cholera begins suddenly with violent diarrhoea, which can be accompanied by vomiting and abdominal pain. The diarrhoea has a characteristic appearance: They are called rice water stools, as the stools are interspersed with white flakes of mucus and thus resemble the colour of rice.
The severe loss of fluid soon leads to acute dehydration (desiccosis and dehydration), which manifests itself by standing skin folds, sunken eyeballs, dry mucous membranes and a constantly falling body temperature. Furthermore, without treatment, cholera eventually leads to circulatory failure. The pulse flattens sharply, blood pressure falls and a state of shock with simultaneous kidney failure can occur.
The extreme loss of electrolytes often causes violent muscle cramps and derails the metabolism, until at some point disturbances of consciousness up to a coma can occur. The diagnosis of cholera is made on the basis of the typical clinical symptoms together with the pathogen detection from the stool or vomit of the affected person. However, it is not advisable to wait until the laboratory result is available before starting treatment, as important time is lost here.
Instead, if cholera is suspected, treatment should be started immediately, especially with fluid replacement. Even the suspicion of the disease must be reported to the World Health Organization WHO and a bacteriologist must be called in. During transport to the laboratory, care must be taken to keep the samples moist, as the pathogens are sensitive to dryness.
If the diagnosis is positive, the curved and mobile bacteria can be observed in masses in the microscopic specimen. In general, two different subgroups (serotypes) of cholera bacteria can be distinguished: O1 as well as O139, both of which are treated in the same way. If cholera is suspected, immediate isolation in a single room and immediate start of therapy is essential.
In the first place, the loss of fluid and electrolytes should be remedied to prevent complications such as circulatory and renal failure. If a quick and sufficient substitution is made, mortality can be greatly reduced. Both drinking and infusion solutions are available for fluid replacement.
In general, infusion solutions are preferable, but these are often not available in sufficient quantities, especially in Third World countries. The WHO has therefore issued a recommendation for mixing a drinking solution. This consists mainly of common salt (sodium chloride) and glucose dissolved in water as well as other electrolytes such as potassium.
Glucose is added because sodium is absorbed into the cells together with the glucose in the intestine. Sodium draws water with it, so that the loss of fluid is reduced. In addition to the fluid balance, an antibiotic is administered which kills the bacteria, but does not contribute significantly to improving the course of the disease.
Only the duration of infectivity is shortened by the drug. Quinolone or macolid preparations are used. The first priority should be adequate drinking water hygiene.
If a supply of hygienically pure drinking water cannot be guaranteed, the water must be filtered or boiled. Food such as fruit should only be eaten peeled. In addition, infected persons should preferably be quarantined in single rooms to prevent further infection.
There is the possibility of an active vaccination. This means that killed cholera bacteria are administered to achieve immunisation. The killed bacteria are no longer able to cause the disease.
However, the vaccination does not offer complete protection and has not yet been approved in Germany. The protection lasts between three and six months up to a maximum of two years. Vaccination is generally not recommended for tourists travelling to endangered areas.
However, it is currently being discussed whether the vaccination is also effective against the much more common travel diarrhoea caused by the bacterium toxin-forming Escherichia coli (ETEC). In addition, in some countries a protective vaccination is mandatory before entering the country. A live vaccine is also currently on the market. The vaccine is administered orally as a twice-inoculation. However, it is important to note that no vaccine has yet been found that protects against cholera type O 139.
