The pathogen, Vibrio cholerae, is a gram-negative, motile, comma-shaped bacterium that can produce an enterotoxin (cholera toxin). Based on surface antigens (O antigen), it is classified into different groups. Groups O1 and O139 (synonym: Bengal) can cause cholera. Serogroup O1 contains two biotypes: Classical and El-Tor. The remaining serogroups - over 200 - are referred to as non-O1/non-O139 V. cholerae and can occasionally cause enteritis and various extraintestinal manifestations such as ear or wound infections.
The pathogen has a worldwide distribution, particularly in the Indian subcontinent, Central and South America. The natural reservoir for V. cholerae is surface waters, including marine waters. Most outbreaks are recorded in tropical and subtropical countries where there is an inadequate central supply of drinking water and where sanitary conditions are poor.
Transmission of V. cholerae is mainly oral, through ingestion of drinking water contaminated with faeces or vomit, or through food. Since Vibrio cholerae is very sensitive to gastric acid, the infectious dose must be relatively high. Infection via contaminated water requires103 -106 bacteria, via food only102 -104 bacteria. In people who produce less gastric acid (e.g. by taking proton pump inhibitors), the necessary infection dose is correspondingly lower.
In most cases, the pathogens are excreted for a few days after the symptoms have subsided. In asymptomatic courses, the pathogens can often be detected for 14 days. Rarely, the pathogens are excreted for months after the disease has passed. However, direct transmission from person to person is rare.
In addition to humans, ecological niches also serve as reservoirs for V. cholerae and other vibrios. If temperature, electrolyte and nutrient levels are appropriate, vibrios can survive in water for years. However, contaminated water can not only play a role in transmission through oral ingestion, but can also lead to infection through direct contact with, for example, wounds.
Cholera (caused by toxin-producing V. cholerae O1 or O139) begins with watery diarrhoea, which may also be accompanied by nausea and vomiting. Severe forms of the disease lead to watery, painless diarrhoea ("rice water stools") with fluid losses of up to 20 l/day. Patients suffer from severe cramps in the calves, there is an increasing loss of water and electrolytes. Asymptomatic courses or even mild courses of the disease, but accompanied by excretion of the pathogen, are very common (the manifestation rate is less than 2%).
Without fluid and electrolyte substitution, death may occur due to renal failure and circulatory collapse. With timely substitution therapy, the prognosis is good (lethality 1%). Infections with V. cholerae non-O1/non-O139 or other Vibrio sp. can cause gastrointestinal infections as well as ear and soft tissue infections and in severe cases lead to sepsis and subsequent death.
After infection, only incomplete immunity can be expected.
The most important measure for the treatment of cholera is the timely and sufficient balancing of the electrolyte and fluid balance. If possible, this can be done orally, e.g. with 20g glucose + 1.5g KCl + 2.5g NaCl + 3.5g Na-bicarbonate. In severe cases infusions have to be administered. The administration of antibiotics plays a minor role. In severe cases, they reduce the duration and intensity of diarrhoea and reduce the duration of pathogen excretion. Suitable drugs are erythromycin, tetracycline, doxycycline or ciprofloxacin. In extraintestinal infections with vibrios, antibiotic therapy should be considered in any case.
For prophylaxis, it is recommended above all to maintain high hygienic standards. After each bowel movement/toilet use and before handling food (including drinking water), extensive hand hygiene (washing hands with soap is sufficient!) must be carried out. In tropical countries, only bottled or boiled drinking water should be used; eating salads, raw vegetables and seafood should be avoided. In addition, disinfectant cleaning should be carried out on all objects and surfaces that have probably/visibly come into contact with the patient's excreta.
In Austria, the oral inactivated vaccine Dukoral is licensed. Vaccination is largely dispensable in tourism and is primarily recommended in this country for specific situations such as disaster missions (cholera outbreaks after natural disasters) or for work in refugee camps. The vaccination schedule and any booster vaccinations can be found in the current"Vaccination Schedule Austria" of the Federal Ministry of Social Affairs, Health, Care and Consumer Protection.
Cultural detection from stool is performed using enrichment and selective media (alkaline peptone water and Thiosulfate Citrate Bile (Salts) Sucrose Agar, TCBS Agar).
For rapid diagnostics, a multiplex PCR (Biofire®) is suitable, which provides a reliable result within a few hours.
For confirmation in case of a positive rapid test for V. cholerae O1 and/or O139, a conventional culture on enrichment and selective media (TCBS agar) is recommended.
For molecular biological diagnostics, real-time PCR and sequencing are also suitable.
The Institute of Medical Microbiology and Hygiene Vienna took over the tasks of a National Reference Centre for Cholera in 2002:
- Differential diagnosis of Vibrio species and related genera by biochemical methods.
- Serological differential diagnosis of V. cholerae O1 and O139 and non-agglutinating Vibriones
- Detection of toxigenic V. cholerae strains by molecular biological methods
- Maintaining a strain collection of epidemiologically important human and environmental isolates
- Participation in research projects on diversity and pathogenicity of cholera vibrios in domestic waters
- Consultation on questions of diagnostics, epidemiology, therapy, measures and prevention
Special Instructions: Submissions should always include information on the origin of the isolates as well as the necessary patient data, clinical and epidemiological data. Please use the corresponding submission form. Fresh cultures in transport medium with appropriate reference to medical-diagnostic material are best suited for the shipment of strains.