Two hundred additional non-toxin producing serotypes (Vibrio cholerae non O1 and non O139) are known, in addition to the toxin-producing Vibrio cholerae strains O1 and O139. They lack the ability to produce the Cholera toxin. As a result, they are referred to as non-cholera vibrio species, to distinguish them clearly from the Cholera agents. Non-cholera vibrio species can also cause infections, although these infections are usually far less severe than a Cholera infection.
Non-cholera vibrio species are spread around the globe and are found predominantly in water. Some species require salt -- i.e. they are found in seawater, lagoons, brackish water (mixture of saltwater and freshwater, e.g. in estuaries) in particular -- but also in landlocked lakes with increased levels of salt. They reproduce excessively at water temperatures over 20° Celsius.
Non-cholera vibrio species may cause diarrhoea, wound infections, middle ear infections (otitis media), the inflammation of subcutaneous tissue and, subsequently, blood poisoning. The incubation period -- i.e. the interval between infection and outbreak -- is between 12 to 24 hours. The therapy applied is based on the type of infection and would consist of antibiotic treatment, but could also require surgery and intensive medical care.
Typical risk groups, according to medical literature, are older people and individuals with weak immune systems. People with a clinical history of liver infections, diabetes mellitus, cancer/chemotherapy and severe heart conditions face a higher risk of suffering severe infections.
Incidence in Austria
Two outbreaks caused by non-cholera vibrio infections were reported in Austria in summer 2015. One of the affected patients, an 80 year-old individual with a medical history died at the end of 2015.
The increased occurrence of non-cholera vibrio in Austrian lakes could be linked to the extreme heat wave and the unusual lack of precipitation last summer. Additional tests carried out by AGES in summer 2015 found non-cholera vibrio in seven more freshwater lakes in Lower Austria and Burgenland. Migrating birds and water birds are believed to be potential sources. The levels of the classic indicator germs enterococcus and E. coli, which are used as indicators for higher levels of risk as part of the EU’s routine bathing water monitoring programme, did not increase during the examination of non-cholera vibrio species. Thus, the EU bathing waters examined conformed to all legal requirements.
The Austrian Federal Ministry of Health (BMG) has commissioned a scientific assessment at the European Centre for Disease Prevention and Control (ECDC) for this – for Austria rather new – topic.
ECDC: Monitoring programme for the Baltic Sea
Heat waves, such as the one last summer, and resulting warmer water temperatures could occur more frequently as part of global warming. This could also increase the likeliness of non-cholera vibrio in our lakes and rivers. To date, the Baltic Sea has been the only region with a potentially increased incidence.
The ECDC has put a monitoring system in place for the Baltic region, which calculates and predicts the probable occurrence of non-cholera vibrio, using the water temperature as a basis.