Vibrio Bacteria

Vibrio vulnificus belongs to the genus Vibrio, which occurs naturally in marine plankton. Of the approximately 150 known Vibrio species, around ten per cent are pathogenic. V. vulnificus is considered the most dangerous of these: it can enter the body through minute skin abrasions whilst swimming or be ingested by eating raw seafood. Particularly in older people or those with weakened immune systems, this can lead to severe wound infections or blood poisoning, which can quickly prove fatal if left untreated. However, if the infection is detected early, it can be effectively treated with antibiotics.Klimawandel fördert die Ausbreitung gefährlicher Vibrionen/Climate change is fuelling the spread of dangerous vibrio bacteria

 

Climate change is fuelling the spread of dangerous vibrio bacteria

Human-induced climate change does not only affect the weather and the oceans, but also the spread of pathogens. A recent study by the IOW provides the first comprehensive insight into how Vibrio vulnificus is distributed in coastal waters worldwide – and why the risk of its increased occurrence is rising as a result of climate change

Worldwide Data

To investigate the global distribution of the bacteria, the Environmental Microbiology working group analysed more than 70,000 environmental DNA data sets from coastal waters around the world. The samples were collected over the past ten years and cover regions between 78 degrees south and 83 degrees north latitude. This data was supplemented by satellite information on water temperature, salinity, currents and the amount of phytoplankton in the water.

Result: Vibrio vulnificus is now found almost everywhere near coastlines – from tropical regions to the southern Baltic Sea. Particularly high relative frequencies were observed in the tropics, where around 45 per cent of all detections were recorded. Other hotspots are located on the east coast of the USA, in East Asia and in the southern Baltic Sea. There is also a noticeable trend towards higher latitudes: between 2013 and 2021, an increasing number of detections were found in more northerly regions. This suggests that rising sea temperatures are facilitating its spread northwards. Areas where there is currently an increased risk of Vibrio vulnificus occurrence are also shown here: Vibrio Mapviewer

Which environmental factors are key?

Using modern machine learning methods, the key factors influencing the occurrence of V. vulnificus have been identified. The most important factor is water temperature: almost all detections have been made in waters with temperatures above 15 °C, and particularly frequently above 18 °C. Rising sea temperatures also extend the so-called ‘Vibrio season’.

Salinity also plays a role. Although V. vulnificus can occur across a wide range of salinity levels, it thrives particularly well in only slightly salty water, as is typical of estuaries or the Baltic Sea. Another important factor is phytoplankton. It is not the algal blooms themselves, but their decomposition that appears to promote bacterial growth: as the algae die, nutrients are released which serve as food for V. vulnificus. Low current speeds further favour this process, whilst strong currents tend to inhibit its occurrence.

Prediction model and its significance for the Baltic Sea

Based on these findings, a model was developed at the IOW that can be used to predict areas with an increased likelihood of a higher incidence of V. vulnificus. Using the Baltic Sea as an example, it was found that the modelled high-risk areas correspond well with known cases of infection in Germany and Sweden – particularly along the southern coasts.

At present, severe Vibrio infections are still rare on the German Baltic coast. However, climate change, more frequent algal blooms and demographic shifts, with a growing number of older people, are increasing the risk. The study highlights how important it is to consider environmental changes and biological processes together. Such models could help in the future to create risk maps and provide early warnings to health authorities and the public.