Early warning systems for Vibrio disease risks

Craig Baker-Austin gave a very interesting talk at PML this week, where he described evidence for emerging Vibrio risk at high latitudes in response to ocean warming. Several previous posts have covered similar topics:  Oliver wrote about Vezzulli et al.’s (2012) paper in the blog ‘Evidence from the Vibrios as to the effects that ocean warming has on the prokaryotic community’, Sophie reviewed Schets et al.’s paper (2011) in her blog ‘Potentially Human Pathogenic Vibrios in Marine and Fresh Bathing Waters Related to Environmental Conditions and Disease Outcome’, and finally Harri’s ‘Microbes on the March’ on Langer et al. (2013) describes shifts in distribution ranges due to temperature increases. Together these papers illustrate how temperature changes can influence distribution ranges of organisms with potential impacts on human health.

Baker-Austin et al. (2013) used multidecadal long-term sea surface temperature data sets from the Baltic Sea in combination with reports of Vibrio infections in northern Europe to study the correlation between temperature increases and Vibrio diseases. In fact, vibrios grow preferentially in warm (> 15°C), low-salinity (< 25 ppt NaCl) sea water, which is why the Baltic Sea provides a particularly interesting regions to study emerging Vibrio disease, as it forms one of the largest low-salinity marine ecosystems on Earth as well as having the fastest net SST warming trend of any large marine ecosystem between 1982 and 2007. They showed that maximum annual SST showed a very strong association with the number of Vibrio cases reported, as especially during years with extreme warm summers (1994, 2003, and 2006) an unusually high number of Vibrio-associated wound infections and fatalities were reported.  While not per se evidence for a causal link between temperature and Vibrio infections, some biologically plausible explanations support this idea: high temperatures increase bacterial replication, Vibrio vulnificus abundance peaks at > 19°C, regulation of pathogenic competence of some Vibrio species may be temperature mediated, and of course, the increased risk resulting from higher use of coastal waters for leisure activities with higher temperatures (during summer).

However, models showed that SST alone could only predict about half of the reported Vibrio cases, while models including both SST and time substantially improved the accuracy, predicting around 70% of the cases from 2006. The time component could be the result of increased awareness of Vibrio infection over time or increased exposure due to shifts in population density along coastal areas. Overall it shows that sea surface temperature can be used as predictor to identify areas at high risk, but additional unknown factors still remain to be explained to increase accuracy of models.

Baker-Austin et al., (2012). provide strong evidence that SST can be used as a predictor of risk for high abundance of pathogenic vibrios. They predict a northward shift of the areas of maximum risk of infection in the Baltic according to the model and expected warming rates in the Baltic Sea. Personally I find the proposition of an early warning system to forecast the health risks of Vibrio disease by creating risk maps based on near-real-time remote sensing data most interesting. These maps would then be made available to the public to prevent infections and fatalities; maybe one day we will have a map showing risk of Vibrio disease just after the weather forecast!

Craig Baker-Austin had some neat animations of those risk maps in his presentations, but I couldn’t find them online. But the supplementary material for this article shows some maps (3S) from remote sensing data in 2006 and risk maps for the Baltic Sea (4S).

Baker-Austin, C., Trinanes, J. a., Taylor, N. G. H., Hartnell, R., Siitonen, A. & Martinez-Urtaza, J. 2012. Emerging Vibrio risk at high latitudes in response toocean warming. Nature Climate Change, 3, 73–77.

Supplementary material: http://www.nature.com/nclimate/journal/v3/n1/extref/nclimate1628-s1.pdf

Also interesting: www.coastalWarming.com, a compilation of temperature maps.