When I think of cholera, I usually envision a third world country where untreated sewage flows into drinking water. But the microbes that cause cholera (and other infections) are natives here in Chesapeake Bay. Rita Colwell, past director of the National Science Foundation did pioneering work on this topic. Several types of Vibrio bacteria live in the Bay. One species found in low salinity regions, V. cholarae, can cause cholera when contaminated shellfish or untreated water are ingested. Around 80 people get sick from this bacteria in the United States every year (Scallan et al. 2011). V. vulnificus is a different species that grows in higher salinity regions. Only about 100 V. vulnificus infections occur each year in the United States, but this infection can be dangerous, with nearly 85% of patients requiring hospitalization and a fatality rate of over 30% (Scallan et al. 2011).
To forecast V. cholera (Louis et al. 2003; De Magny et al. 2009) and V. vulnificus (Jacobs et al. 2014) in Chesapeake Bay, scientists have developed models based on observing what are the typical temperature and salinity when Vibrio occurs. In both models, higher temperatures suggest more Vibrio. This means that increasing temperatures could both increase the likelihood that Vibrio is present, and also lengthen the time period over which the bacteria occur.
These models have been applied across the bay using hydrodynamic models to predict the temperature and salinity of the environment (Brown et al. 2012; Jacobs et al. 2014). However, at the largely freshwater Jug Bay CBNERR site (Maryland) and the mesohaline Taskinas Creek CBNERR site (Virginia), the SWMP data allow us to predict the likelihood of Vibrio species using data. The predicted seasonal pattern of V. cholarae at Jug Bay is high in summer due to high water temperatures, with little interannual variability. The early winter and spring seasons have much higher interannual variability, though probabilities generally remain below 50%. Most of this is due to temperature fluctuations. In contrast, the predicted seasonal cycle in V. vulnificus at Taskinas Creek is more concentrated around peak summertime temperatures with much lower probability of occurrence in late fall through early spring. Spring interannual variability is due to temperature variations, however the variability in late summer and fall is due more to salinity variability.
Stay tuned for Part 2 next week!
Brown, C.W., R.R. Hood, W. Long, J. Jacobs, D.L. Ramers, C. Wazniak, J.D. Wiggert, R. Wood, and J. Xu. 2013. Ecological forecasting in Chesapeake Bay: Using a mechanistic–empirical modeling approach. Journal of Marine Systems 125: 113–125. doi:10.1016/j.jmarsys.2012.12.007.
Jacobs, John M, Matt Rhodes, Christopher W Brown, Raleigh R Hood, Andrew Leight, Wen Long, and Robert Wood. 2014. Modeling and Forecasting the Distribution of Vibrio vulnificus in Chesapeake Bay. Journal of Applied Microbiology. doi:10.1111/jam.12624.
Louis, V.R., Estelle Russek-Cohen, Nipa Choopun, Irma N G Rivera, Brian Gangle, Sunny C Jiang, Andrea Rubin, Jonathan a Patz, Anwar Huq, and Rita R Colwell. 2003. Predictability of Vibrio cholerae in Chesapeake Bay. Applied and environmental microbiology 69: 2773–2785. doi:10.1128/AEM.69.5.2773.
De Magny, Guillaume Constantin, Wen Long, Christopher W. Brown, Raleigh R. Hood, Anwar Huq, Raghu Murtugudde, and Rita R. Colwell. 2009. Predicting the distribution of Vibrio spp. in the Chesapeake Bay: A vibrio cholerae case study. EcoHealth 6: 378–389. doi:10.1007/s10393-009-0273-6.
Newton, Anna, Magdalena Kendall, Duc J. Vugia, Olga L. Henao, and Barbara E. Mahon. 2012. Increasing Rates of Vibriosis in the United States, 1996–2010: Review of Surveillance Data From 2 Systems. Clin Infect Dis. 54: S391–S395. doi:10.1093/cid/cis243.Increasing.
Scallan, Elaine, Robert M. Hoekstra, Frederick J. Angulo, Robert V. Tauxe, Marc Alain Widdowson, Sharon L. Roy, Jeffery L. Jones, and Patricia M. Griffin. 2011. Foodborne illness acquired in the United States-Major pathogens. Emerging Infectious Diseases 17: 7–15. doi:10.3201/eid1701.P11101.