According to a recently published study by oceanographers at the University of Hawaii (UH) at Manoa and Hawaii Pacific University, the abundance ofVibrio vulnificus, an infectious bacterium, is particularly influenced by the amount of rainfall in the surrounding areas.
Oliver Johnson, a graduate student in oceanography at UHM and now a HPU assistant professor, died of aV.vulnificusinfection after having cuts and scrapes exposed to the Ala Wai Harbor water.
After a number of days of intense rainfall, Steward said the exposure might have been an exacerbating factor. At the time, we discovered there was almost no information on the ecology ofV.vulnificusin the canal or in Hawaii generally, and remarkably, very little in tropical waters anywhere.
After a quick pilot study in 2006 that showed the bacteria are in high, but not unexpected numbers, the team decided to embark on a year-long research in 20082009, which aimed at understanding the abundance variation in a seasonal cycle.
When temperatures fall, the abundance ofV. vulnificus manifests a very severe seasonal cycle. In Hawaii, temperatures are mild year-round, so freshwater input becomes a more powerful control.
V.vulnificus appears naturally in warm, brackish waters, according to Nigro. So we expect this bacteria to live anywhere where temperatures are warm and freshwater and seawater mix in about equal proportions. When conditions are right, the Ala Wai Canal may be a great incubator for this bacteria!
According to researchers, rainfall has a varying incidence depending on the amount of precipitation.
Too little rainfall causes much of the canal to fall above the optimal forV. vulnificusgrowth, too much rainfall, and the canal is fresher than the bacterium likes, according to Nigro. We also discovered that because of the flushing effect of intense rainfall, the highest abundance ofV. vulnificus was shifted from inside the canal out into the harbor.
During a time of moderate rainfall, moderate salinities, and a moderate flushing of the canal, canal managers observed the highest canal-wide average abundances.
Although rainfall is more frequent in winter on average, significant rainfall may also occur in summer, therefore spikes inV. Vulnificuscan can be a problem any time of year, making it difficult to estimate when and where the pathogen will be present. However, based on a few variablesrainfall and the apparent salinity and flushing of the canal, the relative risk of exposure to this pathogen might be projected as an average for the system.
With additional years of information to better understand howV. vulnificusvaries in space and time, it might be possible to provide real-time predictions of when and where the bacterium is likely to have abnormally high concentrations, which is one component in determining the risk of infection.
According to Steward, V. vulnificuscan can cause serious or even fatal illnesses, but it generally becomes a problem for individuals with chronic illness. Hence, people should not panic about incidental exposure to canal water. However, it is wise to wash off with soap and water after exposure, and one should avoid applying open wounds to canal water.