Correlations between environmental conditions and Vibrio parahaemolyticus or Vibrio vulnificus in Pacific oysters from New Zealand coastal waters

ABSTRACT

Vibrio parahaemolyticus and Vibrio vulnificus can be found in oysters in coastal environments. Vibrio vulnificus can induce life-threatening illness when ingested with oysters, while V. parahaemolyticus usually causes self-limiting gastroenteritis. This study investigated correlations between concentrations of these Vibrio species in Pacific oysters from eight New Zealand coastal regions (2008–2017), and seawater surface temperature (SST), salinity and rainfall. In the pooled data, most (88%) of the oyster samples were collected during summer and autumn. The prevalence of V. parahaemolyticus and V. vulnificus was 85% and 15%, respectively. Vibrio vulnificus was always detected in the presence of V. parahaemolyticus. Across all regions, V. parahaemolyticus concentration positively correlated with SST (r_S = 0.60), but not with salinity (r_S = −0.01). Vibrio vulnificus concentration weakly correlated with SST (r_S = 0.26) and salinity (r_S = −0.21). Linear and generalised additive models were investigated but none were satisfactory for prediction. Salinity and SST explained < 50% of the variability in V. parahaemolyticus concentrations, indicating that other environmental or biological factors contributed. When SST, salinity and rainfall 15 days prior to harvesting were investigated for one region, SST was the best pre-harvest indicator for elevated concentrations of both Vibrio species.

KEYWORDS:

• Vibrio parahaemolyticus
• Vibrio vulnificus
• Pacific oysters
• New Zealand
• temperature
• salinity

Acknowledgments

The authors’ thank A. van Laanen (Cawthron Institute) for retrieving 2008/09 survey data and working through inconsistencies, S. Paine (ESR) for providing public health surveillance data (and the New Zealand Ministry of Health as the owners of these data), B. Horn (ESR) for providing advice on modelling approaches, B. Armstrong (ESR) for assisting with post-review editing, Water and Atmosphere Ltd. for rainfall data, and those working in New Zealand’s shellfish industry and/or contributing to the Ministry of Business, Innovation and Employment’s Safe Seafood Program who have supported the field studies underpinning this work.

Data availability

Supplementary information is available in the supplementary online material. The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by the New Zealand Ministry for Primary Industries (17068 – The funders had no role in study design, data analyses and interpretation but were critical in providing data.