Remote sensing measurements of sea surface temperature as an indicator of Vibrio parahaemolyticus in oyster meat and human illnesses

Eleni Galanis,Peggy Paduraru,Stephanie Konrad,Sarah B Henderson,Pablo Romero-Barrios

doi:10.1186/s12940-017-0301-x

Abstract

BackgroundVibrio parahaemolyticus (Vp) is a naturally occurring bacterium found in marine environments worldwide. It can cause gastrointestinal illness in humans, primarily through raw oyster consumption. Water temperatures, and potentially other environmental factors, play an important role in the growth and proliferation of Vp in the environment. Quantifying the relationships between environmental variables and indicators or incidence of Vp illness is valuable for public health surveillance to inform and enable suitable preventative measures. This study aimed to assess the relationship between environmental parameters and Vp in British Columbia (BC), Canada.MethodsThe study used Vp counts in oyster meat from 2002-2015 and laboratory confirmed Vp illnesses from 2011-2015 for the province of BC. The data were matched to environmental parameters from publicly available sources, including remote sensing measurements of nighttime sea surface temperature (SST) obtained from satellite readings at a spatial resolution of 1 km. Using three separate models, this paper assessed the relationship between (1) daily SST and Vp counts in oyster meat, (2) weekly mean Vp counts in oysters and weekly Vp illnesses, and (3) weekly mean SST and weekly Vp illnesses. The effects of salinity and chlorophyll a were also evaluated. Linear regression was used to quantify the relationship between SST and Vp, and piecewise regression was used to identify SST thresholds of concern.ResultsA total of 2327 oyster samples and 293 laboratory confirmed illnesses were included. In model 1, both SST and salinity were significant predictors of log(Vp) counts in oyster meat. In model 2, the mean log(Vp) count in oyster meat was a significant predictor of Vp illnesses. In model 3, weekly mean SST was a significant predictor of weekly Vp illnesses. The piecewise regression models identified a SST threshold of approximately 14oC for both model 1 and 3, indicating increased risk of Vp in oyster meat and Vp illnesses at higher temperatures.ConclusionMonitoring of SST, particularly through readily accessible remote sensing data, could serve as a warning signal for Vp and help inform the introduction and cessation of preventative or control measures.

Highlights

Vibrio parahaemolyticus (Vp) is a naturally occurring bacterium found in marine environments worldwide
There was no association between chlorophyll a and log(Vp), and this variable was removed from further analyses (Table 2)
The multiple linear regression model found that both SST0 and salinity were significant predictors of log(Vp), and that these relationships were not affected by inclusion of the harvest area, year, and month variables

Summary

Introduction

Vibrio parahaemolyticus (Vp) is a naturally occurring bacterium found in marine environments worldwide. It can cause gastrointestinal illness in humans, primarily through raw oyster consumption. On the Pacific coast of North America, which includes the study area of British Columbia (BC), Canada, the incidence of Vp illnesses has continually increased since the mid-2000s, though the underlying causes remain unclear [2,3,4]. Notable Vp outbreaks affecting the Pacific Northwest occurred in 1997 and 2015 [5, 6] Both of these outbreaks were associated with raw oyster consumption and above average sea water temperatures [5, 7]. Systemic infection and death rarely occur [8]

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