We compared different ways of collecting natural seawater and plankton samples in order to detect of OsHV-1 DNA and we determined whether detection of such environmental DNA was useful for disease risk prediction.
Liu O, Paul-Pont I, Rubio A, Dhand N and Whittington RJ (2019). Detection of Ostreid herpesvirus-1 in plankton and seawater samples at estuary scale. Diseases of Aquatic Organisms (in press)
Summary: Ostreid herpesvirus-1 (OsHV-1) is known to associate with particles in seawater, leading to infection and disease in the Pacific oyster, Crassostrea gigas. The estuarine environment is highly complex and changeable, which needs to be considered when collecting environmental samples for pathogen detection. The aims of this study were to (1) compare different aspects of collection natural seawater and plankton samples for detection of OsHV-1 DNA and (2) determine whether detection of OsHV-1 DNA in such environmental samples has merit for disease risk prediction. The results of one experiment suggested that sampling on the outgoing tide may improve the detection of OsHV-1 DNA in seawater and plankton tow samples (odds ratio 2.71). This statistical comparison was not possible in two other experiments. The method (plankton tow or beta bottle) and depth of collection (range 250-1250 mm) had no effect on the likelihood of detection of OsHV-1. OsHV-1 DNA was found at low concentrations in plankton tow and seawater samples, and only when outbreaks of mortality associated with OsHV-1 were observed in nearby experimental or farmed populations of C. gigas. This suggests that single point in time environmental samples of seawater or plankton would not be sufficient to rule out the presence of OsHV-1 in an estuary. The association of OsHV-1 with particles in seawater needs to be better understood in order to determine whether more selective and sensitive methods can be devised to detect it, before environmental samples could be reliably used in disease risk prediction.
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