Detection of salmonid alphavirus RNA in Celtic and Irish Sea flatfish

Pancreas disease (PD) caused by the salmonid alphavirus (SAV) has been the most significant cause of mortalities in Irish farmed salmon Salmo salar L. over the past decade. SAV is a single-strand positive-sense RNA virus, originally thought to be unique to salmonids, but has recently been detected using real-time RT-PCR in a number of wild non-salmonid fish. In the present report, 610 wild flatfish (common dab Limanda limanda, plaice Pleuronectes platessa and megrim Lepidorhombus whiffiagonis) were caught from the Irish and Celtic Seas and screened for SAV using real-time RT-PCR and sequencing. In general, a very low prevalence was recorded in common dab and plaice, except for 1 haul in Dublin Bay where 25% of common dab were SAV-positive. SAV sequence analysis supported the fact that real-time RT-PCR detections were specific and further characterised the detected viruses within SAV Subtype I, the predominant subtype found in farmed salmon in Ireland.