Use of the polymerase chain reaction (PCR) to differentiate serologically similar viral haemorrhagic septicaemia (VHS) virus isolates from Europe and America.

Since 1988, VHSV (viral haemorrhagic septicaemia virus) has occasionally been isolated from salmonids and marine fish in USA. The isolates are so far serologically indistinguishable from the European VHSV reference strain F1. However, the nucleotide sequence of an American isolate (Makah) revealed a unique 20 nucleotide sequence in close proximity to the N gene. This sequence is not present in the European VHSV isolates. Through the use of PCR (polymerase chain reaction) and specific primer sets for the amplification of N gene fragments, it is now possible to distinguish between the European and American isolates within half a day.