Detection and prevalence of the nonsyncytial American grass carp reovirus Aquareovirus G by quantitative reverse transcriptase polymerase chain reaction.

The American grass carp reovirus (AGCRV) Aquareovirus G is not strongly associated with disease in fish, but it is often detected by cell culture during routine inspections of healthy fish. The cytopathic effect of AGCRV does not involve the typical syncytia associated with most aquareoviruses. Instead, the AGCRV produces a pattern of cell rounding that is very similar to that produced by rhabdoviruses, including those that are highly regulated. We have developed a quantitative polymerase chain reaction assay that can be used to identify AGCRV in cell cultures or directly on fish tissues. The assay detects as few as two copies of the plasmid template, has a coefficient of variation of 15% among assays performed on different days, and does not cross-react with any other aquareoviruses tested. Assays performed on tissues of cultured golden shiners Notemigonus crysoleucas and fathead minnow Pimephales promelas revealed a high prevalence of infection among healthy fish but no association with disease.