Improved diagnosis of spring viremia of carp by nested reverse-transcription PCR: Development of a chimeric positive control for prevention of false-positive diagnosis

► Chimeric plasmids were developed to minimize false-positive diagnosis by PCR. ► An ampicillin resistance gene replaced an SVCV gene in the chimeric plasmids. ► A PCR positive control, without pathogenic nucleic acid, can be employed by this method.