Development of a consensus reverse transcription PCR assay for the specific detection of tortoise picornaviruses

Picornaviruses (PVs) of different terrestrial tortoise species, previously designated as Virus “X,” have been frequently detected from various tissues by virus isolation in Terrapene heart cell culture as the preferred laboratory method for diagnosis. Here, we describe the development of 2 diagnostic reverse transcription (RT)-PCR–based assays for the identification and characterization of tortoise PVs belonging to the tentative genus Topivirus. To test the novel diagnostic systems, PVs were isolated from swab and tissue samples collected in Germany, Italy, and Hungary between 2000 and 2013. All 25 tested isolates gave positive results with both novel consensus primer sets. Sequencing of the amplified products confirmed that all studied viruses were members of the new proposed genus Topivirus. Phylogenetic analyses clearly distinguished 2 lineages within the genus. Based on sequence analysis, no association was observed between the geographic distribution and genetic relatedness. Furthermore, no strict host specificity was indicated. The PCR-based diagnosis may provide a time-saving and sensitive method to detect tortoise PVs, and evaluation of PV presence in these animals may help control virus spread.