Discovery and genetic characterization of novel caliciviruses in German and Dutch poultry
Caliciviruses (CV) were identified in the intestinal contents of five chickens and one turkey from various regions in Germany between 2009 and 2011 by degenerate reverse transcription PCR. The full 7,656-nt-long genomic sequence of the turkey CV L11043 was determined. Partial nucleotide sequences were determined for nine chicken strains. Phylogenetic analysis based on partial deduced amino acid sequences of the protease and RNA polymerase and the complete VP1 capsid sequence identified two distinct clusters of avian CVs, the first of which contained chicken CVs that were closely related to strains found in German chickens in Bavaria and that had been proposed to form a novel CV genus (proposed name: Bavovirus). In contrast, the turkey CV strain L11043 and three chicken CV strains formed a genetically distinct second cluster. Distance analysis suggested that the strains of the second cluster may represent members of two distinct genogroups of another novel CV genus (proposed name: Nacovirus). Based on the newly obtained sequence information, two real-time RT-PCR assays were developed and used to identify bavovirus and nacovirus in pooled intestinal contents from 24 chicken farms in Germany and the Netherlands. Of these, 20 (83 %) were positive for bavovirus, 11 (46 %) were positive for nacovirus, and nine (38 %) were positive for both bavovirus and nacovirus. Attempts were made to propagate chicken and turkey CVs from both the bavovirus and nacovirus clusters in primary chicken cecal cells, embryonal liver cells and fibroblast cells, but these attempts were not successful.