Genetic Diversity of Bovine Viral Diarrhea Virus 1: Italian Isolates Clustered in at Least Seven Subgenotypes

Abstract

Bovine viral diarrhea virus (BVDV) is an economically important pathogen of cattle. Two approved species are recognized, namely BVDV-1 and BVDV-2. To date, only 4 subgenotypes of BVDV-2 are known, and at least 11 distinct subgenotypes have been detected for BVDV-1. In a previous study, the genetic characteristics of 38 field isolates of BVDV from northern Italy were investigated, and all 38 isolates were classified as BVDV-1 and could be assigned to 5 different subgenotypes, namely BVDV-1b, BVDV-1d, BVDV-1e, BVDV-1h, and BVDV-1f. However, the circulation of BVDV-2 has been reported in Italy as well. The aim of the current study was to type 88 BVD viruses found throughout Italy. Genetic study was based on the 5′-UTR, supported by select comparison within the Npro coding region. Phylogenetic analysis showed that 5 isolates could be typed as BVDV-2a. The remaining 83 isolates were typed as BVDV-1 and were found to belong to 7 distinct subgenotypes, namely BVDV-1a ( n = 8), BVDV-1b ( n = 37), BVDV-1d ( n = 3), BVDV-1e ( n = 22), BVDV-1f ( n = 4), BVDV-1g ( n = 4), and BVDV-1h ( n = 5). The majority of cattle farms in the current study were predominately infected by BVDV-1b and BVDV-1e isolates, whereas the other BVDV subgenotypes occurred only sporadically. The results also provided evidence for circulation of additional subgenotypes BVDV-1a and BVDV-1g. The occurrence of BVDV-2 was also reconfirmed.