Bovine viral diarrhea virus (BVDV) is a globally-distributed agent responsible for numerous clinical syndromes that lead to major economic losses. Two species, BVDV-1 and BVDV-2, discriminated on the basis of genetic and antigenic differences, are classified in the genus Pestivirus within the Flaviviridae family and distributed on all of the continents. BVDV-1 can be segregated into at least twenty-one subgenotypes (1a–1u), while four subgenotypes have been described for BVDV-2 (2a–2d). With respect to published sequences, the number of virus isolates described for BVDV-1 (88.2%) is considerably higher than for BVDV-2 (11.8%). The most frequently-reported BVDV-1 subgenotype are 1b, followed by 1a and 1c. The highest number of various BVDV subgenotypes has been documented in European countries, indicating greater genetic diversity of the virus on this continent. Current segregation of BVDV field isolates and the designation of subgenotypes are not harmonized. While the species BVDV-1 and BVDV-2 can be clearly differentiated independently from the portion of the genome being compared, analysis of different genomic regions can result in inconsistent assignment of some BVDV isolates to defined subgenotypes. To avoid non-conformities the authors recommend the development of a harmonized system for subdivision of BVDV isolates into defined subgenotypes.

This study reports the high prevalence and molecular characterization of BoHV-1 infection in imported cattle with respiratory system disease after international transport. A high mortality rate of 14.16% (51/360) was reported in a group of animals imported from Hungary to Turkey in 2019. A total of 17 samples were evaluated (3 lung tissue and 14 nasal swab samples) from 15 cattle aged 6 to 9 months not vaccinated against BoHV-1. Virus isolation, polymerase chain reaction (PCR) and restriction endonuclease analysis (REA) procedures were performed within the scope of this study. By virus isolation in MDBK cells, cytopathologic effects was detected in 8 samples (3 lung tissue and 5 nasal swabs samples). The same eight samples were also found positive by BoHV-1 PCR targeting gC (UL44) gene region. According to the sequencing result, the sample (ID: 10054) dropped into a cluster of BoHV-1.1. The REA was applied to the samples to confirm the results of phylogenetic analysis. All of the isolates were identified in the subgroup BoHV-1.1 by REA. These results showed a high mortality risk for imported animals and the possibility for BoHV-1 entering the receiving country via imported animals after transport. This event is a serious problem both for the control of BoHV-1 as well as for animal health and welfare.

Bovine viral diarrhea virus continues to threaten animal health with serious economic losses worldwide. Various killed, live-modified, or recombinant vaccine strategies are being developed for protection and control against this virus. The most important thing discovered is the choice of local and widespread strains in the vaccine content. In this study, the effectiveness of a Montanide^® ISA 206 adjuvanted killed trivalent vaccine containing endemic local strains (TR-21 [BVDV-1l], TR-26 [BVDV-1f], and TR-15 [BVDV-2b]) isolated from Türkiye, was evaluated with a cattle challenge study. Experimental groups were designed as single dose vaccination (Group-I, n:11), two dose vaccination (Group-II, n:11), and unvaccinated (Group-III, n:6) with male calves aged about 6 months. Following the immunization, challenge virus (TR-72 [BVDV-1l], TCID₅₀ 10^6.5) was given intranasally to each group (5 animals in Group-I and II and 4 animals in Group-III), and clinical findings, hematological changes, virus shedding, side effects, and viremia were monitored for 14 days after inoculation. Serological monitoring of the remaining animals against homologous and heterologous strains was carried out at one-month intervals between the 21st and 201st days after the first vaccination. The obtained results showed that the viremia, hematological changes, and clinical findings shown in unvaccinated animals (Group-III) were significantly suppressed (p < 0.05) in the vaccinated groups (Group-I and II). In addition, it was found that serologically monitored animals maintained protective neutralizing antibody (nAb) titers ≥ 8 log₂ for vaccinal and also for all reference BVDV-1 strains, which is more than three-fold protective antibody response, lasting more than 7 months after the first vaccination, whether in single or two dose application. The rise of nAbs was also detected for heterogous BVDV strains. The detected nAb titers were significantly higher (p < 0.05) in the two dose vaccination group. Based on the results, it was concluded that this trivalent- inactivated vaccine candidate can protect cattle against acute BVDV infections.