Phylogenetic analysis of the sequenced segments of the env gene locus of the BLV provirus and the PCR RFLP genotyping strategy proposed in our works that is consistent with phylogenetic classification of this pathogenic agent allowed the taxonomic identification of BLV isolates identified in cattle in Tatarstan (Russian Federation) as representatives of BLV genotypes 4, 7, and 8. Of the 100 isolates identified, 64 were attributed to BLV genotype 4; 28 BLV representatives belong to the cluster of genotype 7; and the remaining 8 samples of the provirus belong to new genotype 8 of the pathogenic agent. The strategy of BLV PCR RFLP genotyping proposed in our work on the basis of five restriction endonucleases (PvuII, SspI, HphI, HaeIII, and BstYI) allowed for correct genotyping identification of the viral pathogen.

Molecular genetic research methods make it possible to evaluate the genetic diversity of bovine leukemia virus (BLV) and are the most informative approaches to its genetic identification. Molecular genetic research methods work well for the phylogenetic analysis of sequenced nucleotide DNA sequences of the provirus, as well as for the polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) according to the phylogenetic classification of the pathogen. The purpose of the research was to study the scientific and methodological approaches to the genetic identification of bovine leukemia virus, integrated into the molecular monitoring of infection of cattle with BLV genotypes. The authors used PCR-RFLP-genotyping and comparative phylogenetic analysis of aligned nucleotide sequences of the env gene fragment of the BLV provirus isolates to detect the genotypic affiliation of the cattle from twenty-one livestock farms of the Republic of Tatarstan. As a result, isolates of four out of ten BLV genotypes were found in the Tatarstani cattle, namely genotypes 1, 4, 7, and 8. The research involved a comparative analysis of 505 nucleotide sequences of a fragment of the BLV env gene, including those deposited in GenBank NCBI. The analysis confirms the inconsistency of several earlier PCR-RFLP typing strategies with the current approach in assessing the genotypic diversity by phylogenetic analysis. The improved strategy of PCR-RFLP genotyping of BLV corresponds with its modern phylogenetic classification. The strategy makes it possible to identify all the known genotypes of the viral pathogen. Its validity has been proved by in silico modelling of restrictogrammes and a phylogenetic analysis of the env gene fragment of 57 reference isolates of ten BLV genotypes that generate 57 genotype-associated combinations of diagnostically significant PCR-RFLP profiles.

Parainfluenza virus-3 is the most common etiological agent in mixed respiratory diseases of calves with high concentrations of animals. The more severe course of the disease is observed with complications from bacterial or other viral infections. This article presents the results of clinical and epizootic, serological, virological and molecular genetic studies. A cytopathogenic agent was isolated from a pathological material taken from patients with respiratory diseases of calves in a BEK cell culture. Based on the results of serological and molecular biological studies, this isolate ("LD-9") was identified as the parainfluenza-3 virus in cattle.

ФГБОУ ВО «Казанская государственная академия ветеринарной медицины имени Н.Э. Баумана» (ФГБОУ ВО Казанская ГАВМ) FSBEI HE «Kazan Bauman State Academy of Veterinary Medicine»(FSBEI HE KSAVM) Печатается по решению редакционной коллегии Казанской государственной академии ветеринарной медицины им. Н.Э. Баумана от 15 Сентября 2018 г

This study reports on the molecular-genetic characterization of a field strain of BPIV-3 isolated in the Republic of Tatarstan. M gene fragments of the Russian isolate LD-9 and the vaccine strain PTK/86 were sequenced and aligned with the corresponding sequences of the virus strains presented in GenBank. The results of the phylogenetic analysis showed that the Russian isolate LD-9 (MW52481) and the vaccine strain PTK45/86 belong to the genotype A of the parainfluenza virus-3, as well as the reference strain SF-4. The Russian isolate LD-9 showed 98.3 % similarity with the reference strain SF-4, and the Russian vaccine strain PTK-45/86 was 100 % identical to the reference strain.