Sequence analysis of Turkish field strains of bovine torovirus shows unique amino acid changes in the partial M gene

Objective: To investigate the presence, prevalence and phylogenetic classification of bovine torovirus (BToV). Methods: Stool samples from 72 calves, which were negative for primary gastroenteritis agents, were examined with the nested PCR method by using BToV M gene-specific primers. Results: BToV was detected in 12 (16.7%) out of 72 samples. Phylogenetic analysis was performed using nucleotide and amino acid sequences. In the phylogenetic tree, European, American, Far East and Turkish strains were found to be divided into different branches. Interestingly, it was observed that Turkish strains were divided into two subgroups. Considering the amino acid sequences of these strains having differences at nucleotide level, the change at the 3rd amino acid of the partial M gene in Turkish strains has made Turkish strains different from all other strains. Similarly, the differences were observed in the 18th, 20th, 63rd and 93rd amino acids of the partial M gene only in Turkish field strains. Conclusions: This study revealed that Turkish strains of BToV constitute a separate phylogenetic group and can be divided into two subgroups. In addition, BToV was found to be a common pathogen causing diarrhea in calves in Turkey, and it is a necessity to consider BToV in cases of diarrhea with unknown cause.