Cattle Review: May–June 2021

Mycobacterium avium subsp. paratuberculosis (MAP) is a causative agent of Johne's disease, which is a chronic granulomatous enteropathy in ruminants. In a study by Lim et al (2021) (Veterinary Research https://doi.org/10.1186/s13567-021-00905-1) whole genome-based alignment and comparative analysis were performed using 40 publicly available MAP genomes. The authors state that determining the genetic diversity of MAP is necessary to understand the epidemiology and biology of MAP, as well as establishing disease control strategies. First, whole genome-based alignment was employed to identify new genomic structures in MAP genomes. Second, the genomic diversity of the MAP population was described by pangenome analysis. A phylogenetic tree based on the core genome and pangenome showed that the MAP was differentiated into two major types (C- and S-type), which was in keeping with the findings of previous studies. Finally, functional analysis of the pangenome was performed using three virulence factor databases to predict the phenotypic diversity of MAP in terms of pathogenicity. Based on the results of the pangenome analysis, the research team developed a real-time PCR technique to distinguish among S-, B- and C-type strains. In conclusion, the results of their study suggest that the phenotypic differences between MAP strains can be explained by their genetic polymorphisms. Perhaps in future we will not simply try to determine if MAP is, or is not, present on a farm, but will use much refined approaches considering both the genotype and phenotype of the MAP on our client's farms.