Studies on pathology, cytokine gene expression and molecular typing of Mycobacterium avium subsp. paratuberculosis of naturally occurring Johne's disease in bullocks

•Pathological lesions of JD in bullocks were characterized.•Bacterial culture and PCR confirmed the prevalence of JD in bullocks.•Tissue cytokine gene expression was studied in bullocks positive for JD.•Molecular typing identified Map strains of bullocks as bison (B) type.

Pathology of Johne's disease (JD) in bullocks (castrated, adult male cattle) is rarely studied. Here, we report the pathology and cytokine gene expression of naturally occurring JD in bullocks. The small intestine and mesenteric lymph nodes collected from 404 bullocks, aged between 5 and 10 years, were examined for JD lesions and detection of Mycobacterium avium subsp. paratuberculosis (Map). A total of 8.7% bullocks exhibited JD lesions, which were classified into multibacillary-diffuse granulomatous (n = 2), paucibacillary-focal granulomatous (n = 18) and paucibacillary-diffuse lymphocytic (n = 15) lesions. The tissue cytokine gene expression profiles in all three forms of lesions corroborated with different immuno-pathological processes of JD in bullocks. The molecular typing and gene sequencing identified Map isolates from bullocks as bison type.