Present study was aimed to diagnose early cases of paratuberculosis by demonstration and isolation of the Mycobacterium avium subsp. paratuberculosis (Bison type) in faecal and tissue samples. ELISA test and pathomorphological lesions were studied in experimentally produced paratuberculosis using MAP (Bison type) S-5 strain. Faecal sample from 142 goats from various organized herds of North India were subjected to smear (using centrifugation and decontamination method) and cultural examinations. Isolation of the mycobacteria was performed in all faecal samples and 74 tissue samples on HEY medium with or without Mycobactin-J after decontamination with 0.9% HPC. Experimental study was conducted on 13 goats (10 infected and 3 controls) where pathogenicity of S-5 strain was tested positively by gross and histopathological lesions (using routine H& E and ZN as special stain) and plate-ELISA test. Pathogenicity of the S-5 strain was proved and characteristics gross and microscopic lesions were observed on 90 DPI and onwards. Lesions showing infiltration of macrophages with AFB without granuloma formation simulating lepromatous form of human leprosy and typical granuloma as in tuberculoid form were found. Positive humoral immune response by using plate ELISA was observed on 90 DPI onwards showing antibody titer above the cut off value. There was an apparent linear correlation between the antibody level and days post infection. The performance of the different diagnostics test like examination of faecal smear by direct microscopy, faecal culture, scraping smear examination of organism from tissue pathomorphology and plate ELISA test had a linear relationship among them