A composition and method for immunizing a mammal infected with Mycobacterium are disclosed. The genes gcpE, pstA, kdpC, papA2, impA, umaA1, fabG2_2, aceAB, mbtH2, lpqP, map0834c, cspB, lipN, or map1634 of M. paratuberculosis and their products that they encode are vaccine targets for Johne's and Crohn's disease. Eighteen M. paratuberculosis-specific genomic islands (MAPs) were identified. Three inverted large genomic fragments in M. paratuberculosis (INV) were also identified. These genomic identifiers represent novel virulence determinants that can be used as targets for vaccines and for developments of drugs against Johne's disease. The method can be used to deliver an immunizing compounds to a mammal, to provide an immune response against Johne's or Crohn's disease in the mammal.
