Mycobacterium avium subspecies paratuberculosis (MAP) is a member of the M. avium complex.1 The total GC-rich genome sequence comprises 4.83 mega base pairs encoding a predicted 4350 open reading frames. A little over 96 per cent of its DNA is virtually identical in sequence and genetic organization to that of the generally non-pathogenic M. avium. The remainder of the genome, comprising fewer than 200 open reading frames, is either unique to MAP or homologous to genes associated with pathogenicity in other organisms.