Distribution of Mycobacterium avium subsp. paratuberculosis in tissues of naturally infected cattle as affected by age

The objectives of this study were to investigate Mycobacterium avium subsp. paratuberculosis (MAP) distribution in various tissues, in faeces and in milk samples from 131 animals originating from one imported Jersey cattle herd from Denmark. MAP was detected by culture in 37.4% animals. Massive MAP growth was most often observed in the small intestines (48 animals). The lowest levels of MAP were found in spleen and mammary gland samples. MAP was detected in the faeces of 8.4% animals; however, milk samples were MAP negative by culture. The highest prevalence of MAP infection (42.9%) was in age Group B (1.6 to 3 years) and the lowest (6.1%) in group D (more than 8 years). Seven positive calves were detected in the youngest age group; one of them was less than one month of age, which could imply an intrauterine infection. MAP shedding in faeces by a five-month-old calf was also confirmed. The IS900 RFLP (restriction fragment length polymorphism) type B-C1 was identified in all animals