IS900 RFLP types of Mycobacterium avium subsp paratuberculosis in faeces and environmental samples on four dairy cattle farms

Mycobacterium avium subsp. paratuberculosis ( MAP) is the causative agent of paratuberculosis, an economically serious, chronic and progressive intestinal disease of ruminants. MAP is shed into the environment particularly in the faeces of ruminants. The purpose of the present study was to monitor MAP occurrence in animal faeces and different components of the environment in four herds of infected cattle and to investigate the distribution of different restriction fragment length polymorphism ( RFLP) types. Faecal and environmental samples were tested by cultivation and identified using a Mycobactin J dependence test and IS900 polymerase chain reaction. Randomly selected MAP isolates were typed using a standardised IS900 RFLP method. A total of 2 410 samples were examined by culture. MAP isolates were detected in 111 (6.4%) faecal samples, 25 (3.9%) environmental samples and two (5.1%) small terrestrial mammals: common vole (Microtus arvalis) and lesser white-toothed shrew (Crocidura suaveolens). On farms A1 and A2 ( animals were shifted between farms A1 and A2), the same four IS900 RFLP types (A-C10, B-C10, B-C1 and B-C9) of faecal isolates were detected. Three RFLP types (except for RFLP type B-C10) were also detected in the stable environment on both farms. On farms B1 and B2 (animals were shifted between farms B1 and B2), two identical IS900 RFLP types (B-C1 and E-C1) were detected in faeces and in the stable environment. The risk of MAP transmission through water was not confirmed in our study. Animals could be infected with different RFLP types of MAP if the environment was highly contaminated with the causative agent. On some cattle farms, MAP sources in the environment could help explain the relatively long-term persistence of MAP in our animal subjects.