Correlation of Mycobacterium avium subsp. paratuberculosis counts in gastrointestinal tract, muscles of the diaphragm and the masseter of dairy cattle and potential risk for consumers

Tissues of cattle intended for human consumption can be contaminated by Mycobacterium avium subsp. paratuberculosis (MAP). Although different studies attribute varying roles of MAP in Crohn's disease progression it is thought that the exposure of humans to this bacterium should in any case be minimised. In this study, we have collected samples of intestine, mesenteric lymph nodes, muscles of diaphragm (musculus diaphragma) and masseter muscles (musculus masseter) from twenty-five cows in a slaughterhouse. The infectious status of all animals was confirmed by culture of faeces. MAP was found in almost all the intestines and mesenteric lymph nodes examined, including three faecal culture-negative animals indicating intermittent shedding. As intestine is used for the traditional production of sausages, it is alarming that 84.2% of intestine samples were positive for MAP. F57 and IS900 real time PCR revealed MAP in 40 to 68% of diaphragms and 11.1 to 38.9% of masseters. A noticeable dependence of the probability of MAP positivity of faeces versus gastrointestinal tract (GIT) and of GIT and muscles was observed. Due to the changing behaviour of consumers, both of these muscles have started to be widely used in cuisine. Therefore, the results of this paper imply that the processing of cows with paratuberculosis in abattoirs without any precautions (restrictions) and the usage of meat for human consumption should be rethought.

► We examined gastrointestinal tract and muscles of cows infected with Mycobacterium avium subsp. paratuberculosis (MAP).
► MAP was found in almost all the intestines and mesenteric lymph nodes examined.
► MAP DNA in 40 to 68% of diaphragms and 11.1 to 38.9% of masseters.
► Dependence of the probability of MAP positivity of faeces versus GIT and of GIT and muscles was observed.
► Usage of meat from paratuberculosis cows for human consumption should be rethought.