Distribution of Mycobacterium avium subsp paratuberculosis in the gastrointestinal tract of shedding cows and its application to laparoscopic biopsy

The gastrointestinal tract (GIT) is a major target for Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) in cattle. Culture examination was achieved in tissue samples obtained from 10 different regions of the GIT (proximal and distal parts of the duodenum, proximal, middle and distal parts of the jejunum, proximal and distal parts of the ileum, the ileocecal valve, the caecum and the rectum) and their adjacent lymph nodes. The culture results were statistically analysed to elucidate the distribution of M. a. paratuberculosis in the GIT. A total of 63 cows older than 24 months were diagnosed with paratuberculosis by faecal and tissue cultures. The better detection rate of M. a. paratuberculosis was found in the mucosae from the jejunum to the ileocecal valve and in the lymph nodes from the jejunum to the caecum. The mean number of colony forming units (CFU) in the mucosae and the lymph nodes of the distal jejunum and the proximal ileum was significantly higher than that in the mucosae of the duodenum, the caecum and the rectum, and in the lymph nodes of the duodenum and the rectum, respectively (P < 0.05). Laparoscopic biopsy attempted out on 4 animals to test its potential use for sample collection from the statistically optimal mesenteric lymph nodes; but resulted in an abortive attempt because these targets were encircled by the intestines, the pressure of which complicated the laparoscopic approach.