Avian tuberculosis in pigs: Mycobacterium intracellulare infection in a breeding herd

Lymphadenitis of pigs caused by Mycobacterium intracellulare is widely recognised in continental Europe but this is the first report of it in England. No disease was seen on the farm but condemnations of tissues and organs at the slaughterhouse were often than 100 a week and in one week were in excess of 200. The loss was greater to the slaughterhouse than to the farmer because of the constant disruption to the production line. There was no evidence that diseased pigs performed less well than healthy pigs. M intracellulare types 4 and 6 and M xenopi were isolated from diseased pigs. The source of the infection was traced to the sawdust bedding supplied by a local sawmill set in the middle of a forest. Changing the bedding to straw halted the outbreak. From the sawdust M avium types 1 and 4, M fortuitum and M intracellulare type 4 were isolated. The wildlife round the sawmill was investigated as a source of infection. Although M intracellulare type 4 and M avium were isolated from moles and a hedgehog, it was concluded that the wildlife was not involved. There was no evidence of pig to pig transmission.