An epizootic of Mycobacterium intracellulare, serotype 8 infection in swine.

Eight strains of mycobacteria isolated from tuberculous lymph nodes of swine were identified as Mycobacterium intracellulare, serotype 8. The infected swine were borne in a large breeding herd and as 8 weeks old piglets distributed to a number of farms for fattening. Autopsy material from the breeding herd, incriminated as the primary source of M. intracellulare, serotype 8 infection, has not been available for bacteriological examination, but none of a number of sows slaughtered showed any visible lesions. The organism, however, was isolated from sawdust-bedding and dust collected in pigpens. Eight samples of water collected from the well and several pipelines and taps of the automatic watering system in the infected pigpens all turned out negative. Results of medical examination of 7 farmworkers from farm G excluded the possibility of a human source of infection. Altogether 799 out of about 2000 piglets raised at farm G. and distributed for fattening to 7 different farms were detained for tuberculosis-like lesions when slaughtered some three months later. In none of the seven farms did spread of the infection occur, and despite no special measures of segregation and disinfection were taken, the M. intracellulare infection left the premises with the last pig from farm G. Neither in sow herd G. animal to animal infection seemed important. Following a rigid practice of cleaning and disinfection of the sow pens in between each litter, the infection which apparently had persisted in the environment for about nine months, disappeared and the sow herd could be saved.