Experimental infections were performed to study the horizontal transmission of Mycobacterium avium-intracellulare (MAI) in swine. Twelve 35 to 42 day-old pigs were divided into three groups of four pigs each. Each group was housed in separate rooms, and inoculated with three MAI strains: VPS1, SC1 and ATCC-13950. After inoculation, four non-inoculated swines were added to each group and maintained in the same pen up to 150 days of age, when were slaughtered. Other four non-inoculated swines were maintained as a control group. The infection was diagnosed by the tuberculin test at 140 days of age, by detection of macroscopic lesions at slaughter and histopathologic and bacteriologic examination of tissues collected at necropsy. Culture of fecal samples were made during the experiment indicating active excretion of MAI between 14 and 42 days post-inoculation. Transmission of MAI among pigs kept in the same pen was observed with all the three strains used. The most evident transmission was with strain SC1, in which four "in contact" pigs were infected, followed by ATCC-13950 (two pigs) and VPS1 (one pig). These results indicate that infected swine can be an important source of infection, favoring the dissemination of this disease.
Swine; transmission; Mycobacterium avium-intracellulare
