Pathological changes in calves injected intradermally with Mycobacterium intracellulare serotype Davis and M. avium...

Three strains of the M. intracellulare-M. avium complex were injected intradermally into 12 calves. M. intracellulare serotype Davis (M. avium complex serotype 8) was injected into five calves. One calf died with disseminated caseous granulomas at 79 days; three calves killed between 56 and 82 days after inoculation had widely disseminated caseous or caseous or caseocalcareous granulomas. One calf killed at 173 days had only encapsulated granulomas at the injection site and its regional lymph node. Two strains of M. avium serotype 2 (M. avium complex serotype 2) were injected intradermally into seven calves. Six had disseminated granulomas when killed 54-170 days after inoculation. One calf killed at 55 days had granulomas confined to the inoculation sites and their regional lymph nodes. Lesions induced by both M. avium serotype 2 and M. intracellulare serotype Davis were initially caseocalcareous granulomas which became encapsulated and nonprogressive after about 112 days. Two calves inoculated with similar doses of M. bovis and killed in extremis at 37 and 65 days after inoculation had disseminated progressive lesions without encapsulation.