[Mycoplasma mastitis of cattle. 8. Pathological anatomy and histology of experimental Mycoplasma bovis mastitis].

Macroscopic and histological findings, obtained from 60 udders, are described in this paper. The animals had been infected with mycoplasma bovis and slaughtered, after something between two and 21 days had elapsed from infection. The infections and, consequently, pathologico-anatomic and histological changes were found to expand rapidly over the infected quarter and, with only little time lag, across non-infected control quarters. Roughly one week from infection, the affected quarters appeared engorged, slightly enlarged, and of tough consistence, their cutting surfaces being nodular and of moderate grey-yellowish discoloration. The same quarters were clearly reduced in size, between two and three weeks after infection, and still of tough consistence, their cutting surfaces being light brown to brown-yellow and smooth. Pronounced degeneration of alveolar epithelium, exudation of neutrophilic granulocytes, differentiated in intensity, and intra-alveolar accumulation of strongly eosin-coloured homogenous substance were the histological findings recorded between four and nine days from infection. The same alterations, yet, less strongly pronounced, continued to be recordable from now reduced alveoli, between two and three weeks from infection. Lactating tissue had entirely vanished by that time. The general pattern then was characterised by extensive alveolar atrophy and inter-alveolar infiltration of plasma cells, lymphocytes, and histiocytes. These changes proved useful in diagnosis.