A pathological and immunohistochemical study of caprine pleuropneumonia induced by subspecies of Mycoplasma mycoides.

In a population of 700 goats, 150 died; of these, 29 were necropsied. Ten of the 29 goats had pleuropneumonia. Mycoplasma mycoides subsp. mycoides (Large Colony) (MmmLC), Mycoplasma mycoides subsp. capri (Mmc), and Pasteurella multocida were isolated from five of the pleuropneumonic goats. Gross and microscopical lesions were typical of caprine pleuropneumonia (CPP), with bronchopneumonia, fibrinopurulent or fibrinonecrotic pleuropneumonia and dilatation of the interlobular septa and pleura. Immunohistochemical examination with antisera against MmmLC and Mmc showed mycoplasma antigens in all 10 goats with CPP. In all cases, both MmmLC and Mmc antigens were detected together. Mycoplasma antigens were present in the lumina of the airways and alveoli, mainly inside the cytoplasm of neutrophils and macrophages, but extracellular antigen was demonstrated in areas of necrosis. Pasteurella antigens were detected in four of the 10 animals with CPP. From the histological, immunohistochemical and microbiological results it was concluded that the two mycoplasmas, acting together, caused the pleuropneumonia, with P. multocida playing a subsidiary synergistic role.