Pathology of acute aspergillosis in turkeys.

Pathologic changes were characterized by gross examination and light microscopy after intra-air sac inoculation of 9- and 19-wk-old turkeys with Aspergillus fumigatus conidia. Turkeys were euthanatized and examined at 24, 48, 72, and 96 hr postinoculation (PI). Lesions were largely confined to air sac membrane and lung tissues and were similar between the two age groups. There was progressive severity of gross lesions in both organs and of microscopic lesions in lung tissue. The character and severity of histologic lesions in air sac membranes were roughly similar at 24 through 96 hr PI, but there was an increasing amount and consolidation of exudate adherent to the epithelial surface. Lesions in air sac membranes included edema, heterophil and macrophage infiltrates, granulomas, lymphohistiocytic perivasculitis, necrosis, epithelial loss, and surface exudate. Discreet granulomas containing multinucleate giant cells were present at 24 hr PI and thereafter. Lung lesions progressed from mild interstitial pneumonia to extensive effacement by multifocal coalescing granulomas, necrosis, and hemorrhage. Severe pleuritis with local extension into lung parenchyma was seen at all time points. Numbers of intralesional fungal elements seen histologically were similar between age groups and appeared to decrease in air sac membranes and increase in lung tissues from 24 to 96 hr PI. Lung tissue of the 19-wk-old turkeys contained fewer colony-forming units per gram at time points after 24 hr PI.