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Nineteen goslings with pulmonary and systemic aspergillosis were the subject of the study. The lungs and air sacs were the main sites affected by the disease, and were generally characterised by diffuse yellowish-white granulomas. In 7 cases with pulmonary and air-sac involvement the granulomas were scattered to the serosal linings of the gastrointestinal and upper respiratory tracts, to the liver, spleen and kidneys, and in two cases also to the bursa of Fabricius, musculus (m.) longus colli and adventitia of aorta. The granulomas were often characterised by a necrotic centre surrounded by heterophils, macrophages, lymphocyte and plasma cells, and in late granulomas by multinucleated foreign-body giant cells, and again by an outer thin fibrous capsule. Numerous fungal hyphae were found within the necrotic debris of the granulomas by Gridley and PAS staining techniques. Immunohistochemistry reliably confirmed aspergillosis in all of the cases. Fungal elements in the lungs of goslings severely affected by the disease stained heavily within the centre of the granulomas, whereas few antigens reacted in the chronic cases. Fungal fragments, which were not discernible using routine fungal stains, reacted clearly in the cytoplasm of macrophages and giant cells. Thus, although fungal elements within the granulomas were histologically indicative of aspergillosis, immunohistochemistry also had to be applied to obtain a definitive diagnosis of the disease and to differentiate it from many of the filamentous fungi.

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Twenty-five bovine fetuses naturally infected with Brucella abortus were morphologically and immunohistochemically evaluated in association with bacteriologic culture. Histopathological changes were mainly bronchopneumonia in the lungs, lymphoid hyperplasia and lymphoreticular hyperplasia in the liver and spleen. Histopathologic changes in other organs and tissues revealed hematogenous spread of the infection. Immunoreactivity to Brucella abortus was detected in all the lungs (25 fetuses) examined. However, the antigen was not detected in any of the thymus examined. Intracellular antigenic localization was identified mainly in macrophages, neutrophils and hepatocytes. In addition, B. abortus strains were isolated from abomasal contents and lungs of 22 fetuses. Eighteen of the strains were biotype 1 and the remaining four were biotype 3. These findings indicate the usefulness of immunohistochemistry in suspected cases where bacteriologic culture is negative and in cases where serology is not possible or material fixed in formalin.

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