Dr. Murai Éva szerk.: Parasitologia Hungarica 16. (Budapest, 1983)

The tunica externa wiedened and contained haemorrhages and oedema (Fig. 6). The disintegration to smaller granules of masses of protozoa scattered in the tissues was a frequent finding (Fig. 7). By using GIEMSA' s tissue staining it could be followed that masses of protozoa within a mother cell consisted of dividing, so-called daughter cells, and after disintegration of the capsule of the mother cell, they dispersed to the tissues. In histological sections, these small parasites (tertiary cells) of approximately 1 um in size resembled lesions of karyorhexis (Fig. 7). No bacteria could be demonstrated in acute cases, and the virological examination was also negative. In subacute cases, with the progression of the inflammatory process, the tunica externa in many cases could no longer be removed from the tunica interna. Between these two layers debris, and in the lumen also the accumulation of fluids, was seen. In more severe cases, adhesion to the neighbouring tissues was also apparent. Histopathological examination revealed protozoa in the layers of the swim bladder only occasionally. The different layers, and primarily the loose connective tissue were infiltrated by numerous eosinophil ceUs (Fig. 8). These cells were 8 to 10/um in size, their oval nucleus showed a peripheral localization, the cells were PAS-positive and contained granules staining brilliant red with haematoxylin and eosin. Occasionally degeneration was demonstrable in the walls of blood vessels already in the acute and subacute stages of inflammation, in the layer of connective tissue and smooth muscle fibres as well (Fig. 9). Chronic cases were characterized by considerable thickening of the swim bladder wall, and in some cases also by lesions of the posterior sac. In sections, this thickening was expressed mainly as widening of the loose connective tissue (Fig. 10). The tunica interna contained large numbers of disintegrated erythrocytes and showed severe degeneration of connective tissue fibres. The tunica externa and interna was connected by angiofibroblast tissue which, and also the other layers, contained numerous bacteria. The chronic course was characterized also by peritonitis, when the thickened peritoneum adhered to the tunica externa (Fig. 11). The eosinophil cells infiltrating the loose connective tissue became bluish, numerous macrophag cells 15/um in size and staining yellowish with haematoxylin and eosin appeared and smaller inflammatory cells 4 urn in size and having lobular nuclei were also observable. Major lesions in the posterior sac were found only in chronic cases. Histologically it was characterized by chronic inflammatory changes similar to those observed in the anterior sac. Apart from peritonitis, of lesions of other organs the change of the kidney was also pathognomic. In both acute and chronic swim bladder inflammation, different developmental stages of Sphaerospora angulata were demonstrable in the lumina of the convoluted tubuli of the kidney. DISCUSSION In general, the authors who suggested a viral aetiology failed to perform histopathological examinations in SBI of the common carp fry, except NEGELE (1977) who infected common carp fry with rhabdovirus, and followed the changes occurring in various organs also histopathologically. The severity of lesions in order of succession was the following: most severe lesions were found in the liver, then in the peritoneum, intestine, spleen, kidney, swim bladder and heart. Thus, the swim bladder was one of the affected organs. Histopathologically, NEGELE (1977) found the following changes in the swim bladder: the epithelium became multilayered, the cytoplasm of epithelial cells contained vacuoles, the submucosa showed haemorrhages, and certain layers were infiltrated by lymphocytes and histiocytes. Rhabdoviral swim bladder inflammation studied by NEGELE (1977) is in many respects similar to SBI of parasitic origin, but while lesions due to the virus can be observed in all in-