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

Parasit, hung. 16. 1983. Histopathological studies on protozoan swimm bladder imflammation of common carp fry Dr. Éva KOVÁCS-GAYER Central Veterinary Institute, Budapest, Hungary "Histopathological studies on protozoan swim bladder inflammation of common carp fry" - Kovács-Gayer, É. - Parasit, hung. , 1_6: 39-46. 1983. ABSTRACT. In acute and subacute cases of swim bladder inflammation (SBI) of common carp fry, numerous protozoa were demonstrated by histopathological examination. These parasites can be observed in the swim bladder approximately for 10 days, and a causal relationship can be established between them and the inflammatory process. The protozoa (Myxozoa) were easiest to follow in the tunica interna of the anterior sac of the swim bladder, in its loose connective tissue, and the most severe lesions developed also here. In acute swim bladder inflammation, no bacteria were demonstrable. The accompanying bacterial infections were responsible for the more severe lesions characteristic of the chronic stage on inflammation. KEY WORDS: Swim bladder inflammation, histopathological studies, common carp fry, Myxozoa. Swim bladder inflammation (SBI) of the common carp is a well-known disease of economic importance. It was first described by HOFER (1904). In Hungary, SZAKOLCZAI (1967) was the first to observe the disease among two- and three-summer old carp. Swim bladder inflammation (SBI) of the common carp was described histopathologically by JAHNEL (1938), SZAKOLCZAI (1967), GRISHCHENKO (1967), BRAUN (1969), KOKURITSEVA (1969) and PAN DEY (1974), in the majority of cases in two- and three-summer old carp. As regards the pathogenesis of the disease, the following observations were made: In acute SBI, the epithelium became multilayered, the epithelial cells contained vacuoles and were oedematous in both sacs of the swim bladder. As the process progressed, the epithelium became infiltrated by lymphocytes, while the fibres of the tunica interna by histiocytes and lymphocytes. In the central layer of the swim bladder wall the loose connective tissue widened, and, besides infiltration by the above cell types, erythrocytes and PAS-positive cells were also demonstrable. The endothelial cells of blood vessels showed severe swelling and later became vacuolated. The tunica externa rarely showed any change. The loose connective tissue of the posterior sac widened even more strikingly. Chronic SBI is characterized by further aggravation of the condition: primarily in the anterior sac, the epithelial layer detached from its connective tissue base, and cave-like formations appeared in it. In the cavity thus formed, destroyed erythrocytes and leucocytes were seen. Focal necroses and PAS-positive formations were present between the muscle fibres. According to SZAKOLCZAI ( 1967), chronic SBI is characterized by necrosis. The most severe lesions were in the central loose connective tissue where SZAKOLCZAI (1967)