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

WALUGA and BUDZYNSKA (1980) described a generalized type of sphaerosporosis in common carp fry, and reported that they had observed developmental stages of sphaerospora in the different organs. The aim of the present paper is to demonstrate the role of the protozoon shown to occur in the swim bladder of common carp fry in producing swim bladder inflammation, by the help of histopathological examinations. MATERIALS AND METHODS Three weeks old to one-summer old carp fry were used in the present studies. In the period between 1979 and 1982, partly the routine diagnostic material, partly common carp fry submitted to the laboratory for research purposes, on the whole several thousands of fish, were examined. The majority of fry were derived from two commercial fish-farms and from further two experimental farms operating with warm water. In addition to detailed pathological examinations, the fish were subjected to parasitological, bacteriological and virological examinations as well. In some cases, electron microscopic preparations were also made from the affected swim bladders. Prior to collection of material for histopathological examination, the condition of the swim bladder was examined at the time of opening the abdominal wall. In some cases the tunica externa of the swim bladder was partly removed. Swim bladders were as a rule fixed in their entirety in buffered (4%) formaldehyde solution and BOUIN's solution. Sections were prepared partly with the freezing method, partly after embedding in paraffin. For general examination, the sections were stained with P. MAYER's acidic haemalaun-eosin solution, while for demonstrating the connective tissue substance van GIESON's and FARKAS-MALLOR

Y

' s techniques were applied. GIEMSA'

s staining was applied regularly, whereas a procedure based on the PAS reaction occasionally. In addition to the swim bladders, the kidney, intestine, liver and gills were also processed. The nomenclature of the tissue structure of swim bladder of healthy common carp fry constituting the basis of the histopathological examinations has not been uniformly used by the different authors, and it pertained to two- or three-summer old carp. When comparing my own studies on the tissue layers of the swim bladder of fry with descriptions by the above authors, I used the nomenclature proposed by OPPEL (1904), distinguishing two layers which are apparent also on dissection, together with the detailed histological description of PANDEY (1974). For comparison with the older nomenclature, I remark that the name "external connective tissue layer" corresponds to "tunica externa", and the central layer containing blood vessels and the internal layer correspond to "tunica interna". RESULTS Epidemiological data and clinical observations The incidence of SBI in the common carp fry population of the fish-farms studied was between 5 and 3 0%. At earliest, the disease occurred at the age of 4 to 6 weeks, usually in the end of July. By November, the frequency of SBI had markedly decreased, and in the autumn acute cases were demonstrable only in warm-water systems. Gross pathological and histopathological examinations No evaluation has been made in cases of mortality definitely due to SBI. In cases when the damage of the swim bladder wall was of a moderate degree, the fish did not exhibit clinical