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Six myxosporidian species were found in chub (Leuciscus cephalus) originating from Lower Austrian rivers. The frequency of the parasites and their localization was recorded. In all chub, independent of size and origin, Myxobolus cyprini occurred predominantly in the macrophage centres (MCs) of the haematopoietic organs, spleen and kidney. Exclusively in the head kidney of young fish not yet described vermicular plasmodia containing spores of M. cyprini were found. In muscle tissue the prevalence of M. cyprini was comparatively low. Other species of Myxobolus characterized by plasmodial cysts frequently occurred in gills and swimbladder but were rarely detected, and only in small numbers, in the haematopoietic organs. The number of M. cyprini spores and the relative volume of MCs in the haematopoietic organs were estimated in order to examine possible correlations. Significant interrelated changes were found only in juvenile fish up to a size of 15 cm. In bigger fish, the number and size of macrophage aggregates were highly variable and independent of infection intensity and fish size, but the number of spores never exceeded that of the aggregated macrophages. The data suggest that due to an early date of infection M. cyprini is the only species which is closely associated with macrophage aggregation.

Summary Between April and November 2003, parasitological examinations of the nase Chondrostoma nasus L. and the chub Leuciscus cephalus L. from the neighbouring Melk and Pielach rivers in Lower Austria were conducted. Amongst various gill parasites, Lamproglena pulchella Nordmann 1832 was detected on both fish species, which was the first record of this parasitic crustacean in Austria. Physico‐chemical examinations of water samples of the two rivers were carried out during the same period. The results indicate that general water parameters in the Melk were subjected to more vigorous changes than in the Pielach. Critical temperature levels and ammonia concentration as well as drastic changes in the ionic composition occurred more frequently in the Melk River. The observed distribution of L. pulchella indicates its sensitivity to such stress factors: there was no evidence of the parasite in the Melk River until late November and it only then occurred on the gills of L. cephalus with a prevalence of 20% and a mean intensity of 2. In the Pielach River, infestation on chub had already occurred in June with a prevalence of 40% and a mean intensity of 3, rising to 60% and 7 in November; 45% of the nase was also infested in November at a mean intensity of 3.

Spring viraemia of carp (SVC) is a viral disease that mainly affects carp Cyprinus carpio and other cyprinid fish, causing severe economic losses. Rapid detection and identification of spring viraemia of carp virus (SVCV) is crucial for effective disease management. Recent advances in nanoscience are having a significant impact on many scientific fields, especially biodiagnostics, where a number of nanoparticle-based assays have been introduced for biomolecular detection. Single-and double-stranded oligonucleotides can be adsorbed on gold nanoparticles (AuNPs) in colloidal solution under certain conditions. We exploited this phenomenon to develop a specific hybridization assay for direct detection of SVCV-RNA without prior amplification. The result of the hybridization process could be detected visually within 1 min when the colour of the reaction mixture changed from red to blue (positive reaction) or remains red (negative). The lower detection limit of the assay was estimated to be 10 −3 TCID 50 ml −1 SVCV-RNA, and it has the feasibility to detect the target virus-RNA in clinical specimens without previous amplification. In order to obtain an indication of the assay's performance on clinical samples we compared the optimized assay with nested RT-PCR in detection of SVCV-RNA in infected fish samples. The concordance of the 2 methods was defined as 100% when compared to nested RT-PCR positive and negative samples. The SVC-AuNPs assay requires only 15 min, eliminates the need for thermal cycling or detection instruments and is a specific and rapid tool for detection of SVCV-RNA directly from clinical samples. KEY WORDS: SVCV · AuNPs · Colorimetric detection · Diagnosis Resale or republication not permitted without written consent of the publisherDis Aquat Org 100: [3][4][5][6][7][8][9][10] 2012 rescence, immunoperoxidase, and ELISA (Amos 1985, OIE 2009). Rapid ad vances in molecular biology techniques have led to the development of several molecular methods for SVCV detection, including hybridization assays, RT-PCR, nested RT-PCR (nRT-PCR) and real-time PCR (Oreshkova et al. 1999, Koutná et al. 2003, Yue et al. 2008. Although these assays are specific and sen sitive, they are time consuming and require sophis ticated apparatus and complex post-run manipu lations.Recently, noble metal nanoparticles, particularly gold nanoparticles (AuNPs), have been introduced as a promising approach to the development of the next generation of diagnostic assays (Mirkin et al. 1996, Storhoff et al. 2000. AuNPs have become an important alternative as imaging agents due to their noncytotoxicity, facile immunotargeting and nonsusceptibility to photobleaching or chemical/thermal de naturation, a problem commonly associated with dyes (Jain et al. 2006). Advances in functionalizing particles with oligonucleotides and tailoring their surface properties have paved the way to design a series of new and practical systems for nucleic acid detection (Mirkin et al. 1996, Elghanian et al. 1997, Storhoff et al. 2000, Daniel & Astru...