Genotyping and pathogenicity of viral hemorrhagic septicemia virus from free-living turbot (Psetta maxima) in a Turkish coastal area of the Black Sea.
(65/202)
Viral hemorrhagic septicemia (VHS) is one of the most serious fish viral diseases for cultured rainbow trout (Oncorhynchus mykiss), although VHS virus (VHSV) seems to be ubiquitous among marine fishes. In the present study, VHSV isolation was performed with free-living and cultured turbot (Psetta maxima) in the Trabzon coastal area of the Black Sea to evaluate participation of VHSV in mass mortalities of seed-produced turbot larvae. VHSV was detected in 14 of 66 free-living spawners (positive ratio, 21.2%), 1 of 65 free-living immature fish (1.5%) and 7 of 40 cultured brood stock (17.5%), respectively. Based on a partial glycoprotein gene nucleotide sequence, Turkish VHSV isolates were classified into the class I-e of genotype I and were the most closely related to the GE-1.2 isolate (>98% identity), which was found >20 years ago in Georgia. Thus, it was revealed that Turkish VHSV isolates were not introduced from European countries, it could be an indigenous type of VHSV distributing in the Black Sea environment. In pathogenicity tests, the Turkish isolates did not induce mortality in turbot larvae and rainbow trout fingerlings. Mass mortalities at a rate of approximately 90% occurred in turbot larvae produced by experimental seeding, although VHSV was not detected in any dead fish. Thus, it was concluded that mass mortality in the seed-produced turbot larvae was not caused by VHSV infection. (+info)
Scrapie infectivity is quickly cleared in tissues of orally-infected farmed fish.
(66/202)
BACKGROUND: Scrapie and bovine spongiform encephalopathy (BSE) belongs to the group of animal transmissible spongiform encephalopathy (TSE). BSE epidemic in the UK and elsewhere in Europe has been linked to the use of bovine meat and bone meals (MBM) in the feeding of cattle. There is concern that pigs, poultry and fish bred for human consumption and fed with infected MBM would eventually develop BSE or carry residual infectivity without disease. Although there has been no evidence of infection in these species, experimental data on the susceptibility to the BSE agent of farm animals other than sheep and cow are limited only to pigs and domestic chicken. In the framework of a EU-granted project we have challenged two species of fish largely used in human food consumption, rainbow trout (Oncorhynchus mykiss) and turbot (Scophthalmus maximus), with a mouse-adapted TSE strain (scrapie 139A), to assess the risk related to oral consumption of TSE contaminated food. In trout, we also checked the "in vitro" ability of the pathological isoform of the mouse prion protein (PrPSc) to cross the intestinal epithelium when added to the mucosal side of everted intestine. RESULTS: Fish challenged with a large amount of scrapie mouse brain homogenate by either oral or parenteral routes, showed the ability to clear the majority of infectivity load. None of the fish tissues taken at different time points after oral or parenteral inoculation was able to provoke scrapie disease after intracerebral inoculation in recipient mice. However, a few recipient mice were positive for PrPSc and spongiform lesions in the brain. We also showed a specific binding of PrPSc to the mucosal side of fish intestine in the absence of an active uptake of the prion protein through the intestinal wall. CONCLUSION: These results indicate that scrapie 139A, and possibly BSE, is quickly removed from fish tissues despite evidence of a prion like protein in fish and of a specific binding of PrPSc to the mucosal side of fish intestine. (+info)
Post-embryonic remodelling of neurocranial elements: a comparative study of normal versus abnormal eye migration in a flatfish, the Atlantic halibut.
(67/202)
The process of eye migration in bilaterally symmetrical flatfish larvae starts with asymmetrical growth of the dorsomedial parts of the ethmoid plate together with the frontal bones, structures initially found in a symmetrical position between the eyes. The movement of these structures in the future ocular direction exerts a stretch on the fibroblasts in the connective tissue found between the moving structures and the eye that is to migrate. Secondarily, a dense cell population of fibroblasts ventral to the eye starts to proliferate, possibly cued by the pulling forces exerted by the eye. The increased growth ventral to the eye pushes the eye dorsally. Osteoblasts are deposited in the dense cell layer, forming the dermal part of the lateral ethmoid, and at full eye migration this will cover the area vacated by the migrated eye. When the migrating eye catches up with the previous migrated dermal bones, the frontals, these bones will be remodelled to accommodate the eye. Our findings suggest that a combination of extremely localized signals and more distant factors may impinge upon the outcome of the tissue remodelling. Early normal asymmetry of signalling factors may cascade on a series of events. (+info)
A single residue change in Vibrio harveyi hemolysin results in the loss of phospholipase and hemolytic activities and pathogenicity for turbot (Scophthalmus maximus).
(68/202)
Vibrio harveyi hemolysin, an important virulence determinant in fish pathogenesis, was further characterized, and the enzyme was identified as a phospholipase B by gas chromatography. Site-directed mutagenesis revealed that a specific residue, Ser153, was critical for its enzymatic activity and for its virulence in fish. (+info)
Morphological, cytochemical, and cytofluorimetric features of supramedullary neurons of the fish Solea ocellata.
(69/202)
Various teleost species belonging to different orders possess a particular neuronal system formed by giant supramedullary neurons (SNs). In some species, SNs are scattered along the spinal cord; in others they are organized in a compacted and well-defined cluster located at the boundary between the medulla oblongata and spinal cord. In addition to the many morphological, physiological, and histochemical studies performed both in vivo and in vitro by several authors since the end of the 19th century, quantitative microfluorometric evaluation of the DNA content of SNs has showed that clustered SNs but not aligned SNs have a DNA content much greater than the normal value of 2C. Such a high DNA content is exceptional for vertebrate neurons. In the present study, we extend this analysis of SNs to the fish Solea ocellata. Our results show that the organization of the SNs of S. ocellata is neither strictly aligned nor clustered, but somewhere in between, and that this is also true of both their morphological characteristics and DNA content values. Interspecific differences in the distribution and morphology of SNs may reflect functional differences, possibly related to environmental or behavioral differences among species. In addition, the possible functional significance of endoreplication in SNs is discussed. (+info)
Isolation and characterization of Scophthalmus maximus rhabdovirus.
(70/202)
A rhabdovirus associated with a lethal hemorrhagic disease in cultured turbot Scophthalmus maximus Linnaeus was isolated. The virus induced typical cytopathogenic effects (CPE) in 9 of 15 fish cell lines examined and was then propagated and isolated from infected carp leucocyte cells (CLC). Electron microscopy observations revealed that the negatively stained virions had a typical bullet-shaped morphology with one rounded end and one flat base end. The bullet-shaped morphology was more obvious and clear in ultrathin sections of infected cells. Experimental infections also indicated that the S. maximus rhabdovirus (SMRV) was not only a viral pathogen for cultured turbot, but also had the ability to infect other fish species, such as freshwater grass carp. A partial nucleotide sequence of the SMRV polymerase gene was determined by RT-PCR using 2 pairs of degenerate primers designed according to the conserved sequences of rhabdovirus polymerase genes. Homology analysis, amino acid sequence alignment, and phylogenetic relationship analysis of the partial SMRV polymerase sequence indicated that SMRV was genetically distinct from other rhabdoviruses. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified SMRV revealed 5 major structural proteins, and their molecular masses were estimated to be about 250, 58, 47, 42, and 28 kDa. Significant serological reactivity differences were also observed between SMRV and its nearest neighbor, spring viremia of carp virus (SVCV). The data suggest that SMRV is likely a novel fish rhabdovirus, although it is closely related to rhabdoviruses in the genus Vesiculovirus. (+info)
Scuticociliate infection and pathology in cultured turbot Scophthalmus maximus from the north of Portugal.
(71/202)
During the years 2004 and 2005 high mortalities in turbot Scophthalmus maximus (L.) from a fish farm in the north of Portugal were observed. Moribund fish showed darkening of the ventral skin, reddening of the fin bases and distended abdominal cavities caused by the accumulation of ascitic fluid. Ciliates were detected in fresh mounts from skin, gill and ascitic fluid. Histological examination revealed hyperplasia and necrosis of the gills, epidermis, dermis and muscular tissue. An inflammatory response was never observed. The ciliates were not identified to species level, but the morphological characteristics revealed by light and electronic scanning microscopes indicated that these ciliates belonged to the order Philasterida. To our knowledge this is the first report of the occurrence of epizootic disease outbreaks caused by scuticociliates in marine fish farms in Portugal. (+info)
Microarray analyses of gene expression in Japanese flounder Paralichthys olivaceus leucocytes during monogenean parasite Neoheterobothrium hirame infection.
(72/202)
In this study, the gene expression patterns of peripheral blood leucocytes (PBL) from Japanese flounder Paralichthys olivaceus were analyzed during the course of monogenean parasite Neoheterobothrium hirame infection in order to select candidates for molecular biomarkers of infection. cDNA microarray analysis was performed to compare the gene expression patterns of PBL between infected and non-infected fishes. Among the 797 genes analyzed, 45 genes (5.6%) changed their expression levels. These genes included specific and non-specific immune-related genes (matrix metalloproteinase[MMP]-9, MMP-13, leukotriene B4 receptor, CD20 receptor, MHC [major histocompatibility complex] Class I, MHC Class II beta-chain, immunoglobulin light chain and immunoglobulin heavy chain). Significant up- and down-regulation of some unknown genes was also observed. Several candidates for infection-marker genes were selected for further study. These genes included MMP-9, MMP-13, leukotriene b4 receptor, CD20 receptor, immunoglobulin heavy chain, immunoglobulin light chain and unknown genes coded as B613, E25, LB3(8), WE2(3), WE8-18R and WF12-18R. (+info)