摘要:

Abstract.The range of branchial lesions associated with bacterial gill disease (BGD) in rainbow trout,Oncorhynchus mykiss(Richardson), was investigated through the ultrastructural examination of 23 separate outbreaks of the disease condition within commercially reared stocks. Diseased branchial tissues had a large and diffusely distributed monomorphic population of filamentous bacteria which were strictly epicellular. Although bacterial colonization was restricted to the branchial cavity, it was neither site nor cell specific: epithelial and chloride cells of the lamellae, filaments and lining tissues of the branchial cavity were all uniformly affected. The bacteria possessed an extensive glycocalyx which appeared to facilitate adhesion to the apices of the microridged sub‐unit modifications of the cell surface. Sites of colonization were accompanied by a diffuse pattern of cellular degeneration and necrosis that was generally restricted to the outer layers of epithelium. The polarity and nature of these changes suggest that the mechanism of interaction between the bacteria and host cells includes progressive hydropic change as a sequel to primary membrane damage and consequent increased cell permeability. These cellular changes were accompanied by the range of stereotypical responses of the gill to damage frequently reported for BGD including lamellar fusion, epithelial hyperplasia, and squamous and mucous cell metaplasia, in addition to lamellar spongiosi

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00572.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.This study examines the sequential pattern of bacterial colonization and the sequential development of branchial lesions during typical outbreaks of bacterial gill disease (BGD) among four groups of commercially reared rainbow trout fingerlings,Oncorhynchus mykiss(Richardson). During a 5‐month monitoring regime, prior to the onset of natural outbreaks of BGD, gill morphology of examined fish remained unaltered. Bacterial colonization of the gills was immediately preceded by several gill changes which were widely present in fish from all groups under study. These changes, which were detectable at the ultrastructural level only, included cytoplasmic blistering and degeneration of the microridges of the superficial filament epithelium, in addition to slight topographical irregularity of the filament tips suggestive of mild hyperplasia. Bacterial colonization began at these altered filament tips before spreading to more proximal regions of the filament and adjacent lamellar surfaces. Explosive increases in proportional morbidity and mortality coincided with the development of the following gill lesions: extensive bacterial colonization of lamellar surfaces, lamellar epithelial hydropic degeneration and necrosis, and lamellar oedema. In contrast, gill lesions such as lamellar fusion, epithelial hyperplasia and various metaplastic responses were detected later either as subacute (3–5 days) or chronic (7–14 days) changes. The role of epithelial necrosis as an important event during BGD is discussed as a possible mechanism leading to the development of sub‐acute and chronic gill

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00573.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Microsporidiosis in the freshwater crayfishCherax tenuimanus(Smith), or marron, was found to be due to a pleistophorid characterized by a single sporulation sequence producing eight, 16, 32 or 64 monomorphometric spores in a sporophorous vesicle with a fine two‐layered wall. Infection occurred predominantly in locomotor, cardiac and gastrointestinal striated muscle. The disease ranged from subclinical infections where haemocytic encapsulation and infiltration of the spore masses controlled its progress, to fulminant disease with multifocal infection in the absence of effective haemocytic responses. The lethal lesions in the latter cases appeared to be those in the proventriculus. Prevalence of infection and incidence of mortality were low. The same microsporidian was found in subclinically infectedC. quinquecarinatus(Gray) andC. quadricarinatus(von Mortens

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00574.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Myoliquefaction occurred post‐mortem in wild and cultured mahi mahi,Coryphaena hippurusL., stored on ice, and the flesh disintegrated upon cooking. The condition was associated with multifocal infection of muscle withKudoa thyrsites(Gilchrist). Histiolysis is presumably due to enzymes excreted by the parasite, including collagenases, as the collagen fibres of the intermyotomal connective tissues were ruptured and hypochromatic. Myofibre changes were limited to hyaline degeneration and loss of myofibrillar detail.Kudoa thyrsitesoccurs commonly in Australian populations of the type host species,Thyrsites atun(Euphrasen), which represent a partly sympatric reservoir of infection forC. hippurus.The successful culture ofC. hippurusmay require selection of disease‐free sites or use of filtered water suppl

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00575.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Using Western blot to examine the nature of soluble antigens produced byRenibacterium salmoninarum, it was found that the major 57‐kilodalton (kDa) antigen was unstable, SDS‐PAGE of extracellular product (ECP) fractions showed that degradation of the 57‐kDa protein increased with time and increased temperature. Several lower molecular mass pcptides accumulated temporarily from this degradation. Phenylmethylsulphonyl fluoride prevented breakdown of the 57‐kDa protein suggesting a scrine protease present in the ECPs was responsible. The results indicated that most, if not all, immunoreactive bands in ECP fractions, other than the 57‐kDa protein, arose as a result of degradation of this protein. Western blot analysis of two dimensional gels revealed that the presumptive proteolytic activity was associated with the 57‐kDa antigen and several of the apparent degradation products. Many common peptide fragments appeared to be generated from heat‐induced proteolysis of these protein moieties, confirming the familial relationship between much of the immunoreactive material in ECP fractions. The results suggested that the 57‐kDa antigen is autolytic. Western blot analysis of tissue samples from Atlantic salmon,Satmo solarL., infected withR. salmoninarumsuggested that this lability of the 57‐kDa antigen als

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00576.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.A mature microsporidian infection of the skeletal muscles of Norway pout,Trisopterus esmarkiiNilsson, is described. Infected fish had noticeable liquefaction of the muscle. The white foci of infection contained packed microsporidian spores, and the surrounding infected muscle fibres were degenerate. The host response involved invasion by phagocytic cells and encapsulation by fibroblasts, forming large granulomas. Macrophages, 17–20 μm in diameter, were actively ingesting the spores and typically had a foamy cytoplasm. Some had formed Langhans‐type giant cells, 35 μm in diameter, with peripherally arranged nuclei. Sporulation was complete and appeared to have occurred within sporo‐ phorous vacuoles in which numerous spores were formed. Individual spores measured 2·8 × 1·5 μm and were characterized by irregular electron dense areas, a short polar filament with four coils and a large posterior vacuole with three

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00577.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Specificities of polyclonal salmon antisera made against the fish pathogensVibrio salmonicidaandVibrio anguillarumwere studied. Using ELISA and Western blot techniques, antisera made againstV. salmonicidaorV. anguillarumserovar 1 demonstrated high responses against the homologous bacterium or its isolated LPS. In contrast, antisera obtained after immunization withV. anguillarumserovar 2 displayed low antibody titres against homologous antigens. Elcctrophoretic transfer of SDS‐PAGE separatedV. salmonicidaLPS antigen to nitrocellulose strips and subsequent immunostaining with salmon antisera revealed a strong reaction exclusively in the low molecular weight region (<14kD). On the other hand, immunoblots ofV. anguillarumLPS preparations using salmon immunesera raised against this species showed a heterogenous staining pattern ranging from high to medium LPS‐size. In addition, most of the salmon antisera made againstV. anguillarumserovar 2 also reacted with a low molecular weight LPS antigen b

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00578.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The effectiveness of three different growth media KDM‐2, S‐KDM and S‐KDM‐C for primary isolation ofRenibacterium salmoninarumwas examined over a 14‐week incubation period. Kidney samples were taken from Atlantic salmon,Salmo salarL., broodfish returning to a sea ranch after 2 years at sea. Homogenized samples were inoculated onto two selective media, S‐KDM supplemented with lamb serum and S‐KDM‐C supplemented with activated charcoal. The third medium was the non‐selective serum supplemented KDM‐2.Renibacterium salmoninarumwas isolated from 112 samples on one or more of the media used. Of all positive samples, 91% were positive on S‐KDM, 60% on S‐KDM‐C and 35% on KDM‐2. These results demonstrate that selectivity significantly enhances the isolation capacity of the medium and that supplementing with serum is significantly more effective than

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00579.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Cultivation plates for the primary isolation of Renibacterium salmoninarum were incubated for 12 or more weeks over 3.5 years. The incubation time for sample of two groups of Atlantic salmon,Salmo solarL., broodfish on a selective agar medium is reported. Samples turned positive over a long time‐span. but the longest incubation time recorded for growth of the bacterium was 19 week. In one group, 79% of all positive samples form fish with macroscopic signs of bacterial kidney disease were positive after 6 weeks of incubation and the highest incidence of positive samples occured during the sixth week. From covertly infected fish within the same group.42% of sample were positive after 6 weeks of incubation, and the highest incidence of positive sample occured during the sixth and the ninth weeks of incubation. The growth pattern of the bacterium at primary isolation was characterized by a prolonged lag phase followed by a relatively growth in one week from microscopic to macroscopic size of the colonie

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00580.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00581.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY