摘要:

Abstract.A rickettsia‐like organism (RLO) was isolated from infected coho salmon,Oncorhynchus kisutch(Walbaum), in cultures from six fish cell lines, but could not be cultured on 41 artificial media. The organism was confirmed by Koch's postulates as the aetiological agent of a systemic disease causing signifieant mortality among coho in Chile. The organism was a Gram‐negative, obligate intracellular pathogen frequently observed within intracyto‐plasmic vacuoles or inclusions of host cells, and appears to belong to the order Rickettsiales, family Rickettsiaceae and possibly the tribe Ehrlichiae. The organism, as well as the clinical signs and pathology it produces, is described. The disease, originally observed only in coho raised in seawater net pens, was reproduced experimentally in fish in both freshwater and seawater aquaria. Horizontal transmission without parasite vectors was observed in fish in both aquaria. The organism was shown, for the first time, to cause disease and mortality in Atlantic,Salmo salarL., and Chinook,O. tshawytscha(Walbaum), salmon and rainbow trout,O. mykiss(Walbaum). Because of the systemic nature of the disease, it is proposed that it be called ‘salmonid rickettsial septi

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00584.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.High levels of mortalities have been experienced in farmed coho salmon,Oncorhynchus kisuteh(Walbaum), in the Gulf of Ancud, southern Chile. Most affected fish had similar skin lesions ranging from small areas of raised scales through white raised plaques to shallow ulcers. The fish were also generally dark, lethargic and anorexic. However, some affected fish appeared grossly normal with no skin lesions. Internal pathology consisted of varying degrees of ascites, peritonitis and general pallor. Spleens were generally enlarged. Kidneys and livers were swollen and grey in colour, often with pale focal lesions. Extensive histopathology was present in affected fish with tissue necrosis, intravascular necrotic thrombi, large basophilic cells and basophilic granules, some free in the tissues, some contained within cells. The basophilic granules, known locally as the ‘UA’, or unidentified agent, were thought to be the main aetiological agent, and are likely to be a rickettsia‐like org

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00585.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Epizootic haematopoietic necrosis virus (EHNV) has been isolated from redfin perch,Perca fluviatilisL., and cultured rainbow trout,Oncorhynchus mykiss(Walbaum), in Victoria and New South Wales, Australia. On the basis of virion size, icosahedral morphology and ultrastructural characteristics of virus‐infected cells, EHNV was designated as an iridovirus. The following observations outlined in this paper confirm the designation: (1) The number and complexity of proteins in purified EHNV and the ordered appearance of virus‐specific proteins in infected cells are similar to that described for the iridovirus, frog virus 3 (FV3). (2) EHNV isolated from the cytoplasm of infected cells contains a lipid membrane associated with 7–9 nm capsomeric subunits containing a 52‐kD protein. (3) The morphogenesis of EHNV within cytoplasmic inclusion bodies resembles that of FV3 and a piscine iridovirus isolated from goldfish,Carassius auratus(L.) (4) EHNV also resembles FV3 in its association with the cytoskeleton of infected cells. (5) EHNV DNA, like that of other iridoviruses, is resistant to digestion with HpaII, a restriction endonuclease which does not cleave DNA at CCGG sequences where the internal cytosine is met

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00586.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Traditional biochemieal techniques and a stain to detect proteases in polyacrylamide gels were used to identify and partially characterize three proteases, P1, P2 and P3, produced byAeromonas hydrophilastrain Ah 22. P1 was found to be a heat‐labile serine protease with an optimum pH of 7·5, while P2 is a heat‐stable metalloprotease with an optimum pH of 8·0, and P3 is a moderately heat‐stable metalloprotease with peak activity beween pH 7 and 11. A comparison of 17 other strains of theA. hydrophilacomplex indicated that four produced P1, P2 and P3. Two strains produced just P1 and P3; one produced only P3; six produced two different serine proteases, P2a and P2b; and two produced a number of uncharacterized proteases. Virulence studies in age‐0 + channel catfish indicated no correlation between either quantitative or qualitative protease production and

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00587.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Vibrio anguillarumisolated from diseased cod,Gadus morhuaL., were serotyped by use of a panel of monoclonal antibodies. Four serotypes could be distinguished, having different lipopolysaccharide determinants. These phenotypic differences were also reflected in the genetic map, as revealed by fingerprinting of bacterial DNA. Antisera were raised in cod after immunization with theV. anguillarumserotypes, and Western blot techniques demonstrated production of specific antibodies mainly to LPS‐antigens. The immune system in cod discriminates to a eertain degree between the four serotypes as shown by crossreactions of the immune sera inelisa. Moreover, it was also shown that natural antibodies to bacterial antigens are present in non‐immune sera, but these specificities are non‐LPS in nature. As a consequence of the heterogeneity of theV. anguillarumstrains, vaccination experiments were performed under laboratory conditions to compare the effectiveness of bacterins based on either single vaccines or polyvaccines. The results from these experiments were promising since challenge with one strain demonstrated 100% protection both in fish vaccinated with the homologous serotype as well as a mixture of all the four sero

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00588.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Eggs of female rainbow trout,Oncorhynchus mykiss(Walbaum), were fertilized and subsequently exposed to high eoncentrations ofPseudomonas fluorescensorCytophagasp. (106cells/ml) for 45 min during water hardening. Eggs were placed in horizontal hatchery trays alongside sterile water‐treated eggs and mortality rates were observed daily throughout incubation. Numbers and species of bacteria present on egg surfaces and within egg contents were monitored at the green stage (unfertilized), after hardening, and at 12h, 7 days, 14 days, 21 days and 28 days incubation. Surfaces of the incubating eggs of all groups, irrespective of treatment at water hardening, were eventually colonized by considerable numbers ofCytophagasp.,P. fluorescensand to a lesser extentPseudomonassp. andAeromonas hydrophila.Few bacteria were recovered from inside eggs. Overall, no correlation was found between bacteria on the egg surface and egg death. However, a significantly higher ‘rate’ of egg death during early stages of incubation was found amongst eggs exposed toP. fluorescensat water hardening. Thus, high numbers ofP. fluorescenson egg surfaces during initial stages of incubation might pose a potential threat to egg survival. Therefore, it is suggested that strenuous efforts are made at time of hardening to obtain the purest available source of

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00589.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Sanguinicoliasis is a serious disease of cultured carp causing high mortality in early fry. Experimental infections were used to study the pattern of penetration, and subsequent behaviour and development of the parasite. Maximum penetration of cercariae was achieved within 30 min, followed by a period of rapid development and growth marked by a doubling in length within the first 12 h. Subsequent growth was slower, during which major organ development took place, with gonadal maturity being completed between 60 and 90 days p.i. Penetration occurred mainly through the fins, particularly the caudal fin, and large numbers of worms remained in the skin where they continued to develop to maturity. A small proportion of the worms were found in the heart and gill vessels soon after infection. However, migration from the skin began at 60 days p.i. and greater numbers (57%) of the worms were found in heart and gill vessels at 90 days, coinciding with onset of egg production. Decline in worm numbers in the gill/heart region began after 120 days. Gill/heart worms differed in a number of features from skin worms, but egg production occurred simultaneously in both sites.

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00590.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The biotypes, serotypes and outer membrane protein‐types (OMP‐types) of 135 isolates ofYersinia ruckeriwere analysed in an attempt to identify clonoal groups and to examine to further detail the relationships between islotes from wide geographic areas. Each isolate could be assigned to one of two biotypes (1 and 2). one of five 0‐serotypes (01, 02, 05, 06 and 07), and one of five OMP‐types (1–5). Outer membrane protein analysis was able to differentiate between isolates within a given serotype. Thus, serotype 01 isolates types 1 and 2. and serotype 07 isolates consisted of OMP‐types 1 and 5. Whereas OMPwith serotype 07, OMP‐types 1 and 2 were associated with serotypes 01, 02, 05, 06 and 07, for the majority of the disease outbreaks in Europe and represented 79% of the European isolates. A combination of biotype, serotype and OMP‐type analysis was demonstrated to be useful in epidemiological studi

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00591.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Ten isolates ofAeromonas hydrophilaand two ofA. sobriawere investigated with regard to elastase and caseinase production, and the pI, heat and EDTA sensitivity of extracellular caseinase enzymes. An extreme degree of heterogeneity amongst the strains was observed. In isoelectricfocusing, the ECP of the various strains possessed between 19 and 31 proteins, and the number of extracellular proteases ranged from one to 12. Similarities between strains using one criterion of comparison (e.g. IEF patterns) did not hold true by other criteria (e.g. heat or EDTA sensitivity of proteases).

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00592.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Intestinal parasitism by the coccidianGoussia lomiwas associated with morbidity and histological lesions in aquarium‐reared Murray cod fry,Maccullochella peeli(Mitchell), at a hatchery near Narrandera, New South Wales, Australia. Coccidial infection was not found in pond‐reared Murray cod of the same age, nor in trout cod,M. macquariensis(Cuvier&Valenciennes), reared under similar conditions at the same hatchery. Overcrowding may have predisposed Murray cod in aquaria to heavy infection withG. lomi.Clinical coccidiosis was expressed in a small proportion of infected fish. Large numbers of coccidial developmental forms were detected histologically in the intestinal mucosa of affected fish in association with a necrotic enteropathy. Using a method of intestinal trypsin digestion and flotation, 2000 coccidial oocysts were counted in one 0‐05g

ISSN:0140-7775    

DOI:10.1111/j.1365-2761.1991.tb00593.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY