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1.
Abstract Two groups of European catfish, Silurus glanis L., fingerlings were infected with channel catfish virus (CCV) by either intraperitoneal injection with 105 TCID50 of CCV, or bathing in water containing 105 TCID50 of CCV per 1·0 ml. The virus was isolated from spleen, intestine and brain of CCV-injected fish at day 1 and the titres ranged from 102·1 to 103·3 TCID50/g. However, the tissue distribution of CCV was irregular and no virus was isolated after day 3 post-exposure. In CCV-bathed fish, the virus was isolated only from the liver of one specimen at day 3 post-exposure. No clinical signs of CCV disease developed in any of the fish. Specimens in each regime from all sampling periods showed some minor histopathological changes, but there were no differences between treatments. Lesions included oedema and focal haemorrhage in the liver and the spleen was congested. Electron micrographs of tissue samples showed the presence of a few virus particles around the nuclei of kidney, spleen and intestinal cells, and in or around a myelinated nerve within the optic lobes of infected fish during the first 4 days of infection.  相似文献   

2.
Abstract. An enzyme-linked immunosorbent assay (ELISA) for the demonstration of the virus of spring viraemia of carp (SVCV) in liver, kidney and spleen homogenates, and in infected cell cultures is described. The sensitivity of the method is 102·8–103·5 TCID50 0·lml−1 of the examined fluid. The specificity has been confirmed by the ELISA inhibition test and by results of virological examinations. Contamination with bacteria or fungi of samples taken from dead fish had no effect on the results of ELISA. Specific anti-SVCV sera were used successfully for the production of conjugates for the direct immunoperoxidase and immunofluorescence detection of SVCV in infected cell cultures.  相似文献   

3.
This study investigated infection dynamics of infectious salmon anaemia virus (ISAV) by conducting two experiments to examine minimum infective dose and viral shedding of ISAV. In terms of minimum infective dose, the high variability between replicate tanks and the relatively slow spread of infection through the population at 1 × 101 TCID50 mL−1 indicated this dose is approaching the minimum infective dose for ISAV in seawater salmon populations. A novel qPCR assay incorporating an influenza virus control standard with each seawater sample was developed that enabled the quantity of ISAV shed from infected populations to be estimated in values equivalent to viral titres. Viral shedding was first detected at 7 days post-challenge (5.8 × 10−2 TCID50 mL−1 kg−1) and rose to levels above the minimum infective dose (4.2 × 101 TCID50 mL−1 kg−1) on day 11 post-challenge, 2 days before mortalities in ISAV inoculated fish started. These results clearly demonstrate that a large viral shedding event occurs before death. Viral titres peaked at 7.0 × 101 TCID50 mL−1 kg−1 15 days post-infection. These data provide important information relevant to the management of ISA.  相似文献   

4.
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5.
Abstract. Cyprinid herpesvirus 1 (CHV) or Herpesvirus cyprini was virulent for carp, Cyprinus carpio L., fry following 1 h immersion in water at 20 °C. Cumulative mortality for carp fry was 86–97% in 2-week-old common carp, 20% in 4-week-old fancy carp, and 0% in both 8-week-old common and fancy carp. The virus did not produce mortality in fry of crucian carp, grass carp or other cyprinids. It was also oncogenic in carp, inducing papillomas to the extent of 55% among both common and fancy carp fry. The neoplasms appeared 5–6 months after carp had been exposed to the virus by immersion and recurred at an incidence of 83% in carp 7·5 months post-desquamation of the tumour. The CHV was reisolated from all moribund fish and from all survivors. It also induced papillomas at an incidence of 13% in adult mirror carp and at 10% in adult fancy carp 5 months after intraperitoneal inoculation of 105 TCID50 ml-1 fish. The virus was rcisolated only from the ncoplastic tissue and not from internal organs. The neoplasms were normally located on fin, skin or mandible, at the intraperitoneal inoculation site. Specific fluorescence for CHV antigen was frequently detected in the gills, liver, kidneys and intestine of 2-week-old fry from 3 to 21 days following challenge with CHV. It was found in greater concentrations in experimentally induced papillomata on 2-week-old carp fry survivors examined 24 weeks after challenge than in naturally occurring neoplasms.  相似文献   

6.
Abstract. The immuno dot blot technique is a rapid, sensitive and quantitative method for the diagnosis of infectious pancreatic necrosis virus ( ipnv ) in both infected tissue culture lysates and tissue homogenates of fish. Uninfected tissue culture lysates and fish homogenates do not react in the peroxidase dot blot system after appropriate treatment. The immuno dot blot method takes 4h to complete, and the dot blot membrane can be stored in the dark for a long period. The viral proteins in the infected tissue culture cells could be detected at 3h post-infection if an initial high MOI was used. The minimum dose of ipnv-ab strain which could be detected using homologous serum was 2·5 ng purified ipnv protein/dot. The smallest infectious dose of VR-299, SP, AB, EVE and CY-1 ipnv which could be detected by the immuno dot blot system was 104 to 105 TCID50. When one μg of purified ipnv was used, a 1·6 × 104 dilution of rabbit anti-AB antisera could be detected.  相似文献   

7.
Abstract. Infection trials using two serotypes of VHS viruses (type 1 and 23/75) demonstrated that Atlantic salmon fry were susceptible to the disease when injected intraperitoneally (i.p.) with 103 pfu of virus/fish but resistant to infection by a bath method when exposed for 3 h in water containing 5 × 104 pfu of virus/ml. In the i.p.-infected fish, mortality reached 78 and 67% within 13 days with VHSV1 nad 23/75 serotypes, respectively. High virus yields were recovered from infected fish and virus shedding was demonstrated by the onset of VHS in rainbow trout kept in the outflow water from the aquaria containing infected salmon. Neither mortality nor virus shedding occurred in salmon infected by the water route but virus multiplication was demonstrated in 2 of 60 fish with VHSV1 and 3 of 60 fish with virus 23/75. On day 79 post-infection the sera from surviving salmon of both i.p. and bath infection trials exhibited good neutralizing titres (around 1000) against the homologous viruses.  相似文献   

8.
Abstract. Viral haemorrhagic septicaemia (VHS) is reported for the first time in sea-water cultured rainbow trout. Heavy mortalities with typical signs and lesions A VHS virus (serotype 1) was isolated from the diseased fish. The mortalities were caused only by the VHS virus and 80 days post transfer of trout to sea-water the mortalities reached 85%, of the initial population.
The disease was experimentally transmitted to rainbow trout, both in sea-water 3·104 pfu/ml of virus or by intramuscular injection of various doses of VHS1 (7·101 7·104 or 7·104 pfu per fish). Death occurred in all infected groups and started earlier in sea-water. Typical signs of VHS were observed in moribund fish. Viral multiplication was demonstrated to have occurred in fish organs.  相似文献   

9.
Molecular characterization was carried out on an iridovirus isolated from yellow grouper, Epinephelus awoara . The major capsid protein (MCP) gene was located, sequenced and compared with homologous genes from other iridoviruses. The nucleotide sequence is 1392 bases long and contains a single open reading frame beginning at an ATG codon from the 5' end and terminating at a TAA codon at the 3' end. The open reading frame encodes a protein of 463 amino acids with a predicted molecular weight of 50 272 Da. Pairwise amino acid alignments detected a high degree of sequence identity between grouper iridovirus (GIV) MCP and the homologous genes of other iridoviruses. The MCP gene of GIV was most similar to the MCP gene from frog virus 3 (FV3) with 70% nucleotide and 73% amino acid sequence identity. The predicted molecular weight of the protein of this gene is comparable with the apparent weight obtained by SDS–PAGE. Pathogenicity of the GIV was investigated in yellow grouper by intraperitoneal injection of 107 and 104 TCID50 virus. Cumulative mortalities reached 100% within 11 and 25 days post-infection, respectively, while no grouper died in the control group. The molecular studies demonstrated that GIV is a member of the genus Ranavirus .  相似文献   

10.
Rainbow trout, Oncorhynchus mykiss (Walbaum), were exposed continuously to infectious pancreatic necrosis virus (IPNV) at 0, 101, 103 or 105 plaque forming units (pfu) L−1 of water to estimate the effects of chronic IPNV exposure on early life stages. Fish density averaged 35 fish L−1 (low density) or 140 fish L−1 (high density), and the tank flow rate was 250 mL−1 min. Virus exposure began at 6 days before hatch and continued until fish were 44 days old. Cumulative per cent mortality, analysis of survival and hazard functions, and discrete-time event analysis were used to explore the patterns of survival and mortality. In eggs and fish exposed to IPNV, mortality significantly greater than in the 0 pfu L−1 exposure did not occur until IPNV concentration was 105 pfu L−1 at low fish density and 103 pfu IPNV L−1 at high fish density. These results suggest that in the natural aquatic environment, where rainbow trout densities are likely to be considerably lower than in this study, mortality resulting from infection with IPNV will very likely not occur when ambient concentrations of virus are ≤103 pfu IPNV L−1. In aquaculture rearing units, trout density is likely to be as high or higher than the densities used in this study. Therefore, continuous inputs of virus at concentrations greater than 101 pfu L−1 may result in IPN epidemics in aquaculture facilities.  相似文献   

11.
A nodavirus was isolated from diseased yellow grouper, Epinephelus awoara , larvae cultured in southern Taiwan. The histopathology and RT–PCR results confirmed that it was a fish nodavirus; its coat protein gene sequence was similar to that of red spotted grouper nervous necrosis virus (RGNNV) and it is named yellow grouper nervous necrosis virus (YGNNV). A new nodavirus-susceptible cell line, grouper brain (GB) was established and characterized from the brain tissue of yellow grouper. The GB cells multiplied well in Leibovitz's L-15 medium supplemented with 10% foetal bovine serum at temperatures between 24 and 32 °C, and have been subcultured more than 80 times, becoming a continuous cell line. The GB cell line consists of fibroblast-like cells and some epithelioid cells. The cell line yielded titres of YGNNV up to 108.5 TCID50 mL–1. The GB cells effectively replicated the virus at 28 °C, which could be purified to homogeneity by caesium chloride gradient centrifugation. Electron microscopy studies showed that purified virus particles were 25–30 nm in diameter. The cytoplasm of infected cells was filled with aggregates of virus particles. These results indicate that the GB cell line is a significant tool for the study of fish nodaviruses.  相似文献   

12.
Abstract. A double antibody enzyme-linked immunosorbent assay (ELISA) for the detection of infectious pancreatic necrosis virus (IPNV) is described. The sensitivity of the assay reached 102 TCID50 per 0·1 ml of culture fluid. The specificity of anti-IPNV sera and of the assay was confirmed by agar-gel immunodiffusion, by the direct immunoperoxidase technique for the deletion of IPNV in tissue cultures and by the ELISA inhibition test. High values of specific inhibition (over 90% at serum dilutions 1:40–1:2560) and low values of non-specific inhibition (8·4% at serum dilution 1:160) demonstrated the quality of the rabbit anti-IPNV serum. The results of ELISA agreed well with those of virological examinations. The potential of ELISA for investigations of a large series of field samples is discussed.  相似文献   

13.
Abstract. The infectivity of the bacterial fish pathogen Aeromonas salmonicida subsp. salmonicida to Atlantic salmon, Salmo salar L., in sea water was investigated and found to be similar to that reported for fresh water. The minimal infective dose in short duration bath exposures (1–3 days) was 104 colony-forming units (cfu) per ml, while prolonged exposure for three weeks, but not for 1 week, produced infection with 102 cfu/ml. Intragastric intubation of A. salmonicida established infection with doses of >105 cfu. Release of bacteria from dead or morbid infected fish was monitored and found to be in the order of 105–108 cfu/fish/h. These results emphasize the importance of removing dead fish from farm sites.  相似文献   

14.
The field use of a staphylococcal coagglutination (COA) test for the detection of infectious pancreatic necrosis virus (IPNV) in tissue samples from Atlantic salmon, Salmo salar L., was evaluated. The COA test was compared with an immunohistochemical (IHC) method for the detection of clinical outbreaks of infectious pancreatic necrosis (IPN). The present paper describes the evaluation of 320 COA test results performed at local fish health laboratories in Norway from 1994 to 1996, and COA test results from two infection trials with IPNV. The agreement between the COA test and the IHC was very good. The agreement beyond chance, measured as kappa values, was 0.74 in individuals and 0.90 in pooled samples. Thus, the COA test was suited for the detection of outbreaks of IPN. Covert infections with IPNV remained undetected by the COA test. The minimum IPNV titre needed to obtain a positive COA test was ≈ 105 TCID50 mL–1.  相似文献   

15.
Abstract. The causative agent of streptococcal infection of yellowtails has been isolated but no information is presently available with respect to the mechanism of infection. The present study deals with the growth of the bacteria in the fish body at various periods after either per-oral or per-cutaneous challenge with Streptococcus sp. YT-3 strain at different passage levels. After percutaneous challenge with bacteria of high virulence, the kidneys retained the bacteria with the relatively high count of 107 cells per gram of tissue while in other organs, although high concentrations of 105-106 cells were detected in 10 min, this was followed by a progressive decrease up to 24 h post-inoculation with a subsequent rapid increase during the later stages of the disease process. The highest rate of growth was obtained in the intestine, where 107 cells were detected at 72 h after inoculation. After oral challenge, the bacteria were detected at high levels from organs and blood within 10 min but they were completely removed from all organs except the intestine within 24 h.  相似文献   

16.
Olive flounder artificially infected with lymphocystis disease virus (LCDV) were reared at 10, 20 and 30 °C for 60 days, to compare LCD-incidence. In the fish reared at 20 °C, lymphocystis cells appeared on the skin and fins at 35 days post-challenge, and the cumulative LCD-incidence was 80% at 60 days. High levels of LCDV, with a mean polymerase chain reaction (PCR) titre of 106 PCR-U mg−1 tissue, were detected in the fins and skin of LCD-affected fish at 20 °C, but were not detected in the spleen, kidney, brain and intestinal tissues of these fish. No LCD clinical signs were observed in the fish reared at 10 °C and 30 °C; however, a low level of LCDV (103 PCR-U mg−1 tissue) was detected in the fins and skin of these fish. By increasing the rearing temperature from 10 to 20 °C, lymphocystis clusters appeared on the skin and fins of the fish with no previous LCD clinical signs within 33 days after the temperature change. It was shown that permissive cells for LCDV infection exist in the epidermis of olive flounder. At low temperatures, small amounts of LCDV were able to persist over a period extended for a further 45 days in the fish epidermis, even though the fish showed no LCD clinical signs. The optimum growth temperature of LCDV is near 20 °C.  相似文献   

17.
Abstract. The pathogenicity of Renibacterium salmoninarum to carp, Cyprinus carpio L., and rainbow trout, Salmo gairdneri Richardson, was investigated. All carp injected with 4·8 × 108 cells/fish, or 4·8 × 107 cells/fish survived for 38 days. R. salmoninarum was isolated from all moribund fish, but not from the kidney of surviving fish, although R. salmoninarum antigen was detected in several of these fish by the dot blot assay. On the other hand, mortality in rainbow trout was 95% in the fish injected with 4·8 × 108 cells/fish, and 15% in those which received 4·8 × 107 cells/fish. R. salmoninarum antigen was detected by the dot blot assay in all surviving rainbow trout. The number of R. salmoninarum cells was immediately decreased by carp or rainbow trout serum, and the serum bactericidal activity of carp was higher than that of rainbow trout. Carp blood leucocytes had higher phagocytic activity than those of rainbow trout.  相似文献   

18.
The in vitro metabolism of 14CD3 and 3H25OHD3 was investigated in different tissues from Atlantic salmon Salmo salar , Atlantic mackerel Scomber scombrus , Atlantic halibut Hippoglossus hippoglossus and Atlantic cod Gadus morhua . The tissues analysed were liver, kidney, head kidney, gills, spleen and intestine. The metabolites were extracted in methanol–chloroform and separated by normal-phase high-pressure liquid chromatography (HPLC) followed by scintillation counting. Identification of the metabolites was by comigration with standards on normal and reversed-phase HPLC systems and by protein-binding assays. All tissues from all species analysed produced hydroxylated derivatives identified as 25OHD3, 24,25(OH)2D3 and 1,25(OH)2D3. In addition, some unidentified derivatives were recorded, one probably being 25,26(OH)2D3. Organs producing great amounts of one metabolite also produced considerable amounts of the other possible derivatives, suggesting a lower degree of specificity in fish organs than in human organs. The predominating metabolite was 24,25(OH)2D3 in all organs from salmon and mackerel during incubation with 14CD3 and within most organs from all species during 3H25OHD3 incubation. The latter observation probably results from the need for decreasing rather than increasing the calcium absorption in these species, which live at least some periods of life in a marine environment.  相似文献   

19.
Intraperitoneal (IP) injection, cohabitation and immersion routes of infection were used to determine if Atlantic cod, Gadus morhua (L.), of 1 and 3 g are susceptible to infectious pancreatic necrosis (IPN). Mortalities of cod injected IP were significantly higher when challenged with infectious pancreatic necrosis virus (IPNV) than with phosphate buffered saline. This is the first report of Atlantic cod mortalities caused by IPNV. Fish challenged by cohabitation had significantly higher mortalities than the controls, but mortalities of Atlantic cod challenged with IPNV by immersion were not significantly different from controls. Titres of IPNV in the tissues of infected fish were sometimes very high (range 102–1010 infectious units per gram of tissue) suggesting virus replication and titres of fish that died were generally higher than those of fish which survived. However, the relatively low mortality rates when challenged by cohabitation and immersion (20% and 17%, respectively), compared to the IP injection challenge (100%) suggest that 1 and 3 g cod have low susceptibility to IPN when challenged by more natural routes. These data strongly suggest that the cause of death of experimentally challenged cod was IPNV and further histological evidence for this came from 1 g cod challenged IP with IPNV in which the pancreas showed severe necrosis and heavy immunostaining for IPNV coincidentally with the peak of mortalities.  相似文献   

20.
In the present study cod were separately placed in fish metabolic chambers. Ten individuals were injected with a dose of 1 μCi 14C-glucose, in addition to 1 g pure glucose per kg live weight, and 10 individuals were kept under the same conditions and sham injected with 9 g L−1 (0.9%) sterile saline solution.
Of the injected 14C-glucose, 3% was recovered in plasma, 2.9% in liver, 1.7% in red muscle, 18.2% in white muscle, 0.2% in heart, 1.9% in gills and 12.1% in gill-surrounding water. Of the 12.1% in gill-surrounding water, 9.1% was found to be in the form of CO2, leaving 3% to pure glucose and lactate. These results indicate a relatively high production of CO2 from glucose showing a utilization for energy, and a possible route of excretion of excess glucose via the gill membrane.
Activity of 14C-glucose on a concentration basis showed in descending order the following organs to be metabolically active in glucose utilization: gills > plasma (as a transporter) > heart > red muscle > liver > white muscle.
Of the total amount of 14C-glucose injected, only 0.3% was recovered in the liver lipid fraction, and mainly as triacylglyceroles; minor 14C-activity was found in mono- and diacylglyceroles and free fatty acids. These results show very low activity of de novo syntheses of lipid from injected glucose in the cod.  相似文献   

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