首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Three different concentrations (107, 105 and 103 TCID50 ml-1) of infectious pancreatic necrosis virus (IPNV) serotype Sp isolated from Atlantic halibut, Hippoglossus hippoglossus L., were used to bath-challenge Atlantic halibut yolk-sac larvae. The larvae challenged with 107 TCID50 ml-1 suffered significantly higher cumulative mortality than the other challenged groups and the control group, and affected individuals displayed necrosis of the intestine, liver and kidney. In larvae from the groups challenged with 107 and 105 TCID50 ml-1, IPNV was detected by immunohistochemistry and in situ RNA/DNA hybridization in the intestine, liver and kidney. In addition, some individuals stained IPNV-positive in the heart and eye/brain region. Detection by in situ hybridization did not appear to be more sensitive than immunohistochemistry. However, background staining was virtually absent in comparison with immunohistochemistry, and the staining seemed to be more distinctly localized to the cytoplasm of infected cells. The results show that farmed halibut yolk-sac larvae can be infected by IPNV immediately after hatching, with resulting high mortality. As the larvae are not immunologically mature at this stage of development, vaccination is not recommended.  相似文献   

2.
Infectious dose and shedding rates are important parameters to estimate in order to understand the transmission of infectious pancreatic necrosis virus (IPNV). Bath challenge of Atlantic salmon post‐smolts was selected as the route of experimental infection as this mimics a major natural route of exposure to IPNV infection. Doses ranging from 102 to 10?4 50% end‐point tissue culture infectious dose (TCID50) mL?1 sea water were used to estimate the minimum infectious dose for a Scottish isolate of IPNV. The minimum dose required to induce infection in Atlantic salmon post‐smolts was <10?1 TCID50 mL?1 by bath immersion (4 h at 10 °C). The peak shedding rate for IPNV following intraperitoneal challenge using post‐smolts was estimated to be 6.8 × 103 TCID50 h?1 kg?1 and occurred 11 days post‐challenge. This information may be incorporated into mathematical models to increase the understanding of the dispersal of IPNV from marine salmon sites.  相似文献   

3.
Australian bass Macquaria novemaculeata were challenged by immersion with nervous necrosis virus (NNV) at different ages and under controlled conditions to investigate factors affecting disease expression. Fish challenged at 3 weeks of age with 103 TCID50/ml and higher doses developed clinical disease; a lower dose of 102 TCID50/ml resulted in incidence below 100% and 101 TCID50/ml was insufficient to cause infection. Additionally, fish were challenged at 5, 6 and 13 weeks of age at 17 and 21°C to assess the role of the age of the host and water temperature on disease expression. Although Australian bass challenged at all ages had evidence of replication of NNV, only those challenged at 3 weeks of age (20 and 24 days post?hatch [dph]) developed clinical disease. Higher water temperature had an additive effect on disease expression in larvae challenged at 24 dph, but it did not affect the disease outcome in older fish. Finally, isolates of NNV derived from fish with clinical or subclinical disease presentations caused similar cumulative mortality and clinical signs when larvae at 24 dph were challenged, suggesting that agent variation was not responsible for variation in clinical presentation in these field outbreaks of NNV infection.  相似文献   

4.
A red-spotted grouper Epinephelus akaara skin (RGS) cell line was established and characterized. RGS cells had a normal diploid chromosome number of 2n = 48, the morphology of which was fibroblastic-like in 3 days and epithelial-like over 5 after 16 passages. The cells multiplied well in Dulbecco’s modified Eagle’s medium supplemented with 10% of fetal bovine serum at 25°C. Susceptibilities of RGS and grass carp ovary (GCO) cells to two viruses were tested, and the results showed that the titer of an iridovirus Rana grylio virus (RGV) in RGS cells was 103.5 TCID50 ml?1, which was much higher than a rhabdovirus spring viremia of carp virus (SVCV) in the cells (100.5 TCID50 ml?1). The titers of RGV and SVCV in GCO were 106.0 TCID50 ml?1 and 108.0 TCID50 ml?1, respectively, which were higher than those in RGS cells. The data may imply that RGS cells could be selectively resistible to some viruses during infection. RT-PCR analysis of RGV-infected RGS cells showed that RGV could replicate in RGS cells. Further study of virus replications in RGS cells was conducted by electron microscopy and immunofluorescence microscopy has shown that virus particles scattered in the cytoplasm and virus protein appeared in both the cytoplasm and nucleus. The results suggested that RGS cells could be used as a potential in vitro model to study the cutaneous barrier function against virus infection.  相似文献   

5.
Largemouth bass virus (LMBV) is a recently discovered iridovirus that causes a fatal disease of largemouth bass, Micropterus salmoides (Lacepède). Fish can become infected by waterborne LMBV, but oral transmission of this virus has not been demonstrated previously. Largemouth bass were gavaged with guppies, Poecilia reticulata Peters, which had been injected with LMBV, and then sampled periodically during a 7‐week observation period. The dose of LMBV averaged 105.6 tissue culture infectious doses – 50% cytopathic endpoint (TCID50) per largemouth bass. Five of 24 largemouth bass exposed to LMBV became infected with the virus, but none of the fish had clinical signs typical of LMBV disease. Virus titres in largemouth bass were highest in swim bladder (105.5–9.5 TCID50 g?1) and were 105.2 TCID50 g?1 or lower in cutaneous mucus, head kidney, trunk kidney, spleen, gonad and intestine. These results indicate that LMBV can be transmitted orally to largemouth bass, but further study is needed to determine the factors affecting pathogenicity of the virus.  相似文献   

6.
Total ammonia content (TAmm) and excretion (JAmm), and ionic content (K+, Na+, Cl-) have been studied in embryos and yolk-sac larvae of Atlantic halibut (Hippoglossus hippoglossus L.) maintained in darkness (6 °C and 34% S) or in light (light-arrested, nonon-hatching embryos). The TAmm of the eggs increased from 250-300 nmol ind-1 during the first 5-10 days post fertilization (dPF) to 400-500 nmol ind-1 at the time of natural hatching in darkness. TAmm did not start to decrease before 2-5 days after hatch, and yolk-sac larvae had a higher TAmm compared to the light-arrested embryos of the same age and batch. JAmm increased exponentially rom about 0.05 nmol ind-1 h-1 at 10 dPF to about 3 nmol ind-1 h-1 at hatch. Embryos undergoing hatching showed a significantly higher JAmm than non-hatching, light-arrested embryos of the same age. The content of K+ in distilled water rinsed eggs declined from about 0.85 µmol ind-1 at 2-4 dPF to about 0.15 µmol ind-1 at hatch, while that of Cl- remained constant at about t 0.85 µmol in-1, and that of Na+ increased slowly from 0.10 to 0.20 µmol ind-1 . Based on the measured ions, there was an anionic deficit in the egg, especially during the first week of development. When exposed to increased ambient total ammonia (0-27 mM NH4Cl), no mortality occurred, and no significant increase was found in the TAmm of the Atlantic halibut egg before 9.2 dPF despite an estimated large inward diffusion gradient for the un-ionized ammonia species (NH3). The delayed release of TAmm comp ared to embryos and yolk-sac larvae of other marine teleosts, may relate to the deep-water spawning of the Atlantic halibut, and the buoyancy regulation of the yolk-sac larvae.  相似文献   

7.
Atlantic salmon smolts, previously unexposed to infectious pancreatic necrosis virus (IPNV), were placed into tanks of sea water at 10 °C. After 4 weeks, 40 fish were injected intraperitoneally (i.p.) with homogenized and filter‐sterilized kidney material obtained from salmon with clinical IPN in a marine farm in Shetland. The injected fish were cohabited with 40 untreated fish. Mortalities began in the injected fish on day 7 and reached a peak of 48% on day 14. In the cohabitation group, mortalities began on day 14 and reached a peak of 70% on day 27. The IPNV in the Shetland kidney homogenate was cultured in Chinook salmon embryo (CHSE) cells and passed twice. This cultured virus was injected i.p. into fish at various doses ranging from 10 to 107 TCID50 fish?1 4 weeks after seawater transfer. Challenge tanks contained 30 injected fish and 30 cohabitees. Mortality rates and levels were dose‐dependent. The highest dose used resulted in a similar mortality pattern as obtained with a similar dose of the Shetland kidney homogenate, indicating that virulence was retained after two passes in tissue culture. Even with the lowest dose, mortality reached 12% in the injected group and 23% in the cohabitees. The IPNV titres were high (106?109 i.u. g?1 kidney) in fish which died during the experiment and low (<105 i.u. g?1 kidney) or undetectable in surviving fish. The cultured virus (pass 3) was used in a challenge model where the population density of fish in the tanks was high (50 injected and 50 cohabitees) or low (15 injected and 15 cohabitees). In the high stocking density tank, mortalities peaked at about 35% in the injected group and at 52% in the cohabitees. In the low stocking density tank, mortalities peaked at about 40% in the injected fish but no mortality occurred in the cohabitees. However, IPNV was detected (up to 104 i.u. g?1 kidney) in 82% of cohabitees sampled on day 30. These data suggest that lethal lateral transmission of the virus is dependent on the infectious pressure from the injected group. A further trial was conducted to investigate the effect of time post‐seawater transfer on the susceptibility of post‐smolts to IPN. Groups of fish were challenged every 2 weeks from week 0–10. Few mortalities occurred at week 0 and virus titres were high in these fish. Most survivors became carriers, some with titres >106 i.u. IPNV g?1 kidney. From 2 to 10 weeks after seawater transfer, mortalities in both injected and cohabitees were substantial with viral titres >107 i.u. g?1 kidney. Survivors had lower titres and in many virus was undetectable. Throughout the experiments, moribund fish were sampled for histology and all showed typical IPN histopathology.  相似文献   

8.
Infectious pancreatic necrosis virus (IPNV) is an important virus which affects the salmonid aquaculture industry worldwide; therefore, it is important to develop rapid and reliable methods of diagnosis to detect the disease at early stages. Nowadays, RT‐qPCR is replacing other methods because it provides additional information on the viral load, which is important to have a better understanding of the virus replication level and of the stage of the infection and its risk level. The main problem stems from the high diversity of this virus, which can compromise the reliability of the diagnosis. In this study, we have designed an RT‐qPCR procedure for diagnosis and quantification of IPNV based on a single pair of primers targeted to segment B. The procedure has been validated, in vitro and in vivo, testing two different types of standards against seven reference strains and 23 field isolates from different types. The procedure is reliable for the detection of any type, with a detection limit of 31 TCID50 mL?1, 50 pfu mL?1 or 66 RNA copies mL?1, depending on the standard. All the standard curves showed high reliability (R2 > 0.95). The results support the high reliability of this new procedure for the diagnosis and quantification of IPNV.  相似文献   

9.
The growth and activity of Atlantic halibut, Hippoglossus hippoglossus L., yolk-sac larvae exposed to light of differing intensities and wavelengths were investigated every fifth day. The experiments were conducted at 6 oC from day 1 until day 34 post hatch. Four intensities of constant white light (2.0, 0.3, 0.03 and 0.005 μ Em?2 s?1, λmax 590 nm), and constant coloured light of equal intensities (0.03μ Em?2s?1) in the blue, green and red spectrums (λmax 450, 560 and 670 nm, respectively) were used. In addition to a control treatment in constant darkness, one treatment was incubated in a 12:12 h light: dark photoperiod. The light treatments did not have any discernible effect on the total length, myotome height, dry weights or yolk conversion efficiencies. The most intense white light resulted in an increased activity on days 24 and 30 post hatch, resulting in a temporarily reduced length and myotome height for the larvae in these groups compared to the other treatments. Larvae from all treatments were of the same size 34 days post hatch. The dry weights of the larvae and yolk-sacs were unaffected by light treatment. The activity increased independently of light treatment until 120 degree-days, and thereafter, the strongest white light resulted in an temporarily increased activity. The distribution of activity changed independently of light regime in the beakers during development.  相似文献   

10.
An inactivated betanodavirus, red‐spotted grouper nervous necrosis virus (RGNNV), is a vaccine candidate for viral nervous necrosis (VNN). The present study was conducted to examine inoculation doses of the vaccine and neutralizing antibody titre levels to protect fish against VNN. Young sevenband grouper, Epinephelus septemfasciatus, averaging 25.4 g, were immunized at 25 °C water temperature by a single intraperitoneal injection of formalin‐inactivated RGNNV. Fish immunized at vaccine doses of 108.5, 108.0, 107.5, 107.0 and 106.5 TCID50 per fish produced antibodies at mean titres of 1:907, 1:511, 1:259, 1:197 and 1:96, respectively, at 20 days post‐immunization (p.i.). Neutralizing antibodies were not detected in any control fish (titre <1:80). When fish were challenged with RGNNV (105.0 and 104.0 TCID50/fish) at 20 days p.i., cumulative mortalities of the fish groups immunized with 108.5, 108.0, 107.5 and 107.0 TCID50 per fish were significantly lower than those of the control group, and the relative percent survival values were higher than 60% in fish groups immunized with 107.5 TCID50 per fish or higher doses. However, no significant differences were found in mortality between the group immunized with 106.5 TCID50 per fish and the control group. From these results, it was deduced that the minimum effective inoculation dose of the vaccine is 107.0 TCID50 per fish and the minimum mean neutralizing antibody titre giving significant protection is approximately 1:200. This antibody titre level is a possible measure of vaccine efficacy against VNN in sevenband grouper, instead of a virus challenge test.  相似文献   

11.
Total lipid, lipid classes and their associated fatty acids have been measured in whole halibut, Hippoglossus hippoglossus (L.) larvae and in dissected animals separated into yolk and body compartments. At hatching the larval body contained 17 μg ind?1 of lipid (11% of larval body dry weight), while the yolk contained 190 μg ind?1. Phosphatidylcholine (PC) accounted for 57% of total yolk lipids while phosphatidylethanolamine (PE), triacylglycerol (TAG), cholesterol and sterol ester (SE) accounted for 12%, 12%, 9% and 6% respectively. The main fatty acids in the PC fraction were 22:6n-3 (25.6 μg ind?1), 16:0 (19.2 μg ind?1) and 20:5n-3 (12.6 μg ind?1). Between hatch and 200 day-degrees post hatch (D°PH) a net decline in total lipids of 29% was seen. There seemed to be some, but relatively minor, changes in the relative composition of lipids in the yolk throughout development, which are indicative of a non-selective endocytotic bulk uptake of lipids from the yolk. Towards first-feeding there was a selective catabolism of PC and a net synthesis of PE in the developing body, resulting in a shift in the lipid class composition in the body compared with that of the yolk. The fatty acids released from lipid hydrolysis were mainly used as energy substrates by the growing halibut larvae; 22:6n-3 was quantitatively one of the most important fatty acid fuel in energy metabolism. At the same time 38% and 23% of the 22:6n-3 released from PC was retained by the PE and neutral lipids in the growing larval body respectively. Except for 20:5n-3 (2%, 14%) no similar retention was seen in any of the other fatty acids. The observed net synthesis of PE in developing yolk-sac larvae of Atlantic halibut and the preferential retention of 22:6n-3 into it, increasing from 28% at hatching to 45% at 200 D°PH, may point to a high biological value of this compound.  相似文献   

12.
Folate mobilization from the yolk compartment during larval development was studied by analysing the folate concentration in whole body, embryo and yolk in a single batch of Atlantic halibut, Hippoglossus hippoglossus L., eggs and larvae that showed successful fertilization and development. There was a net loss of approx. 50% of folate from yolk during endogenous feeding. Further, only 23% of the decrease in yolk folate was retained in the larval body. The data suggest a need for folate for metabolic and growth purposes during embryogenesis of approximately 2 μg g?1 weight gain. Relative to these data and published folate requirement for cold‐water species, batches of egg from 16 Atlantic halibut brood fish contained variable and, for some batches, critically low levels of folate. This may constitute a potential problem for larval development until start feeding.  相似文献   

13.
First‐feeding halibut larvae (245‐day degrees; 40 days post hatch), reared at 34 g L?1 salinity and 7°C, were subjected to handling and allowed to recover in a range of salinities (0–34 g L?1) and at 10°C. Survival of the unfed larvae was determined daily for 18 days. Mortality rates approached 0 after 4 days in all treatments and presumed starvation‐induced mortality started at about 11 days post handling. By 20 days post treatments, all larvae had died. Salinities in the range of 10–20 g L?1 produced significantly (anova , P<0.01) higher initial survival (71–95%) than salinities above 20 g L?1 (24–48%) or below 10 g L?1 (0–19%) and this survival pattern changed little in unfed larvae for the first 10 days following the stressor. For example, 24 hour post handling, survival of halibut was improved from 28.7±16.5% (mean±standard error, n=3) at 34.0 g L?1 to 95.2±4.8% at 13 g L?1. A second‐order polynomial regression of 4‐day post‐handling survival data (y=?0.002x 2+0.0603x+0.0699, r2=0.3936) predicted a maximum survival at 15.1 g L?1 salinity. These results have important implications for halibut aquaculture and research when handling of larvae is unavoidable. For practical applications, we recommend reducing salinity of receiving waters to 15–20 g L?1 with a slow (3–4 days) reacclimation to ambient conditions.  相似文献   

14.
  相似文献   

15.
The first attempts to rear Atlantic halibut, Hippoglossus hippoglossus L., larvae were carried out in Norway in the period from 1974 to 1980, when ripe adult specimens of Atlantic halibut were net-caught, and stripped for eggs and milt. Both incubation of yolk-sac larvae and first-feeding were carried out in large submerged plastic bags and the larval food consisted of natural zooplankton collected from surrounding lagoon water. This semi-extensive production method was further developed and led to the establishment of several commercial production trials by the end of the 1980s. During recent years, research has been focused on intensive methods for first-feeding and the combined effort of several research institutes has resulted in a reliable production method. During the late 1980s and early 1990s, the main research activity was focused on the biology of and rearing techniques for eggs and yolk-sac larvae. These techniques provided satisfactory yields for several years. However, during the past few years, a certain decrease in survival through the yolk-sac stage has been experienced at several hatcheries. Since the early 1990s, the first-feeding period has represented the bottleneck in the development of a reliable rearing method. The main effort has been concentrated on system configuration and on improving live prey quality. In the future, new feeding strategies including further improvement of live prey (i.e. Artemia), the use of copepods and early weaning onto a formulated diets should be emphasized. Further research on hygiene and technological improvements is needed to increase growth and survival through metamorphosis.  相似文献   

16.
A challenge model for pancreas disease in Atlantic salmon, Salmo salar L. fry, was developed comparing two salmonid alphavirus (SAV) subtypes: SAV1 and SAV5. Viral doses of 3 × 105 TCID50 mL−1 for SAV1 and 3 × 104 for SAV5 were tested in triplicate tanks, each containing 450 salmon fry. Cumulative mortalities of 1.2% were recorded. Titres of virus recovered from the mortalities ranged from 102 to 107 TCID50 mL−1. Fry were sampled at 3, 5 and 7.5 weeks post-challenge. Sampling after 3 weeks revealed a high prevalence of infection in the absence of clinical signs, and infectious virus was recovered from 80% and 43% of sampled fry infected with SAV1 and SAV5, respectively. After 5 weeks pancreas, heart and red skeletal muscle lesions were generally observed, whilst degeneration in white skeletal muscle was observed only in fish infected with SAV1. In situ hybridisation confirmed the presence of viral genome in infected pancreas, heart and muscle. After 7.5 weeks, infectious virus (both isolates) was recovered from 13.3% of the fish sampled, with a viral titre of 102 TCID50 mL−1. Clearly, salmon fry are susceptible to SAV infection and pancreas disease.  相似文献   

17.
This study investigated the use of alkaline hydrolysis at ambient temperature for inactivation of selected fish pathogens in fish tissues under conditions approximating those that are likely to be found in the aquaculture industry. Infectious salmon anaemia virus (ISAV) and Lactococcus garvieae have been determined in a previous study to be the most resistant virus and bacteria to pH 12 from a wide range of viruses and bacteria tested. They were spiked at high titres into fish extracts that were then treated with 1 m sodium hydroxide (NaOH). Viable L. garvieae was not detected in the treated fish extract after 1 h, and ISAV was not detected after 24‐h exposure. Field mortalities of Atlantic salmon, Salmo salar L., caused by infectious pancreatic necrosis virus were treated by alkaline hydrolysis at ambient temperature. The macerated fish mortalities contained a high titre of virus (3.38 × 108 TCID50 g?1) that was reduced to approximately 2.2 × 103 TCID50 g?1 after 24‐h exposure to NaOH, and virus was not detected after exposure for 48 h. The results suggest that alkaline hydrolysis at ambient temperature has potential as a biosecure treatment method for fish by‐products containing fish pathogens.  相似文献   

18.
Two populations of catarina scallop, Argopecten ventricosus (= circularis) (Sowerby II, 1842), were evaluated for their larval growth and survival responses to different stocking densities. Larvae from the Magdalena population had a significantly higher growth but equal survival at a density of 10 larvae ml?1 compared with 20 larvae ml?1. Larvae from the Concepcion population grew better at densities of 15 and 20 larvae ml?1 than at densities of 5 and 10 larvae ml?1, although survival was lower at higher densities. The differing response of these two populations to increased stocking densities is explained as a possible consequence of different population adaptations related to behavioural and physiological mechanisms. The importance of establishing optimum stocking densities for molluscan larvae is stressed in two contexts: maximizing growth and survival for different populations when artificially reared, and understanding the effects of stocking densities on phenotypic variance, especially during the course of genetic studies.  相似文献   

19.
Major challenges in culture of Atlantic halibut larvae have been slow growth during the late larval stages and inferior juvenile quality due to pigmentation errors and incomplete eye migration during metamorphosis. The hypothesis of this study was that feeding on‐grown Artemia would alleviate these problems. Artemia were grown for 3–4 days on Origreen or Origo. The growth and nutrient composition of Artemia nauplii and on‐grown Artemia were analysed, and both Artemia types were fed to Atlantic halibut larvae, on‐grown Artemia from 15 days post‐first feeding (dpff). The body length of Artemia increased with 20%–70% in response to on‐growing. In all experiments, protein, free amino acids and the ratio of phospholipid to total lipid increased, while lipid and glycogen decreased. The fatty acid composition improved in some cases and not in others. The micronutrient profiles were not negatively affected in on‐grown Artemia. All these changes are thought to be beneficial for marine fish larvae. The final weight of Atlantic halibut postlarvae was similar, and 90% of the juveniles had complete eye migration in both groups. It is concluded that the present version of Artemia nauplii probably covers the nutrient requirements of Atlantic halibut larvae.  相似文献   

20.
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号