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1.
In spring 2008, infectious hematopoietic necrosis virus (IHNV) was detected for the first time in the Netherlands. The virus was isolated from rainbow trout, Oncorhynchus mykiss (Walbaum), from a put‐and‐take fishery with angling ponds. IHNV is the causative agent of a serious fish disease, infectious hematopoietic necrosis (IHN). From 2008 to 2011, we diagnosed eight IHNV infections in rainbow trout originating from six put‐and‐take fisheries (symptomatic and asymptomatic fish), and four IHNV infections from three rainbow trout farms (of which two were co‐infected by infectious pancreatic necrosis virus, IPNV), at water temperatures between 5 and 15 °C. At least one farm delivered trout to four of these eight IHNV‐positive farms. Mortalities related to IHNV were mostly <40%, but increased to nearly 100% in case of IHNV and IPNV co‐infection. Subsequent phylogenetic analysis revealed that these 12 isolates clustered into two different monophyletic groups within the European IHNV genogroup E. One of these two groups indicates a virus‐introduction event by a German trout import, whereas the second group indicates that IHNV was already (several years) in the Netherlands before its discovery in 2008.  相似文献   

2.
During a 3‐month period from June to the end of August 2016, ~5% mortalities were observed in a farm with rainbow trout (Oncorhynchus mykiss Walbaum) and one farm of common carp (Cyprinus carpio L.) in Bulgaria. The disease was manifested by gill ulcers/rot, asphyxiation and bloody ascites. Aeromonas hydrophila was isolated from the internal organs of all the diseased fish. Bacillus mycoides or B. pseudomycoides were recovered from the gill lesions on diseased carp and rainbow trout, respectively, with identification achieved by conventional phenotyping and by sequencing of the 16S rRNA gene. In vivo experiments confirmed that all three organisms were pathogenic to rainbow trout.  相似文献   

3.
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4.
A rhabdovirus was isolated in cell culture inoculated with tissue material from diseased grayling, Thymallus thymallus (L.), originating from a fish farm affected by a mortality episode in Poland. Diagnostics tests showed that the virus was not related to novirhabdoviruses known in Europe, nor to vesiculovirus‐like species, except perch rhabdovirus (PRhV) with which it shared moderate serological relations. However, RT‐PCR with PRhV probes gave negative results. To identify the virus, a random‐priming sequence‐independent single primer amplification was adopted. Surprisingly, two of the obtained sequences exhibited a high identity (>99%) with hirame rhabdovirus (HIRRV), a novirhabdovirus usually found in fish in marine Asiatic countries, for instance Japan, China and Korea. The full‐length sequence of the phosphoprotein gene (P) demonstrated a higher identity of the present isolate with HIRRV from China compared with the Korean isolate. An identical viral sequence was also found in brown trout, Salmo trutta trutta L., affected by mortalities in a second farm in the same region, after a likely contamination from the grayling farm. To our knowledge, this is the first report of HIRRV in Europe, and in two hosts from fresh water that have not been described before as susceptible species.  相似文献   

5.
Although Carnobacterium maltaromaticum has been used as a probiotic in fish, it was reported to cause disease for the first time in Korea. The objective of this study was to understand the differences between pathogenic and non-pathogenic strains. Pathogenicity was tested by challenging rainbow trout with C. maltaromaticum ATCC35586 and 18ISCm isolated from diseased fish, and DSM20342 isolated from a dairy product. We also compared 24 genomes of C. maltaromaticum strains plus the genome of our isolate 18ISCm sequenced in this study. Only the strains from diseased fish caused high mortality with severe histopathological changes. Although all strains shared more than 90% of Ko_id, wecC and xtmA were found only in strains from diseased fish. Interestingly, only strains from diseased fish harboured two wecC paralogs involved in the production of D-mannosaminuronic acid which is a major component of a well-known virulence factor, teichuronic acid. Two wecC paralogs of 18ISCm were increased when they were co-cultured with trout blood cells, suggesting that wecC genes might play a role in virulence. The results of this study show that strains isolated from diseased fish are different from strains derived from food in terms of pathogenicity to fish and the presence of virulence-related genes.  相似文献   

6.
Co‐infection of rainbow trout with infections haematopoietic necrosis virus (IHNV) and Flavobacterium psychrophilum is known to occur, and it has been speculated that a combined infection can result in dramatic losses. Both pathogens can persist in fish in an asymptomatic carrier state, but the impact of co‐infection has not been well characterized or documented. In this study, it was hypothesized that fish co‐infected with F. psychrophilum and IHNV would exhibit greater mortality than fish infected with either pathogen alone. To test this, juvenile rainbow trout were co‐infected with low doses of either IHNV or F. psychrophilum, and at 2 days post‐initial challenge, they were given a low dose of the reciprocal pathogen. This combined infection caused high mortality (76.2%–100%), while mortality from a single pathogen infection with the same respective dose was low (5%–20%). The onset of mortality was earlier in the co‐infected group (3–4 days) when compared with fish infected with F. psychrophilum alone (6 days) or IHNV (5 days), confirming the synergistic interaction between both pathogens. Co‐infection led to a significant increase in the number of F. psychrophilum colony‐forming units and IHNV plaque‐forming units within tissues. This finding confirms that when present together in co‐infected fish, both pathogens are more efficiently recovered from tissues. Furthermore, pathogen genes were significantly increased in co‐infected groups, which parallel the findings of increased systemic pathogen load. Extensive tissue necrosis and abundant pathogen present intracellularly and extracellularly in haematopoietic tissue. This was pronounced in co‐infected fish and likely contributed to the exacerbated clinical signs and higher mortality. This study provides novel insight into host–pathogen interactions related to co‐infection by aquatic bacterial and viral pathogens and supports our hypothesis. Such findings confirm that mortality in fish exposed to both pathogens is greatly elevated compared to a single pathogen infection.  相似文献   

7.
Infectious haematopoietic necrosis virus (IHNV) is a serious pathogenic threat to rainbow trout (Oncorhynchus mykiss) and other salmonids. Major histocompatibility complex (MHC) polymorphisms have been closely linked to disease susceptibility. In this study, polymerase chain reaction‐single‐strand conformation polymorphism, cloning and sequencing were used to examine MHC class II β chain gene (DAB) polymorphisms and analyse their association with IHNV in rainbow trout. The DAB exon 2 was amplified from 104 resistant and 91 susceptible fish. Forty‐five different alleles were identified, 30 of which were novel. Individuals possessed between one and four alleles, indicating that the genome harbours at least two closely related DAB exon 2 loci. The percentages of amino acid mutations in the peptide binding region (PBR) and non‐PBR were 66.67% and 45.28% respectively. The rate of non‐synonymous substitutions occurred at a significantly higher frequency than synonymous substitutions, suggesting the existence of balancing selection for maintenance of polymorphisms at the DAB exon 2 locus. The alleles Onmy‐DAB*0201 (P < 0.001), Onmy‐DAB*0904 (P < 0.001) and Onmy‐DAB*1102 (P < 0.01) were associated with susceptibility to IHNV, while Onmy‐DAB*0103, Onmy‐DAB*0601 and Onmy‐DAB*1402 were associated with resistance (P < 0.001). These alleles could be used as molecular markers for IHNV resistance breeding in rainbow trout.  相似文献   

8.
Infectious haematopoietic necrosis virus (IHNV) is the causative agent of infectious haematopoietic necrosis, a disease of salmonid responsible for great economic losses. The disease occurs in most parts of the world where rainbow trout is reared but has not been previously reported in Kenya. In this study, rainbow trout fry and growers from two farms in Nyeri County were screened for IHNV. Whole fry (n = 4 from each farm) and kidney samples from growers (n = 15 and n = 6 from the two farms, respectively) were collected and preserved for cell culture examination or PCR analysis. Screening of samples was done by PCR followed by sequencing of the glycoprotein gene of the virus. Demonstration of the virus was done by propagation in EPC cells followed by the indirect fluorescence antibody test (IFAT). The results revealed the presence of IHNV at low prevalence of 0.1 and 0.4 for the two farms. The virus was confirmed both by IFAT and by partial sequencing of the G gene. Phylogenetic analysis revealed that the Kenyan isolates were identical to those of the J genogroup found mostly in Asia. The findings have implications for biosecurity measures and import regulations for the Kenyan rainbow trout industry.  相似文献   

9.
Salmonid fish viruses, such as infectious haematopoietic necrosis virus (IHNV), are responsible for serious losses in the rainbow trout and salmon‐farming industries, and they have been the subject of intense research in the field of aquaculture. Thus, the aim of this work is to study the antiviral effect of milk‐derived proteins as bovine caseins or casein‐derived peptides at different stages during the course of IHNV infection. The results indicate that the 3‐h fraction of casein and αS2‐casein hydrolysates reduced the yield of infectious IHNV in a dose‐dependent manner and impaired the production of IHNV‐specific antigens. Hydrolysates of total casein and αS2‐casein target the initial and later stages of viral infection, as demonstrated by the reduction in the infective titre observed throughout multiple stages and cycles. In vivo, more than 50% protection was observed in the casein‐treated fish, and the kidney sections exhibited none of the histopathological characteristics of IHNV infection. The active fractions from casein were identified, as well as one of the individual IHNV‐inhibiting peptides. Further studies will be required to determine which other peptides possess this activity. These findings provide a basis for future investigations on the efficacy of these compounds in treating other viral diseases in farmed fish and to elucidate the underlying molecular mechanisms of action. However, the present results provide convincing evidence in support of a role for several milk casein fractions as suitable candidates to prevent and treat some fish viral infections.  相似文献   

10.
Infectious haematopoietic necrosis virus from salmonids cultured in Korea   总被引：1，自引：0，他引：1  
Abstract. Four isolates of infectious haematopoietic necrosis virus (IHNV) were obtained from rainbow trout, Oncorhynchus mykiss (Walbaum), and masu salmon, Oncorhynchus masou (Walbaum), fry during epizootics at hatcheries in Korea. The four isolates of IHNV were compared with three from salmonids in the USA (SRCV, OSV and RB-76) by analysis of virion proteins in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and neutralization tests, with two monoclonal antibodies raised against SRCV (MAb SRCV/A4) and RB-76 (MAb RB/B5). Based on the antigenicity and the size of the structural proteins, one Korean isolate from masu salmon (SCS) is similar to RB-76 and is an electropherotype 1. The other three isolates from rainbow trout (PRT, YRT and MRT) were identical to each other in the mobilities of their virion proteins in SDS-PAGE, and although their nucleocapsid (N) proteins comigrated with that of the RB-76 isolate, they differed from RB-76 in the smaller matrix 2 (M2) protein they contained. In addition, the three Korean isolates (PRT, YRT and MRT) could be divided into two groups by reactivity with MAb RB/B5. While the YRT isolate was neutralized by this MAb, the PRT and MRT isolates were not, suggesting that there are at least two neutralizing antigenic variants of IHNV in Korea.  相似文献   

11.
This is the first study to isolate, identify and characterize Streptococcus iniae as the causative disease agent in two tilapia (Oreochromis aureus) populations. The populations were geographically isolated, of distinct origins, and did not share water sources. Affected fish showed various external (e.g., exophthalmia and cachexia, among others) and internal (e.g., granulomatous septicaemia and interstitial nephritis, among others) signs. All internal organ samples produced pure cultures, two of which (one from each farm, termed S‐1 and S‐2) were subjected to biochemical, PCR and 16S rRNA sequencing (99.5% similarity) analyses, confirming S. iniae identification. The two isolates presented genetic homogeneity regardless of technique (i.e., RAPD, REP‐PCR and ERIC‐PCR analyses). Pathogenic potentials were assessed through intraperitoneal injection challenges in rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio). Rainbow trout mortalities were respectively 40% and 70% at 104 and 106 CFU per fish with the S‐1 isolate, while 100% mortality rates were recorded in zebrafish at 102 and 104 CFU per fish with the S‐2 isolate. The obtained data clearly indicate a relationship between intensified aquaculture activities in Mexico and new disease appearances. Future studies should establish clinical significances for the tilapia industry.  相似文献   

12.
A comparative bacteriological and virological survey was conducted in two fish farms in the North of Portugal. The fish species examined included cultured rainbow trout, Oncorhynchus mykiss (Walbaum), and brown trout, Salmo trutta L., as well as wild fish captured near both facilities. The microbial load in the internal organs of apparently healthy fish was nonitored over a year, an all the disease problems occurring during this period were investigated. Although both farms presented intermediate levels of infection(30–40% infected fish), farm B showed the poorest microbiological quality since constant but low mortalities were observed throughout the year. Flavobacterium and Psedomonas-Xanthomonas were the predominant bacterial groups, comprising around 40–50% of the isolates from each farm. In farm B, members of the Enterobacteriaceae and mortile Aeromonas also showed significant prevalence (about 20%). The only outbreak of a notifiable disease was an occurrence of furunculosis, caused by Aeromonas salmonicida subsp. salmoncida, in farm A. However, Yersinia ruckeri was isolated not only from diseased fish, but also from asymptomatic fish, usually in mixed infections with motile Aeromonas or infections with motile Aeromonas or infectious pancreatic necrosis virus (IPNV). While Y. ruckeri isolates associated with mortalities belonged to the serotype O1 (subgroup a), those isolated from asymtomatic fish corresponded to serotype O3. Two strains of IPNV (serotype Ab) were isolated in farm B, which represents the first viral agent detected in Portuguese aquaculture. Qualitative and quantitative differences in microbial load were observed between cultured and wild fish. No notifiable bacterial or viral pathogens were detected in any of the feral species studied.  相似文献   

13.
Three experiments were conducted in order to evaluate the effects of urea and trimethylamine oxide (TMAO) supplementation in diets for seawater‐farmed rainbow trout Oncorhynchus mykiss. In all experiments, commercial extruded feed was used as basal control diet, whereas experimental diets were the basal diet supplemented with either 10 g kg–1 TMAO, 10 g kg–1 urea or 10 g kg–1 TMAO and 10 g kg–1 urea. The experiments were conducted both in research units and in a commercial fish farm. Quality was evaluated in three different commercial slaughterhouses, sorting the rainbow trout into superior, ordinary or processing grade. Significantly more TMAO was observed in muscle of rainbow trout given dietary supplementation of TMAO. However, the levels were low compared with levels in marine fish in general. Trimethylamine (TMA) was not found. No increase in muscle urea content was observed in trout fed urea in the diet. Significantly reduced fat belching, seen as reduced number of fat droplets surfacing in the net pen, was observed in groups given TMAO‐supplemented feeds. At least twice as many rainbow trout with skin vesicles were observed in the control group as in the group fed urea‐supplemented diet. In addition, skin vesicles developed into open sores in the winter only in rainbow trout fed control diet. In a large‐scale trial, quality grading of almost 200 000 market‐sized rainbow trout showed significantly more (88 vs. 83%) trout of superior grade in the group fed dietary urea compared with fish fed control diet. The main reason for downgrading from superior to ordinary and processing grade was skin lesions, supporting the observations made in the experimental units.  相似文献   

14.
Viral haemorrhagic septicaemia (VHS) was diagnosed in rainbow trout in the UK in May 2006. VHS virus (VHSV) was isolated from fingerlings showing typical histopathological lesions at a single rainbow trout farm site experiencing high mortality. The virus was confirmed as VHSV by serological and molecular biological tests. Phylogenetic analysis based on the complete glycoprotein gene sequence revealed that the isolate was closely related (99% nucleotide identity) to several Danish isolates from 1991 to 2000 and was assigned to VHSV genogroup Ia. The pathogenicity of the isolate was determined in infection experiments using rainbow trout fry. Following waterborne challenge, cumulative mortalities reached 96.67-100% by 12 days post-infection. This represents the first isolation of a pathogenic freshwater VHSV in the UK.  相似文献   

15.
Haemorrhagic areas in the mouth of farmed turbot, Scophthalmus maximus (L.)   总被引：4，自引：0，他引：4  
Abstract. An epizootic in juvenile turbol reared on a farm located in The Ria de Vigo, Galicia, Northwest Spain, is described. The diseased turbot did not display unusual swimming behavior; the external signs of the disease were abdominal distension and haemorrbagic areas in the mouth. Internal examination of the fist showed an accumulation of reddish fluid in the peritoneal cavity. Microbiological analysis of the diseased fish revealed the presence, in pure culture in all the organs and lesions examined, of a bacterium which was characterized biochemically as Vibrio splendidus biotype I. The virulence tests showed that the V. splendidus biotype I isolate was pathogenic for rainbow trout (LD50: 2.2 × 104) and also for turbot (LD50: 1.2 × 104). The treatment of the fish using flumequine incorporated into the feed was effective in offsetting the mortality rate.  相似文献   

16.
Abstract. The epidemiology of epizootic haematopoietic necrosis virus (EHNV) infection was studied in farmed rainbow trout, Oncorhynchus mykiss (Walbaum). Estimates of mortality during five outbreaks on a commercial farm from 1986 to 1992 ranged from 0033 to 0.2% per day and total mortality did not exceed 3–4% in any outbreak. Affected fish were 0+ and less than 125 mm forklength. Clinical signs were non-specific, and laboratory examination was required to confirm the diagnosis. At the height of the outbreak in 1992, EHNV was demonstrated by virus isolation and antigen capture ELISA in 89% of clinically affected fish and 51% of dead fish, while the prevalence of infection in apparently healthy in-contact fish was 4%. Two and 4 months later the virus was not detected in a group of apparently healthy fish that had been affected earlier. Antibodies specific for EHNV were not found in rainbow trout from the infected farm; however, strong humoral responses were detected by ELISA in two immunized fish, indicating that the virus was immunogenic. These data suggested that EHNV was poorly infective but highly virulent in rainbow trout. Clinical EHNV infection was positively correlated with high rearing density and a low rate of water exchange, and therefore, with presumed poor water quality. Water temperature, which ranged from 11 to 17°C during outbreaks, did not appear to determine the incidence of clinical infection. EHNV infection in farmed rainbow trout was preceded by infection in free-living redfin perch, Perca fluviatilis L., in the water catchment, but it was uncertain whether this represented the source of infection for rainbow trout.  相似文献   

17.
Flavobacterium psychrophilum is one of the most important pathogens affecting cultured rainbow trout (Oncorhynchus mykiss). Recent information from UK salmonid farms showed country‐wide distribution of genetically and serologically divergent clones, which has hampered the development of a vaccine for rainbow trout fry syndrome. The current study assessed the efficacy of an injectable polyvalent vaccine containing formalin‐inactivated F. psychrophilum in rainbow trout. The vaccine was formulated with an oil adjuvant (Montanide ISA 760VG) or formalin‐killed cells alone. Duplicate groups of trout (60 ± 13 g) were given phosphate‐buffered saline or vaccine formulated with Montanide by intra‐peritoneal (i.p.) injection and challenged by intra‐muscular (i.m.) injection with a homologous and a heterologous isolate of F. psychrophilum at 525 degree days post‐vaccination (dd pv). Significant protection was achieved in vaccinated fish (p = 0.0001, RPS 76% homologous, 88% heterologous). Efficacy of the adjuvanted vaccine was also demonstrated by heterologous challenge at 1155 dd pv resulting in 100% protection, whereas survival in the un‐adjuvanted group was not significantly different from control fish. Levels of specific antibody at 1155 dd pv, as measured by ELISA, were significantly higher in the fish vaccinated with adjuvant when compared with unvaccinated fish.  相似文献   

18.
Infectious hematopoietic necrosis virus (IHNV) is a major constraint to rainbow trout culture. Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) have greater resistance to this virus than do rainbow trout (O. mykiss), but the genetic mechanism of this resistance is not understood. We conducted a genome scan using a backcross of cutthroat trout into a rainbow trout background to estimate the number and locations of quantitative trait loci (QTL) associated with IHNV resistance and growth in trout. IHNV resistance was considered in terms of both survival (binary trait) and days to death (quantitative trait). The genetic map was scanned using interval mapping via two different approaches: one model considered survival alone and a second two-part model combined both survival and days to death. Three QTL were significantly (P ≤ 0.05) associated with virus resistance genome-wide, explaining 32.5% of the phenotypic variation. Cutthroat alleles at two of these QTL resulted in increased resistance to the pathogen, as expected. No growth QTL were detected in this cross. We suggest that these traits are genetically independent.  相似文献   

19.
Water as a habitat is highly variable in terms of the physico‐chemical properties. The aim of the studies was to analyze the quality of the technology by evaluating the non‐specific cellular defence potential of rainbow trout (Oncorhynchus mykiss) in diversified intensity culture systems and in different periods of the breeding cycle. The evaluation was conducted in order to establish the scientific basis for the development of principles for recognition of the culture of this species as ‘organic’. Six rainbow trout rearing farms were selected for the studies and divided into two equal groups according to the production technology: farms with a flow through system (with single water usage – OOH) and facilities with multiple water usage via its backflow (re‐circulating system – RAS). The samples for tests were taken from 20 individuals from each fish farm. In all fish that originated both from OOH‐type farms and RAS operations, an increase in the activity of non‐specific cellular immunity in the autumn was observed. Statistically significant reduction in the activity of cellular defensive mechanisms in small (300–500 g) and big (501–850 g) fish occurred on two 3‐OOH and 3‐RAS farms in spring and autumn in 2011. During these periods, the research has shown the presence of Infectious Pancreatic Necrosis Virus (IPNV), which provoked an immune suppression. Based on the obtained results it is concluded that there were no significant differences in the parameters of non‐specific cellular immunity in rainbow trout originating from different farming systems OOH and RAS.  相似文献   

20.
Northern Lake Huron (Ontario, Canada) supports the largest concentration of freshwater salmonid cage culture farms in Canada and receives inputs of domestic‐strain rainbow trout (Oncorhynchus mykiss) through escapement. We assessed the potential effects of these domestic fish on the naturalised rainbow trout of this ecosystem by comparing their respective ecologies. Mature adults were sampled from spawning tributaries, primarily in spring, and to a lesser extent in fall. Fish of domestic origin comprised ~80% of rainbow trout sampled from sites near cage culture facilities but <20% of rainbow trout sampled from more distant sites. Domestic adults in spawning condition (gametes free‐flowing) were present in the spawning tributaries in both spring and fall sampling seasons, whereas naturalised fish in spawning condition were only observed in the spring. Domestic adults were younger and smaller (in length), appeared to have shorter lifespan and had a higher male to female ratio compared with their naturalised counterparts. Growth rates (change in length with age) of naturalised and domestic females in the wild were similar, but domestic males grew more slowly than naturalised males. Domestic females also produced smaller eggs than naturalised females. Food web positions (inferred from δ13C and δ15N) of domestic and naturalised fish were very similar but varied more strongly with body size in the former. Domestic‐strain rainbow trout of cage culture origin can survive, grow and attempt to spawn in northern Lake Huron and have the potential to compete for food, mates and spawning habitat with naturalised rainbow trout.  相似文献   

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