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1.
A microsporidian species with 98.3–98.4% nucleotide identity to Tetramicra brevifilum (Journal of Fish Diseases, 3 , 1980, 495) was diagnosed in lumpfish (Cyclopterus lumpus, L.) broodstock held at a breeding and rearing facility in western Ireland. The fish were wild‐caught from the west coast of Ireland, and the first case was diagnosed one year after capture. Clinical signs included severe bloating, lethargy, exophthalmos, anorexia, white patches on the cornea and externally visible parasitic cysts on skin and fins. Necropsy revealed severe ascites, white nodules and vacuoles in all the internal organs and partial liquefaction of the skeletal muscle. On histological examination, microsporidian xenomas were observed in all internal organs, the skin, skeletal muscle, gills and the eyes. The microsporidian species was identified by molecular analysis and transmission electron microscopy. This is the first record of T. brevifilum infecting lumpfish, and the disease is considered to be of potential significance to the rising aquaculture industry of this species.  相似文献   

2.
In order to develop a microsatellite typing system for Lepeophtheirus salmonis (Krøyer), a DNA preparation method for individual sea lice suitable for analysis by polymerase chain reaction (PCR) was designed, and the DNA sequences of 50 L. salmonis microsatellite elements were determined. The microsatellites were composed of 60% perfect, 25% imperfect, and 15% compound repeats. Based on the flanking DNA sequences, four microsatellite‐PCR assays were optimized and used in a pilot study to analyse L. salmonis samples collected in Ireland, Norway and Scotland. Two of the microsatellite‐PCR assays targeted polymorphic loci amplifying seven and 10 alleles respectively. The results showed that microsatellite‐PCR typing could detect genetic variation both within and between the L. salmonis groups, and also was capable of amplifying group‐specific alleles.  相似文献   

3.
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4.
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5.
Atlantic lumpfish (Cyclopterus lumpus L.) is used as a biological delousing agent for sea lice (Lepeophtheirus salmonis K.) infestations in Norwegian aquaculture. Here, we present a study on the antibody response and vaccine side effects after intramuscular and intraperitoneal injection of lumpfish with two vaccines. Both vaccines contained bacterial antigens from atypical Aeromonas salmonicida A‐layer types V and VI, Vibrio anguillarum serotype O1 and Moritella viscosa sp., but one vaccine contained a vegetable oil‐based adjuvant, while the other contained a mineral oil‐based adjuvant. Intramuscular injection of the mineral oil‐based vaccine caused a high acute mortality of fish within 48 hr after immunization. Intraperitoneal injection of the mineral oil‐based vaccine resulted in a lower severity of intra‐abdominal side effects than the vegetable oil‐based vaccine. Intramuscular injection of the mineral oil‐based vaccine resulted in a significantly higher antibody response against A. salmonicida when compared to controls and the vegetable oil‐based vaccine group. The antibody response was poor against V. anguillarum and M. viscosa for all groups. Our results indicate that intramuscular injection of oil‐based vaccines might be feasible for providing immunological protection for Atlantic lumpfish against bacterial diseases, especially atypical A. salmonicida, but more work is required to identity optimal adjuvants.  相似文献   

6.
The reproductive success of Lepeophtheirus salmonis settled on host and non‐host fish has been compared. Triplicate single species tanks of Atlantic salmon, marine three‐spined sticklebacks, saithe and Atlantic cod were exposed to 10 adult female L. salmonis per tank (n=30 lice per species). Adult female L. salmonis settlement and egg string production occurred only on salmon and cod, with no egg production occurring on saithe and three‐spined sticklebacks. The number of eggs in egg strings, hatching success of eggs and the survival of all larval stages to the copepodid stage were severely affected by the species of fish on which female L. salmonis had settled. L. salmonis settled on cod produced significantly fewer eggs, lower hatching rates and lower survival rates of larvae than females on Atlantic salmon. The production of egg strings by L. salmonis females infecting cod, which successfully hatch and moult through to the infective copepodid stage, albeit in small numbers, is discussed in terms of the implications to aquaculture and salmon and cod farming scenarios.  相似文献   

7.
This study assessed the effects of Hexamita salmonis (Moore) on metabolism of rainbow trout Oncorhynchus mykiss (Walbaum) and its effect on the host's susceptibility to infectious pancreatic necrosis virus (IPNV) after antiparasitic treatment. Rainbow trout naturally infected with H. salmonis were treated with 10 mg metronidazole kg fish?1 per day, and their physiological recovery was assessed through measuring resting metabolism on the 7th, 14th, 21st and 28th day after treatment. In addition, we exposed the naïve fish to H. salmonis and measured the resting metabolism (oxygen consumption as mg O2 kg?1 per hour) on the 10th, 20th and 30th day after the exposure to assess the variation in metabolic rates after infection. Significantly lower rates of metabolic activity (P < 0.05) were anticipated 20 days after infection with H. salmonis compared with the fish infected with H. salmonis for 10 days or with the parasite‐free fish. Similarly, the treated fish needed about 20 days to fully recover from hexamitiasis. The susceptibility of rainbow trout to IPNV remained unchanged in the presence of H. salmonis. Weight loss was significantly higher (P < 0.05) in infected than that in the parasite‐free fish. Fish should be examined regularly for H. salmonis and treated immediately whether found to prevent economic losses and excessive size variation.  相似文献   

8.
The sea louse, Lepeophtheirus salmonis (Krøyer 1837), is a significant parasite of farmed salmon throughout the Northern Hemisphere. Management of on‐farm louse populations can be improved by understanding the role that wild fish play in sustaining and providing refuge for the local population of sea lice. In this study, 1,064 sticklebacks were captured. Of these animals, 176 individuals were carrying a total of 238 sea lice, yielding a prevalence and intensity of 16.5% and 1.4 lice per fish, respectively. Detailed examination of the sea lice on the three‐spined sticklebacks captured in Cobscook Bay found two L. salmonis individuals using three‐spined sticklebacks as hosts. A 2012 survey of wild fish in Cobscook Bay, Maine, found multiple wild hosts for Caligus elongatus (von Nordmann 1832), including three‐spined sticklebacks (Gasterosteus aculeatus L.), but no L. salmonis were found in this earlier study.  相似文献   

9.
Lumpfish (Cyclopterus lumpus), a native fish of the North Atlantic Ocean, is utilized as cleaner fish to biocontrol sea lice infestations in Atlantic salmon aquaculture. However, bacterial infections are affecting cleaner fish performance. Vibrio anguillarum, the aetiological agent of vibriosis, is one of the most frequent bacterial infections in lumpfish, and effective vaccine programmes against this pathogen have been identified as a high priority for lumpfish. Vibrogen‐2 is a commercial polyvalent bath vaccine that contains formalin‐inactivated cultures of V. anguillarum serotypes O1 and O2, and Vibrio ordalii. In this study, we evaluated Vibrogen‐2 efficacy in lumpfish against a local isolated V. anguillarum strain. Two groups of 125 lumpfish were bath‐immunized, bath‐boost‐immunized at four weeks post‐primary immunization, and intraperitoneally (i.p.) boost‐immunized at eight weeks post‐primary immunization. The control groups were i.p. mock‐immunized with PBS. Twenty‐seven weeks post‐primary immunization, the fish were i.p. challenged with 10 or 100 times the V. anguillarum J360 LD50 dose. After the challenge, survival was monitored daily, and samples of tissues were collected at ten days post‐challenge. Commercial vaccine Vibrogen‐2 reduced V. anguillarum tissue colonization and delayed mortality but did not confer immune protection to C. lumpus against the V. anguillarum i.p. challenge.  相似文献   

10.
Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis, a disease which affects a variety of teleost species and that is particularly severe in salmonid fish. Bacterial‐free supernatants, obtained from cultures of three isolates of Piscirickettsia salmonis, were inoculated in Atlantic salmon, Salmo salar L., and in three continuous cell lines in an effort to determine the presence of secretion of extracellular products (ECPs) by this microorganism. Although steatosis was found in some liver samples, no mortalities or clinical signs occurred in the inoculated fish. Clear cytotoxicity was observed after inoculation in the cell lines CHSE‐214 and ASK, derived from salmonid tissues, but not in MDBK, which is of mammalian origin. The degree of cytotoxicity of the ECPs was different among the P. salmonis isolates tested. The isolate that evidenced the highest cytotoxicity in its ECPs exhibited only an intermediate virulence level after challenging fish with bacterial suspensions of the three P. salmonis isolates. Almost complete inhibition of the cytotoxic activity of ECPs was seen after proteinase K treatment, indicating their peptidic nature, and a total preclusion of the cytotoxicity was shown after their incubation at 50 °C for 30 min. Results show that P. salmonis can produce ECPs and at least some of them are thermolabile exotoxins that probably play a role in the pathogenesis of piscirickettsiosis.  相似文献   

11.
A bacteria–parasite challenge model was used to study the role of sea lice, Lepeophtheirus salmonis (Copepoda), as a vector of Aeromonas salmonicida subsp. salmonicida. Three hypotheses were tested: (i) L. salmonis can acquire A. salmonicida subsp. salmonicida via water bath exposure; (ii) L. salmonis can acquire the bacteria via parasitizing infected Atlantic salmon, Salmo salar; and (iii) L. salmonis can transmit the bacteria to naïve Atlantic salmon via parasitism. Adult L. salmonis exposed to varying A. salmonicida subsp. salmonicida suspensions (101–107 cells mL?1) for 1.0, 3.0 or 6.0 h acquired the bacteria externally (12.5–100%) and internally (10.0–100%), with higher prevalences associated with the highest concentrations and exposures. After exposure to 107 cells mL?1, viable A. salmonicida subsp. salmonicida could be isolated from the external carapace of L. salmonis for 120 h. Lepeophtheirus salmonis also acquired the bacteria externally and internally from parasitizing infected fish. Bacterial transmission was observed only when L. salmonis had acquired the pathogen internally via feeding on ‘donor fish’ and then by parasitizing smaller (<50 g) ‘naive’ fish. Under specific experimental conditions, L. salmonis can transfer A. salmonicida subsp. salmonicida via parasitism; however, its role as a mechanical or biological vector was not defined.  相似文献   

12.
While co‐infections are common in both wild and cultured fish, knowledge of the interactive effects of multiple pathogens on host physiology, gene expression and immune response is limited. To evaluate the impact of co‐infection on host survival, physiology and gene expression, sockeye salmon Oncorhynchus nerka smolts were infected with the salmon louse Lepeophtheirus salmonis (V?/SL+), infectious hematopoietic necrosis virus (IHNV; V+/SL?), both (V+/SL+), or neither (V?/SL?). Survival in the V+/SL+ group was significantly lower than the V?/SL? and V?/SL+ groups (p = 0.024). Co‐infected salmon had elevated osmoregulatory indicators and lowered haematocrit values as compared to the uninfected control. Expression of 12 genes associated with the host immune response was analysed in anterior kidney and skin. The only evidence of L. salmonis‐induced modulation of the host antiviral response was down‐regulation of mhc I although the possibility of modulation cannot be ruled out for mx‐1 and rsad2. Co‐infection did not influence the expression of genes associated with the host response to L. salmonis. Therefore, we conclude that the reduced survival in co‐infected sockeye salmon resulted from the osmoregulatory consequences of the sea lice infections which were amplified due to infection with IHNV.  相似文献   

13.
Piscirickettsiosis, caused by the intracellular Gram‐negative bacteria Piscirickettsia salmonis, is at present the most devastating disease in the Chilean salmon industry. The aim of this study was to analyse disease development after challenge with a P. salmonis strain (EM90‐like) under a controlled environment by comparing intraperitoneal challenge with cohabitation challenge. The P. salmonis EM90‐like isolate was cultured in a liquid medium for the challenge of 400 Atlantic salmon (Salmo salar) smolts. Cumulative mortality was registered, necropsy was performed, and bacterial distribution in the tissues and histopathological changes were analysed. The results revealed a similar progression of the disease for the two different challenge models. Pathological and histopathological changes became more visible during the development of the clinical phase of the disease. Bacterial DNA was identified in all the analysed tissues indicating a systemic infection. Bacterial tropism to visceral organs was demonstrated by real‐time quantitative PCR and immunohistochemistry. Better knowledge of disease development during P. salmonis infection may contribute to further development of challenge models that mimic the field situation during piscirickettsiosis outbreaks. The models can be used to develop and test future preventive measures against the disease.  相似文献   

14.
To improve the understanding of the piscirickettsiosis pathogenesis, the in vivo apoptosis modulation of peritoneal macrophages and lymphocytes was studied in juvenile Salmo salar intraperitoneally injected with Piscirickettsia salmonis. Five fish were sampled at post‐exposure days 1, 5, 8 (preclinical), 20 (clinical) and 40 (post‐clinical period of the disease), and the leucocytes of their coelomic washings were analysed by flow cytometry (using the JC‐1 cationic dye), TUNEL and cytology to detect apoptotic cells. A selective and temporal pattern of apoptosis modulation by P. salmonis infection was observed. Apoptosis in lymphocytes was not affected, whereas it was inhibited in macrophages but only during the preclinical stage of the induced piscirickettsiosis. Hence, it is postulated that P. salmonis inhibits macrophage apoptosis at the beginning of the disease development to survive, multiply and probably be transported inside these phagocytes; once this process is complete, macrophage apoptosis is no longer inhibited, thus facilitating the exit of the bacteria from the infected cells for continuing their life cycle.  相似文献   

15.
A novel viral haemorrhagic septicaemia virus (VHSV) of genotype IV was isolated from wild lumpfish (Cyclopterus lumpus), brought to a land‐based farm in Iceland, to serve as broodfish. Two groups of lumpfish juveniles, kept in tanks in the same facility, got infected. The virus isolated was identified as VHSV by ELISA and real‐time RT‐PCR. Phylogenetic analysis, based on the glycoprotein (G) gene sequences, may indicate a novel subgroup of VHSV genotype IV. In controlled laboratory exposure studies with this new isolate, there was 3% survival in the I.P. injection challenged group while there was 90% survival in the immersion group. VHSV was not re‐isolated from fish challenged by immersion. In a cohabitation trial, lumpfish infected I.P. (shedders) were placed in tanks with naïve lumpfish as well as naïve Atlantic salmon (Salmo salar L.). 10% of the lumpfish shedders and 43%–50% of the cohabiting lumpfish survived after 4 weeks. 80%–92% of the Atlantic salmon survived, but no viral RNA was detected by real‐time RT‐PCR nor VHSV was isolated from Atlantic salmon. This is the first isolation of a notifiable virus in Iceland and the first report of VHSV of genotype IV in European waters.  相似文献   

16.
Piscirickettsia salmonisis the causative bacterial pathogen of piscirickettsiosis, a salmonid disease that causes notable mortalities in the worldwide aquaculture industry. Published research describes the phenotypic traits, virulence factors, pathogenicity and antibiotic‐resistance potential for various P. salmonisstrains. However, evolutionary and genetic information is scarce for P. salmonis. The present study used multilocus sequence typing (MLST) to gain insight into the population structure and evolution of P. salmonis. Forty‐two Chilean P. salmonisisolates, as well as the type strain LF‐89T, were recovered from diseased Salmo salar, Oncorhynchus kisutchand Oncorhynchus mykissfrom two Chilean Regions. MLST assessed the loci sequences of dnaK, efp, fumC, glyA, murG, rpoD and trpB. Bioinformatics analyses established the genetic diversity among P. salmonis isolates (H = 0.5810). A total of 23 sequence types (ST) were identified, 53.48% of which were represented by ST1, ST5 and ST2. Population structure analysis through polymorphism patterns showed few polymorphic sites (218 nucleotides from 4,010 bp), while dN/dS ratio analysis indicated purifying selection for dnaK, epf, fumC, murG, and rpoD but neutral selection for the trpB loci. The standardized index of association indicated strong linkage disequilibrium, suggesting clonal population structure. However, recombination events were detected in a group of seven isolates. Findings included genogroups homologous to the LF‐89T and EM‐90 strains, as well as a seven‐isolate hybrid genogroup recovered from both assessed regions (three O. mykiss and four S. salar isolates). The presented MLST scheme has comparative potential, with promising applications in studying distinct P. salmonis isolates (e.g., from different hosts, farms, geographical areas) and in understanding the epidemiology of this pathogen.  相似文献   

17.
The efficacy of teflubenzuron (Calicide®) for the treatment of farmed Atlantic salmon (Salmo salar L.) infested with sea lice [Lepeophtheirus salmonis (Krøyer)] was investigated on two commercial salmon farms. Teflubenzuron (Calicide®) coated onto commercial feed pellets was administered orally at 10 mg per kg body weight per day for seven consecutive days. Fish were randomly sampled and lice numbers recorded from both treated and control groups on four sampling occasions post‐medication. Statistically significant reductions in the number of L. salmonis per fish were recorded. Maximum efficacy was observed toward chalimus and preadult stages of L. salmonis, and was achieved about 7 days post‐medication. No apparent effect was observed on adult lice. No adverse drug reactions or palatability problems were associated with the treatments.  相似文献   

18.
Piscirickettsia salmonis, the aetiological agent of salmonid rickettsial septicaemia (SRS), is a global pathogen of wild and cultured marine salmonids. Here, we describe the development and application of a reproducible, standardized immersion challenge model to induce clinical SRS in juvenile pink (Oncorhynchus gorbuscha), Atlantic (Salmo salar) and sockeye salmon (O. nerka). Following a 1‐hr immersion in 105 colony‐forming units/ml, cumulative mortality in Atlantic salmon was 63.2% while mortality in sockeye salmon was 10%. Prevalence and levels of the bacterium in kidney prior to onset of mortality were lower in sockeye compared with Atlantic or pink salmon. The timing and magnitude of bacterial shedding were estimated from water samples collected during the exposure trials. Shedding was estimated to be 82‐fold higher in Atlantic salmon as compared to sockeye salmon and peaked in the Atlantic salmon trial at 36 d post‐immersion. These data suggest sockeye salmon are less susceptible to P. salmonis than Atlantic or pink salmon. Finally, skin lesions were observed on infected fish during all trials, often in the absence of detectable infection in kidney. As a result, we hypothesize that skin is the primary point of entry for P. salmonis during the immersion challenge.  相似文献   

19.
The bacterium Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis a severe disease that has caused major economic losses in the aquaculture industry since its appearance in 1989. Recent reports of P. salmonis or P. salmonis‐like organisms in new fish hosts and geographical regions have increased interest in the bacterium. Because this gram‐negative bacterium is still poorly understood, many relevant aspects of its life cycle, virulence and pathogenesis must be investigated before prophylactic procedures can be properly designed. The development of effective control strategies for the disease has been limited due to a lack of knowledge about the biology, intracellular growth, transmission and virulence of the organism. Piscirickettsiosis has been difficult to control; the failure of antibiotic treatment is common, and currently used vaccines show variable long‐term efficacy. This review summarizes the biology and characteristics of the bacterium, including its virulence; the infective strategy of P. salmonis for survival and evasion of the host immune response; the host immune response to invasion by this pathogen; and newly described features of the pathology, pathogenesis, epidemiology and transmission. Current approaches to the prevention of and treatment for piscirickettsiosis are discussed.  相似文献   

20.
Piscirickettsiosis is a threatening infectious disease for the salmon industry, due to it being responsible for significant economic losses. The control of outbreaks also poses considerable environmental challenges. Despite Piscirickettsia salmonis having been discovered as the aetiological agent of the disease more than 25 years ago, its pathogenicity remains poorly understood. Among virulence factors identified so far, type four secretion systems (T4SS) seem to play a key role during the infection caused by the bacterium. We report here the genetic manipulation of P. salmonis by means of the transference of plasmid DNA in mating assays. An insertion cassette was engineered for targeting the icmB gene, which encodes a putative T4SS‐ATPase and is carried by one of the chromosomal T4SS clusters found within the genome of P. salmonis PM15972A1, a virulent representative of the EM‐90‐like strain. The molecular characterization of the resulting mutant strain demonstrated that the insertion interrupted the target gene. Further in vitro testing of the icmB mutant showed a dramatic drop in infectivity as tested in CHSE‐214 cells, which is in agreement with its attenuated behaviour observed in vivo. Altogether, our results demonstrate that, similar to other facultative intracellular pathogens, P. salmonis’ virulence relies on an intact T4SS.  相似文献   

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