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1.
Int J Parasitol ; 40(12): 1455-67, 2010 Oct.
Article in English | MEDLINE | ID: mdl-20595003

ABSTRACT

Despite routine screening requirements for the notifiable fish pathogen Gyrodactylus salaris, no standard operating procedure exists for its rapid identification and discrimination from other species of Gyrodactylus. This study assessed screening and identification efficiencies under real-world conditions for the most commonly employed identification methodologies: visual, morphometric and molecular analyses. Obtained data were used to design a best-practice processing and decision-making protocol allowing rapid specimen throughput and maximal classification accuracy. True specimen identities were established using a consensus from all three identification methods, coupled with the use of host and location information. The most experienced salmonid gyrodactylid expert correctly identified 95.1% of G. salaris specimens. Statistical methods of classification identified 66.7% of the G. salaris, demonstrating the need for much wider training. Molecular techniques (internal transcribed spacer region-restriction fragment length polymorphism (ITS-RFLP)/cytochrome c oxidase I (COI) sequencing) conducted in the diagnostic laboratory most experienced in the analysis of gyrodactylid material, identified 100% of the true G. salaris specimens. Taking into account causes of potential specimen loss, the probabilities of a specimen being accurately identified were 95%, 87% and 92% for visual, morphometric and molecular techniques, respectively, and the probabilities of correctly identifying a specimen of G. salaris by each method were 81%, 58% and 92%. Inter-analyst agreement for 189 gyrodactylids assessed by all three methods using Fleiss' Kappa suggested substantial agreement in identification between the methods. During routine surveillance periods when low numbers of specimens are analysed, we recommend that specimens be analysed using the ITS-RFLP approach followed by sequencing of specimens with a "G. salaris-like" (i.e. G. salaris, Gyrodactylus thymalli) banding pattern. During periods of suspected outbreaks, where a high volume of specimens is expected, we recommended that specimens be identified using visual identification, as the fastest processing method, to select "G. salaris-like" specimens, which are subsequently identified by molecular-based techniques.


Subject(s)
Fish Diseases/parasitology , Parasitology/methods , Trematoda/isolation & purification , Trematode Infections/veterinary , Animals , DNA, Helminth/genetics , DNA, Ribosomal/genetics , Fish Diseases/diagnosis , Phylogeny , Salmonidae/parasitology , Trematoda/classification , Trematoda/genetics , Trematode Infections/parasitology
2.
J Fish Dis ; 32(6): 481-9, 2009 Jun.
Article in English | MEDLINE | ID: mdl-19538641

ABSTRACT

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 x 10(1) TCID(50) 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 x 10(-2) TCID(50) mL(-1)kg(-1)) and rose to levels above the minimum infective dose (4.2 x 10(1) TCID(50) 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 x 10(1) TCID(50) mL(-1)kg(-1) 15 days post-infection. These data provide important information relevant to the management of ISA.


Subject(s)
Fish Diseases/transmission , Fish Diseases/virology , Isavirus , Orthomyxoviridae Infections/veterinary , Salmo salar , Virus Shedding/physiology , Animals , Oligonucleotides/genetics , Orthomyxoviridae Infections/transmission , Polymerase Chain Reaction/veterinary , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Seawater
3.
J Fish Dis ; 31(12): 879-87, 2008 Dec.
Article in English | MEDLINE | ID: mdl-19017067

ABSTRACT

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 10(2) to 10(-4) 50% end-point tissue culture infectious dose (TCID(50)) 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) TCID(50) mL(-1) by bath immersion (4 h at 10 degrees C). The peak shedding rate for IPNV following intraperitoneal challenge using post-smolts was estimated to be 6.8 x 10(3) TCID(50) 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.


Subject(s)
Birnaviridae Infections/veterinary , Fish Diseases/transmission , Fish Diseases/virology , Infectious pancreatic necrosis virus/physiology , Salmo salar/virology , Virus Shedding/physiology , Animals , Birnaviridae Infections/mortality , Birnaviridae Infections/transmission , Birnaviridae Infections/virology , Fish Diseases/mortality , Specific Pathogen-Free Organisms , Time Factors
4.
J Fish Dis ; 31(3): 177-86, 2008 Mar.
Article in English | MEDLINE | ID: mdl-18261031

ABSTRACT

This study represents the first large-scale investigation of IPNV in Scottish wild marine fish. Kidney samples were taken from 30 627 fish comprising 37 species and 45 isolations were made from nine different species, illustrating these as reservoirs of IPNV in Scottish waters. The estimated prevalence of IPNV in the Scottish marine environment was low at 0.15% (90% confidence intervals, (CI) of 0.11-0.19%). This was significantly greater in fish caught less than 5.0 km from IPN-positive fish farms in Shetland, at 0.58% (90% CI of 0.45-0.77%). This prevalence persisted and did not significantly decrease over the 16-month period of study. The estimated prevalence of IPNV for each positive species was less than 1% with the statistically non-significant exceptions of flounder, Platichthys flesus (L.), at 12.5% (90% CI of 0.64-47.06%) and saithe, Pollachius virens (L.), at 1.11% (90% CI of 0.49-2.19%). The 45 isolates were titrated and all but two were below the detection limit of the test (<55 PFU g(-1)). Titres of 3.8 x 10(2) PFU g(-1) and 2.8 x 10(1) PFU g(-1) were calculated from common dab, Limanda limanda (L.), and saithe, respectively. This study provides evidence that clinical outbreaks of IPN in farmed Atlantic salmon may cause a localized small increase in the prevalence of IPNV in wild marine fish.


Subject(s)
Birnaviridae Infections/veterinary , Fish Diseases/epidemiology , Infectious pancreatic necrosis virus/isolation & purification , Animals , Birnaviridae Infections/epidemiology , Birnaviridae Infections/transmission , Fish Diseases/transmission , Fish Diseases/virology , Fisheries , Fishes , Oceans and Seas , Prevalence , Salmo salar/virology , Scotland
5.
J Fish Dis ; 31(1): 37-47, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18086033

ABSTRACT

Infectious pancreatic necrosis (IPN) is a highly contagious disease of young salmonid fish, and is one of the most serious economic diseases in aquaculture. In Scotland, an increase in IPN virus (IPNV) outbreaks in seawater Atlantic salmon, Salmo salar, has been reported in recent years. The aim of this study was to analyse the VP2 gene from recent IPNV isolates from Scotland, to determine whether there are epidemiological links between IPNV isolates from farms (13), wild fish (17) and the environment (6) in order to investigate potential wild and farmed fish interactions. Comparison of the nucleotide sequence of the VP2 gene revealed that 34 of 36 isolates were 97.1-100% similar and the deduced amino acid sequences showed 97-100% identity. Two isolates from wild fish exhibited the most divergence at 85-87.3% similarity to the other isolates at the nucleotide level and 88.2-90.8% identity at the deduced amino acid level. Phylogenetic analyses revealed that 34 of 36 of the isolates from Scotland were genetically closely related to the A2 (Sp) serotype of IPNV. The two wild isolates from seatrout, Salmo trutta, and flounder, Platichthys flesus, were most closely related to the European A5 (Te) serotype. This study represents a comprehensive IPNV phylogenetic study that indicates that there are closely related or identical isolates in circulation in the marine environment, which adds evidence that disease interactions between wild and farmed fish may occur. This type of analysis is a useful tool in the management and control of fish diseases because it can assist in the identification of epidemiological links and highlight potential risks to aquaculture.


Subject(s)
Birnaviridae Infections/veterinary , Fish Diseases/virology , Infectious pancreatic necrosis virus/genetics , Viral Structural Proteins/genetics , Amino Acid Sequence , Animals , Base Sequence , Birnaviridae Infections/epidemiology , Birnaviridae Infections/virology , Cell Line , Fish Diseases/epidemiology , Fisheries , Fishes/virology , Geologic Sediments/virology , Infectious pancreatic necrosis virus/classification , Infectious pancreatic necrosis virus/pathogenicity , Molecular Sequence Data , Phylogeny , Scotland/epidemiology , Seawater/virology , Sequence Homology, Amino Acid , Sequence Homology, Nucleic Acid , Virus Cultivation
6.
J Fish Dis ; 30(10): 621-30, 2007 Oct.
Article in English | MEDLINE | ID: mdl-17850578

ABSTRACT

Infectious pancreatic necrosis virus (IPNV) has been isolated from mussels, sediment and surface water in the vicinity of clinically infected salmon farms, at shore bases supplying the farms and for several hundred metres distance from farms in the direction of current flow. There was evidence of decreasing prevalence of IPNV in mussels from Shetland once IPN outbreaks subsided, indicating they are an unlikely source of re-infection on farms. There was little evidence of persistence in the environment, although conclusions were complicated by the presence of IPNV on neighbouring farms 1 year after the outbreak.


Subject(s)
Birnaviridae Infections/veterinary , Environmental Microbiology , Fish Diseases/virology , Infectious pancreatic necrosis virus/isolation & purification , Salmo salar , Animals , Base Sequence , Birnaviridae Infections/mortality , Birnaviridae Infections/virology , Cell Line , Fish Diseases/mortality , Fisheries , Geologic Sediments/virology , Molecular Sequence Data , Mytilus edulis/virology , Scotland/epidemiology , Seawater/virology , Time Factors , Viral Structural Proteins/genetics
7.
Dev Biol (Basel) ; 129: 41-51, 2007.
Article in English | MEDLINE | ID: mdl-18306518

ABSTRACT

Modelling is a useful tool for the understanding and hence, potentially, control of disease. In an emergency situation, obtaining data to validate detailed models may be difficult. However, modelling can be useful in aiding the management of disease, if the objectives are not too ambitious. For example, import risk analysis can use models to minimise the risk of outbreaks. Modelling can also be used to maximise the power of surveillance data to ensure that any outbreak is detected as rapidly as possible. Methods of modelling spread of disease, and measures to prevent this, including SIR-style epidemiological models, models of disease control zones and contact network models can be used to identify and minimise the potential scale of an epidemic. Finally, economic and ecological models can be used to assess the impact of outbreaks. A range of simple models is likely to be of more use than a single comprehensive model.


Subject(s)
Disease Transmission, Infectious/veterinary , Models, Biological , Public Health Informatics/methods , Animals , Aquaculture/methods , Civil Defense , Communicable Disease Control , Models, Statistical , Risk Management
8.
Dis Aquat Organ ; 73(1): 23-31, 2006 Nov 21.
Article in English | MEDLINE | ID: mdl-17240749

ABSTRACT

A total of 14 viral haemorrhagic septicaemia virus (VHSV) isolates obtained from Greenland halibut Reinhardtius hippoglossoides caught at the Flemish Cap, a fishing ground in the North Atlantic Ocean near Newfoundland, were characterised using restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis. RFLP analysis was performed on a 1259 bp fragment of the glycoprotein (G) gene, and a 305 nucleotide region within the nucleoprotein (N) gene was used for sequence analysis. Representative strains of the 4 established genotypes were employed for comparative purposes. Sequencing analysis indicated that the Flemish cap isolates grouped in Genotype 3, which also includes isolates from wild fish caught in the North Sea and coastal waters of the UK and Ireland, isolates derived from outbreaks of VHS in turbot farms in the British Isles, and an isolate from European eel Anguilla anguilla caught in northern France. Characterisation using RFLPs resulted in the development of a simple and reliable method of typing VHSV at the genotype level using a 2-step restriction analysis (2-SRA) assay.


Subject(s)
Fish Diseases/virology , Flounder/virology , Novirhabdovirus/genetics , Rhabdoviridae Infections/veterinary , Animals , Base Sequence/genetics , DNA Primers/chemistry , DNA Restriction Enzymes/metabolism , Genotype , Glycoproteins/genetics , Molecular Sequence Data , Novirhabdovirus/classification , Nucleoproteins/genetics , Phylogeny , Polymorphism, Restriction Fragment Length , RNA, Viral/chemistry , Restriction Mapping , Rhabdoviridae Infections/virology , Sequence Analysis, RNA
9.
J Fish Dis ; 28(12): 737-42, 2005 Dec.
Article in English | MEDLINE | ID: mdl-16336475

ABSTRACT

Viral haemorrhagic septicaemia (VHS) is a well-characterized disease of rainbow trout, Oncorhynchus mykiss, which has also caused economic losses in marine turbot farms in the British Isles. We have previously demonstrated that turbot, Scophthalmus maximus, are susceptible to isolates of viral haemorrhagic septicaemia virus (VHSV) that are endemic in the marine environment, highlighting a potential risk to marine aquaculture. Given the increasing interest in the intensive rearing of additional aquaculture species such as Atlantic cod, Gadus morhua, and Atlantic halibut, Hippoglossus hippoglossus, this study aimed at investigating the susceptibility of these species to VHSV. Both species were found to be largely resistant to VHS following immersion challenge with a selection of 18 isolates, representing the known marine VHSV genotypes. Only one and two VHSV-associated mortalities occurred out of a total of 1710 and 1254 halibut and cod, respectively. These findings suggest that there is a low direct risk to the development of commercial cod and halibut aquaculture from the existing endemic reservoir of VHSV. This study, coupled to field observations has, however, highlighted the fact that both species can become infected with VHSV. The known adaptability of RNA viruses, together with the selection pressures associated with intensive aquaculture would thus advocate a cautious approach to VHSV surveillance within these emerging industries.


Subject(s)
Disease Susceptibility/veterinary , Fishes , Hemorrhagic Septicemia, Viral/immunology , Novirhabdovirus/genetics , Novirhabdovirus/pathogenicity , Animals , Aquaculture , Cell Line , Disease Susceptibility/immunology , Genotype , Species Specificity
10.
Vet Pathol ; 42(1): 9-18, 2005 Jan.
Article in English | MEDLINE | ID: mdl-15657267

ABSTRACT

Three marine viral hemorrhagic septicemia virus isolates were used to bath challenge turbot with the purpose of studying mortality and the pathology and antigen distribution over time. Two high-virulence isolates, 860/94, 4p168 and a low-virulence isolate 1p3 from a Baltic Sea herring were used. Organ samples were collected sequentially at 2, 4, 7, 10, 15, 20, 25, and 45 days postinfection. Specimens were processed for virology, histopathology, and immunohistochemistry. Organs during the early stages of infection (from 2 to 7 days) had virus isolation from all three groups only on day 7. Virus titer in kidney and heart sampled at day 25 was higher for the two virulent isolates compared with the low-virulence isolate. The viral distribution in situ of the two more virulent isolates from turbot (860/94) and herring (4p168) resembled viral hemorrhagic septicemia in rainbow trout with regard to the target organs. Early infection of endothelial cells in both kidney and heart was observed. Accumulated mean mortality was 41.5% for the turbot isolate 860/94, 48% for the herring isolate 4p168, and 3.5% for the herring isolate 1p3. This study revealed that the isolates from turbot (860/94) and herring (4p168) induced significantly higher mortality compared with the virus-free control and the herring isolate (1p3). The onset of mortality is markedly later in turbot compared with what is seen in rainbow trout.


Subject(s)
Fish Diseases/pathology , Fish Diseases/virology , Flatfishes , Hemorrhagic Septicemia, Viral/pathology , Novirhabdovirus/pathogenicity , Animals , Antigens, Viral/analysis , Fish Diseases/mortality , Gills/pathology , Gills/virology , Heart/virology , Hemorrhagic Septicemia, Viral/mortality , Hemorrhagic Septicemia, Viral/virology , Immunohistochemistry/veterinary , Kidney/pathology , Kidney/virology , Myocardium/pathology , Spleen/pathology , Spleen/virology , Virulence
11.
Dis Aquat Organ ; 67(1-2): 31-8, 2005 Nov 09.
Article in English | MEDLINE | ID: mdl-16385805

ABSTRACT

Viral haemorrhagic septicaemia (VHS) disease has exerted a significant impact on the development of turbot aquaculture in the British Isles. The source of such outbreaks is believed to be naturally occurring marine isolates of viral haemorrhagic septicaemia virus (VHSV), which are endemic in the marine environment of Northern Europe. Genetic studies have classified these marine VHSV isolates into genotypes based on their geographic rather than host-species origin. This study set out to explore the hypothesis that susceptibility of turbot to VHSV might be genotype specific. Immersion infection of turbot with a range of isolates, selected according to genotype, identified significant differences between susceptibility and genotype. Viruses belonging to Genotypes Ib (Baltic marine isolates) and III (North Sea/E. Atlantic marine isolates) caused significantly higher mortality than isolates from Genotypes Ia (isolates associated with rainbow trout aquaculture) and II (Baltic marine isolates). This study serves to highlight the importance of thoroughly investigating the susceptibility of any given species to the range of pathogens to which they might be exposed prior to considering them resistant to any disease. Furthermore, it highlights different risk factors that might be associated with turbot aquaculture undertaken in different environments. Finally, an increased knowledge of the relative virulence of different isolates in turbot will assist in understanding virulence determinants, which could lead to advances in disease control.


Subject(s)
Fish Diseases/genetics , Fish Diseases/virology , Flatfishes , Novirhabdovirus/genetics , Novirhabdovirus/pathogenicity , Rhabdoviridae Infections/veterinary , Animals , Aquaculture , Disease Susceptibility/veterinary , Genotype , Rhabdoviridae Infections/genetics , Species Specificity , United Kingdom , Virulence
12.
Dis Aquat Organ ; 61(1-2): 11-21, 2004 Oct 21.
Article in English | MEDLINE | ID: mdl-15584406

ABSTRACT

The nucleotide sequences of a specific region of the nucleoprotein gene were compared in order to investigate the genetic population structure of marine viral haemorrhagic septicaemia virus (VHSV). Analysis of the sequence from 128 isolates of diverse geographic and host origin renders this the most comprehensive molecular epidemiological study of marine VHSV conducted to date. Phylogenetic analysis of nucleoprotein gene sequences confirmed the existence of the 4 major genotypes previously identified based on N- and subsequent G-gene based analyses. The range of Genotype I included subgroups of isolates associated with rainbow trout aquaculture (Genotype Ia) and those from the Baltic marine environment (Genotype Ib) to emphasise the relatively close genetic relationship between these isolates. The existence of an additional genotype circulating within the Baltic Sea (Genotype II) was also confirmed. Genotype III included marine isolates from around the British Isles in addition to those associated with turbot mariculture, highlighting a continued risk to the development of this industry. Genotype IV consisted of isolates from the marine environment in North America. Taken together, these findings suggest a marine origin of VHSV in rainbow trout aquaculture. The implications of these findings with respect to the future control of VHSV are discussed. The capacity for molecular phylogenetic analysis to resolve complex epidemiological problems is also demonstrated and its likely future importance to disease management issues highlighted.


Subject(s)
Fishes/virology , Genetics, Population , Novirhabdovirus/genetics , Nucleoproteins/genetics , Phylogeny , Animals , Aquaculture/methods , Base Sequence , Cells, Cultured , DNA Primers , Genotype , Geography , Likelihood Functions , Models, Genetic , Molecular Sequence Data , Oceans and Seas , Reverse Transcriptase Polymerase Chain Reaction , Sequence Analysis, DNA
13.
J Fish Dis ; 26(3): 135-45, 2003 03.
Article in English | MEDLINE | ID: mdl-12962223

ABSTRACT

Four commonly used diagnostic tests [reverse transcription polymerase chain reaction (RT-PCR), indirect fluorescent antibody test (IFAT), virus culture and light microscopy] were evaluated for their ability to detect infectious salmon anaemia virus (ISAV) or tissue pathology following experimental infection of Atlantic salmon. Fish were infected with ISAV by water-borne exposure which mimics the route of natural infection. Forty-five per cent of pre-clinical fish tested yielded positive results by RT-PCR for at least one of the organs tested (kidney, heart, gill, liver, blood). No significant difference was detected between organs in the number or time of first occurrence of positive result. Virus culture identified a total of 14% of pre-clinical fish as ISAV-infected. The presence of ISAV in heart tissue was particularly notable (13% of fish sampled) as was the inability to culture virus from spleen tissue. In the case of IFAT, 15% of fish sampled were positive, although tissue other than kidney proved unsuitable for use in this method. Only limited ISAV-specific pathology was detectable by histological examination of fish prior to the onset of clinical disease. These findings reveal important information regarding the optimal choice of both tissue sample and diagnostic test for the routine diagnosis of ISAV.


Subject(s)
Anemia/veterinary , Fish Diseases/diagnosis , Orthomyxoviridae Infections/veterinary , Salmo salar , Anemia/diagnosis , Anemia/pathology , Animals , Fish Diseases/pathology , Fish Diseases/virology , Fluorescent Antibody Technique, Indirect/methods , Fluorescent Antibody Technique, Indirect/veterinary , Gills/virology , Heart/virology , Intestines/virology , Kidney/virology , Liver/virology , Microscopy, Electron/methods , Microscopy, Electron/veterinary , Muscles/virology , Orthomyxoviridae/isolation & purification , Orthomyxoviridae Infections/diagnosis , Orthomyxoviridae Infections/pathology , Reverse Transcriptase Polymerase Chain Reaction/methods , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Sensitivity and Specificity , Spleen/virology
14.
Dis Aquat Organ ; 50(1): 13-8, 2002 Jun 21.
Article in English | MEDLINE | ID: mdl-12152900

ABSTRACT

Wild-caught saithe Pollachius virens were experimentally exposed to an isolate of infectious salmon anaemia virus (ISAV) of Norwegian origin. Mortality attributable to ISAV did not occur following exposure by intra-peritoneal (i.p.) injection of virus or by cohabitation with ISAV-infected Atlantic salmon Salmo salar. Despite the individual testing of 120 ISAV-exposed saithe, ISAV was not detectable using RT-PCR, the most sensitive ISAV diagnostic tool demonstrated to date. Furthermore, saithe exposed to ISAV-infected salmon were not capable of transmitting virus when transferred to tanks containing naïve salmon. Thus saithe appear to be resistant to this Norwegian isolate of ISAV and incapable of supporting its replication. Saithe which co-exist with salmon in and around aqua-culture facilities are considered unlikely to have a significant impact on the epizootiology of ISAV.


Subject(s)
Fish Diseases/virology , Orthomyxoviridae Infections/veterinary , Orthomyxoviridae/pathogenicity , Animals , Cell Line , Disease Susceptibility , Disease Vectors , Fish Diseases/immunology , Fishes , Immunity, Innate , Orthomyxoviridae/isolation & purification , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/virology , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Salmo salar , Species Specificity
15.
Dis Aquat Organ ; 46(2): 93-100, 2001 Sep 12.
Article in English | MEDLINE | ID: mdl-11678233

ABSTRACT

Following the outbreak of infectious salmon anaemia (ISA) at salmon farms in Scotland, UK, a survey was established to determine the extent of infection in wild fish. All fish tested were free from the clinical symptoms of ISA. Isolations of ISAV were made from 5 sea trout within areas where ISA affected salmon farms were located. Evidence for ISAV in other sea trout was provided by ISA RT-PCR diagnostic tests. Results from ISA RT-PCR tests reveal evidence for ISAV being present in salmon parr, adult salmon and juvenile brown trout in rivers distant from salmon farms and indicate that, at the time of the survey (1998-1999), ISAV may have been widely distributed. Nucleotide sequence analysis of segments 2 and 8 showed that for most sequences from wild fish there was 100% homology with ISAV isolated from clinically affected farmed fish although evidence is presented which indicates variability in ISAV sequences from wild fish. Modelling the RT-PCR findings indicates that ISAV among salmonid fish was spatially non-random. Brown trout, sea trout and salmon (adult and parr) show a pattern of occasionally large numbers of positive samples against a background of very low numbers.


Subject(s)
Fish Diseases/virology , Orthomyxoviridae Infections/veterinary , Orthomyxoviridae/isolation & purification , Salmonidae , Animals , Animals, Wild , DNA, Viral/chemistry , Fish Diseases/epidemiology , Fishes , Orthomyxoviridae/genetics , Orthomyxoviridae/growth & development , Orthomyxoviridae Infections/epidemiology , Orthomyxoviridae Infections/virology , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Scotland/epidemiology , Sequence Analysis, Protein , Sequence Homology
16.
Dis Aquat Organ ; 47(3): 169-74, 2001 Dec 05.
Article in English | MEDLINE | ID: mdl-11804415

ABSTRACT

Infection models for both fresh and seawater salmon were established using a Scottish isolate of infectious salmon anaemia virus (ISAV). Modes of infection were intra-peritoneal injection, cohabitation and immersion exposure, and a range of doses was tested. Development of these models using a Scottish isolate of ISAV provided an approximation of the minimum infective dose leading to mortality under different infection regimens. The models also allow prediction of the time to first mortality and an estimation of expected total mortality following the various routes of infection. Such knowledge is important to the development of anti-ISAV vaccines and to future studies aimed at understanding the biology of ISAV in general.


Subject(s)
Fish Diseases/virology , Orthomyxoviridae Infections/veterinary , Orthomyxoviridae/pathogenicity , Salmo salar , Animals , Base Sequence , Disease Models, Animal , Disease Susceptibility/veterinary , Fish Diseases/immunology , Fresh Water , Injections, Intraperitoneal/veterinary , Molecular Sequence Data , Orthomyxoviridae/genetics , Orthomyxoviridae/immunology , Orthomyxoviridae Infections/immunology , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Seawater , Specific Pathogen-Free Organisms
17.
Dis Aquat Organ ; 47(1): 25-31, 2001 Oct 29.
Article in English | MEDLINE | ID: mdl-11797912

ABSTRACT

A number of viral haemorrhagic septicaemia (VHS) virus isolates of European marine origin were shown to be of low pathogenicity or non-pathogenic to Atlantic salmon parr by water-borne infection. A reference freshwater VHS virus isolate known to be highly pathogenic to rainbow trout was also of low pathogenicity to Atlantic salmon. Virus was detected in some mortalities, however, demonstrating viral entry and replication. European marine VHS virus isolates do not appear to pose an imminent threat to the Atlantic salmon culture industry. Turbot were found to be refractive or of low susceptibility to marine VHS virus isolates of sprat origin and to a reference freshwater isolate, with mortalities of 0 to 13.5%. Conversely, turbot were susceptible by varying degrees to a number of VHS virus isolates taken from herring, with mortalities ranging from 16 to 68%. These results emphasise the vulnerability of turbot culture to the VHS virus isolates that are enzootic to the European marine environment.


Subject(s)
Fish Diseases/virology , Flatfishes/virology , Novirhabdovirus/pathogenicity , Rhabdoviridae Infections/veterinary , Salmo salar/virology , Animals , Aquaculture , Disease Susceptibility/veterinary , Disease Transmission, Infectious/prevention & control , Disease Transmission, Infectious/veterinary , Fish Diseases/mortality , Fish Diseases/transmission , Rhabdoviridae Infections/mortality , Rhabdoviridae Infections/transmission , Rhabdoviridae Infections/virology
18.
Dis Aquat Organ ; 47(2): 81-6, 2001 Nov 08.
Article in English | MEDLINE | ID: mdl-11775798

ABSTRACT

A surveillance programme was initiated on the occurrence and distribution of viral haemorrhagic septicaemia virus (VHSV) in wild marine fish. Six research cruises were undertaken in an 18 mo period during 1997 and 1998, covering the North Sea, the Atlantic waters off the north and west coasts of Scotland and the Irish Sea. A total of 19,293 fish were sampled from 23 different species including cod, haddock, Norway pout, herring and sprat. Individual fish lengths were recorded and the fish were checked for lesions, haemorrhaging and other signs of disease. Pools of organ samples were taken for virus assay. The majority of fish sampled did not display clinical signs indicative of viral haemorrhagic septicaemia. A small number of cod were found with skin lesions and haddock with skin haemorrhaging. Of the 2081 organ and skin sample pools collected, 21 tested positive for VHSV by tissue culture and enzyme-linked immunosorbent assay. Seventeen of the isolates originated from Norway pout Trisopterus esmarkii, one from cod Gadus morhua (skin lesion), one from herring Clupea harengus, one from whiting Merlangius merlangus, and one from a previously unreported host species, poor cod Trisopterus minutus.


Subject(s)
Fish Diseases/epidemiology , Novirhabdovirus/isolation & purification , Rhabdoviridae Infections/veterinary , Animals , Animals, Wild , Atlantic Ocean , Fish Diseases/pathology , Fish Diseases/virology , Fishes , North Sea , Rhabdoviridae Infections/epidemiology , Skin/pathology , Skin/virology
19.
Int J Psychiatry Med ; 31(3): 311-20, 2001.
Article in English | MEDLINE | ID: mdl-11841128

ABSTRACT

OBJECTIVE: A postinfectious, autoimmune response may be associated with the development of pediatric obsessive-compulsive disorder (OCD). According to this model, antistreptococcal antibodies cross-react with basal ganglia neurons following streptococcus infection. This autoimmune reaction disrupts a basal ganglia-thalamocortical circuit and generates obsessive-compulsive symptoms. One implication of this model is that prolonged immunologic stress may be a risk factor for OCD. That is, immunologic stress may compromise the blood-brain barrier and permit the influx of antistriatal antibodies into the central nervous system. This article explores one part of this putative relationship by investigating whether adult OCD patients, compared to members of other psychiatric groups, demonstrate a higher incidence of recurrent infections and other conditions suggestive of compromised immune function. METHOD: To test this hypothesis, we conducted a medical records review of 100 consecutive patients evaluated at a private psychiatric clinic specializing in the treatment of anxiety disorders. Sixty-five patients met diagnostic criteria for an Axis-I syndrome. Primary diagnoses included OCD, posttraumatic stress disorder, social anxiety disorder, generalized anxiety disorder, panic disorder with agoraphobia, and dysthymic disorder. Each medical record was reviewed for the presence of target syndromes or presenting symptoms suggestive of compromised immune function. RESULTS: Chart review revealed an increased rate of immune-related symptoms and syndromes among OCD patients in comparison to other anxiety and mood disorder groups. Groups did not differ significantly in the incidence of non-immune symptoms and syndromes. CONCLUSION: Adult OCD patients appear to have an increased rate of immune-related diseases above and beyond that seen in other psychiatric disorders.


Subject(s)
Immunoglobulin A/immunology , Obsessive-Compulsive Disorder/immunology , Adult , Aged , Arthritis/epidemiology , Arthritis/immunology , Asthma/epidemiology , Asthma/immunology , Bacterial Infections/epidemiology , Bacterial Infections/immunology , Basal Ganglia/physiopathology , Bronchitis/epidemiology , Bronchitis/immunology , Diarrhea/epidemiology , Diarrhea/immunology , Female , Humans , Immunoglobulin A/blood , Male , Middle Aged , Obsessive-Compulsive Disorder/epidemiology , Obsessive-Compulsive Disorder/physiopathology , Thalamus/physiopathology
20.
Psychiatry ; 62(4): 313-24, 1999.
Article in English | MEDLINE | ID: mdl-10693226

ABSTRACT

This paper presents a three-factor causal model of obsessive-compulsive disorder (OCD), which posits that exposure to long-term traumatic stress generates an inordinate degree of anxiety during the psychological development of the premorbid OCD child. In response to these conditions the child evolves a distinct cognitive style characterized by exaggerated threat appraisal and magical beliefs, and experiences alterations in brain metabolism. An entire functional brain system (a basal ganglia-orbitofrontal circuit) enters into a state of enhanced responsiveness following exposure to protracted threat. Over time the threshold for stimulation is dramatically lowered, resulting in a hypersensitivity to cues that signify potential harm. Individuals adapt to this hypersensitivity through a variety of strategies, which constitute OCD.


Subject(s)
Obsessive-Compulsive Disorder/psychology , Stress Disorders, Post-Traumatic/psychology , Adaptation, Psychological/physiology , Arousal/physiology , Basal Ganglia/physiopathology , Defense Mechanisms , Frontal Lobe/physiopathology , Humans , Nerve Net/physiopathology , Obsessive-Compulsive Disorder/diagnosis , Obsessive-Compulsive Disorder/physiopathology , Stress Disorders, Post-Traumatic/diagnosis , Stress Disorders, Post-Traumatic/physiopathology
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