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Infectious salmon anaemia ( ISA) is a serious disease of farmed Atlantic salmon caused by the aquatic orthomyxovirus infectious salmon anaemia virus ( ISAV). ISA was first detected in Norway in 1984 and was characterized by severe anaemia and circulatory disturbances. This review elucidates factors related to the pathogenesis of ISA in Atlantic salmon, the dissemination of the virus in the host and the general distribution of the 4- O-acetylated sialic acids ISAV receptor. The knowledge contributes to the understanding of this disease, and why, almost 30 years after the first detection, it is still causing problems for the aquaculture industry. [ABSTRACT FROM AUTHOR]

The article examines the microbiology and pathology of proliferative gill inflammation in farmed Atlantic salmon in Norway. Materials and methods used to store tissue samples and extract DNA and RNA are described. The epidemiology and histopathology of seawater-reared fish is discussed. An analysis of tissue samples has detected Candidatus Piscichlamydia salmonis in seawater-reared fish. Freshwater stage observations show no increased mortality or disease from the hatcheries. The histology of freshwater-reared smolts is discussed.

The article presents information on a study analyzing the etiological agent of infectious salmon anemia (ISA) affecting farmed Atlantic salmon in Norway. The most typical signs in the terminal stage of the disease are anemia, leucopenia, ascites and haemorrhagic liver necrosis. According to the research, the aetiological agent is most probably a virus. The target cells of the tentative ISA-virus have not been identified. All attempts to propagate the aetiological ISA-agent in cell cultures have failed.

A panel of 11 monoclonal antibodies (MAbs) was used in an immunodot assay to investigate the antigenic relationships of a representative selection of aquatic birnaviruses isolated in Norway from different species of both carrier and diseased fish. All the 81 isolates shared a serogroup A-specific epitope, and 67 of them had a reaction pattern identical to the Sp-type strain. Of the other 14 isolates, nine resembled the Sp-type strain, two resembled both Sp- and He-type strains, two were closest to the Ab-type strain and one resembled the Te-type strain. Sp-related strains were predominant from all nine host groups, including from both Atlantic salmon, Salmo salar L., with infectious pancreatic necrosis (IPN) and healthy Atlantic salmon. The N1 strain reacted identically ton the Sp-type strain. [ABSTRACT FROM AUTHOR]

Abstract: Proliferative gill inflammation, a respiratory disease of apparently multifactorial aetiology, affects seawater-farmed Atlantic salmon in Norway and may be associated with significant losses. In the present study, the gill-associated bacterial community in fish suffering PGI as diagnosed by histology was compared with that of clinically healthy fish by Reverse Transcriptase Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis. ‘Candidatus Piscichlamydia salmonis’, which forms histologically detectable intracellular inclusions commonly called epitheliocysts, was identified in 16 of 21 fish displaying PGI, normally as the dominant phylotype. Although identified by RT-DGGE in many clinically healthy fish from PGI affected farms, this bacterium was only detected in 7 of 48 fish from PGI-free farms, of which all positives interestingly originated from a single farm. Taken together, these results reveal a positive association between ‘Candidatus Piscichlamydia salmonis’ and PGI in the investigated material from 10 geographically distinct farms. Furthermore, a wide distribution of γ-proteobacteria was detected, but the bacterial communities of individual fish gills were generally quite simple and often dominated by one or two phylotypes, most commonly Burkholderia-like bacteria (previously Pseudomonads) and Psychrobacter spp. Representatives of spoilage or fish pathogenic genera e.g. Photobacterium, Flavobacterium, Aliivibrio, Shewanella and Tenacibaculum, were less frequently identified and apparently in low numbers. Sequences representing at least one undescribed species closely related to fish pathogenic Francisella spp. were also identified. [Copyright &y& Elsevier]

All viruses infecting fish must cross the surface mucosal barrier to successfully enter a host. Infectious salmon anaemia virus (ISAV), the causative agent of the economically important infectious salmon anaemia (ISA) in Atlantic salmon, Salmo salar L., has been shown to use the gills as its entry point. However, other entry ports have not been investigated despite the expression of virus receptors on the surface of epithelial cells in the skin, the gastrointestinal (GI) tract and the conjunctiva. Here we investigate the ISAV mucosal infection in Atlantic salmon after experimental immersion (bath) challenge and in farmed fish collected from a confirmed outbreak of ISA in Norway. We show for the first time evidence of early replication in several mucosal surfaces in addition to the gills, including the pectoral fin, skin and GI tract suggesting several potential entry points for the virus. Initially, the infection is localized and primarily infecting epithelial cells, however at later stages it becomes systemic, infecting the endothelial cells lining the circulatory system. Viruses of low and high virulence used in the challenge revealed possible variation in virus progression during infection at the mucosal surfaces.

It is widely accepted that melanin formation may play an immunologic role in invertebrates and ectothermic vertebrates. In farmed Atlantic salmon, cardiomyopathy syndrome (CMS) is a common viral disease associated with severe cardiac inflammation that may be accompanied by heavy melanisation of the heart. By the use of histology, laser capture microdissection and transcription analysis of tyrosinase genes, we here show that this melanisation is linked to de novo melanogenesis by melanomacrophages, suggesting an active part in the inflammatory reaction. No general systemic activation of the extracutaneous pigmentary system in response to viral infections with affinity to the heart was observed.

The prevalence and geographical distribution of the recently described endosymbiont 'Candidatus Branchiomonas cysticola' in Atlantic salmon Salmo salar gill epithelial cell cysts was investigated in seawater-farmed fish suffering proliferative gill inflammation (PGI). To this end, we developed a specific and sensitive real-time PCR assay for detection of the bacterium. 'Ca. B. cysticola' was found to be highly prevalent in Atlantic salmon gills sampled over 7 yr and from 17 geographically distant seawater locations in Norway and Ireland. 'Ca. B. cysticola' was found in significantly greater quantities in fish with large numbers of epitheliocysts, and fluorescence in situ hybridization confirmed its localisation within cysts. 'Ca. Piscichlamydia salmonis', a bacterium previously linked to epitheliocysts, was identified at relatively low levels of infection, apparently independent of epitheliocyst prevalence. These results suggest that 'Ca. B. cysticola' is the main cyst-forming bacterium in seawater-farmed Atlantic salmon in the studied countries. Our results also suggest a relationship between load of 'Ca. B. cysticola' and extent of pathological changes. Taken together with a previously described association between epitheliocyst load and severity of PGI in Norwegian salmon, the results could indicate a role for 'Ca. B. cysticola' in gill diseases such as PGI.

Epitheliocystis, a disease characterised by cytoplasmic bacterial inclusions (cysts) in the gill and less commonly skin epithelial cells, has been reported in many marine and freshwater fish species and may be associated with mortality. Previously, molecular and ultrastructural analyses have exclusively associated members of the Chlamydiae with such inclusions. Here we investigated a population of farmed Atlantic salmon from the west coast of Norway displaying gill epitheliocystis. Although 'Candidatus Piscichlamydia salmonis', previously reported to be present in such cysts, was detected by PCR in most of the gill samples analysed, this bacterium was found to be a rare member of the gill microbiota, and not associated with the observed cysts as demonstrated by fluorescence in situ hybridization assays. The application of a broad range 16 S rRNA targeted PCR assay instead identified a novel betaproteobacterium as an abundant member of the gill microbiota. Fluorescence in situ hybridization demonstrated that this bacterium, tentatively classified as 'Candidatus Branchiomonas cysticola', was the cyst-forming agent in these samples. While histology and ultrastructure of 'Ca. B. cysticola' cysts revealed forms similar to the reticulate and intermediate bodies described in earlier reports from salmon in seawater, no elementary bodies typical of the chlamydial developmental cycle were observed. In conclusion, this study identified a novel agent of epitheliocystis in sea-farmed Atlantic salmon and demonstrated that these cysts can be caused by bacteria phylogenetically distinct from the Chlamydiae.

Proliferative gill inflammation (PGI) causes significant losses in farmed Atlantic salmon Salmo salar L. in Norway, especially during the first months following seawater transfer. The aetiology is apparently multifactorial, including infection with chlamydia-like bacteria and Atlantic salmon paramyxovirus (ASPV). In the present study, gills from diseased fish from 3 farms on the western coast of Norway were sampled. The pathological changes were briefly described and the aetiological significance of ASPV studied by immunofluorescent staining of cryosections and by immunohistochemistry on sections of formalin-fixed and paraffin-embedded tissue. The pathological changes were macroscopically characterized by palour of the gills, and histologically by inflammation, circulatory disturbances, cell death and epithelial cell proliferation. ASPV was demonstrated in fish from all farms studied, as immunostaining consistent with ASPV was obtained in lamellar epithelial and endothelial cells of pathologically altered tissues. It is concluded that ASPV is at least a contributing cause of PGI. As far as we know, this is the first demonstration of fish disease related to infection with a paramyxovirus.

Heart and skeletal muscle inflammation (HSMI) is a disease syndrome of unknown aetiology first observed in farmed Atlantic salmon, Salmo salar, in 1999. In the present study we have demonstrated for the first time that HSMI is an infectious disease. It was induced in Atlantic salmon post-smolts after injection with tissue homogenate from farmed Atlantic salmon previously diagnosed with HSMI. The lesions were also induced in cohabitating salmon given a corresponding injection without tissue homogenate. Six weeks post-challenge the fish that had been injected with tissue homogenate developed a serious epicarditis and myocarditis with mononuclear cell infiltrations in compact and spongy layers of the heart. Similar lesions were found in cohabitants after 10 weeks. The lesions were consistent with samples from field outbreaks of HSMI. No lesions were found in control fish. A viral aetiology is strongly suggested, as no difference in disease induction between an inoculum containing antibiotics and a non-treated inoculum was found. Further investigations are required in order to make conclusions regarding the cause and pathogenesis of HSMI.

Infectious salmon anemia (ISA) is caused by a virus that probably belongs to the Orthomyxoviridae and was first recorded in Norway in 1984. The disease has since spread along the Norwegian coast and has later been found in Canada, Scotland, the Faroe Islands, Chile, and the USA. This study presents sequence variation of the hemagglutinin gene from 37 ISA virus isolates, viz. one isolate from Scotland, one from Canada and 35 from Norway. The hemagglutinin gene contains a highly polymorphic region (HPR), which together with the rest of the gene sequence provides a good tool for studies of epizootics. The gene shows temporal and geographical sequence variation, where certain areas are dominated by distinct groups of isolates. Evidence of transmission of ISA virus isolates within and between regions is given. It is suggested that the hemagglutinin gene from different isolates may recombine. Possible recombination sites are found within the HPR and in the 5'-end flanking region close to the HPR.

The sequences of gene segments 2 and 8 from 10 different isolates of infectious salmon anaemia virus (ISAV) sampled in Norway, Canada and Scotland between 1987 and 1999 were determined and compared. Pairwise comparisons revealed a high degree of homology between the European isolates, with identities of 98 to 100% for both genes examined. The Canadian isolate showed identities of 84 and 87 to 88% with the European isolates for the nucleotide sequence of segments 2 and 8, respectively. Phylogenetic analyses were performed to establish the interrelationship between the European virus isolates. The evolutionary rate based on 4 Norwegian isolates clustered together in the analysis of segment 2 was calculated to be 0.96 x 10(-3) nucleotides site(-1) yr(-1). On the basis of this mutation rate it was estimated that the Norwegian Glesvaer 90 and Canadian Bay of Fundy 97 isolates diverged around 1900, which coincides with transportation of salmonids between Europe and North America starting in the late nineteenth century.

Introduction: Thrombolytic treatment is central in the treatment of patients with myocardial infarction., Material and Methods: A cross-sectional study was conducted to determine the time delay incurred in thrombolytic treatment of patients with myocardial infarction in Ostfold Hospital, Fredrikstad, Norway. Over a seven-month period, 317 patients were diagnosed as having myocardial infarction. 80 patients (25%) received thrombolytic therapy, 68 of whom (85%) were eligible for the study. 12 patients were excluded either because of not meeting the inclusion criteria or because of incomplete data., Results: The following median times were recorded: from onset of chest pain till first contact with the health care services, 59 minutes; from first contact till arrival at hospital, 32 minutes; from hospital arrival till initiation of treatment, 40 minutes; from onset of chest pain till initiation of treatment, 147 minutes. 38% of the patients received thrombolysis within 120 minutes of pain onset, and 35% received treatment within 30 minutes of arrival in hospital. There was no difference in time delay before contacting health care services among patients with or without a previous history of coronary heart disease, except for those who took nitroglycerine at onset of symptoms. They had the longest time delay., Interpretation: In order to reduce time delay, doctors should give better instructions to patients with a previous history of coronary heart disease and conduct regular training programmes for hospital interns and nurses. It is further assumed that prehospital ECG and direct admission to the coronary care unit, or initiation of thrombolysis in the emergency department or in the ambulance, would result in a considerable reduction in time delay.

Blood samples from 777 pigs, originating from 9 different herds, were collected at slaughter and examined for antibodies to Mycoplasma hyopneumoniae and Actinobacillus (Haemophilus) pleuropneumoniae by the indirect hemagglutination assay (IHA) and the complement fixation (CF) test, respectively. Results were compared to pathological and microbiological findings. Antibodies to M. hyopneumoniae in positive titers of 1/80 or higher were found in 62% of the samples. The relationship between positive IHA titers to M. hyopneumoniae and gross findings indicative of enzootic pneumonia of pigs (EPP), histological findings indicative of EPP, the isolation of M. hyopneumoniae and the demonstration of M. hyopneumoniae by indirect immunofluorescent testing ranged from 64% to 68%. No correlation was noted between positive IHA titers and the isolation of Mycoplasma flocculare. Positive antibody titers to A. pleuropneumoniae of 1/10 or higher were detected in 5% to 85% of the samples from individual herds. Positive titers to A. pleuropneumoniae serotype 2 were found in 71% to 79% of the sampled animals from herds with high frequencies of pneumonic lesions indicative of pleuropneumonia. In herds with low frequencies of pleuropneumonia, positive titers were recorded in from 0 to 4% of the tested pigs. However, no statistical association was found between pleuropneumonia and positive titers to A. pleuropneumoniae serotype 2 in individual animals. Twenty-one per cent of samples with positive CF titers to A. pleuropneumoniae showed antibodies to more than one serotype.

The prevalence and pathomorphology of gross lung lesions were studied in 855 slaughter weight pigs from 9 selected herds in south-eastern Norway. Pneumonic or pleuritic lesions were found in 84% of the lungs, ranging from 37% in the least affected herd to 97% in the one most affected. Bronchopneumonia indicative of a primary Mycoplasma hyopneumoniae infection was found in 70% of the lungs, ranging from 9% to 82% in the individual herds. The amount of bronchopneumonic lesions in individual lungs ranged from 0 to 69%, with an average of 7.8%. Pleuropneumonia indicative of Actinobacillus (Haemophilus) pleuropneumoniae infection was found in 29% of the lungs ranging from 0 in the least affected herd to 58% in the most affected. Diffuse pleuritis was found in 41% of the lungs and the prevalence ranged from 4% to 63%.

Lungs from 191 slaughter pigs with gross lesions indicative of enzootic pneumonia of pigs (EPP) and 80 grossly normal lungs, all originating from 9 different herds, were subjected to microbiological and pathological examinations. The microbiological studies included both bacterial and mycoplasmal culture and also testing for Mycoplasma hyopneumoniae antigen in tissue by indirect immunofluorescent technique. M. hyopneumoniae, Pasteurella multocida and Mycoplasma hyorhinis were detected in 83%, 43% and 37% of the pneumonic lungs, respectively. Mycoplasma flocculare was the most frequently isolated organism in the non-pneumonic lungs. The greatest amounts of macroscopic pneumonia (25.2%) were recorded in lungs with all the three agents M. hyopneumoniae, P. multocida and M. hyorhinis present. The amounts of pneumonia in lungs with M. hyopneumoniae alone and in concurrence with P. multocida, were 9.3% and 15.6%, respectively. M. hyorhinis was also, in this study, associated with higher frequency of diffuse pleuritis. These findings indicate that M. hyorhinis might be involved in the pathogenesis of pneumonia in slaughter pigs. Ninety-six per cent of the isolates of P. multocida from pneumonic lungs could be characterized as type A. In the herds which had the most severe pneumonia problems, toxin production was detected in 83% of the P. multocida strains while only 28% were toxigenic in herds with subclinical to moderate pneumonia problems.