Showing papers in "Journal of Fish Diseases in 2000"
TL;DR: The results suggest that toxic/antigenic component(s) of SBM affect the differentiation of the distal intestinal epithelial cells and may help explain the reduced nutrient digestibilities previously reported in salmonids fed extracted SBM.
Abstract: Extracted soybean meal (SBM) in the diet for Atlantic salmon, Salmo salar L., causes an inflammatory response in the distal intestine. The morphological changes of the epithelial cells and a characterization of the inflammatory cell infiltrate of the distal intestinal mucosa were studied using a panel of enzyme and immunohistochemical markers. The salmon (average body weight 927 g) used in the study were fed either a fishmeal-based diet (control diet) or a diet in which 30% of the fishmeal protein was replaced with SBM protein (SBM diet). In salmon fed SBM, there were markedly reduced enzyme reactivities in the distal intestinal epithelial cells, both in the brush border [5′-nucleotidase (5′N), Mg2+-ATPase, alkaline phosphatase (ALP) and leucine aminopeptidase (LAP)] and in the intracellular structures [alkaline and acid phosphatase, non-specific esterase (NSE) and alanine aminopeptidase (AAP)]. There appeared to be an increased presence of cells of monocytic lineage, including macrophages, as well as neutrophilic granulocytes and immunoglobulin (Ig) M in the lamina propria of the SBM-fed fish. The mid intestine showed little response to the diet. The results suggest that toxic/antigenic component(s) of SBM affect the differentiation of the distal intestinal epithelial cells and may help explain the reduced nutrient digestibilities previously reported in salmonids fed extracted SBM.
220 citations
TL;DR: Vibrio harveyi VIB 645, which was the most pathogenic isolate, produced ECPs with a maximal effect on salmonids from preparations obtained by using cellophane overlays on tryptone soya agar supplemented with 1% sodium chloride with incubation at 28 °C for 24 h.
Abstract: Out of 19 Vibrio harveyi isolates obtained from a diversity of hosts and geographical locations, 14 were pathogenic to rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., with mortalities of up to 100% following intraperitoneal injections of 106 cells fish−1. The extracellular products (ECPs) of only five pathogenic isolates were harmful to fish. Both pathogenic and non-pathogenic cultures produced ECPs containing caseinase, gelatinase, phospholipase, lipase and haemolysins. Vibrio harveyi VIB 645, which was the most pathogenic isolate, produced ECPs with a maximal effect on salmonids from preparations obtained by using cellophane overlays on tryptone soya agar supplemented with 1% (w/v) sodium chloride with incubation at 28 °C for 24 h. This preparation contained the highest titre of haemolytic activity to Atlantic salmon (1:256) and rainbow trout (1:32) erythrocytes.
220 citations
185 citations
173 citations
TL;DR: The physiological response of salmon to the stress of sea lice infestation was examined to examine the level of host damage and correlations between the stress indicators, the number of copepods per fish and the life stage of the copepod were examined.
Abstract: The sea louse, Lepeophtheirus salmonis, is an ectoparasitic copepod of Atlantic salmon, Salmo salar L., capable of causing severe damage. This study was conducted to examine the physiological response of salmon to the stress of sea lice infestation. Smoltified salmon were acclimatized in 30‰ saltwater and exposed to high levels of lice infestation. The number of copepods per fish ranged from 15 to 285, with a mean of 106. The infested salmon were sampled six times over the 29-d experimental duration and examined for alterations in the primary and secondary stress indicators, including plasma concentrations of cortisol, glucose, electrolytes, thyroid hormones T3 and T4, as well as the haematocrit level. The results were examined for correlations between the stress indicators, the number of copepods per fish and the life stage of the copepods. The presence of L. salmonis elevated stress indicators in relation to the specific sea lice stage. By day 21, both cortisol (mean 63.1 nmol L−1 controls: 179.8 nmol L−1 for parasitized) and glucose (mean 3.545 mmol L−1 controls: 4.567 mmol L−1 for parasitized) levels were significantly increased due to the presence of the lice. This was believed to be a direct result of the sea lice development into the larger life stages, thus increasing the level of host damage.
159 citations
TL;DR: Serological investigations of F. psychrophilum showed that serotype Th was the dominant serotype found, and the serotypes Th and Fd were involved in disease outbreaks of fry and larger fish, and showed resistance to oxolinic acid and oxytetracycline.
Abstract: During a 2-year period, bacterial fish pathogens were monitored on five rainbow trout, Oncorhynchus mykiss (Walbaum), freshwater farms in Denmark. A total of 1206 fish were examined and 361 bacterial isolates were identified phenotypically. Enteric redmouth disease, furunculosis and rainbow trout fry syndrome/coldwater disease were recorded. Infections caused by Flavobacterium psychrophilum occurred most frequently, but only one outbreak of enteric redmouth disease caused by Yersinia ruckeri serotype O1 and one of furunculosis caused by Aeromonas salmonicida were recorded during the monitoring period. Flavobacterium psychrophilum was isolated on all farms, both during disease outbreaks and from fish without any signs of disease. Serological investigations of F. psychrophilum showed that serotype Th was the dominant serotype found. The serotypes Th and Fd were involved in disease outbreaks of fry and larger fish. All isolates of F. psychrophilum showed proteolytic activities; however, a few isolates, belonging to serotype FpT did not degrade elastin and were not associated with mortality. Increasing resistance problems to oxytetracycline were demonstrated. More than half of the F. psychrophilum isolates showed resistance to oxolinic acid and oxytetracycline. No antibiotic resistant isolates were found among Y. ruckeri and A. salmonicida.
148 citations
TL;DR: Copepodids settled on all of the external surfaces of the salmon, although the proportion on different surfaces varied between experiments; the gills, particularly at low temperatures, the body surface, and the pectoral and dorsal fins were especially favoured.
Abstract: The effects of temperature and salinity on the settlement, subsequent survival and development of the copepodids of Lepeophtheirus salmonis on Atlantic salmon were investigated experimentally. There was a significantly greater settlement and survival of copepodids at 10 days post-infection (dpi) at 12 °C compared with at 7 °C at a constant salinity of 34‰. Development of L. salmonis was also more rapid at 12 °C. Settlement was significantly greater at a salinity of 34‰ than at 24‰. In one experiment, survival at 10 dpi was significantly greater at 34‰; however, a second experiment found that there was no significant difference between the two saline levels. This may have been because of a rise in water temperature for 2 dpi, which appears to have overridden the effect of low salinity. Development of L. salmonis was more rapid at 34‰. Copepodids settled on all of the external surfaces of the salmon, although the proportion on different surfaces varied between experiments. The gills, particularly at low temperatures, the body surface, and the pectoral and dorsal fins were especially favoured.
114 citations
TL;DR: Ribotyping and plasmid profiling were carried out on Danish Flavobacterium psychrophilum isolates from farmed rainbow trout, Oncorhynchus mykiss, and a relationship between the serotypes Fd and Th, certain ribotypes, and virulence was found.
Abstract: Ribotyping and plasmid profiling were carried out on 299 Danish Flavobacterium psychrophilum isolates from farmed rainbow trout, Oncorhynchus mykiss (Walbaum). The isolates had been characterized biochemically and serologically in another study. The isolates were very homogeneous, 254 isolates had the same ribotype A (restriction enzyme EcoRI) and 284 isolates harboured one 3.3 kb plasmid. Seventy-five per cent of the F. psychrophilum isolates had ribotype A, one 3.3 kb plasmid and belonged to either serotype Th or Fd. Virulence studies with representatives of the dominant groups classified such isolates as virulent, and an extra small or large plasmid did not change the virulence level. A relationship between the serotypes Fd and Th, certain ribotypes, and virulence was found. The isolates belonging to serotype FpT and to ribotype B were less virulent. Only a few isolates with other ribotypes were found and these were also less virulent. Isolates that did not have the 3.3 kb plasmid were also less virulent. The virulent isolates all harboured the 3.3 kb plasmid; however, there was no clear correlation between virulence and plasmid content as a 3.3 kb plasmid was also found in less virulent isolates.
94 citations
TL;DR: The inclusion of nested PCR in the assay appears to be necessary to screen out NNV-positive broodfish by blood sampling and testing of their larval progeny, and to confirm the specificity of the first amplification.
Abstract: A polymerase chain reaction (PCR)-based assay to detect nervous necrosis virus (NNV) in fish was developed by using two sets of primers designed on a highly conserved region of the coat protein gene encoded by RNA2 of NNV. The first pair of primers amplified a fragment of 605 bp by one-step reverse-transcription (RT)-PCR, while the second pair amplified an internal segment of 255 bp by nested PCR. Addition of nested PCR increased the assay sensitivity 100-fold when carried out in a separate tube (two-step assay) and 10-fold when performed in the same tube (one-step assay). The sensitivity of the two-step assay was 104 times higher than that of virus cultivation. Nested PCR served also to confirm the specificity of the first amplification, as verified also by Southern hybridization analysis and direct sequencing. In species known to be susceptible to infection, such as European sea bass, Dicentrarchus labrax, and gilthead seabream, Sparus aurata, NNV was often detectable in brain tissue by RT-PCR alone but only by the two-step assay in blood, sperm, ovarian tissue or larvae. The same was true for sperm and ovarian tissue of shi drum, Umbrina cirrosa. NNV was also detected in the brains of Japanese red seabream, Pagrus major and brown meagre, Sciaena umbra, suggesting that these species can also be infected. No NNV was detected in samples of Artemia salina nauplii and rotifers obtained from a fish farm with an NNV outbreak. The inclusion of nested PCR in the assay appears to be necessary to screen out NNV-positive broodfish by blood sampling and testing of their larval progeny.
90 citations
TL;DR: Histophagous ciliates caused high mortality among turbot in a commercial fish farm in southern Norway and were predominantly found in the central nervous system, causing liquefaction of the nervous tissue.
Abstract: Histophagous ciliates caused high mortality among turbot in a commercial fish farm in southern Norway. The ciliates spread systemically in fry (< 0.3 g). In the early stages of infection the ciliates were found in connective tissue in skin and fins, as well as in nervous tissue. In terminal stages the whole organism was infected. In large turbot (500–1000 g), the ciliates were predominantly found in the central nervous system, causing liquefaction of the nervous tissue. The ciliates were not identified to species but resembled species in the genus Uronema (Scuticociliatida).
83 citations
TL;DR: Two iridovirus-susceptible cell lines were established and characterized from grouper Epinephelus awoara kidney and liver tissues and effectively replicated the virus, which could be purified to homogeneity by cesium chloride gradient centrifugation.
Abstract: Two iridovirus-susceptible cell lines were established and characterized from grouper Epinephelus awoara kidney and liver tissues. These cell lines have been designated GK and GL, respectively. The cells multiplied well in Leibovitz’s L-15 medium, supplemented with 10% foetal bovine serum, at temperatures between 20 and 32 °C, and have been subcultured more than 120 times, becoming continuous cell lines. The cell lines consist of a heterogeneous mixture of fibroblastic and epithelial cells. The viability of cells, stored frozen in liquid nitrogen (196 °C), was 95% after 1 year. Chromosome morphologies of GK and GL cells were homogeneous. Both cell lines were susceptible to grouper iridovirus, and yielded high titres of up to 10 8 TCID50 mL 1 . In addition, both cell lines effectively replicated the virus, which could be purified to homogeneity by cesium chloride gradient centrifugation. Electron microscopy studies showed that purified virus particles were 170910 nm in diameter, and were hexagonal in shape. Virus-infected cells showed an abundance of virus particles inside the cytoplasm. These results show that the GK and GL cell lines effectively replicate grouper iridovirus, and can be used as a tool for studying fish iridoviruses.
TL;DR: The duration of efficacy of emamectin benzoate in the oral treatment of sea lice, Lepeophtheirus salmonis, infesting Atlantic salmon, Salmo salar L., was evaluated in a tank study and survival of chalimus to adult stages was lower than on control fish.
Abstract: The duration of efficacy of emamectin benzoate in the oral treatment of sea lice, Lepeophtheirus salmonis, infesting Atlantic salmon, Salmo salar L., was evaluated in a tank study. One group of salmon was treated at a nominal dose of 50 μg kg−1 biomass day−1 for 7 consecutive days and a second group was untreated. Fish were then redistributed to 16 tanks, each holding 17 control and 17 treated fish. On days 34, 41, 48, 55, 62, 69, 76 and 83, two tanks were challenged with L. salmonis copepodites. Eight to 14 days after each challenge, fish were anaesthetized and numbers of lice recorded. Treatment with emamectin benzoate prevented development of copepodites for up to 62 days from the start of treatment, and chalimus numbers remained low for 69 days. Treated fish, challenged from days 34 to 69, had significantly (P<0.01) fewer lice than control fish. Treated fish challenged at days 76 and 83 still had fewer lice than control groups, although differences were not statistically significant for both replicates. When chalimus appeared on treated fish challenged at days 69–83, survival of chalimus to adult stages was lower than on control fish. Louse egg production on treated fish challenged at days 62–83 was not reduced compared to control groups.
TL;DR: Sea water-adapted Atlantic salmon, Salmo salar L., were given a 2-h bath in a 2.5 mg L -1 levamisole solution and subjected to a number of immunological assays, indicating that levam isole is effective in augmenting parts of the nonspecific defence system of Atlantic salmon.
Abstract: Sea water-adapted Atlantic salmon, Salmo salar L., were given a 2-h bath in a 2.5 mg L -1 levamisole (as levamisole hydrochloride) solution in fresh-water. Following bathing, the fish were held in full salinity sea water for 2 weeks before being subjected to a number of immunological assays. Heightened activity of the nonspecific defence system was demonstrated by increases in phagocytic index, phagocytic capacity and phagocytic activity, increased levels of the reactive oxygen intermediate, superoxide anion, and an increased lytic activity of both the mucus and the serum. These results indicate that levamisole is effective in augmenting parts of the nonspecific defence system of Atlantic salmon. This is the first record of the use and efficacy of levamisole as an immunomodulator in Atlantic salmon.
TL;DR: Histologically, Paramoeba sp.
Abstract: Atlantic salmon were exposed to amoebic gill disease (AGD) immediately following their acclimatization to sea water (group 1), or following a 2 week period of maintenance in sea water (group 2). Three fish from each group were sampled on days 0, 1, 2, 4, 7, 14 and 28 post-infection. Characteristic gill lesions began to occur between days 2 and 4, and dramatically increased by day 7. The number of gill lesions on fish from group 2 was significantly higher than on fish from group 1 on days 7 and 14 (P<0.001), but the two groups did not differ in any other parameter. Histologically, Paramoeba sp., the aetiological agent of AGD, could be seen on the gills of fish as soon as 1 day post-exposure, attached to healthy-appearing gills. Gill pathology in the form of hyperplasia and lamellar fusion followed shortly. AGD infection was accompanied by a significant increase in the number of gill mucous cells (P= 0.002). Different methods for the diagnosis of AGD are discussed.
TL;DR: Based on the growth characteristics, morphological and biochemical properties of the bacterium, and histopathological changes, the isolated bacteria were identified as Nocardiaseriolae, the first report of N. seriolae-infected sea bass in aquaculture.
Abstract: An epizootic in pond cultured sea bass, Lateolabrax japonicus, was caused by Nocardia sp. in Taiwan, in September and October 1997. The cumulative mortality within 1 month was 17.5% (3500 out of 20 000 fish) and diseased fish were 7 months old with total lengths from 25 to 30 cm. Multiple, yellowish white nodules, 0.1–0.2 cm in diameter, were scattered in the gill, heart, liver, spleen and kidney. Histopathologically, typical granulomatous lesions appeared in those organs. The morphology of isolated bacteria from brain heart infusion (BHI) medium or Lowenstein–Jensen medium (LJM) were bead-like filaments, as shown by Ziehl-Neelsen's (ZN) staining method. The gross lesion and histopathological changes found in experimentally infected fish were similar to those in naturally infected fish. Based on the growth characteristics, morphological and biochemical properties of the bacterium, and histopathological changes, the isolated bacteria were identified as Nocardiaseriolae. This is the first report of N. seriolae-infected sea bass in aquaculture.
TL;DR: Levamisole, a known T-cell stimulator and immunomodulator in mammals, has been demonstrated to enhance resistance to amoebic gill disease in Atlantic salmon, Salmo salar L.
Abstract: Levamisole, a known T-cell stimulator and immunomodulator in mammals, has been demonstrated to enhance resistance to amoebic gill disease in Atlantic salmon, Salmo salar L. When used in fresh water baths, dose rates of 1.25, 2.5 and 5 ppm levamisole stimulated resistance to reinfection with Paramoeba sp. that was evident from 2-3 weeks post-treatment. It is proposed that this response is related to enhancement of the non-specific immune system.
TL;DR: Univ Montpellier 2, IFREMER, CNRS, UMR 219, Montpelliers, France; Chinese Acad Sci, Wuhan Inst Virol,Wuhan, Hubei, Peoples R China
Abstract: Univ Montpellier 2, IFREMER, CNRS, UMR 219, Montpellier, France; Chinese Acad Sci, Wuhan Inst Virol, Wuhan, Hubei, Peoples R China; Chinese Acad Sci, Wuhan Inst Hydrobiol, Wuhan, Hubei, Peoples R China
TL;DR: Evidence is provided for the role of the neuroendocrine system of S. trutta in the modulation of inflammatory responses to C. truncatus and a peptidergic involvement and host immune response to an intestinal tapeworm.
Abstract: Pathological and immunohistochemical investigations were carried out on the middle intestine of uninfected and parasitized brown trout, Salmo trutta L., from the Ceresone Channel in North Italy. Eighty-six brown trout were sampled by electrofishing, and 32 (37.2%) were infected with Cyathocephalus truncatus Pallas, 1781 (Cestoda). The intensity of infection ranged from 1 to 82 parasites per host and the most infected segments were the anterior (near the pyloric caeca region) and the central part of the middle intestine. Immunohistochemical tests were applied on sections of intestinal tissue of healthy and infected fish, and the presence of substance P (SP), calcitonin gene related peptide (CGRP), met-enkephalin, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and serotonin (5-HT) was documented. Endocrine epithelial cells of the tunica mucosa were positive to SP-, CGRP-, met-enkephalin-, and NPY-like peptides and 5-HT antisera; moreover, a higher number of these cells were recorded in the intestine of infected trout in comparison to uninfected fish. In addition, in parasitized S. trutta, SP-like and 5-HT immunoreactivities were found in likely immuno-related cells of the tunica propria-submucosa. Nerve cell bodies and terminals in the myenteric plexus were immunoreactive to almost all the tested peptides and 5-HT antisera. These data provide evidence for the role of the neuroendocrine system of S. trutta in the modulation of inflammatory responses to C. truncatus. Results are discussed with respect to a peptidergic involvement and host immune response to an intestinal tapeworm.
TL;DR: The total procedure for the diagnosis of L. garvieae infections in fish, from the point of DNA extraction to observation in an agarose gel following electrophoresis, can be performed in less than 4 h.
Abstract: A dihydropteroate synthase gene from the chromosomal DNA of the fish-pathogenic bacteria Lactococcus garvieae (formerly Enterococcus seriolicida) was cloned. This gene was then chosen as the target for polymerase chain reaction (PCR). The designated PCR primer set only amplified a 709-bp DNA fragment from L. garvieae strains, and did not amplify the same molecular size fragment from related species of L. lactis, Enterococcus faecalis, E. faecium or β-haemolytic Streptococcus sp. The kidney tissue of yellowtail, Seriola quinqueradiata (Temminck and Schlegel), a species which is naturally infected with L. garvieae, and also kidney tissue samples of healthy yellowtail were stored in TNES-Urea. The DNA was extracted from tissue samples by a modification of the standard method and by a boiled-extraction method. In particular, template DNA was utilized within 30 min following extraction and purification by the boiled-extraction method. These species-specific PCR primers could amplify a L. garvieae target sequence from yellowtail which were naturally infected with L. garvieae. The total procedure for the diagnosis of L. garvieae infections in fish, from the point of DNA extraction to observation in an agarose gel following electrophoresis, can be performed in less than 4 h.
TL;DR: In vitro and in vivo activity was restored following the addition of 1 m m zinc chloride to the protease inhibitor-treated CEP, suggesting that this strain of F. psychrophilum secretes a protein complex with zinc metalloprotease-like activity that appears to be involved in the pathogenesis of necrotic myositis in rainbow trout.
Abstract: A crude extracellular preparation (CEP) from a strain of Flavobacteriumpsychrophilum recovered from a case of necrotic myositis affecting rainbow trout was capable of causing severe muscle necrosis in rainbow trout following intramuscular injection. Cell wall-associated preparations, however, were unable to produce similar lesions in experimentally injected fish. The CEP degraded gelatin and type II collagen but not type I or type IV collagen. Furthermore, the CEP did not degrade 2-furanacryloyl- l-leucylglycyl- l-prolyl-alanine (FALGPA), chondroitin sulphates A, B or C, heparan sulphate, keratan sulphate, hyaluronic acid, elastin or rainbow trout erythrocytes. The addition of the protease inhibitors 1,10-phenanthroline, ethylenediamine-tetraacetic acid (EDTA) and EGTA to the CEP halted its ability to degrade gelatin in vitro and to produce muscle necrosis in rainbow trout in vivo. In vitro and in vivo activity was restored following the addition of 1 m m zinc chloride to the protease inhibitor-treated CEP, suggesting that this strain of F. psychrophilum secretes a protein complex with zinc metalloprotease-like activity. This protein complex, therefore, appears to be involved in the pathogenesis of necrotic myositis in rainbow trout.
TL;DR: Anti-adhesin serum obtained from fish after booster immunization exhibited very strong ability in agglutinating bacterial cells, and showed that the major adhesin could provide significant protective immunity to fish against the challenge by homologous and heterologous strains of A. hydrophila and one virulent strain of Vibrio anguillarum.
Abstract: Blue gourami, Trichogaster trichopterus (Pallas), were intraperitoneally immunized with major adhesin, a 43 kDa OMP protein isolated from fish Aeromonas hydrophila, in the presence of Freund's complete adjuvant (FCA). Three weeks later, a booster injection of adhesin without FCA was administered. Control group fish were similarly treated with phosphate-buffered saline (PBS) and FCA. Results showed that anti-adhesin serum obtained from fish after booster immunization exhibited very strong ability in agglutinating bacterial cells. Although this antiserum had no bactericidal effect, it could significantly inhibit serologically different strains of A. hydrophila from invading EPC (Epithelioma papillosum of carp) cells in vitro. In addition, the proliferative response of head kidney leucocytes of these immune fish was significantly increased as compared to that of the control. The results also showed that the major adhesin could provide significant protective immunity to fish against the challenge by homologous and heterologous strains of A. hydrophila and one virulent strain of Vibrio anguillarum.
TL;DR: Chinese Acad Sci, S China Sea Inst Oceanol, Ctr Marine Dis Control, Guangzhou 510301, Peoples R China
Abstract: Chinese Acad Sci, S China Sea Inst Oceanol, Ctr Marine Dis Control, Guangzhou 510301, Peoples R China
TL;DR: The development of myxobolus dispar was first observed light microscopically 21 days after initial exposure by Thelohan, 1895, a myxosporean parasite of the gills of common carp (Cyprinus carpio L.) was studied in experimentally infected oligochaetes tubifex Muller.
Abstract: The development of Myxobolus dispar Thelohan, 1895, a myxosporean parasite of the gills of common carp (Cyprinus carpio L.) was studied in experimentally infected oligochaetes Tubifex tubifex Muller. After infection of uninfected tubificids with mature spores of M. dispar, development of actinosporean stages was first observed light microscopically 21 days after initial exposure. In histological sections, early pansporocysts were located in the gut epithelium of experimental oligochaetes, while advanced stages occupied mostly the outer layers of the gut and the coelozoic space. Mature pansporocysts, each containing 8 raabeia spores, appeared 199 days after initial exposure. Following damage of the intestinal wall and rupture of the pansporocysts, free actinosporean stages were found in the gut lumen of the oligochaetes. Actinospores of M. dispar emerged from the worms after 217 days of intra-oligochaete development. They were floating in the water and showed a unique raabeia form. Each raabeia spore had three pyriform polar capsules and a cylindrical-shaped sporoplasm with approximately 32 secondary cells. The spore body joined the three caudal projections without a style. Caudal projections were bifurcated at the end and the two main branches had further small bifurcations. The total length of the raabeia spore was approximately 158 µm. The prevalence of infection in 240 experimentally infected Tubifex specimens was 99.2%. No infection was found in the control oligochaetes.
TL;DR: The results of the immunostaining and the PCR demonstrate that T. bryosalmonae occurs in the tubules of grayling Thymallus thymalus L., brown trout, Salmo trutta L. and Atlantic salmon, SalMo salar L. outside of the PKD season (June-September) in the UK.
Abstract: Tetracapsula bryosalmonae, previously referred to as PKX, causes proliferative kidney disease (PKD) in salmonids and is an economically important myxozoan pathogen in salmonid culture. A variety of molecular and immunological tools have been developed to detect the parasite. To determine the specificity of four monoclonal antibodies (MAbs) raised against T. bryosalmonae, archive material of fish infected with various myxosporean species was obtained and immunostained. Wild fish were also collected from enzootic waters and examined for T. bryosalmonae infection using immunohistochemistry and the polymerase chain reaction (PCR). Three of the MAb probes appear to be specific for T. bryosalmonae while only two of the five sets of primers tested appeared to specifically amplify T. bryosalmonae DNA. The results of the immunostaining and the PCR demonstrate that T. bryosalmonae occurs in the tubules of grayling Thymallus thymallus L., brown trout, Salmo trutta L. and Atlantic salmon, Salmo salar L. outside of the PKD season (June-September) in the UK. This confirms the results of previous studies that these species are the preferred fish hosts for the parasite in the UK.
TL;DR: A post-capture, abdominal muscle necrosis of rapid onset has been identified in Norway lobsters, Nephrops norvegicus, captured off the West coast of Scotland, and damage to the integument in conjunction with exposure to various stressors during and immediately after capture is the most likely cause.
Abstract: A post-capture, abdominal muscle necrosis of rapid onset has been identified in Norway lobsters, Nephrops norvegicus (L.), captured off the West coast of Scotland. Economic losses, as a result of the mortality of these animals in transport, were encountered by Scottish wholesalers during the summer and autumn of 1999. Affected animals show a characteristic whitening of individual muscle fibres and fibre bundles of the abdomen within hours of capture, with a progression towards complete opacity of the abdominal musculature within a number of days. The pathology causes a loss of the normal function of the abdomen; thus, preventing the normal ‘tail flip’ swimming. Electron microscopy failed to reveal any obvious causative agent but showed that affected tissue displayed a progressive disruption of sarcomere organization, loss of Z-line material, condensation of myofibrils and infiltration of necrotic regions by granulocytes. SDS‐PAGE of affected muscle tissue showed that there was a great reduction of most of the major contractile proteins. The condition most closely resembles idiopathic or spontaneous muscle necrosis, a pathology previously reported from both wild and cultured crustaceans. Damage to the integument in conjunction with exposure to various stressors during and immediately after capture is the most likely cause of the pathology. The rapid onset of the pathology has implications for the post-capture handling procedure for N. norvegicus and their subsequent vivier transport to market. It may also be partially responsible for the high mortality rate of undersized N. norvegicus returned to the sea after capture and aerial emersion.
TL;DR: The normal life cycle of L. salmonae may depend on the completion of relatively lengthy, but yet unknown, stages of development within the heart, prior to reaching the gill, and this development may be adversely affected by temperature, and explain the temperature limits of this parasite.
Abstract: Temperatures above 20 °C or below 9 °C interrupt the life cycle of the gill intracellular microsporidian parasite Loma salmonae (Microspora) prior to sporogony, inhibiting the production of xenomas. This study intended to characterize this life-cycle failure. Juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), were experimentally infected with L. salmonae spores, and the effect of water temperature on the progress of infection, as determined by polymerase chain reaction, was compared for fish held at water temperatures of 5, 15 and 21 °C. At 15 °C, parasite DNA was first detected in the heart (3 days post-exposure [PE]), and then in the gills and spleen (2 weeks PE). Branchial xenomas developed by week 4 PE. In contrast, at 5 °C, the arrival of the parasite in the heart was delayed until 7 days PE. However, even though parasite DNA was detected in the gills at 7 days PE, xenomas failed to form in the gill, and by week 4 PE, parasite DNA was no longer detected. In fish held at 21 °C, parasite DNA was detected in the heart, gills and spleen by 3 days post-infection, and similar results were observed at 7 days PE. Xenomas also failed to form in these fish and parasite DNA was no longer detected by week 2 PE. Within the range of temperatures tested in this study, spore germination and delivery of their DNA into the host through the intestinal wall was not blocked by temperature. At 5 or 21 °C, migration to the heart and gills occurred, but at aberrant periods of time. The normal life cycle of L. salmonae may depend on the completion of relatively lengthy, but yet unknown, stages of development within the heart, prior to reaching the gill. This development may be adversely affected by temperature, and explain the temperature limits of this parasite.
TL;DR: Transmission electron microscopy was used to study the ornamentation of secondary cysts of 52 long-spined Saprolegnia isolates, with and without oogonia, obtained from wild brown trout, Salmo trutta L., and water samples from various rivers in Leon (NW Spain).
Abstract: Transmission electron microscopy was used to study the ornamentation of secondary cysts of 52 long-spined Saprolegnia isolates, with and without oogonia, obtained from wild brown trout, Salmo trutta L., and water samples from various rivers in Leon (NW Spain). All the isolates had secondary cysts with long hooked hairs grouped in bundles, although significant individual differences were observed. There was a direct relationship between the number of bundles per cyst, the number of hairs per bundle and hair length. The isolates were classified into two morphological groups. The isolates with a higher number of bundles per cyst and bundles with a greater number and length of hairs, were included in cyst morphological Group I. The isolates with a smaller number and shorter length of these bundles and hairs were included in cyst morphological Group II. There was a relationship between the type of ornamentation of the secondary cysts and the origin of the isolates. The isolates from salmonids with saprolegniosis belonged to Group II, whereas most isolates from mucus and water belonged to Group I.