Showing papers in "Journal of Fish Diseases in 1999"
TL;DR: A standardized tool for the assessment of histological findings which can be applied to different organs, and methods for the gills, liver, kidney and skin are described.
Abstract: Water pollution induces pathological changes in fish. As an indicator of exposure to contaminants, histology represents a useful tool to assess the degree of pollution, particularly for sub-lethal and chronic effects. However, a standardized method for the description and assessment of histological changes, mainly for use in freshwater fish, is still lacking. In this paper, the present authors propose a standardized tool for the assessment of histological findings which can be applied to different organs. The methodology is based on two factors: (1) the extension of a pathological change is rated with a ‘score value’; and (2) the pathological importance of this alteration is defined as an ‘importance factor’. The sum of the multiplied score values and importance factors of all diagnosed changes results in different indices. With these indices, statistical analysis can be carried out. Assessment methods for the gills, liver, kidney and skin are described.
1,042 citations
TL;DR: The experimental results indicated that GF-1 can effectively proliferate fish nodavirus and is a promising tool for studying fish nodvirus.
Abstract: A new continuous cell line (GF-1) was established and characterized. The GF-1 cell line, derived from the fin tissue of a grouper, Epinephelus coioides (Hamilton), was maintained in L15 medium containing 5% foetal bovine serum (FBS) at 28 ∞C, and has been subcultured more than 160 times since 1995. The majority of GF-1 cells are fibroblast-like, together with some epithelioid cells. Spontaneous transformation of GF-1 cells occurred during subculture 50 to subculture 80, and led to an increase of plating efficiency, less requirement of FBS and de novo susceptibility to grouper nervous necrosis virus (GNNV). Cytopathic effects (CPEs) could be observed in GF-1 cells 3‐5 days postinfection with pancreatic necrosis virus (IPNV), hard clam reovirus (HCRV), eel herpes virus Formosa (EHVF) and GNNV. In addition, abundant GNNV particles were found in the cytoplasm of GNNV-infected GF-1 cells using electron microscopy and nucleic acids of GNNV virus were detected by polymerase chain reaction in the culture medium of GNNV-infected cells after CPE appeared. The experimental results indicated that GF-1 can effectively proliferate fish nodavirus and is a promising tool for studying fish nodavirus.
170 citations
TL;DR: Black spot syndrome virus derived from infected shrimp, Penaeus monodon, is suggested to act as asymptomatic carriers/reservoir hosts of crabs, prawns and lobsters through histological and bioassay evidences, the first report to suggest the carrier/ Reservoir capacity of these hosts through Histological and Bioassay evidence.
Abstract: Experimental studies were conducted by injecting or feeding white spot syndrome virus (WSSV) derived from infected shrimp, Penaeus monodon (Fabricius), collected from the south-east coast of India, to five species of shrimp, two species of freshwater prawns, four species of crabs and three species of lobsters. All species examined were susceptible to the virus. Experimental infections in the shrimp had the same clinical symptoms and histopathological characteristics as in naturally infected P. monodon. A cumulative mortality of 100% was observed within 5–7 days in shrimp injected with WSSV and 7–9 days in shrimp fed with infected tissue. Two species of mud crab, Scylla sp., survived the infection for 30 days without any clinical symptoms. All three species of lobsters, Panulirus sp., and the freshwater prawn, Macrobrachium rosenbergii (De Man), survived the infection for 70 days without clinical symptoms. However, bioassay and histology using healthy P. monodon revealed that crabs, prawns and lobsters may act as asymptomatic carriers/reservoir hosts of WSSV. This is the first report to suggest the carrier/reservoir capacity of these hosts through histological and bioassay evidences. Ultrastructural details of the virus in experimentally infected shrimp, P. vannamei, (Boone), were also studied.
156 citations
TL;DR: The ability of Flavobacterium columnare (Flexibacter columnaris) to attach to the gills of common carp, Cyprinus carpio L., was evaluated using a gill perfusion model and it was observed that adhesion of the high virulence strain was enhanced by a number of factors.
Abstract: The ability of Flavobacterium columnare (Flexibacter columnaris) to attach to the gills of common carp, Cyprinus carpio L., was evaluated using a gill perfusion model. A comparison between a high and a low virulence strain of F. columnare was made and evaluated in comparison to results obtained previously with an in vivo model. The ion composition of the water of the organ bath in which the gills were suspended was varied and the influence on adhesion processes assessed. Experiments were carried out to examine the influence of water quality (i.e. nitrite and organic matter) and temperature on the capacity of the bacteria to adhere. It was found that the high virulence strain adhered more readily than the low virulence strain, as was found during the in vivo experiments. Moreover, it was observed that adhesion of the high virulence strain was enhanced by a number of factors. These were immersion of the gill in bivalent, ion-rich water, the presence of nitrite or organic matter, and high temperatures.
146 citations
TL;DR: The relationship between diagnosis on the basis of gross signs and histological diagnosis was significant, however, the gross diagnosis was unreliable within the lower range, with 31.8% false negatives and 15.9% false positives and kappa value of 0.2742.
Abstract: Amoebic gill disease (AGD) is the most serious health problem in Atlantic salmon cultured in Tasmania. Our field investigation examined prevalence of AGD during 2 years, every year for up to 7 months after transfer to sea water. The relationship between environmental factors and AGD prevalence was determined. Additionally, effects of adding levamisole to freshwater baths were investigated in a field trial. AGD was recorded on all farms, except for farm A, which did not move salmon from a brackish site to a full-salinity site during the study. The prevalence showed a bimodal distribution with the first larger peak in summer (usually in January) and the second smaller peak in autumn (between March and May). During both years the prevalence of AGD was significantly greater in January than any other month. Sampling month and the interaction between farm and month had a statistically significant effect on AGD prevalence. AGD was recorded at a minimum temperature of 10.6 °C and minimum salinity of 7.2 ppt. There was a positive relationship between the time since the freshwater bath and the prevalence of AGD for the first 30 days after the bath, with a dramatic increase in the AGD prevalence about 3 weeks after the bath. After 30 days, there was no statistically significant relationship between AGD prevalence and days since the last bath, except for the second bath. The addition of levamisole to the freshwater bath did not significantly increase the time between treatments. The relationship between diagnosis on the basis of gross signs and histological diagnosis was significant, however, the gross diagnosis was unreliable within the lower range, with 31.8% false negatives and 15.9% false positives and kappa value of 0.2742.
130 citations
TL;DR: Results indicate that a lectin-like carbohydrate-binding substance incorporated in the capsule is responsible for the attachment of F. columnare to the gill tissue.
Abstract: Flavobacterium columnare (Flexibacter columnaris) is an important cause of gill and skin disease in freshwater fish species, often causing high mortality. In previous studies, virulence of F. columnare was correlated with the ability to adhere to the gill tissue. To gain insight into the factors responsible for adherence, a gill perfusion model was used. The bacterial cells of the high virulence strain AJS 1 were exposed to various treatments, after which they were added to the organ bath of an isolated gill arch and adherence to the gill tissue assessed. Adherence capabilities were significantly reduced following treatment of the bacteria with sodium metaperiodate or incubating them with d-glucose, N-acetyl-d-glucosamine, d-galactose and d-sucrose. Incubation of the bacteria with trypsin and pronase did not significantly inhibit adherence. The binding sites for F. columnare on the gill tissue were also partially characterised. Treatment of the gill with sodium metaperiodate reduced adhesion, but treatment with pronase or trypsin did not cause any significant reduction, indicating that the major component of the receptor is of carbohydrate nature. Adherence ability of the bacteria correlated well with their haemagglutination capacity using chicken and guinea pig erythrocytes. Higher haemagglutination titres were obtained with the highly virulent strain AJS 1 than with strain AJS 4, a strain with low virulence and adherence capacity. Haemagglutination was partially inhibited after incubation of the bacteria with d-glucose and N-acetyl-d-glucosamine and after treatment of the bacteria at 41_°C for 10_min (minor heat treatment). It was completely abolished following incubation of the bacterial cells with sodium metaperiodate and intensive heat treatment (65_°C, 25_min). Haemagglutination was also in-sensitive to pronase and trypsin treatment. Transmission electron microscopy (TEM) revealed that the high virulence strain had a thick capsule (120–130_nm) with a regular, dense appearance, whereas the capsule of the low virulence strain was much thinner (80–90_nm) and less dense. TEM also demonstrated the loss of the capsule of the high virulence strain after treatment of the bacterial cells with minor heat and sodium metaperiodate. These results indicate that a lectin-like carbohydrate-binding substance incorporated in the capsule is responsible for the attachment of F. columnare to the gill tissue.
113 citations
TL;DR: Western blotting demonstrated that all the ECP preparations contained low molecular weight lipopolysaccharides, which may constitute the lethal toxin of V. harveyi.
Abstract: Vibrio harveyi recovered from diseased post-larval Penaeus vannamei produced a thermostable exotoxin, which was lethal to Dublin Bay prawns, Nephrops norvegicus L., when injected intramuscularly. The extracellular products (ECPs) concentrated from tryptone soya broth supplemented with 1% (w/v) sodium chloride or from cellophane overlays on marine 2216E agar with incubation at 15, 22 and 27 °C were toxic, with the lethal dose 50% of the crude ECPs estimated to be 4.4 μgprotein prawn−1. Proteolytic, haemolytic and cytotoxic activities were detected, although the occurrence and quantity of these activities were influenced by cultural conditions. The ECPs which had been heated (100 °C for 10 min) or digested with protease K produced the same pathology as crude, untreated ECPs. Western blotting demonstrated that all the ECP preparations contained low molecular weight lipopolysaccharides, which may constitute the lethal toxin of V. harveyi.
69 citations
TL;DR: The first description of pasteurellosis affecting sole, Solea senegalensis (Kaup), cultured in the South-west of Spain is reported and the sensitivity pattern to antimicrobials and the enzymatic activities of the bacterial extracellular products are described.
Abstract: The first description of pasteurellosis affecting sole, Solea senegalensis (Kaup), cultured in the South-west of Spain is reported. Diseased fish showed no apparent lesions except for a dark skin pigmentation and swelling in the abdominal cavity. Internally, affected specimens showed paleness of liver and kidney and typical white tubercles of 1‐2 mm in diameter in the spleen. Microbiological analysis of these fish revealed the presence, in pure culture from all the organs examined, of one type of bacterial colony which was biochemically and serologically characterized as Photobacterium damsela ssp. piscicida. The sensitivity pattern to antimicrobials and the enzymatic activities of the bacterial extracellular products are described.
68 citations
TL;DR: Diagnosis by reverse-transcriptase polymerase chain reaction (RT-PCR) amplification using previously published primers specific for the capsid protein gene of fish nodaviruses detected an isolate of sea bass from the French Mediterranean coast, but did not detect an isolate from the Atlantic coast.
Abstract: Diagnosis by reverse-transcriptase polymerase chain reaction (RT-PCR) amplification using previously published primers specific for the capsid protein gene of fish nodaviruses detected an isolate of sea bass, Dicentrarchus labrax L., nervous necrosis (SBNNV) from the French Mediterranean coast, but did not detect an isolate from the Atlantic coast. The capsid protein coding sequence of the nodavirus of both isolates was cloned. Sequence analysis revealed that the Mediterranean isolate was identical to the sequence previously published for SBNNV, while the Atlantic isolate is related, but carried numerous substitutions, in particular in the region used for RT-PCR diagnosis. A new primer set was tested which detected the viral genome of the Atlantic isolate. Using the new primer set, PCR amplification of a range of 10-fold dilutions of a plasmid containing the capsid protein gene of the Atlantic isolate showed that the limit of detection of the assay was between 10 and 100 copies of plasmid.
62 citations
TL;DR: The culture and market potential of the marinespecies Puntazzo puntazzo Cuvier is considered to be very promising in the Mediterranean area, but high mortality rates have recently been experienced in on-growing facilities, with devastating financial consequences.
Abstract: The culture and market potential of the marinespecies Puntazzo puntazzo Cuvier is considered tobe very promising in the Mediterranean area(Caggiano, Canese, Lupo & Cirillo 1993; Gatland1995; Georgiou & Stephanou 1995). However,despite the successful rearing of the early life stagesof this fish species, high mortality rates (up to 80%)have recently been experienced in on-growingfacilities, with devastating financial consequences.There is little published information regarding thepathology and nutritional requirements of this fish,either in the wild or in intensive culture systems(Ceccarelli, Fresi, Plastina & Scardi 1984; Ken-touri, Divanach & Paris 1984; Le Breton M Drury & Wall-ington 1980; Roberts 1989). Ten per cent of thefish were processed histologically, regardless of thenecropsy findings, as well as all fish with macro-scopic lesions.Samples were taken from the kidneys, spleen,liver and brain, and inoculated in different culturemedia (tryptose soy agar, TCBS, brain heartinfusion agar, McConkey, Ryan and blood agar).The identification of bacterial isolates was based onmorphological (Gram staining) and biochemicalcharacteristics (API 20E, 20NE, API Staph); insome cases, classical biochemical methods were alsoused (Ortigosa, Esteve & Pujalte 1989; Mercedes BBiosca, Esteve, Garay & Amaro 1993; Mercedes B Bakopoulos, Adams & Richards1995; Boira 1996).The pathological conditions found in thecultured fish and their overall prevalence in theeight farms studied are shown in Table 1. The mainconditions causing problems in fish in the earlystages of rearing (< 3 g) were caused by Photo-bacterium var. piscicida, Vibrio alginolyticus andAeromonas hydrophila. These bacteria were alwaysisolated from diseased fish as the sole infectiveagent.
62 citations
TL;DR: The present study demonstrates the importance of this myxosporean disease which represents a serious threat for turbot culture, and also the first record of a member of the Myxosporea in turbot.
Abstract: The present report describes an intestinal disease which causes important losses in farmed turbot. Mortality rates were higher in summer and reached 100% in all tanks where the disease was confirmed. Affected fish showed external signs consisting of anorexia, sunken eyes and a typical prominent bony ridge on the skull. These signs can be considered the pathognomonic signs of the disease, together with the gut lesions seen in the histological study. Pallor of the internal organs, intestinal haemorrhages and the presence of liquid in the intestine were also observed, with ascites in heavily infected fish. Histopathological damage was evident in the gut, with severe enteritis, detachment of epithelium, haemorrhages and inflammation of the subepithelial connective tissue. The myxosporean aetiology was demonstrated in all the fish showing the characteristic signs of disease. Myxosporean stages, including scarce spores, were found in the affected epithelium or free in the intestinal lumen together with epithelial debris. The present study demonstrates the importance of this myxosporean disease which represents a serious threat for turbot culture. This is also the first record of a member of the Myxosporea in turbot.
TL;DR: Preliminary results suggest the possibility of detecting virus-positive or virus-negative animals in attempts to reduce and prevent the vertical transmission of the virus in sea bass hatcheries.
Abstract: The use of an indirect elisa for the detection of the sea bass, Dicentrarchus labrax (L.), antibody to nodavirus is described. The sera of 110 adult sea bass (78 females and 32 males) maintained in captivity were analysed, and the females were individually classified in seropositive (16%) and seronegative (56%) groups, while some fish (28%) with low but detectable antibody levels were not classified. The proportion of seropositive males was smaller (3.1%) than the females. Repeated serological examination of 18 individually labelled females (spawners) revealed no changes over 5 months. The immunization of sea bass females with heat-killed nodavirus induced antibody titre as reflected by corresponding changes in elisa optical density readings. The antibody level increased 4 weeks post-immunization and was still detectable after 41 weeks. These preliminary results suggest the possibility of detecting virus-positive or virus-negative animals in attempts to reduce and prevent the vertical transmission of the virus in sea bass hatcheries.
TL;DR: In this paper, the authors examined the biochemical profiles and genetic relatedness of these isolates by random amplified polymorphic DNA (RAPD) analysis and repetitive primer polymerase chain reaction(REP PCR) to determine whether S. iniae isolates from humans and fish are similar.
Abstract: Streptococcus iniae is an important bacterial pathogen of fish, causing up to 50% mortality in stocks, which has recently been associated with human infections. To determine whether S. iniae isolates from humans and fish are similar, the present authors examined the biochemical profiles and genetic relatedness of these isolates by random amplified polymorphic DNA (RAPD) analysis and repetitive primer polymerase chain reaction(REP PCR). The biochemical profiles differentiated between the human and fish isolates of S. iniae using pyrrolidonyl arylamidase, arginine dehydrogenase, ribose, β-glucoronidase and glycogen as markers. These biochemical results suggest that the fish and human S. iniae isolates are genetically different. However, RAPD and REP PCR do not have the discriminatory power to differentiate between these streptococcus isolates using five different RAPD primers and BoxA primer.
TL;DR: A herpesviral gill disease accompanied by mass mortality occurred in Japanese eels, Anguilla japonica, reared in warm water ponds from 1993 to 1995, and was identified as Herpesvirus anguillae by a neutralization test.
Abstract: A herpesviral gill disease accompanied by mass mortality occurred in Japanese eels, Anguilla japonica (Temminck & Schlegel), reared in warm water ponds from 1993 to 1995. Diseased fish displayed marked haemorrhage and congestion within gill filaments and destruction at the tips of affected filaments with necrosis and inflammation in the central connective tissue and the central sinus. Electron microscopy revealed herpesvirus particles in infected fibrocytes within the filamental connective tissue. The isolate was identified as Herpesvirus anguillae by a neutralization test. Infectivity experiments with the isolates revealed that the virus was pathogenic.
TL;DR: Clinical and biochemical similarities between infections of Y. ruckeri and many warmwater pathogens in affected catfish may lead to incorrect diagnosis of ERM infections.
Abstract: In the winters of 1995 and 1996, unusual disease outbreaks occurred on two separate channel catfish farms in Arkansas, USA. Affected fish exhibited extraordinary haemorrhaged rings around the eyes and raised haemorrhaged areas overlying the frontal foramens. Other signs included abnormal swimming, lethargy, loss of equilibrium, and exophthalmia. Bacterial isolates from the moribund fish were identified as Yersinia ruckeri by biochemical tests, no lysis by the Hafnia-specific bacteriophage 1672, and Y. ruckeri-specific growth patterns on Shotts-Waltman media. Fingerling catfish injected intraperitoneally with the bacterial isolate at 7.8 × 106 bacteria fish−1 developed lesions characteristic of the epizootics at 13, 18, and 22 °C and a biochemically identical isolate was recovered. Fingerling rainbow trout injected with the channel catfish isolate at 1 × 105 bacteria fish−1 and held at 20 °C developed signs typical of enteric redmouth by 4 days post-inoculation and were moribund by 5 days post-inoculation. Some differences of clinical signs occurred between experimentally infected rainbow trout and channel catfish. Clinical and biochemical similarities between infections of Y. ruckeri and many warmwater pathogens in affected catfish may lead to incorrect diagnosis of ERM infections.
TL;DR: There was a significant positive correlation between the levels of radioactivity in the gills and blood, and between the mucus and skin at 2 h post-challenge, and the kidney of fish from all groups contained viable bacteria, whereas the blood was negative.
Abstract: Three groups of Atlantic salmon, Salmo salar L., were exposed to live, colony-forming, radiolabelled Aeromonas salmonicida bacteria in a bath challenge: (1) fish with artificial wounds; (2) fish with a reduced epidermal mucus layer caused by removal of the mucus layer on two occasions by a swabbing procedure; and (3) a control group of untreated fish. Fish were killed 2, 6 and 24 h after challenge, and radioactivity (cpm g–1) was measured in the blood, mucus, skin, wound area, gills, anterior kidney, posterior kidney, spleen, midgut and hindgut. The highest levels of radioactivity were measured in the wound areas and in the gills. There was a significant positive correlation between the levels of radioactivity in the gills and blood, and between the mucus and skin at 2 h post-challenge. Two hours after the bath challenge, live A. salmonicida bacteria were found in the blood of fish in the ‘swabbed’ and ‘artificial wound’ groups, and not in the control group. Twenty-four hours after the bath challenge, the kidney of fish from all groups contained viable bacteria, whereas the blood was negative.
TL;DR: The extrapiscine development of Sphaerospora renicola, a myxosporean parasite of the kidney of common carp, Cyprinus carpio L., was studied in the experimentally infected oligochaetes Tubifex tubifex and Branchiura sowerbyi.
Abstract: The extrapiscine development of Sphaerospora renicola, a myxosporean parasite of the kidney of common carp, Cyprinus carpio L., was studied in the experimentally infected oligochaetes Tubifex tubifex (Muller) and Branchiura sowerbyi (Beddard). After the infection of these tubificids with homo- genized common carp kidneys containing myxos- pores of S. renicola, the development of actinosporean stages was first observed under light microscopy 8 days after infection in pathogen-free T. tubifex. Infection of B. sowerbyi with mature actinosporean stages was first observed 91 days after infection. At that stage of development, panspor- ocysts containing neoactinospores filled the intest- inal epithelium of the worm. Ninety-five days after infection, pansporocysts containing actinospores and free actinospores were found in the gut lumen of B. sowerbyi. Actinospores of S. renicola emerged from B. sowerbyi after 98 days of intraoligochaete development. These were floating in the water and showed the typical form of neoactinospores. The shape of the spores was triangular in apical view and elliptical in lateral view. The prevalence of infection reached 37%. Control specimens of B. sowerbyi proved to be free of neoactinospores. Except for a single specimen of B. sowerbyi, the only early developmental stages (pansporocysts) were found in T. tubifex.
TL;DR: The pharmacokinetic properties of the antibacterial agent oxolinic acid were studied after intravenous, intraperitoneal and oral administration to 1.5–3.0 kg Atlantic halibut and vetoquinol, the carbitol ester of oxolinIC acid, increased the bioavailability of oxoliniic acid to 64% and the total bioavailability to 82%, whereas Cmax and Tmax values were obtained.
Abstract: The pharmacokinetic properties of the antibacterial agent oxolinic acid were studied after intravenous, intraperitoneal and oral administration to 1.5–3.0 kg Atlantic halibut, Hippoglossus hippoglossus L., held in sea water at 9 °C. Following intravenous injection, the plasma drug concentration-time profile showed two distinct phases. The terminal elimination half-life was estimated to be 52 h, whereas total body clearance (ClT) was determined to be 0.044 L kg–1 h–1. The volume of distribution at steady state, Vd(ss), was calculated to be 3.0 L kg–1, indicating good tissue penetration of oxolinic acid in Atlantic halibut. The peak plasma concentration (Cmax) and the time to peak plasma concentration (Tmax) were estimated to be 1.2 and 2.7 μg mL–1, and 21.5 and 80 h, respectively, following oral administration of medicated feed or intraperitoneal injection. The corresponding bioavailabilities were calculated to be 15% and 92%, respectively. Oral administration of vetoquinol, the carbitol ester of oxolinic acid, increased the bioavailability of oxolinic acid to 64% and the total bioavailability (oxolinic acid + vetoquinol) to 82%, whereas Cmax and Tmax values of 6.7 μg mL–1 and 14.5 h, respectively, for oxolinic acid, and 1.0 μg mL–1 and 6.3 h, respectively, for vetoquinol were obtained. Based on a minimum inhibitory concentration (MIC) of 0.0625 μg mL–1 for susceptible strains, a single intraperitoneal injection of 25 mg kg–1 of oxolinic acid maintains plasma levels in excess of 0.25 μg mL–1, corresponding to four times the MIC value, for ≈12 days. The corresponding values for a single oral dose of 25 mg kg–1 of oxolinic acid and vetoquinol were 5 and 10 days, respectively. For resistant strains with a MIC of 1 μg mL–1, a single oral dose of vetoquinol (25 mg kg–1) maintained plasma levels in excess of 4 μg mL–1 for 34 h.
TL;DR: The method identifies CCV DNA in several tissues of acutely infected fish, including the brain, blood, intestine, kidney and liver, which is useful for the diagnosis of acute CCV disease and for studies to investigate the molecular basis of CCV pathogenesis.
Abstract: Channel catfish virus (CCV) causes an acute haemorrhagic disease in channel catfish, Ictalurus punctatus (Rafinesque), fry and fingerlings. The present study describes a polymerase chain reaction (PCR)-based assay for detection of CCV DNA in the tissues of acutely infected juvenile catfish. The assay is rapid, sensitive and specifically detects CCV DNA derived from epidemiologically distinct viral isolates. The use of two independent PCR primers sets, each specific for particular CCV genes (open reading frames 8 and 59), provides a means to confirm the results and minimize false-positive results. The method identifies CCV DNA in several tissues of acutely infected fish, including the brain, blood, intestine, kidney and liver. The CCV PCR assay is useful for the diagnosis of acute CCV disease and for studies to investigate the molecular basis of CCV pathogenesis.
TL;DR: It is suggested that V. anguillarum O2 may have an invasion strategy which does not involve adhesion to mucus, and thus, differs from the other pathogenic bacteria in the present study, which all bound to salmon mucus.
Abstract: Pathogenic and presumed non-pathogenic bacteria isolated from fish were tested for their adhesion to cryosections from different mucosal surfaces of Atlantic salmon, Salmo salar L Adhered bacteria were detected by immunohistochemistry Mucus was stained and fixed with Alcian blue after incubation of bacteria The majority of the bacteria tested, ie Vibrio anguillarum serotype O1, Vibrio salmonicida, Vibrio viscosus, Flexibacter maritimus and ‘gut vibrios’, ie Vibrio iliopiscarius and intestinal isolates of V salmonicida, all adhered to mucus on all salmon epithelial surfaces tested, including sections from the foregut, hindgut, pyloric caeca, gills and skin In contrast, V anguillarum serotype O2, including both serotypes O2a and O2b, did not adhere to mucus, but did adhere to all other components of the tissues As a positive control for adhesion of bacteria on cryosections, Escherichia coli was bound to piglet ileal mucosal lining, and as a negative control for adhesion, Staphylococcus aureus was found not to bind to any of the tissues tested The present study shows that adhesion to mucus was not restricted to pathogenic bacteria, and furthermore, that not all pathogenic bacteria studied adhered to mucus Hence, on the basis of these findings, the present authors suggest that V anguillarum O2 may have an invasion strategy which does not involve adhesion to mucus, and thus, differs from the other pathogenic bacteria in the present study, which all bound to salmon mucus
TL;DR: The high RPS under a severe challenge burden, along with disease signs in experimental freshwater challenges which resembled the saltwater disease condition, indicated that V. viscosus is a contributing factor to winter ulcer and that vaccination will protect against the disease.
Abstract: Coldwater Vibrio species isolated from Atlantic salmon, Salmo salar L., during winter ulcer disease outbreaks at saltwater sites in Norway and Iceland were characterized phenotypically, tested for virulence, and used to evaluate the efficacy of multivalent, oil-adjuvanted vaccines. The intraperitoneal (i.p.) injection of rainbow trout, Oncorhynchus mykiss (Walbaum), in fresh water with one bacteria species isolated during winter ulcer outbreaks, V. ‘viscosus’, produced rapid mortality and disease signs which resembled those observed during natural outbreaks [105 colony-forming units (cfu) fish−−1]. Another species, V. ‘wodanis’, was not virulent to rainbow trout (103–106 cfu fish−−1). Although vaccination of rainbow trout with a mineral-oil-adjuvanted, injectable vaccine containing V. anguillarum (serotypes 01 and 02), V. salmonicida and Aeromonas salmonicida did not provide protection against injection challenge with V. viscosus, vaccines which included V. viscosus produced significant protection in Atlantic salmon and rainbow trout. Atlantic salmon vaccinated with an oil-adjuvanted vaccine containing V. viscosus, V. wodanis and atypical A. salmonicida produced a relative percentage survival (RPS) of 97% when challenged i.p. with V. viscosus, demonstrating cross-protection between strains from Iceland and Norway. Short-term efficacy was demonstrated in rainbow trout by injection challenge at 21 and 43 days post-vaccination with an oil-adjuvanted vaccine containing V. viscosus, V. anguillarum (01/02), V. salmonicida and A. salmonicida, which produced an RPS of 96–99%. Rainbow trout challenged with V. viscosus at 52 and 362 days post-vaccination produced an RPS of 93% and 79%, indicating that vaccination provided long-term protection. In a similar manner, rainbow trout injected i.p. with 0.2 mL of a vaccine containing the five bacteria species and infectious pancreatic necrosis virus produced a 90% RPS when challenged with V. viscosus 66 days later. The high RPS under a severe challenge burden, along with disease signs in experimental freshwater challenges which resembled the saltwater disease condition, indicated that V. viscosus is a contributing factor to winter ulcer and that vaccination will protect against the disease.
TL;DR: Based on histologic pattern, immunohistochemistry and ultrastructural features, these undifferentiated liver lesions are distinct from hepatocellular carcinoma reported in this species and warrant a diagnosis of hepatoblastoma.
Abstract: A detailed histologic, immunohistochemical and ultrastructural description of two cases of hepatoblastoma, a primitive liver cell neoplasm, is provided from mummichog, Fundulus heteroclitus (L.), inhabiting a creosote-contaminated environment in the Elizabeth River, Virginia, USA. Both neoplasms were multifocal and comprised of undifferentiated embryonal cells with a high nuclear to cytoplasmic ratio. One case was characterized by a prominent macrotrabecular arrangement of tumour cells, whereas the other was solid in organization and undifferentiated. Tumour cells in some areas formed rosettes or pseudorosettes characteristic for hepatoblastoma. Focal areas within the macrotrabecular tumour were poorly differentiated, exhibiting a solid cellular arrangement. Strong immunolabelling with antibody C-219 indicated elevation and altered patterns of P-glycoprotein expression in both cases. In case 1, plasma membranes and tumour cell cytoplasm, but not bile canaliculi, were strongly labelled. However, in case 2, the macrotrabecular lesion, bile canaliculi were prominently labelled by the C-219 antibody with only patchy immunolabelling of tumour cell cytoplasm. Ultrastructurally, neoplasms from both specimens were composed of small, closely apposed, undifferentiated embryonal cells with scant cytoplasm resembling developing hepatocytes. The macrotrabecular lesion (case 2) exhibited a prominent tubular organization with well-developed bile canaliculi and constituent cells with abundant organelles. Based on histologic pattern, immunohistochemistry and ultrastructural features, these undifferentiated liver lesions are distinct from hepatocellular carcinoma reported in this species and warrant a diagnosis of hepatoblastoma.
TL;DR: A detailed study of a microsporidian parasite detected in the liver of the greater sand-eel, Hyperoplus lanceolatus (Le Sauvage), is reported in this article.
Abstract: A detailed study of a microsporidian parasite detected in the liver of the greater sand-eel, Hyperoplus lanceolatus (Le Sauvage), is reported. The parasite, originally described as Glugea caulleryi, invades hepatocytes, inducing xenoma formation and marked hypertrophy of the host-cell nucleus. Macroscopically, the infection is characterized by the presence of fibrous whitish structures of about 5 mm in length, each containing several xenomas. The final merogonic stages are rounded plasmodia, about 5 μm in length, which divide by plasmotomy. Meronts are characterized by the abundant membranous structures present in their cytoplasm. It was not possible to characterize the transition from merogonic to sporogonic plasmodia. During sporogony, the parasite remains in direct contact with the host-cell cytoplasm and sporonts produce uninucleate sporoblasts by exogenous budding. The spores are ovoid and uninucleate with a mean size of 1.2 x 2.6 μm, a polar tube coiled between seven and nine times and only a laminar-type polaroplast. In view of these characteristics, it is proposed that this species should be transferred to the genus Microgemma, with the name Microgemma caulleryi comb. nov.
TL;DR: The present authors have compared the bactericidal activity of these two peptides, showing that the killing rate for the selected bacteria was higher for cecropin B than for c Cecropin P1.
Abstract: The antibacterial effects of synthetic cecropin B and cecropin P1 were tested against the fish-pathogenic bacteria Vibrio anguillarum, Vibrio salmonicida, Aeromonas salmonicida, Edwardsiella ictaluri and Yersinia ruckeri. Both cecropins were active against all bacteria tested, but the effect was strongly influenced by the growth media used. In brain heart infusion medium, the minimum inhibitory concentrations of cecropin B ranged from 0.3 to 1.3 μm and from 0.3 to 1.0 μm for cecropin P1, except for E. ictaluri, which was noticeably less sensitive to cecropin P1 (61 μm). The present authors have compared the bactericidal activity of these two peptides, showing that the killing rate for the selected bacteria was higher for cecropin B than for cecropin P1. V. anguillarum was the most sensitive to the cecropins, and in the present study, no colony forming units were detected after 4 and 8 min of treatment with cecropin B and P1, respectively. Electron microscopy was performed to document the effect of cecropin on the bacterial surface.