Showing papers in "Journal of Fish Diseases in 2003"
TL;DR: Recent work suggests that Melano-macrophage centres are a site of primary melanogenesis rather than mere storage, and have been suggested as reliable biomarkers for water quality in terms of both deoxygenation and iatragenic chemical pollution.
Abstract: Melano-macrophage centres, also known as macrophage aggregates, are distinctive groupings of pigment-containing cells within the tissues of heterothermic vertebrates. In fish they are normally located in the stroma of the haemopoietic tissue of the spleen and the kidney, although in amphibians and reptiles, and some fish, they are also found in the liver. They may also develop in association with chronic inflammatory lesions elsewhere in the body and during ovarian atresia. In higher teleosts, they often exist as complex discrete centres, containing lymphocytes and macrophages, and may be primitive analogues of the germinal centres of lymph nodes. Melano-macrophage centres usually contain a variety of pigments, including melanins, and these increase in range and volume in older fish or in the presence of cachectic disease. Melano-macrophage centres act as focal depositories for resistant intracellular bacteria, from which chronic infections may develop. Iron capture and storage in haemolytic diseases appears to be a primary function, but antigen trapping and presentation to lymphocytes, sequestration of products of cellular degradation and potentially toxic tissue materials, such as melanins, free radicals and catabolic breakdown products are among other functions that have been ascribed. Recent work suggests that they are a site of primary melanogenesis rather than mere storage. Melano-macrophage centres increase in size or frequency in conditions of environmental stress and have been suggested as reliable biomarkers for water quality in terms of both deoxygenation and iatragenic chemical pollution.
750 citations
TL;DR: A literature review discusses the agent and the disease it causes, with emphasis on the bacterium-host interactions, and the development of preventive measures to efficiently combat this disease condition.
Abstract: Flavobacterium psychrophilum is the causative agent of bacterial cold water disease and rainbow trout fry syndrome, disease entities responsible for substantial economic losses in salmonid aquaculture. Problems associated with epizootics include high mortality rate, increased susceptibility to other diseases, high labour costs of treatment and the enormous expenditure on chemotherapy. Despite the increasing significance of the disease, the pathogenesis of F. psychrophilum infections has only been partially elucidated, hampering the development of preventive measures to efficiently combat this disease condition. This literature review discusses the agent and the disease it causes, with emphasis on the bacterium-host interactions.
344 citations
TL;DR: The important characteristics of the bacterium including recent taxonomic changes, features of the disease caused by the bacteria including transmission, hosts, reservoirs, diagnostic procedures, and current approaches for prevention and treatment have been discussed.
Abstract: Piscirickettsia salmonis is the first Gram-negative, intracellular bacterial pathogen isolated from fish and is a significant cause of mortality in salmonid fish. Recent reports of P. salmonis or P. salmonis-like organisms from new fish hosts and geographic regions have increased the interest in the bacterium. In this review, the important characteristics of the bacterium including recent taxonomic changes, features of the disease caused by the bacterium including transmission, hosts, reservoirs, diagnostic procedures, and current approaches for prevention and treatment have been discussed. The reader is also directed to other reviews concerning the bacterium and the disease it causes (Fryer & Lannan 1994, 1996; Almendras & Fuentealba 1997; Lannan, Bartholomew & Fryer 1999; House & Fryer 2002; Mauel & Miller 2002).
186 citations
TL;DR: Investigations by transmission electron microscopy after negative staining of diseased PL homogenates showed the presence of two types of viral particles: one, unenveloped, icosahedral in shape, 26-27 nm in diameter, and the second, much smaller, designated extra small virus particle (XSV), which may be a new type of crustacean virus.
Abstract: A disease of Macrobrachium rosenbergii, the giant freshwater prawn, farmed in China was recently recorded in Zhejiang, Jiangsu, Shanghai, Guangxi and Guangdong provinces. The clinical sign of the disease, which develops in post-larvae (PL), is a whitish appearance of the muscles, particularly noticeable in the abdomen. Mortalities may reach 100% in some hatcheries. Investigations by transmission electron microscopy after negative staining of diseased PL homogenates showed the presence of two types of viral particles: one, unenveloped, icosahedral in shape, 26-27 nm in diameter, the second, much smaller, about 14-16 nm in diameter, designated extra small virus particle (XSV). The large virus has a genome with two pieces of ssRNA (RNA-1 and RNA-2), of 3 and 1.2 kb, respectively. Hybridization tests confirmed that this large virus is closely related to M. rosenbergii nodavirus (MrNV) which was isolated from diseased prawns in a hatchery in the French West Indies. Its very small size and hypothesized biochemical and biological characteristics suggest XSV is a new type of crustacean virus. As XSV has always been found associated with the larger virus (nodavirus) and is located in muscle and connective cells of diseased animals, it could be an autonomous virus, a helper-type virus or a satellite-like virus.
172 citations
162 citations
155 citations
TL;DR: Bacteria isolated from an outbreak with moderate mortalities in farmed sole, Solea senegalensis (Kaup), in the south of Spain were identified as Vibrio harveyi and V. parahaemolyticus, and the intramuscular inoculation of the extracellular products (ECPs) of both species produced mortality in inoculated fish and the appearance of surface ulcers in the case of V.Harveyi.
Abstract: Bacteria isolated from an outbreak with moderate mortalities in farmed sole, Solea senegalensis (Kaup), in the south of Spain were identified as Vibrio harveyi and V. parahaemolyticus. Only bacterial strains showing swarming were virulent in sole and caused mortalities in experimentally inoculated fish. However, the signs of the disease were only reproduced with V. harveyi. The intramuscular inoculation of the extracellular products (ECPs) of both species produced mortalities in inoculated fish and the appearance of surface ulcers in the case of V. harveyi. However, the inoculation of sublethal doses of ECPs to fish showed a protective effect against V. harveyi.
155 citations
TL;DR: In this article, the authors describe histopathological observations of amoebic gill disease (AGD) from smolts, sampled weekly, following transfer to estuarine/marine sites.
Abstract: Amoebic gill disease (AGD) affects the marine culture phase of Atlantic salmon, Salmo salar L., in Tasmania. Here, we describe histopathological observations of AGD from smolts, sampled weekly, following transfer to estuarine/marine sites. AGD was initially detected histologically at week 13 post-transfer while gross signs were not observed for a further week post-transfer. Significant increases (P < 0.001) in the proportion of affected gill filaments occurred at weeks 18 and 19 post-transfer coinciding with the cessation of a halocline and increased water temperature at the cage sites. The progression of AGD histopathology, during the sampling period, was characterized by three phases. (1) Primary attachment/interaction associated with extremely localized host cellular alterations, juxtaposed to amoebae, including epithelial desquamation and oedema. (2) Innate immune response activation and initial focal hyperplasia of undifferentiated epithelial cells. (3) Finally, lesion expansion, squamation–stratification of epithelia at lesion surfaces and variable recruitment of mucous cells to these regions. A pattern of preferential colonization of amoebae at lesion margins was apparent during stage 3 of disease development. Together, these data suggest that AGD progression was linked to retraction of the estuarine halocline and increases in water temperature. The host response to gill infection with Neoparamoeba sp. is characterized by a focal fortification strategy concurrent with a migration of immunoregulatory cells to lesion-affected regions.
150 citations
TL;DR: This review is an attempt to bring together the available information on those diseases of Thunnus spp.
Abstract: Much is known about those aspects of tuna health which can be studied in wild populations, e.g. helminth parasites. However, because aquaculture of these species is in its infancy, knowledge of microbial, nutritional and environmental diseases is limited. This review is an attempt to bring together the available information on those diseases of Thunnus spp. which cause significant morbidity, mortality or economic loss. In doing so it has become clear that much more research needs to be undertaken on the physiology of the species (southern, northern and Pacific bluefin tuna) currently used in aquaculture in order for the pathogenesis of some conditions to be properly understood. Attempts at hatchery culture of Pacific bluefin tuna has indicated that Thunnus spp. will be problematic to hatch and propagate.
122 citations
TL;DR: Four tropical marine fish cell lines have been established from the eye, fin, heart and swim bladder of grouper, Epinephelus awoara and produced significant fluorescent signals indicating their utility for exogenous studies.
Abstract: Four tropical marine fish cell lines have been established from the eye, fin, heart and swim bladder of grouper, Epinephelus awoara (Temminck & Schlegel). Optimum media and temperature conditions for maximum growth were standardized. The eye and swim bladder cells were mostly epithelial, but the fin and heart cells were mostly fibroblastic. The viability of cells was 95% after 1 year of storage in liquid nitrogen (-196 degrees C). Besides these four cell lines, previously established grouper brain, kidney and liver cell lines were also used for a viral susceptibility study which showed that all the cell lines were sensitive to grouper iridovirus, whereas only brain, fin and liver cell lines were susceptible to the yellow grouper nervous necrosis virus (a nodavirus). Electron microscopy studies of the grouper irido- and nodaviruses in ultrathin sections of infected cells showed an abundance of viral particles in the cytoplasm of the virus-infected cells indicating the effective replication of these two viruses. It is suggested that these cell lines can be used for the isolation of putative fish specific viruses and provide a valuable tool to study the mechanisms of host-pathogen interactions. Furthermore, these cell lines upon transfection, using pEGFP-C1 and pEGFP-aMT2.5 (ayu metallothionein promoter), produced significant fluorescent signals indicating their utility for exogenous studies.
115 citations
TL;DR: In this article, three epidemiological surveys in Ecuadorian farms were carried out and showed an apparent association between lower temperature and increased mortality rates in commercial ponds in commercial shrimp, Penaeus vannamei (Boone), induced by WSSV.
Abstract: Mortalities of cultured shrimp, Penaeus vannamei (Boone), induced by white spot syndrome virus (WSSV) have occurred in Ecuador since May 1999. Three epidemiological surveys in Ecuadorian farms were carried out and showed an apparent association between lower temperature and increased mortality rates in commercial ponds. Infected animals showed a reddish discolouration and lethargy and occasionally, white spots in the exoskeleton. Histopathological studies revealed that infected cells presented nuclear hypertrophy with eosinophilic to basophilic inclusions. In some cases, two other pathologies were observed: (a) lymphoid organ spheroids and (b) cells with pyknotic and karyorrhectic nuclei in the lymphoid organ, haematopoietic tissue, connective tissue, heart and antennal gland. Occasionally pyknotic cells were encapsulated without apparent injury to the adjacent tissue and without melanization. Transmission electron microscopy showed the presence of WSSV particles in the cytoplasm of cells with pyknotic nuclei in the stomach hypodermis. Viral structure and morphogenesis agreed with previous descriptions by other authors in WSSV-infected shrimp. Occasionally, two nucleocapsids within one envelope were present amongst single enveloped nucleocapsids. A long rod-shaped structure that could reach 2.4 l mi n
TL;DR: It is suggested that in the absence of natural food, juvenile channel catfish should be fed at least once every other day to apparent satiation to maintain normal physiological function and improve resistance to F. columnare.
Abstract: Withholding feed has been suggested as a strategy to manage infectious disease of channel catfish, Ictalurus punctatus (Rafinesque). In a previous study, we demonstrated that deprivation of feed for as little as 7 days reduced innate resistance of catfish to Flavobacterium columnare. This study was conducted to evaluate the effect of feeding regimens [no feeding (NF), fed once every other day to satiation (FEOD) and fed once daily to satiation (FD)] on organosomatic indices, physiological changes and susceptibility of channel catfish to F. columnare. Fish that were not fed for 2 and 4 weeks had a significant increase (P < 0.05) in gutted weight: wet weight ratio and decrease in other organosomatic indices [gut index (GI), mesenteric fat index (MFI) and hepatosomatic index (HSI)]. Haematology was not effected by feeding regimen except at week 4, when a significantly higher haemoglobin level was observed in the NF fish. Serum protein did not differ at week 2, but the level at week 4 of the NF fish (35.91 mg mL - 1 ) was significantly lower than that of the FD fish (41.77 mg mL - 1 ). Significantly lower (P < 0.05) blood glucose (39.5 and 40.3 mg dL - 1 ) and liver glycogen (1.7 and 1.8 mg g - 1 ) were seen in the NF fish at weeks 2 and 4, respectively, as compared with blood glucose and liver glycogen levels of FD fish (67.5 and 92.8 mg dL - 1 and 46.5 and 52.6 mg g - 1 at weeks 2 and 4, respectively) and FEOD (82.8 and 85.5 mg dL - 1 and 45.1 and 51.4 mg g - 1 at weeks 2 and 4, respectively). Mortality in the NF fish caused by F. columnare (78%) was significantly higher (P < 0.05) than mortality in the FD and FEOD treatments (0.0 and 1.7%, respectively). Blood glucose and liver glycogen showed the same trend of low values for NF fish following challenge (week 6). Blood glucose, liver glycogen, GI and HSI are sensitive indicators for channel catfish deprived of feed (NF) for 4 weeks. Blood glucose and liver glycogen levels around 40 mg dL - 1 and 2 mg g - 1 , respectively, are indicative of starvation in juvenile channel catfish. Moreover, NF fish were susceptible to F. columnare infection. Thus, it is suggested that in the absence of natural food, juvenile channel catfish should be fed at least once every other day to apparent satiation to maintain normal physiological function and improve resistance to F. columnare.
TL;DR: Three complementary genome-based methods were developed for the detection of Macrobrachium rosenbergii nodavirus and RT-PCR indicated that infection was confined to the striated muscle tissue, showing the possible use of this method in routine health monitoring.
Abstract: The availability of specific and rapid detection methods is essential for monitoring the health status of farmed species, particularly in viral diseases as in this case early diagnosis is a critical factor in containing disease outbreaks. Three complementary genome-based methods were developed for the detection of Macrobrachium rosenbergii nodavirus (MrNV), i.e. dot-blot hybridization, in situ hybridization and reverse transcriptase-polymerase chain reaction (RT-PCR). Detection limits were established for dot-blot hybridization and RT-PCR and are c. 7 fg and 8 pg of viral RNA, respectively. In situ hybridization indicated that infection was confined to the striated muscle tissue. As a result of its sensitivity, RT-PCR can be used for in-depth investigations to examine the extent of the viral infection and establish the onset of infection in hatcheries. The application of RT-PCR on samples collected from prawn farms in China showed the possible use of this method in routine health monitoring.
TL;DR: It is shown that balancing the diet with respect to pro- and antioxidant nutrients may significantly protect Atlantic salmon against development of cataracts.
Abstract: The development of cataracts in Atlantic salmon, Salmo salar L., was studied in 16 groups of smolts fed diets differing in prooxidant (iron, copper, manganese) and antioxidant (vitamin E, vitamin C, astaxanthin) composition and lipid level for 23 weeks in sea water, using a 2(7-3) reduced factorial design. The seven dietary variables were systematically varied at low (requirement level and 150 g lipid kg(-1)) and high levels (below known toxic levels and 320 g lipid kg(-1)). A mean endpoint cataract incidence of approximately 36% was observed. High dietary levels of vitamin C and astaxanthin reduced cataract frequency, whereas high dietary lipid level, iron and manganese were associated with increased cataract frequencies. Considering the nutritional status of selected organs of the fish, only the status of ascorbic acid correlated negatively to cataract development (P < 0.05). The lens glutathione (GSH) status was not correlated to cataract frequency, nor statistically explained by the dietary variables. However, the study shows that balancing the diet with respect to pro- and antioxidant nutrients may significantly protect Atlantic salmon against development of cataracts. An incidence of reversible osmotic cataract observed at week 14 was positively correlated to plasma glucose concentration.
TL;DR: Salmonid cryptobiosis is caused by Cryptobia (Trypanoplasma) salmositica, and the haemoflagellate has been reported from all species of Pacific Oncorhynchus spp.
Abstract: Salmonid cryptobiosis is caused by Cryptobia (Trypanoplasma) salmositica. The haemoflagellate has been reported from all species of Pacific Oncorhynchus spp. on the west coast of North America. It is normally transmitted by the freshwater leech, Piscicola salmositica, in streams and rivers, and sculpins, Cottus spp., are considered important reservoir hosts. The pathogen can also survive on the body surface of fish because it has a contractile vacuole to osmoregulate when the fish is in fresh water. This allows for direct transmission between fish, especially in aquaculture facilities. The parasite divides rapidly by binary fission in the blood to cause disease, the severity of which is directly related to parasitaemia. Cryptobia salmositica has a mitochondrium and it normally undergoes aerobic respiration; however, if its mitochondrium is damaged it will switch to glycolysis. Its glycolytic enzymes and catalase are contained in glycosomes. Cysteine protease is a metabolic enzyme, and its neutralization inhibits oxygen consumption and multiplication of the parasite. An important virulent factor in cryptobiosis is a secretory metalloprotease. The protective mechanism involves production of complement fixing antibodies, phagocytosis by macrophages, and cell-mediated cytotoxicity. Recovered fish are protected, probably for life as the immunity is non-sterile. Clinical signs of the disease include anaemia, anorexia, splenomegaly, general oedema and abdominal distension with ascites. The metabolism and swimming performance of infected fish are significantly reduced and the bioenergetic cost of the disease is very considerable. Fish are susceptible to hypoxia and their immune system is depressed during acute cryptobiosis. Severity of the disease and mortality rates vary significantly between species and stocks of salmon. Protective strategies include selective breeding of Cryptobia-resistant fish. This is innate resistance to infection and it is controlled by a dominant Mendelian locus. In these fish the parasite is lysed via the alternative pathway of complement activation. In Cryptobia-tolerant fish (infected with the pathogen but which do not suffer from disease) the metalloprotease secreted by the parasite is neutralized by alpha2 macroglobulin. Hence, the production of a transgenic Cryptobia-tolerant salmon is an option. This strategy has the advantage in that human intervention (e.g. vaccination, chemotherapy) is not required once the transgenic fish is produced. Acquired immunity is another option; a single dose of the attenuated live vaccine protects fish for at least 2 years. The protective mechanism in vaccinated fish is similar to that in recovered fish. The trypanocidal drug, isometamidium chloride, is an effective therapeutic and prophylactic agent. It accumulates in the mitochondrium of the parasite and significantly disrupts aerobic respiration by causing lesions in the organelle. Efficacy of the drug is significantly increased after its conjugation to antibodies. This immuno-chemotherapeutic strategy has the advantage in that it will lower the drug dosage and hence side-effects of chemotherapy. It will probably reduce the accumulation of the drug in fish, an important consideration in food fish.
TL;DR: Two new cell cultures from flounder showed cytopathic effects after inoculation of infectious pancreatic necrosis virus, marine birnavirus, chum salmon virus, infectious haematopoietic necrot virus, spring viraemia of carp virus and hirame rhabdovirus, suggesting these new cell lines may be useful for studying a wide range of fish viruses.
Abstract: Two new cell cultures from flounder, Paralichthys olivaceus (Temminck & Schlegel), flounder fin (FFN) cells from fin tissue and flounder spleen (FSP) cells from spleen tissue, were established and characterized. The cells multiplied well in Eagle's minimum essential medium, supplemented with 10% foetal bovine serum, and have been subcultured more than 100 times, becoming continuous cell lines. Modal diploid chromosome number of FFN and FSP cells was 64 and 62, respectively. Polymerase chain reaction products were obtained from FFN and FSP cells with primer sets ofmicrosatellite markers of flounder. Optimal growth temperature was 20 degrees C and consisted of epithelioid cells. FFN and FSP cells showed cytopathic effects after inoculation of infectious pancreatic necrosis virus, marine birnavirus, chum salmon virus, infectious haematopoietic necrosis virus, spring viraemia of carp virus and hirame rhabdovirus. Thus these new cell lines may be useful for studying a wide range of fish viruses.
TL;DR: Results suggest that trout antibody plays a role in conferring protection to F. psychrophilum, but antibody alone is unable to provide complete protection.
Abstract: Flavobacterium psychrophilum, the causative agent of bacterial coldwater disease (CWD) and rainbow trout fry syndrome (RTFS), causes high mortality in cultured salmonids. The present study was designed to determine the role antibody plays in conferring protection to rainbow trout fry, Oncorhynchus mykiss (Walbaum), by passive immunization with convalescent serum or serum from adult rainbow trout immunized with F. psychrophilum, and goat anti-F. psychrophilum serum. In each experiment, rainbow trout fry were injected intraperitoneally with antiserum and challenged by subcutaneous injection with a virulent strain (CSF-259-93) of F. psychrophilum 24-h post-immunization. Relative percentage survival (RPS) ranged from 9-42% when rainbow trout fry (mean weight 1.3 g) were injected with a 1:2 dilution of 25 microL of convalescent serum ranging in enzyme-linked immunosorbent assay antibody titres from 1600-102400. Rainbow trout fry (mean weight 1.0 g) passively immunized with 25 microL of serum from immunized adult fish exhibited RPS values of up to 57%. In each of these experiments, RPS increased with increasing antibody titres against F. psychrophilum. Passive immunization with 25 or 50 microL goat anti-F. psychrophilum serum, however, did not confer protection to fry (mean weight 1.3 g). These results suggest that trout antibody plays a role in conferring protection to F. psychrophilum, but antibody alone is unable to provide complete protection.
TL;DR: Parasitized fish had significantly lowered erythrocyte counts, haematocrit and haemoglobin values and significantly increased leucocyte counts and the fish appear to mount an immune response to the presence of parasites.
Abstract: The effects of the fish parasitic isopod, Ceratothoa oestroides (Risso), on haematological parameters of its cage-cultured sea bass host, Dicentrarchus labrax (L.), were studied. Analyses of blood parameters (cell counts, haemoglobin content and haematocrit) were carried out on parasitized and unparasitized sea bass from a fish farm in Turkey. Parasitized fish had significantly lowered erythrocyte counts, haematocrit and haemoglobin values and significantly increased leucocyte counts. Blood feeding by C. oestroides thus produces a post-haemorrhagic anaemia and the fish appear to mount an immune response to the presence of parasites.
TL;DR: Although the size and some features of epizootics of this virus differed from RSIV in Japan, it shows close genetic affinities with the latter and it is suggested that RSIV has been introduced to Taiwan.
Abstract: Since 1993, an epizootic viral disease has occurred in net-cage cultured red sea bream, Pagrus major (Temminck & Schlegel), in Peng-hu Island located on the south-western coast of Taiwan. The diseased fish exhibited abnormal swimming and were lethargic, but few visible external signs were observed. The cumulative mortality because of the disease sometimes reached 50-90% over 2 months. Histopathogical studies of the affected fish showed enlarged basophilic cells in the gill, kidney, heart, liver and spleen. These necrotic cells were Feulgen-positive and stained blue using Giemsa. Transmission electron microscopy revealed icosahedral virions in the cytoplasm of the necrotic cells. The viral particles consisted of a central nucleocapsid (75-80 nm) and envelope, and were 120-150 nm in diameter. These results suggest that the virus belongs to the Iridoviridae. Using polymerase chain reaction (PCR), approximately 570 bp fragments were produced from the viral DNA using as a template 1-F and 1-R primers derived from red seabream iridovirus (RSIV) from red sea bream in Japan. Similar results were also obtained using nested-PCR with different primer sets (1-F, 2-R and 2-F, 1-R). Although the size and some features of epizootics of this virus differed from RSIV in Japan, it shows close genetic affinities with the latter and it is suggested that RSIV has been introduced to Taiwan.
TL;DR: Tissue extracts from M. rosenbergii infected with MrNV or purified viral extracts (control) were successfully identified in an individual ELISA, thus confirming the validity of the method and is a rapid and inexpensive assay with high specificity and sensitivity.
Abstract: A sandwich enzyme-linked immunosorbent assay (S-ELISA) was developed to improve diagnosis of white tail disease of the giant freshwater prawn, Macrobrachium rosenbergii, caused by the nodavirus, MrNV. Polyclonal antibodies were produced by immunization of Balb/C mice using a purified suspension of the virus and IgG anti-MrNV were purified from ascitic fluid. A sandwich method was successfully developed, coating first with unlabelled antibody and detecting trapped antigens with a second biotinylated antibody. Reaction was demonstrated using an avidin-peroxidase conjugate. Tissue extracts from M. rosenbergii infected with MrNV or purified viral extracts (control) were successfully identified in an individual ELISA, thus confirming the validity of the method. This S-ELISA should be the technique of choice for epidemiological studies of this disease and is a rapid and inexpensive assay with high specificity and sensitivity.
TL;DR: A modified virus neutralization (VN) assay was developed to replace an existing assay read on the presence or absence of virus-induced cytopathic effect (CPE) and was used to test 188 sera collected from wild salmonids in freshwater river systems in Northern Ireland.
Abstract: A modified virus neutralization (VN) assay was developed to replace an existing assay read on the presence or absence of virus-induced cytopathic effect (CPE). The modified assay used a monoclonal antibody to salmon pancreas disease virus as the first layer of an immunoperoxidase (IPX)-based immunostaining technique to detect viral growth. The IPX-based VN assay required only 3 days to perform, and the adoption of a 96-well microtitre format facilitated a high throughput of samples requiring small volumes of serum, cells and virus. When 352 sera from farmed salmon and 302 sera from farmed trout were tested by both the modified and the original CPE-based assays, overall correlations of 97.72 and 96.03% were, respectively, obtained (96.94% combined). When the modified assay was used to test 188 sera collected from wild salmonids in freshwater river systems in Northern Ireland, no positive results were recorded.
TL;DR: Examination of two large national data sets collected over several years contrasts the patterns of sea lice, Lepeophtheirus salmonis (Krøyer, 1837), infections, the use of treatments and the occurrence of chalimus peaks between Norwegian and Scottish farms highlights the importance of ensuring that effective veterinary medicines are available in the UK for the control of infection.
Abstract: This paper examines two large national data sets collected over several years and contrasts the patterns of sea lice, Lepeophtheirus salmonis (Kroyer, 1837), infections, the use of treatments and the occurrence of chalimus peaks between Norwegian and Scottish farms. Infection levels in Scotland were significantly higher in general over the period under study. For the chalimus stage group in the first quarter of the year, Norwegian mean abundance stayed below 10 lice per m2 while Scottish means reached 45 lice per m2 of fish skin per m3 of water. Both countries had more chalimus in summer than at other times of year, but in the last 3 months of the year Scottish fish had, on average, two to four times as many chalimus as Norwegian fish. Peaks of chalimus abundance were more frequent in Scotland, particularly in winter, but the most prominent peaks occurred in summer in both countries. In Scotland a marked mid-year build-up of mobile pre-adult and adult stages was seen, and both countries showed a tendency for mobile counts on the second year fish to increase towards the end of the year. Scottish fish carried, on average, three times as many mobile lice per m2 of skin as Norwegian fish in the last 3 months of the year. The difference in lice loads was reflected in the greater use of veterinary medicines on Scottish farms. The higher infection levels in Scotland may be due to shallower and more enclosed water bodies used for farming, smaller and shallower pens, differences in sea water temperatures or in access to appropriate medication. The results highlight the importance of ensuring that effective veterinary medicines are available in the UK for the control of infection.
TL;DR: Research has focused on the usefulness of inactivated bacterial preparations for the control of atypical Aeromonas salmonicida infections in goldfish, Carassius auratus, following previous success with live and inactivated probiotics in salmonids.
Abstract: There has been increasing interest in the use of probiotics in aquaculture to control fish diseases (e.g. Douillet Langdon 1994; Gildberg, Mikkelsen, Sandaker & Ringo 1997; Kennedy, Tucker, Neidic, Vermeer, Cooper, Jarrell & Sennett 1998; DeSchrijver & Ollevier 2000; Robertson, O'Dowd, Burrells, Williams & Austin 2000), and a diverse range of Gram-positive (such as Carnobacterium inhibens) (Robertson et al. 2000) and Gram-negative bacteria, including Vibrio alginolyticus (Garriques & Arevalo 1995), have been evaluated at various times. However, the possible use of probiotics to control diseases of ornamental fish has been neglected. Consequently, following previous success with live (Irianto & Austin 2002) and inactivated probiotics in salmonids (Irianto & Austin, in press), research has focused on the usefulness of inactivated bacterial preparations for the control of atypical Aeromonas salmonicida infections in goldfish, Carassius auratus (L.). Goldfish, of average 40-50 mm in length, were obtained from a commercial farm in England, and maintained in aerated re-circulating dechlorinated fresh water at 17 degrees C. Their health status was examined immediately upon arrival in the aquaria and at 1-2-week periods thereafter (after Austin & Austin 1989).
TL;DR: Abrasion had significant effects on the early entry of the pathogen and on cumulative percent survival (CPS) in channel catfish, which supports the use of abrasion for the F. columnare challenge model forChannel catfish.
Abstract: The early entry of the fish pathogen Flavobacterium columnare and enhancement by abrasion was studied in channel catfish, Ictalurus punctatus (Rafinesque), using the polymerase chain reaction and a species-specific primer set for a bacterial 16S rRNA gene product. Evaluations were conducted following an abrasion bath immersion challenge with F. columnare. Abrasion, a practice which has historically been used prior to bacterial challenge, had significant effects on the early entry of the pathogen and on cumulative percent survival (CPS). The FvpF1-FvpR1 primer set was useful in detecting the early entry of F. columnare in mucus, skin, gill, blood, liver and trunk kidney tissues in both abraded and unabraded fish following immersion challenge at 29 +/- 2 degrees C. Bacteria were detected earlier in all tissues in abraded fish, except in the trunk kidney. These differences were not significant, except in the case of blood. Mucus, skin and gill tissues were positive for F. columnare earliest regardless of treatment (after 5 min in abraded fish and after 15 min in unabraded fish). CPS following challenge with F. columnare was significantly affected by abrasion, which supports the use of abrasion for the F. columnare challenge model for channel catfish.
TL;DR: In four independent in vivo tank observations of fish affected with saprolegniosis, the daily addition of A199 to tank water contributed to the subsequent swift recovery of affected hosts from invasion by this opportunistic pathogen.
Abstract: A bacteriocin-like inhibitory substance (BLIS) produced by Aeromonas media strain A199 inhibited the growth of Saprolegnia sp. in vitro, an opportunistic pathogen isolated from affected eels, Anguilla australis (Richardson). The presence of BLIS in solid media inhibited the growth of the vegetative state of the aquatic mould as well as the germination of cysts. Uninhibited growth was, however, observed in the presence of inactive BLIS, suggesting that the in vitro antagonism derived from the BLIS of A199. In four independent in vivo tank observations of fish affected with saprolegniosis, the daily addition of A199 to tank water contributed to the subsequent swift recovery of affected hosts from invasion by this opportunistic pathogen.
TL;DR: Vibrio pelagius (Hq 222) was able to grow in sterile sea water when incubated at room temperature or at 15 degrees C and was more adherent to the turbot cell lines TV-1 and TF than Escherichia coli.
Abstract: A bacterial strain, characterized as Vibrio pelagius (Hq 222), was isolated from a turbot, Scophthalmus maximus (L.), larvae mass mortality in a commercial fish farm in Spain. Turbot larvae, post-larvae (0.2 g) and juveniles (5 and 15 g) were experimentally infected. The bacterium appeared to be very virulent for larvae and post-larvae, LD50 being < 5 bacteria mL(-1) for larvae 1 week post-infection and 3.9 x 10(5) bacteria mL(-1) in post-larvae at day 12 post-infection. The bacterial strain was recovered in pure culture from the internal organs of infected fish. Histological lesions in post-larvae exhibited swelling and necrosis of gill secondary lamellae, sloughing of intestinal mucosa and necrosis of haematopoietic tissue in the kidney. Vibrio pelagius (Hq 222) was able to grow in sterile sea water when incubated at room temperature or at 15 degrees C. Vibrio pelagius (Hq 222) was more adherent to the turbot cell lines TV-1 and TF than Escherichia coli. In both cell lines, the number of adhered bacteria increased with incubation time.