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Light is one of the most critical stimuli in the majority of living organisms. In the last two decades, blue light (BL) has become a major subject of attention because of developments in light-emitting diodes (LED). The effects of BL on eukaryotic organisms and phototrophic prokaryotes have been well studied, but the knowledge of its effects on non-phototrophic prokaryotes remains unclear. Since BL can penetrate seawater, it is expected that most prokaryotes living in the ocean possess molecular mechanisms which protect against BL. The aim of this study is to assess the molecular mechanisms of Vibrio parahaemolyticus cells against BL as a marine bacterial model compared to other wavelength light exposures. Physiological and transcriptomic analyses of BL-exposed cells compared to other light treated cells revealed the highest ROS fold change, the highest number of differentially expressed genes (DEGs), and up-regulation in the gene responsible to not only compatible solute such as glycine betaine and ectoine but also iron-sulfur biosynthesis related to ROS formation. Furthermore, red light (RL) up-regulated the expression of cryptochrome DASH, a protein known to be excited by BL, and orange light (OL) decreased the expression of thermostable direct hemolysin (TDH), suggesting that OL attenuates the virulence of V. parahaemolyticus. In addition, the expression of VtrA (V. parahaemolyticus type III secretion system 2 (T3SS2) regulator A) but not VtrB (V. parahaemolyticus T3SS2 regulator B) increased under both light treatments, indicating that light exposure is unlikely to be involved in T3SS2-mediated pathogenicity. These results expand our knowledge on unique light responses in non-phototrophic marine prokaryotes.

Time series of the number of infected individuals is measured to understand the dynamics of an infectious disease and to evaluate the effectiveness of countermeasures against it. However, in fish diseases, it is often difficult to record the time series of the infected fish owing to i) ambiguous clinical symptoms during the onset of disease and ii) cost of diagnosis. To address this issue, we established a mathematical modeling-based method to infer time series of the number of infected fish by coupling the experimental infection and field data on the outbreak of the disease. This method enables to reconstruct time series of the number of infected fish using mortality data obtained from the experimental infection. The reconstructed time series enables to estimate the transmissibility of fish diseases. We studied Oncorhynchus masou virus (salmonid herpesvirus 2) disease (OMVD) using Rainbow trout (Oncorhynchus mykiss) as a model for analysis and estimated the lethality rate of OMVD infection and the basic reproduction number (R0), i.e., transmissibility of OMVD. Our results revealed that larger fish (>= 200 g) showed a higher OMVD lethality rate and R0s when compared with smaller fish (<200 g). This suggests that high mortality among large fish does not inhibit the transmission of pathogen when compared with small fish.

Light is one of the most critical stimuli in the majority of living organisms. In the last two decades, blue light (BL) has become a major subject of attention because of developments in light-emitting diodes (LED). The effects of BL on eukaryotic organisms and phototrophic prokaryotes have been well studied, but the knowledge of its effects on non-phototrophic prokaryotes remains unclear. Since BL can penetrate seawater, it is expected that most prokaryotes living in the ocean possess molecular mechanisms which protect against BL. The aim of this study is to assess the molecular mechanisms of Vibrio parahaemolyticus cells against BL as a marine bacterial model compared to other wavelength light exposures. Physiological and transcriptomic analyses of BL-exposed cells compared to other light treated cells revealed the highest ROS fold change, the highest number of differentially expressed genes (DEGs), and up-regulation in the gene responsible to not only compatible solute such as glycine betaine and ectoine but also iron-sulfur biosynthesis related to ROS formation. Furthermore, red light (RL) up-regulated the expression of cryptochrome DASH, a protein known to be excited by BL, and orange light (OL) decreased the expression of thermostable direct hemolysin (TDH), suggesting that OL attenuates the virulence of V. parahaemolyticus. In addition, the expression of VtrA (V. parahaemolyticus type III secretion system 2 (T3SS2) regulator A) but not VtrB (V. parahaemolyticus T3SS2 regulator B) increased under both light treatments, indicating that light exposure is unlikely to be involved in T3SS2-mediated pathogenicity. These results expand our knowledge on unique light responses in non-phototrophic marine prokaryotes.

The Splendidus clade is the largest clade in Vibrionaceae, and its members are often related to mortality of marine animals with huge economic losses. The molecular bases of their pathogenicity and virulence, however, remain largely unknown. In particular, the complete genome sequences of the Splendidus clade species are rarely registered, which is one of the obstacles to predict core and/or unique genes responsible for their adaptation and pathogenicity, and to perform a fine scale meta-transcriptome during bacterial infection to their hosts. In this study, we obtained the complete genomes of all type strains in the Splendidus clade and revealed that (1) different genome sizes (4.4-5.9 Mb) with V. lentus the biggest and most of them had several big plasmids, likely because of the different features on mobilome elements; (2) the Splendidus clade consists of 19 species except V. cortegadensis, and 3 sub-clades (SC) were defined with the 15 most closely related members as SC1; (3) different carbohydrate degradation preferences may be the result of environmental adaptation; and (4) a broad prediction of virulence factors (VFs) revealed core and species unique VF genes.

Light is one of the most critical stimuli in the majority of living organisms. In the last two decades, blue light (BL) has become a major subject of attention because of developments in light-emitting diodes (LED). The effects of BL on eukaryotic organisms and phototrophic prokaryotes have been well studied, but the knowledge of its effects on non-phototrophic prokaryotes remains unclear. Since BL can penetrate seawater, it is expected that most prokaryotes living in the ocean possess molecular mechanisms which protect against BL. The aim of this study is to assess the molecular mechanisms of Vibrio parahaemolyticus cells against BL as a marine bacterial model compared to other wavelength light exposures. Physiological and transcriptomic analyses of BL-exposed cells compared to other light treated cells revealed the highest ROS fold change, the highest number of differentially expressed genes (DEGs), and up-regulation in the gene responsible to not only compatible solute such as glycine betaine and ectoine but also iron-sulfur biosynthesis related to ROS formation. Furthermore, red light (RL) up-regulated the expression of cryptochrome DASH, a protein known to be excited by BL, and orange light (OL) decreased the expression of thermostable direct hemolysin (TDH), suggesting that OL attenuates the virulence of V. parahaemolyticus. In addition, the expression of VtrA (V. parahaemolyticus type III secretion system 2 (T3SS2) regulator A) but not VtrB (V. parahaemolyticus T3SS2 regulator B) increased under both light treatments, indicating that light exposure is unlikely to be involved in T3SS2-mediated pathogenicity. These results expand our knowledge on unique light responses in non-phototrophic marine prokaryotes.

The Splendidus clade is the largest clade in Vibrionaceae, and its members are often related to mortality of marine animals with huge economic losses. The molecular bases of their pathogenicity and virulence, however, remain largely unknown. In particular, the complete genome sequences of the Splendidus clade species are rarely registered, which is one of the obstacles to predict core and/or unique genes responsible for their adaptation and pathogenicity, and to perform a fine scale meta-transcriptome during bacterial infection to their hosts. In this study, we obtained the complete genomes of all type strains in the Splendidus clade and revealed that (1) different genome sizes (4.4-5.9 Mb) with V. lentus the biggest and most of them had several big plasmids, likely because of the different features on mobilome elements; (2) the Splendidus clade consists of 19 species except V. cortegadensis, and 3 sub-clades (SC) were defined with the 15 most closely related members as SC1; (3) different carbohydrate degradation preferences may be the result of environmental adaptation; and (4) a broad prediction of virulence factors (VFs) revealed core and species unique VF genes.

Light is one of the most critical stimuli in the majority of living organisms. In the last two decades, blue light (BL) has become a major subject of attention because of developments in light-emitting diodes (LED). The effects of BL on eukaryotic organisms and phototrophic prokaryotes have been well studied, but the knowledge of its effects on non-phototrophic prokaryotes remains unclear. Since BL can penetrate seawater, it is expected that most prokaryotes living in the ocean possess molecular mechanisms which protect against BL. The aim of this study is to assess the molecular mechanisms of Vibrio parahaemolyticus cells against BL as a marine bacterial model compared to other wavelength light exposures. Physiological and transcriptomic analyses of BL-exposed cells compared to other light treated cells revealed the highest ROS fold change, the highest number of differentially expressed genes (DEGs), and up-regulation in the gene responsible to not only compatible solute such as glycine betaine and ectoine but also iron-sulfur biosynthesis related to ROS formation. Furthermore, red light (RL) up-regulated the expression of cryptochrome DASH, a protein known to be excited by BL, and orange light (OL) decreased the expression of thermostable direct hemolysin (TDH), suggesting that OL attenuates the virulence of V. parahaemolyticus. In addition, the expression of VtrA (V. parahaemolyticus type III secretion system 2 (T3SS2) regulator A) but not VtrB (V. parahaemolyticus T3SS2 regulator B) increased under both light treatments, indicating that light exposure is unlikely to be involved in T3SS2-mediated pathogenicity. These results expand our knowledge on unique light responses in non-phototrophic marine prokaryotes.

Time series of the number of infected individuals is measured to understand the dynamics of an infectious disease and to evaluate the effectiveness of countermeasures against it. However, in fish diseases, it is often difficult to record the time series of the infected fish owing to i) ambiguous clinical symptoms during the onset of disease and ii) cost of diagnosis. To address this issue, we established a mathematical modeling-based method to infer time series of the number of infected fish by coupling the experimental infection and field data on the outbreak of the disease. This method enables to reconstruct time series of the number of infected fish using mortality data obtained from the experimental infection. The reconstructed time series enables to estimate the transmissibility of fish diseases. We studied Oncorhynchus masou virus (salmonid herpesvirus 2) disease (OMVD) using Rainbow trout (Oncorhynchus mykiss) as a model for analysis and estimated the lethality rate of OMVD infection and the basic reproduction number (R0), i.e., transmissibility of OMVD. Our results revealed that larger fish (>= 200 g) showed a higher OMVD lethality rate and R0s when compared with smaller fish (<200 g). This suggests that high mortality among large fish does not inhibit the transmission of pathogen when compared with small fish.

Current growth in aquaculture production is parallel with the increasing number of disease outbreaks, which negatively affect the production, profitability, and sustainability of global aquaculture industry. Vibriosis is among the most common diseases that leads to massive mortality of cultured shrimp, fish, and shellfish in Asia. High incidence of vibriosis can occur in hatchery and growing‐out facilities, but juveniles are more susceptible to the disease. Various factors, particularly the source of fish, the environmental factors including water quality and farm management and the virulence factors of Vibrio influence the occurrence. Affected fish show weariness with necrosis of skin and appendages leading to body malformation, slow growth, internal organ liquefaction, blindness, muscle opacity, and mortality. Combination of control measures, particularly the disease‐free source of fish, biosecurity of the farm, improved water quality and other preventive measures such as vaccination might be able to control the infection. While some control measures are expensive and less practical, vaccination is effective, relatively cheap and easily implemented. In this review, latest knowledge on the pathogenesis and control of vibriosis, including vaccination are discussed.

Current growth in aquaculture production is parallel with the increasing number of disease outbreaks, which negatively affect the production, profitability, and sustainability of global aquaculture industry. Vibriosis is among the most common diseases that leads to massive mortality of cultured shrimp, fish, and shellfish in Asia. High incidence of vibriosis can occur in hatchery and growing‐out facilities, but juveniles are more susceptible to the disease. Various factors, particularly the source of fish, the environmental factors including water quality and farm management and the virulence factors of Vibrio influence the occurrence. Affected fish show weariness with necrosis of skin and appendages leading to body malformation, slow growth, internal organ liquefaction, blindness, muscle opacity, and mortality. Combination of control measures, particularly the disease‐free source of fish, biosecurity of the farm, improved water quality and other preventive measures such as vaccination might be able to control the infection. While some control measures are expensive and less practical, vaccination is effective, relatively cheap and easily implemented. In this review, latest knowledge on the pathogenesis and control of vibriosis, including vaccination are discussed.

Pathogenicity of a rainbow trout isolate RtNa-0010 of Oncorhynchus masou virus (OMV = salmonid herpesvirus 2) was investigated in salmonids and cyprinids. Immersion method was used to challenge three species of salmonid fish with RtNa-0010 and OMV reference strain 00-7812 at a dose of 100 TCID50/mL for 60 min. Cumulative mortality of rainbow trout was 3 and 51 of 51 fish when challenged with 00-7812 and RtNa-0010 respectively. When six salmonids and three cyprinids were challenged with RtNa-0010 (10(3)TCID(50)/fish) by intraperitoneal injection, mortality rates were 85%, 10% and 0% for rainbow trout, whitefish Coregonus lavaretus maraena and other tested fish respectively.

The success of the methods employed in the detection of Aeromonas salmonicida depends on several factors including detection limits which are not always considered when planning a diagnostic protocol. First, detection limits of A. salmonicida by Coomassie Brilliant Blue Agar (CBBA) culture, Immuno-Fluorescence Antibody Test (IFAT), Coagglutination test (CoAgT) and Polymerase Chain Reaction (PCR) were analyzed, then a controlled wet-lab experiment was conducted using 60 masu salmon (Oncorhynchus masou) fry inoculated with A. salmonicida and based on the results obtained, an epizootiological survey of selected rivers in Hokkaido was then conducted. Detection limits were 10^2 for CBBA, 10^4 for the IFAT, 10^5 for PCR and 10^3 for the CoAgT from an original de A. salmonicida broth culture of 1.3 x 10^8 CFU/mL demonstrating that CBBA and the CoAgT were better at detecting the bacteria at low concentrations. The wet-lab analysis produced results of detection limits of a similar trend, with CBBA, IFAT, PCR and CoAgT at 10^-3, 10^-3, 10^-1 and 10^-3 from kidney samples of 9.9 X 10^4 CFU/g respectively. The results from the epizootiological survey in Hokkaido showed positive from CBBA with IFAT, CoAgT and PCR corroborating them in varying degrees thus demonstrating the importance of a multi-diagnostic approach in scenarios of this nature.

The success of the methods employed in the detection of Aeromonas salmonicida depends on several factors including detection limits which are not always considered when planning a diagnostic protocol. First, detection limits of A. salmonicida by Coomassie Brilliant Blue Agar (CBBA) culture, Immuno-Fluorescence Antibody Test (IFAT), Coagglutination test (CoAgT) and Polymerase Chain Reaction (PCR) were analyzed, then a controlled wet-lab experiment was conducted using 60 masu salmon (Oncorhynchus masou) fry inoculated with A. salmonicida and based on the results obtained, an epizootiological survey of selected rivers in Hokkaido was then conducted. Detection limits were 10^2 for CBBA, 10^4 for the IFAT, 10^5 for PCR and 10^3 for the CoAgT from an original de A. salmonicida broth culture of 1.3 x 10^8 CFU/mL demonstrating that CBBA and the CoAgT were better at detecting the bacteria at low concentrations. The wet-lab analysis produced results of detection limits of a similar trend, with CBBA, IFAT, PCR and CoAgT at 10^-3, 10^-3, 10^-1 and 10^-3 from kidney samples of 9.9 X 10^4 CFU/g respectively. The results from the epizootiological survey in Hokkaido showed positive from CBBA with IFAT, CoAgT and PCR corroborating them in varying degrees thus demonstrating the importance of a multi-diagnostic approach in scenarios of this nature.

The success of the methods employed in the detection of Aeromonas salmonicida depends on several factors including detection limits which are not always considered when planning a diagnostic protocol. First, detection limits of A. salmonicida by Coomassie Brilliant Blue Agar (CBBA) culture, Immuno-Fluorescence Antibody Test (IFAT), Coagglutination test (CoAgT) and Polymerase Chain Reaction (PCR) were analyzed, then a controlled wet-lab experiment was conducted using 60 masu salmon (Oncorhynchus masou) fry inoculated with A. salmonicida and based on the results obtained, an epizootiological survey of selected rivers in Hokkaido was then conducted. Detection limits were 10^2 for CBBA, 10^4 for the IFAT, 10^5 for PCR and 10^3 for the CoAgT from an original de A. salmonicida broth culture of 1.3 x 10^8 CFU/mL demonstrating that CBBA and the CoAgT were better at detecting the bacteria at low concentrations. The wet-lab analysis produced results of detection limits of a similar trend, with CBBA, IFAT, PCR and CoAgT at 10^-3, 10^-3, 10^-1 and 10^-3 from kidney samples of 9.9 X 10^4 CFU/g respectively. The results from the epizootiological survey in Hokkaido showed positive from CBBA with IFAT, CoAgT and PCR corroborating them in varying degrees thus demonstrating the importance of a multi-diagnostic approach in scenarios of this nature.

This paper presents the methods of the development of fishing ports for the supplying of safe seafood products, based on the some rules on food hygiene control and on the eco-label system which is useful for fishery resource management in Japan. First, we analyzed the issue of the hygiene control for fresh fish on the distribution process from the landing places to the consumers and proposed the method to estimate the hygiene level with the two factors; the water quality, control and the sanitary condition of the working areas at the fishing ports, landing places and the auction halls on the distribution process. Secondly, we proposed the method to select whether fishery products contribute to being sustainable or not, so as to secure the validity of the sea food hygiene control at the fishing ports.

This paper presents the methods of the development of fishing ports for the supplying of safe seafood products, based on the some rules on food hygiene control and on the eco-label system which is useful for fishery resource management in Japan. First, we analyzed the issue of the hygiene control for fresh fish on the distribution process from the landing places to the consumers and proposed the method to estimate the hygiene level with the two factors; the water quality, control and the sanitary condition of the working areas at the fishing ports, landing places and the auction halls on the distribution process. Secondly, we proposed the method to select whether fishery products contribute to being sustainable or not, so as to secure the validity of the sea food hygiene control at the fishing ports.

Infectious salmon anemia (ISA) is a virus disease of Atlantic salmon Salmo salar in Europe and the Americas, but it has not been isolated in Far East Asia. In this study, we conducted virus isolation with ASK and ASE cells targeting ISA virus (ISAV) from a total of 5,967 fish belonging to eight salmonid species in Japan from 2005 to 2007. ISAV was not isolated from any fish examined but infectious hematopoietic necrosis virus was isolated from 116 fish belonging to three species, while infectious pancreatic necrosis virus was found in 14 fish from three species. It was considered that Japan is still free from ISAV.

Infectious hematopoietic necrosis virus (IHNV) is the causative agent of IHN, one of the most serious viral diseases of salmonid fish. A total of five major genogroups including JRt for Asian isolates were confirmed among worldwide isolates based on glycoprotein (G) gene nucleotide (nt) sequences. The present study revealed existence of new two lineages, JRt Shizuoka and JRt Nagano, in the genogroup JRt by addition of new isolates obtained in 2006. The maximum nt diversity of G gene within JRt Shizuoka or JRt Nagano lineage was 6.3% or 3.5%, while that between JRt Shizuoka and JRt Nagano lineages was 7.0%. To evaluate influence of the evolutional divergence to virulence of IHNV, experimental challenges to rainbow trout Oncorhynchus mykiss were conducted by bath exposure at 10^4 TCID50/mL of RtShiz06s and RtShiz06a (JRt Shizuoka lineage), RtNag96 and RtNag06a (JRt Nagano lineage), and ChAb76 (a representative of the genogroup U). Distinct difference was observed in IHNV virulence to rainbow trout, i.e. the highest virulence was in RtShiz06s and RtShiz06a (≥ 76% of mortalities), and subsequently in RtNag96 and RtNag06a (20-40%), but scarcely any virulence in ChAb76 (≤ 10%). Thus it was suggested that nt diversity of Japanese IHNV continued rapidly with changing its virulence in rainbow trout farm environments.

The survivability of koi herpesvirus (KHV) in environmental water and sediment was evaluated using CCB cells. Samples were collected from Ibaraki prefecture, Kanagawa prefecture and Hakodate, Hokkaido. Significant reduction in the infectious titer of KHV was observed within 3 days in intact environmental water or sediment. However, KHV infectivity remained for more than 7 days in autoclaved or filtered (0.45 mm) water. In the autoclaved water containing sediment, KHV infectivity dropped below detectable limits within 7 days after inoculation. Ten of the 147 bacterial strains from rivers in Kanagawa, and two of the 62 bacterial strains from water from, Hakodate showed anti-KHV properties. The results suggest that in the absence of hosts, KHV can be rapidly inactivated in environmental water.

A total 645 wild marine fish of 40 species were collected at the north (Wakkanai and Haboro), south (Hakodate) and east (Akkeshi) coasts of Hokkaido from 2000 to 2004 to conduct surveillance of fish viruses. Four fish cell lines (RTG-2, EPC, CHSE-214, FHM) were used for virus isolation from the brain, kidney and spleen of fish. Aquabirnavirus, which was identified as yellowtail ascites virus by a neutralization test, was isolated only from ten fish of four species caught at Akkeshi coastal area in 2002. These species were saffron cod Eleginus gracilis, snowy sculpin Myoxocephalus blandti, Japanese dace Tribolodon hakonensis and rainbow smelt Osmerus eperlanus mordax. Other viruses including viral hemorrhagic septicemia virus were not isolated.

Survival of three salmonid viruses and two marine fish viruses in fish rearing water or coastal sea water were observed at 0, 5, 10 and 15 ℃ for 7 or 14 days. Interaction between viruses and microorganisms present in the rearing water was observed. Infectious pancreatic necrosis virus (IPNV) and fish nodavirus (BF-NNV) were stable in waters used at every temperature tested for 14 days, but it was observed that, for infectious hematopoietic necrosis virus (IHNV), Oncorhynchus masou virus (OMV), and hirame rhabdovirus (HIRRV), as the temperature increased, the loss of infectivity also increased. When IHNV and OMV were suspended in filtrated and autoclaved rearing water, infectivity was reduced in comparison with the untreated water. Subsequently, adsorption of IHNV to mud or small particles was studied. IHNV adsorbed to several clays (kaolin, bentonite, Japanese acid clay) and diatomaceous earth in sterilized water with a wide range of pH (5-11) at concentrations of 1, 10, and 100 mg/mL. Except for bentonite, infectivity of clay-adsorbed IHNV persisted for at least 9 weeks. The clay-adsorbed IHNV also persisted in infectivity to rainbow trout Oncorhynchus mykiss, causing cumulative mortality rates of more than 73 %. Then, inactivation effects of UV irradiation, ozonization, and electrolyzation of water were studied against six fish rhabdoviruses, three fish herpesviruses, one fish birnaviruses, one fish iridovirus, and one fish nodavirus. Six rhabdoviruses, three herpesviruses, and lymphocystis disease virus were found to be sensitive to UV irradiation, ozonization, and electrolyzation. Susceptibility of IPNV, chum salmon virus (CSV), and BFNNV to UV was found to be low. IPNV and CSV were low sensitive to ozonization and electrolyzation. Virucidal effects of six kinds of disinfectants were examined against OMV, IPNV, IHNV, and HIRRV at 15 and 20℃ for 30 sec and 20 min. At 15℃ for 20 min, minimum concentrations showing 100 % plaque reduction of viruses tested by iodoph, Special Issue: International Symposium on Koi Herpesvirus Disease : Strategy for Koi Herpesvirus Disease Control. 13 March 2004. Yokohama, Japan.

Survival of three salmonid viruses and two marine fish viruses in fish rearing water or coastal sea water were observed at 0, 5, 10 and 15 ℃ for 7 or 14 days. Interaction between viruses and microorganisms present in the rearing water was observed. Infectious pancreatic necrosis virus (IPNV) and fish nodavirus (BF-NNV) were stable in waters used at every temperature tested for 14 days, but it was observed that, for infectious hematopoietic necrosis virus (IHNV), Oncorhynchus masou virus (OMV), and hirame rhabdovirus (HIRRV), as the temperature increased, the loss of infectivity also increased. When IHNV and OMV were suspended in filtrated and autoclaved rearing water, infectivity was reduced in comparison with the untreated water. Subsequently, adsorption of IHNV to mud or small particles was studied. IHNV adsorbed to several clays (kaolin, bentonite, Japanese acid clay) and diatomaceous earth in sterilized water with a wide range of pH (5-11) at concentrations of 1, 10, and 100 mg/mL. Except for bentonite, infectivity of clay-adsorbed IHNV persisted for at least 9 weeks. The clay-adsorbed IHNV also persisted in infectivity to rainbow trout Oncorhynchus mykiss, causing cumulative mortality rates of more than 73 %. Then, inactivation effects of UV irradiation, ozonization, and electrolyzation of water were studied against six fish rhabdoviruses, three fish herpesviruses, one fish birnaviruses, one fish iridovirus, and one fish nodavirus. Six rhabdoviruses, three herpesviruses, and lymphocystis disease virus were found to be sensitive to UV irradiation, ozonization, and electrolyzation. Susceptibility of IPNV, chum salmon virus (CSV), and BFNNV to UV was found to be low. IPNV and CSV were low sensitive to ozonization and electrolyzation. Virucidal effects of six kinds of disinfectants were examined against OMV, IPNV, IHNV, and HIRRV at 15 and 20℃ for 30 sec and 20 min. At 15℃ for 20 min, minimum concentrations showing 100 % plaque reduction of viruses tested by iodoph, Special Issue: International Symposium on Koi Herpesvirus Disease : Strategy for Koi Herpesvirus Disease Control. 13 March 2004. Yokohama, Japan.

This study was carried out for the purpose of establishing control methods for furunculosis affecting propagated salmon in Japan. We determined the distribution and prevalence of A. salmonicida among asymptomatic adult chum (Oncorhynchus keta), pink (O. gorbuscha) and masu salmon (O. masou) returning to rivers on the island of Hokkaido and on the mainland of Honshu. During 1979-2002, a total of 22,109 chum, pink and masu salmon were collected from the rivers in Hokkaido and Honshu. We isolated A. salmonicida from the chum salmon in 21 of the 34 rivers examined and the overall prevalence was 12.2 % in the infected stocks. The prevalence of the agent in pink salmon and masu salmon was 4.6 % and 1.4 % respectively. Using CBB medium, we also examined the chum salmon from the Chitose River catching site. The prevalence of the agent on gill surface was high (50%) at the catching site and decreased among fish in the holding pond in the river. The bacteria appear to be spread during fish migration in the river and during transportation of the fish from the capture site to the holding pond. Recently, the agent was isolated from the gill surface of chum salmon caught off the coast of the eastern part of Hokkaido, but the prevalence was low (1.7%). To control furunculosis in salmonids, the fish should be held for maturation in ponds under conditions of low density and the fish should be disinfected to prevent spread of furunculosis before placement in the holding pond., 10th International Symposium for Veterinary Epidemiology and Economics. 17-21 November 2003. Vina Del Mar, Chile.

This study was carried out for the purpose of establishing control methods for furunculosis affecting propagated salmon in Japan. We determined the distribution and prevalence of A. salmonicida among asymptomatic adult chum (Oncorhynchus keta), pink (O. gorbuscha) and masu salmon (O. masou) returning to rivers on the island of Hokkaido and on the mainland of Honshu. During 1979-2002, a total of 22,109 chum, pink and masu salmon were collected from the rivers in Hokkaido and Honshu. We isolated A. salmonicida from the chum salmon in 21 of the 34 rivers examined and the overall prevalence was 12.2 % in the infected stocks. The prevalence of the agent in pink salmon and masu salmon was 4.6 % and 1.4 % respectively. Using CBB medium, we also examined the chum salmon from the Chitose River catching site. The prevalence of the agent on gill surface was high (50%) at the catching site and decreased among fish in the holding pond in the river. The bacteria appear to be spread during fish migration in the river and during transportation of the fish from the capture site to the holding pond. Recently, the agent was isolated from the gill surface of chum salmon caught off the coast of the eastern part of Hokkaido, but the prevalence was low (1.7%). To control furunculosis in salmonids, the fish should be held for maturation in ponds under conditions of low density and the fish should be disinfected to prevent spread of furunculosis before placement in the holding pond., 10th International Symposium for Veterinary Epidemiology and Economics. 17-21 November 2003. Vina Del Mar, Chile.

Disinfection of water for aquaculture is critical for preventing the introduction and spread of infectious disease. A pathogen-free water source is essential for success in aquaculture. Typical treatment systems make use of high efficiency sand filters to clarify the water before treatment with ultraviolet (UV) light or ozonization. Fish pathogens are divided into two groups based on their sensitivity to UV and total residual oxidants (TROs) produced by ozonization of seawater. Hypochlorite produced by electrolysis of seawater (salt water) showed bactericidal and viricidal effects. This method can easily treat large volumes of water, and is suitable for disinfecting wastewater before discharging., International Commemorative Symposium, 70th Anniversary of The Japanese Society of Fisheries Science. 1-5 October 2001. Yokohama, Japan.