Dennis K Gomez

Hiroshima University, Hiroshima-shi, Hiroshima-ken, Japan

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Publications (25)19.56 Total impact

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    ABSTRACT: Aquabirnaviruses (ABVs) cause serious diseases in a variety of fish species used worldwide in aquaculture and have been isolated from a variety of healthy fish and shellfish species. The type species of ABV is Infectious pancreatic necrosis virus (IPNV), which is the causative agent of a highly contagious disease in juvenile salmonid fish. Marine birnaviruses (MABVs) have been isolated from various marine fish and shellfish. In Korea, ABV infection has been identified in several fish and shellfish. The current study presents sequence data from nested polymerase chain reaction products of 3 ABV strains obtained from different species of asymptomatic aquarium fish collected from a private commercial aquarium in Korea. Phylogenetic analysis of these strains, based on the partial nucleotide sequence of the VP2/NS junction, placed them within the genogroup VII (95-99% bootstrap confidence), which also contains MABV. The subclinically infected fish may be a source of MABV infection for other susceptible fish species inside the aquarium and potentially represent a serious challenge for the management of MABV infections. Additionally, the presence of MABV in these subclinically infected aquarium fish imported from other countries indicates that there is a need for the establishment of appropriate quarantine practices.
    Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc 03/2011; 23(2):325-9. · 1.18 Impact Factor
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    ABSTRACT: The presence of koi herpesvirus (KHV) was confirmed in three ornamental koi broodstocks for breeding purposes. The broodstocks showed poor appetite, lethargy, abnormal swimming behavior with gasping movements in shallow water and increased mucus secretion. Histopathologically, the gill showed diffuse necrosis of the branchial epithelial cells and diffuse lymphocytic–monocytic interstitial nephritis with necrosis of the tubular epithelial cells predominantly found in these three broodstocks. The presence of viral intranuclear inclusion bodies were also observed. KHV was not isolated using KF-1 cell line but PCR positive results at 484bp DNA product was confirmed in all organs of the fish and quatification of KHV genomic DNA using real-time Taqman PCR in all organs ranged from 1.32×10−9 to 1.39×10−9 copy numbers. The analysis of sequencing data of 484bp fragments of KHV DNA of three Korean isolates revealed 100% identities with each other and closely related (98 to 99%) to the known CyHV-3 type of KHV. This report confirmed the presence of KHV infection in one koi commercial farm in South Korea using pathological and molecular methods.
    Aquaculture. 01/2011; 311(1):42-47.
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    ABSTRACT: In order to evaluate the genetic variability of the causative agent of cold water disease (CWD), plasmid profiling was used to characterize Flavobacterium (F.) psychrophilum isolates (n = 169). Size analysis of plasmids in F. psychrophilum isolates (n = 128) from several fish species demonstrated that six kinds of plasmids were harbored, and ayu isolates had different profiles compared to other isolates. Moreover, multiple isolates (n = 41) from CWD outbreaks in 2002 to 2003 at a single ayu farm were examined to determine differences between isolates from successive outbreaks and showed different profiles by the sources of seedlings.
    Journal of veterinary science (Suwŏn-si, Korea) 03/2010; 11(1):85-7. · 0.89 Impact Factor
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    ABSTRACT: A total of 360 samples of trash fish/mollusk used for feeding cultured marine fish were collected from 4 stations of National Research Institute of Aquaculture, Fisheries Research Agency, Japan. The brain or eyes of the samples were examined by reverse transcription-polymerase chain reaction (RT-PCR) and nested PCR assays to detect the coat protein gene of betanodavirus. Two species of trash fish/mollusk samples: Japanese jack mackerel Trachrus japonicus and Japanese common squid Todarodes pacificus were positive for betanodavirus and the sequences of the nested PCR products (177 nucleotides) of these two species were closely related (98%) to the redspotted grouper nervous necrosis virus (RGNNV) genotype. Sevenband grouper Epinephelus septemfasciatus were intramuscularly injected (106 TCID50/fish) with betanodavirus isolates from trash fish/mollusk samples. The fish displayed abnormalities typical of viral nervous necrosis (VNN) infection, and mortalities ranged from 90 to 100%. These results suggest that trash fish/mollusk can be a source of betanodaviruses for cultured fish and that they pose a serious risk for outbreaks of VNN in susceptible cultured fish.
    Aquaculture. 01/2010; 302(3):158-163.
  • Journal of the World Aquaculture Society 01/2010; 41:139-144. · 0.75 Impact Factor
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    ABSTRACT: The Egyptian fruit-bat Rousettus aegyptiacus which had been raised at the private commercial aquarium in Seoul, Korea for indoor exhibition was found dead and submitted to College of Veterinary Medicine, Seoul National University for postmortem examination. A pure bacterium of Kluyvera ascorbata was isolated from the blood specimen. The isolation of K. ascorbata from fruit bat is very important, because it is the most infectious agent of the genus Kluyvera that cause serious diseases to animals and human. Fruit-bats which are distributed in pet shops through black-market in Korea although unproven become popular pet nowadays. This situation enhances chance of zoonosis. This paper describes the first isolation of K. ascorbata from the Egyptian fruit-bat.
    Journal of Veterinary Medical Science 11/2009; 72(1):85-7. · 0.88 Impact Factor
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    ABSTRACT: In order to investigate methods for controlling systemic bacterial coldwater disease (CWD), bacteriophages that infect Flavobacterium psychrophilum were isolated by the enrichment method from pond water collected from Japanese ayu farms. The five phages isolated were classified as members of Myoviridae (PFpW-3, PFpC-Y), Podoviridae (PFpW-6, PFpW-7), and Siphoviridae (PFpW-8) and had highly variable patterns of infectivity for different F. psychrophilum isolates (n=128). The stability tests of the phages in different waters, pHs and temperatures were assessed, and the results indicated that none of the phages were affected by ayu farm conditions. Among the phages, PFpW-3 had high infectivity for F. psychrophilum isolated from ayu and other fish and demonstrated sufficient survivability in the stability tests. Thus, PFpW-3 and its indicator strain N2-3 were inoculated into cytophaga broth at different doses of multiplicity of infection (MOI) and proved to be efficient for the reduction of bacterial growth. This study may be the basis for a further evaluation of phage therapy in the treatment of CWD in Japanese ayu farms.
    Veterinary Microbiology 08/2009; 140(1-2):109-15. · 3.13 Impact Factor
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    ABSTRACT: Diseased wild redspotted grouper Epinephelus akaara were collected from Seto Inland Sea, Ehime Prefecture, in August 2002. Fish showed erratic swimming behavior and inflation of the swim bladder. The fish brains were positive for nodavirus in both RT-PCR and nested PCR. The sequence of the nested PCR product (177 nt) was closely related to that of a known betanodavirus, redspotted grouper nervous necrosis virus. When juvenile sevenband grouper E. septemfasciatus were challenged intravitreously with virus, abnormal swimming behavior and high mortality were observed. This is the first report on viral nervous necrosis in a wild population of redspotted grouper with clinical signs.
    Archives of Virology 02/2009; 154(2):343-6. · 2.28 Impact Factor
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    ABSTRACT: The zebra shark Stegostoma fasciatum which had been reared in the commercial aquaria was found dead and submitted for postmortem examination. A pure bacterial culture was isolated from pale and enlarged liver. The analysis of ureC and 16S rRNA genes confirmed the isolate as Photobacterium (P.) damselae subsp. damselae and this pathogen was sensitive to gentamicin. Although, no mortality in mouse was observed in the experimental infection study, the isolation of this pathogen in aquarium fish is significant because it can act as a reservoir to other aquatic animals and can also be zoonotic potential to human during aquarium management. This paper describes the first isolation of P. damselae subsp. damselae from zebra shark.
    Korean Journal of Veterinary Research. 01/2009; 49(1).
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    ABSTRACT: One of the most important factors determining the success of the development of cloned embryos is the cell cycle stage of the donor cells. We investigated the effects of serum starvation, culturing to confluence and roscovitine treatment on the cell cycle synchronization of goldfish caudal fin-derived fibroblasts by flow cytometric analysis. The results show that culturing the cells to confluence (85.5%) and roscovitine treatment (82.71%) yield a significantly higher percentage of cells arrested in the G0/G1 (P<0.05) phase than serum starvation (62.85%). Different concentrations of roscovitine (5, 10, or 15 microM) induce cell cycle arrest at the G0/G1 phase.
    Cell Biology International 10/2008; 33(1):65-70. · 1.64 Impact Factor
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    ABSTRACT: Betanodaviruses causing viral nervous necrosis (VNN) have been detected and isolated from several species of cultured marine fish worldwide. In Korea, VNN was identified in several species of cultured marine fish. This study presents data on the amplified nested PCR product (420 bp) of 11 nodavirus strains from different species of apparently healthy aquarium fish and invertebrates collected in one private commercial aquarium in Korea. Phylogenetic analyses based on the partial nucleotide sequence (177 bases) of the RNA2 coat protein gene were identical to the redspotted grouper nervous necrosis virus (RGNNV) genotype (96%-100%). The presence of the RGNNV type of betanodaviruses in these subclinically infected aquarium fish and invertebrates imported from different countries probably indicates that the samples were contaminated inside the aquarium and represents a serious challenge for its management of viral nervous necrosis. These positive samples can be an inoculum source of betanodavirus infection to other susceptible fish species inside the aquarium.
    Current Microbiology 06/2008; 56(5):499-504. · 1.52 Impact Factor
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    ABSTRACT: One hundred eighteen samples (21 species) of wild marine invertebrates were collected from western and southern coastal area of Korean Peninsula. Four of 78 (18 species) samples collected at Namhae (South) area were positive for nodavirus in nested PCR test. Of the 40 samples (5 species) collected at Hwanghae (West) areas, all samples were negative for nodavirus in both RT-PCR and nested PCR tests. Positive nested PCR results were obtained from the following species: Charybdis bimaculata Charybdid crab; Pandalus hypsinotus Southern humpback shrimp and Mytilus galloprovincialis Mediterranean mussel. Phylogenetic analysis based on the partial nucleotide sequence (177 bases) of the RNA2 coat protein gene showed that the four strains were highly homologous (100%) and closely related to that of the known betanodaviruses, redspotted grouper nervous necrosis virus (RGNNV). These results indicate that nodavirus is present from wild marine invertebrates in the southern coastal areas of Korean Peninsula. These subclinically infected marine invertebrates may constitute an inoculum source for betanodavirus infection and cause mortality in cultured fishes in Korea.
    Journal of Invertebrate Pathology 04/2008; 97(3):197-202. · 2.67 Impact Factor
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    ABSTRACT: Viral nervous necrosis (VNN) is a worldwide disease affecting several species of cultured marine fish. In Korea, VNN has been identified in several species of cultured marine fish. In this study, the authors present data of the amplified nested polymerase chain reaction product (420 bp) of 21 nodavirus strains from different species of apparently healthy wild marine fish on the southern coast of Korea. Phylogenetic analysis based on the partial nucleotide sequence (177 bases) of the RNA2 coat protein gene of 21 strains was highly homologous (93-100%) and closely related to that of the known betanodavirus, redspotted grouper nervous necrosis virus. These results indicate that betanodaviruses occur in large populations of wild marine fish in the southern part of the Korean peninsula, suggesting the importance of these subclinically infected fish as an inoculum source of betanodavirus that is horizontally transmitted to susceptible cultured fish species.
    Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc 02/2008; 20(1):38-44. · 1.18 Impact Factor
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    ABSTRACT: Betanodaviruses are the causative agents of viral nervous necrosis (VNN) in cultured marine fish. A total of 237 apparently healthy aquarium fish, marine (65 species) and freshwater (12 species) fishes and marine invertebrates (4 species), which were stocked in a commercial aquarium in Seoul, South Korea, were collected from November 2005 to February 2006. The brains of the fish and other tissues of the invertebrates were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR to detect betanodavirus. Positive nested PCR results were obtained from the brains of 8 marine fish species (shrimp fish Aeoliscus strigatus, milkfish Chanos chanos, three spot damsel Dascyllus trimaculatus, Japanese anchovy Engraulis japonicus, pinecone fish Monocentris japonica, blue ribbon eel Rhinomuraena quaesita, look down fish Selene vomer, yellow tang Zebrasoma flavesenes), 1 marine invertebrate species (spiny lobster Pamulirus versicolor), and 2 freshwater fish species (South American leaf fish Monocirrhus polyacanthus and red piranha Pygocentrus nattereri). The detection rate in nested PCR was 11/237 (4.64%). These subclinically infected aquarium fish and invertebrates may constitute an inoculum source of betanodaviruses for cultured fishes in the Korean Peninsula.
    Journal of Veterinary Science 01/2007; 7(4):369-74. · 0.93 Impact Factor
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    ABSTRACT: The possibility of trash fish food-direct pathogen infection to cultured flounder is a very important concern of fish farmers in Korea. A total of 26 groups of trash fish and shrimp samples were collected from 11 hatcheries on Jeju Island. Four groups and two groups of homogenized frozen trash fish samples were directly isolated and confirmed by PCR assays with S. iniae and S. parauberis, respectively. One iridovirus PCR positive result was obtained from one group of mixed trash fish samples. Phylogenetic analysis based on the MCP gene from one iridovirus strain was genetically closely related to seabass, red sea bream, rock bream, turbot, and Korean flounder iridovirus. Betanodaviruses were not detected from the trash fish samples. Based on these results, trash fish can be one of the sources or carriers of bacterial and viral pathogens for feeding cultured flounder in Korea.
    Aquaculture. 01/2007; 272(1):105-110.
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    ABSTRACT: Streptococcus sp. is gram-positive coccus that causes streptococcal infections in fish due to intensification of aquaculture and caused significant economic losses in fish farm industry. A streptococcal infection occurred from cultured diseased olive flounder (Paralichthys olivaceus) in May, 2005 at a fish farm in Jeju Island, Korea. The diseased flounder exhibited bilateral exophthalmic eyes and rotten gills; water temperature was 16-18 degrees C when samples were collected. Of the 22 fish samples collected, 3 samples were identified as Lactococcus garvieae and 18 samples were identified as Streptococcus parauberis by culture-based, biochemical test. Serological methods such as slide agglutination, hemolysis and antimicrobial susceptibility test were also used as well as multiplex PCR-based method to simultaneously detect and confirm the pathogens involved in the infection. S. parauberis and L. garvieae have a target region of 700 and 1100 bp., respectively. One fish sample was not identified because of the difference in the different biochemical and serological tests and was negative in PCR assay. In the present study, it showed that S. parauberis was the dominant species that caused streptococcosis in the cultured diseased flounder.
    Journal of Veterinary Science 04/2006; 7(1):53-8. · 0.93 Impact Factor
  • Fish Pathology - FISH PATHOL. 01/2006; 41(4):171-173.
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    ABSTRACT: An acute mortality caused by an uncertain agent occurred in wild golden grey mullet (Liza auratus) population in the Iranian side of the Caspian Sea in February, 2004. Clinical signs of the moribund fish were erratic behavior such as spiral swimming, belly-up at rest and over inflation of swim bladder. Histological examination of brain of dead fish revealed hyperaemia, degeneration and necrosis in external granular layers as well as focal extension in intestine. Severe leucopenia was also observed. No putative causal factors were suggested by bacteriological, parasitological or environmental examinations. In virological examinations, however brains of affected golden grey mullet were positive in the reverse transcriptase-polymerase chain reaction test for piscine nodavirus (Nodaviridae, Betanodavirus), the causative agent of Encephalopathy and retinopathy (VER), otherwise known as viral nervous necrosis (VNN) in a variety of cultured marine fishes worldwide. Nucleotide sequence of the PCR amplicons is closely related with the coat protein gene of piscine nodaviruses, particularly redspotted grouper nervous necrosis virus (RGNNV). Although, it was not succeeded to isolate the virus, experimental infection with the brain homogenates of the affected fish in sevenband grouper (Epinephelus septemfasciatus), which is highly susceptible to RGNNV, produced neurological abnormality followed by mortality. These results suggest that the mortality observed in golden grey mullet in the Caspian Sea might have been associated with piscine nodavirus infection.
    Iranian Journal Fisheries Science (IJFS). 01/2005; 4:pp: 43-58.

Publication Stats

140 Citations
19.56 Total Impact Points

Institutions

  • 2004–2013
    • Hiroshima University
      • Graduate School of Biosphere Sciences
      Hiroshima-shi, Hiroshima-ken, Japan
  • 2011
    • University of the Philippines Visayas
      • Institute of Aquaculture
      Miagao Town, Western Visayas, Philippines
  • 2007–2011
    • Seoul National University
      • College of Veterinary Medicine
      Seoul, Seoul, South Korea
  • 2006
    • Pukyong National University
      • Department of Oceanography
      Pusan, Busan, South Korea