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NO42 - 3

Identification of Additional Quantitative Trait Loci (QTL) Responsible for Susceptibility to Infectious Pancreatic Necrosis Virus in Rainbow Trout

<>Akiyuki Ozaki1, 2*, Sok-Kean Khoo2, 3, Yasutoshi Yoshiura4, Mitsuru Ototake4, Takashi Sakamoto2, Johannes Martinus Dijkstra4, 5 and Nobuaki Okamoto2<>1 National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan
2 Faculty of Marine Science, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan
3Laboratory of Cancer Genetics, Van Andel Institute, Grand Rapids, Michigan 49503, USA
4 Tamaki Station, National Research Institute of Aquaculture, Fisheries Research Agency, Tamaki, Mie 519-0423, Japan
5Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan
(Received March 13, 2007)
ABSTRACT猶revious typing of microsatellite markers in a BC1F1 backcross rainbow trout Oncorhynchus mykiss revealed two quantitative trait loci (QTL) with a significant impact on susceptibility to infectious pancreatic necrosis. In the present study, additional genetic markers were mapped using the same strain in order to increase QTL resolution. A total of 199 individuals were screened at 226 marker loci (106 microsatellites, 116 amplified fragment length polymorphism markers, classical major histocompatibility complex molecules [MHC class I, nonclassical MHC class I, MHC class II] and tyrosinase) and the QTL were determined by single-point and interval mappings. Seven QTL were distinguished in the linkage groups RT-11, 12, 17, 23, 26, 29 and 31, in addition to the two already known in RT-3 and 22. The major QTL were those in RT-3, 12 and 22; whereas the classical MHC class I locus Onmy-UBA and the MHC class II locus Onmy-DAB were not associated with any of the QTL, a nonclassical MHC class I region with Onmy-UCA, Onmy-UDA, and Onmy-UEA mapped to the major QTL on RT-3.

Keywords: quantitative trait loci, QTL, infectious pancreatic necrosis,錨isease resistance, Oncorhynchus mykiss, major histocompatibility complex, IPN, MHC

Mass Mortality of Cultured Kuruma Prawn Penaeus japonicus Caused by Vibrio nigripulchritudo

<>Takamitsu Sakai1*, Tatsumu Hirae2, Kei Yuasa1, Takashi Kamaishi1, Tomomasa Matsuyama1, Satoshi Miwa3, Norihisa Oseko1 and Takaji Iida1<>1National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan
2Kagoshima Prefectural Fisheries Technology and Development Center, Ibusuki, Kagoshima 891-0315, Japan
3Tamaki Station, National Research Institute of Aquaculture, Fisheries Research Agency, Tamaki, Mie 519-0423, Japan
(Received April 9, 2007)

ABSTRACT輸 mass mortality of cultured kuruma prawn Penaeus japonicus occurred in Kagoshima Prefecture in June, 2005. Affected prawns displayed a sluggish behavior or swimming on their side. The mean water temperature during the disease outbreak was 27゚C. A black pigment-producing bacterium was isolated from the diseased prawns and was identified as Vibrio nigripulchritudo by bacteriological tests, 16S rDNA sequence analysis and DNA array for discrimination of Vibrio species. High pathogenicity of the isolated bacterium to healthy kuruma prawn was confirmed by intramuscular injection. This is the first report of V. nigripulchritudo infection in kuruma prawn.

Key words: Vibrio nigripulchritudo, Penaeus japonicus, black pigment, mass mortality, kuruma prawn

Comparison of Susceptibility to Kabatana takedai (Microspora) among Salmonid Fishes

<>Seiji Miyajima1, Shigehiko Urawa2, Hiroshi Yokoyama1* and Kazuo Ogawa1<>1Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
2National Salmon Resources Center, Fisheries Research Agency, Sapporo 062-0922, Japan
(Received May 25, 2007)

ABSTRACT揖abatana takedai (Microspora) is known as an enzootic pathogen of salmonids in limited water systems such as the Chitose River in Hokkaido, northern Japan. In this study, susceptibility to K. takedai was compared among masu salmon Oncorhynchus masou originating from the Chitose River, Shiribetsu River and Shari River, and rainbow trout O. mykiss from Shizuoka Prefecture, Japan. After exposure of fish to the Chitose River water, cysts of K. takedai in the heart and trunk muscle were examined by microscopy. Prevalence and intensity of infection were not considerably different among the three populations of masu salmon, whereas rainbow trout was more susceptible to K. takedai than masu salmon, particularly in the heart. A newly developed PCR test showed the higher percentage of fish with pre-cyst stage of K. takedai in the heart of rainbow trout than in masu salmon, suggesting that K. takedai established the cardiac infection at early stages more in rainbow trout than in masu salmon. A histopathological observation indicated that K. takedai infection in the heart caused granulomatous inflammation characterized by fibrinoid degeneration, but there was no difference in the progress of the inflammation between the two fish species.

Key words: Kabatana takedai, microsporidian, susceptibility, Oncorhynchus masou, Oncorhynchus mykiss, salmonid, masu salmon, rainbow trout

The Resistance of Ayu Plecoglossus altivelis Recovered from Bacterial Coldwater Disease against Reinfection with Flavobacterium psychrophilum

<>Hiroaki Kintsuji*, Michitaka Yamamoto and Koji Ninomiya<>Shiga Prefectural Experimental Station, Hikone, Shiga 522-0057, Japan

(Received September 22, 2006)

ABSTRACT輸yu Plecoglossus altivelis that survived from bacterial coldwater disease (BCWD) were reinfected with Flavobacterium psychrophilum. Artificial reinfection challenge showed that the survival rate of ayu recovered from BCWD was significantly higher (84%) than that of naive ayu (2%) or ayu immunized with FKC vaccine (18%).

Key words: bacterial coldwater disease, Flavobacterium psychrophilum, disease resistance, Plecoglossus altivelis, ayu

Distribution of Nervous Necrosis Virus in Orange-Spotted Grouper Epinephelus coioides with Asymptomatic Infection

<>Ikunari Kiryu1,2*, Leobert D. de la Pe3 and Yukio Maeno4<>1Fisheries Division, Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan
2National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan
3Aquaculture Department, Southeast Asian Fisheries Development, Center Tigbauan 5021, Iloilo, Philippines
4Seikai National Fisheries Research Institute, Fisheries Research Agency, Taira, Nagasaki 851-2213, Japan

(Received December 31, 2006)

ABSTRACT優istribution of nervous necrosis virus in asymptomatically infected orange-spotted grouper Epinephelus coioides was determined by PCR assay in this study. Fourteen different tissues and organs were collected from apparently healthy groupers including seven individuals of broodstock and 17 juveniles with body weight ranging from 4 to 12 kg and from 2 to 9 g, respectively. No cytopathic effects were found in E-11 cells inoculated with filtrates of sample homogenates. However, all the broodstock and juveniles were positive by nested PCR test except for one juvenile. One hundred percent detection rate of the virus was obtained only from the brain.

Keywords: viral nervous necrosis, Epinephelus coioides, distribution, orange-spotted grouper, broodstock