魚病研究
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51 巻 , 3 号
選択された号の論文の8件中1~8を表示しています
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総説
  • 飯田 貴次, 坂井 貴光, 高野 倫一
    51 巻 (2016) 3 号 p. 87-91
    公開日: 2016/10/07
    ジャーナル フリー
    Edwardsiellosis in fish caused by Edwardiella tarda and E. ictaluri is reviewed. Genus Edwardsiella belongs to the Enterobacteriaceae family, and E. tarda produces both hydrogen sulfide and indole, whereas E. ictaluri does neither. E. tarda was first isolated from diseased eel in Japan, and infects freshwater fish as well as marine fish. E. ictaluri has been detected in only freshwater fish after described as a new species from diseased channel catfish in the United States. The two pathogens survive in phagocytic cells, and hosts affected with edwardsiellosis die from septicemia. There were no reports about E. ictaluri infection in Japan before E. ictaluri was isolated from diseased wild ayu in 2007. Recently, the vaccine against edwardsiellosis of Japanese flounder was officially approved in Japan.
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  • 白樫 正, 小川 和夫
    51 巻 (2016) 3 号 p. 92-98
    公開日: 2016/10/07
    ジャーナル フリー
    Fish blood flukes (FBFs) are the most important digenean parasites in marine finfish aquaculture due to their high pathogenicity. Numerous eggs accumulate in gill lamellae and capillary vessels in various organs, interfere the blood flow. This causes fish to suffocate to death or leads to other fatal health problems. In Japan, important culture fish, such as amberjacks, bluefin tuna and tiger puffer are affected by FBFs of different taxa; namely Paradeontacylix spp., Cardicola spp. and Psettarium spp., respectively. FBFs are relatively host specific and utilize a complex two-host lifecycle. To date, the lifecycles have been elucidated for only a handful marine FBF species and all use terebellid polychaetes as the intermediate host. Chemotherapy with the oral treatment of praziquantel is effective and commonly used in fish farms as a sole control measure against FBFs. The development of prevention method is expected with the recent advances in knowledge on the biology of FBFs.
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  • 湯浅 啓
    51 巻 (2016) 3 号 p. 99-102
    公開日: 2016/10/07
    ジャーナル フリー
    Koi herpesvirus (KHV) disease caused by cyprinid herpesvirus 3 (CyHV-3) affects carp Cyprinus carpio and its varieties. The disease is listed by the OIE and is also designated as “Specific diseases” in a Japanese law. In Japan, the disease first occurred in 2003 and has quickly spread to all prefectures by distributing infected fish. This review describes basic information on KHV/KHV disease such as its pathogenicity, diagnostic methods, control measures and status of virus distribution in Japan.
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論文
  • 今城 雅之, 森光 一幸, 助田 将樹, 梅﨑 拓也, 門野 真弥, 合田 暉, 久保 栄作, 大嶋 俊一郎
    51 巻 (2016) 3 号 p. 103-111
    公開日: 2016/10/07
    ジャーナル フリー
     高知県野見湾のC. irritansの分布と動態を,5.8S rRNAのTaqManリアルタイムPCRにより調べた。10月に行った20時間の連続測定では,午前4時に最も高いコピー数が得られた。10月上旬と11月下旬に湾口部の漁場のカンパチ生簀で海産白点病が発生したが,この間,被害のあった生簀近傍では,5.8S rRNA遺伝子の平均コピー数から,4,465~6,590虫体/Lの存在が推定された。また,湾奥部に位置する別の漁場でも同程度のコピー数が11月20日と12月16日に検出され,底泥における 5.8S rRNA遺伝子の検出頻度は同漁場で最も高くなり,シストの分布は潮流の影響を受けていると推測された。18S rRNA-ITS1 領域の分子系統解析から,感染漁場のC. irritansは中国分離株を主とするグループに属しており,カンパチ種苗の輸入に伴う中国南部からの持ち込みが疑われた。
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  • Yuho Watanabe, Sayoko Nishida, Kosuke Zenke, How Kah Hui, Naoki Itoh, ...
    51 巻 (2016) 3 号 p. 112-120
    公開日: 2016/10/07
    ジャーナル フリー
    We investigated the development of the macronucleus of Cryptocaryon irritans, and the ingestion and digestion of host cells by the parasite. All developmental stages of the parasite except the theront (trophont, protomont and tomont) were examined with histological staining and/or whole-mount staining. The sections were also subjected to in situ hybridization targeting the 18S rRNA gene of the host fish. The macronucleus developed negligibly, maintaining its four-segmented shape in trophonts, elongated and formed a massive nucleus in tomonts before cell division, and subsequently underwent repeated divisions to generate theronts. Denatured host cells, examined in situ hybridization, were accumulated in trophonts, and disappeared in tomonts by the beginning of cell division. Denatured host cells were also observed in the host tissue surrounding trophonts. They had condensed nuclei. Protomonts filled with denatured host cells presented a 180-bp DNA ladder in gel electrophoresis, suggesting apoptosis of the host cells. These results indicate that DNA synthesis occurs exclusively in the early stage of the tomont and that host cells are fed and accumulated, probably as apoptotic cells, in the trophont and are digested in the early tomont stage.
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