魚病研究
Online ISSN : 1881-7335
Print ISSN : 0388-788X
ISSN-L : 0388-788X
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論文
  • Kaho Araki, Issei Nishiki, Terutoyo Yoshida
    原稿種別: Research Article
    2024 年 59 巻 4 号 p. 119-126
    発行日: 2024/12/15
    公開日: 2024/12/28
    ジャーナル 認証あり HTML

    Lactococcus garvieae serotype III, a newly emerging pathogen that causes lactococcal infection, has been detected in fish farms since 2021. This pathogen has caused severe damage to the striped jack Pseudocaranx dentex and greater amberjack Seriola dumerili. This study collected strains from various fish species on farms between 2021 and 2023 and conducted an epidemiological and characterization study of L. garvieae serotype III using biochemical characterization tests, agglutinating titers against diagnostic antisera, biased sinusoidal field gel electrophoresis (BSFGE), and drug susceptibility tests. Capsule-like structures were found on the cell surfaces of L. garvieae serotype III strains, and strains showed similar characteristics except for the reaction of acidification ribose in biochemical characterization test using the API 20 STREP system. All strains were agglutinated with antiserum raised against L. garvieae serotype III and lower or non-agglutinated with antiserum raised against L. garvieae serotype I. BSFGE analysis identified three types of electrophoretic pattern: A, B, and C. BSFGE types A and B spread to fish farms in 2021, while type C found in 2022. All strains analyzed in this study were thought to be resistant to lincomycin but not to erythromycin.

  • Yuta Matsuura, Tomoaki Yoshino, Yoshiko Shimahara, Ikki Yamamoto, Nats ...
    原稿種別: Research Article
    2024 年 59 巻 4 号 p. 127-134
    発行日: 2024/12/15
    公開日: 2024/12/28
    ジャーナル 認証あり HTML

    We investigated the antibody dynamics at different growth stages of Japanese amberjack Seriola quinqueradiata to determine the timing of first IgM production. Vaccination trials of juveniles were then conducted using a formalin-inactivated Vibrio anguillarum serotype J-O-3 vaccine to characterize the changes in vaccine-specific IgM and efficacy at each growth stage. In whole-body analyses, although total IgM was slightly detected at 1 day post-hatching (dph), it was undetectable until 15 dph and then increased from 23 to 57 dph. Levels of IgM specific to V. anguillarum J-O-3 were significantly elevated in fish vaccinated at and after 60 dph. Relative percentage survival of vaccinated fish was 52.6% and 100% at 51 dph and ≥61 dph, respectively. These results suggest that the IgM response to the vaccine developed between 51 and 60 dph (body weight: 0.45 ± 0.04 to 1.15 ± 0.06 g; standard length: 2.68 ± 0.09 to 3.90 ± 0.08 cm), coinciding with the increase in vaccine efficacy. These data also suggest that development of the humoral immunity was delayed from the initiation of IgM production.

短報
情報
  • 四宮 陽一, 田頭 亮臣, 河野 啓介
    原稿種別: 情報
    2024 年 59 巻 4 号 p. 143-146
    発行日: 2024/12/15
    公開日: 2024/12/28
    ジャーナル 認証あり HTML

    宇和海中部海域の既存漁場から距離が離れた避難漁場において,アコヤガイ稚貝の夏季萎縮症に関するモニタリング調査を実施した。既存漁場では水温19°C以上となった5月下旬に本病の原因であるPinctada birnavirus(PiBV)が検出され,外套膜萎縮を呈する個体が増加した。避難漁場では検出されるウイルスゲノムコピー数の増加時期が遅れ,ゲノムコピー数が高い期間が短く,外套膜萎縮を呈する個体も少なかった。既存漁場では,外套膜萎縮を呈する個体が認められたのちに死亡するケースが目立った。また,外套膜萎縮が観察された期間は稚貝の成長が停滞し,発病貝が見られなくなると成長が回復する傾向が認められた。稚貝の死亡はPiBVの増加および発症に遅れて発生することから,PiBVの量的検出や症状の定期的な調査により,死亡時期の予測が可能と考えられた。さらに,避難漁場の設置は発病の低減と成長の向上が期待でき,本症の対策の1つとして有効と思われた。

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