Tissue distribution of striped jack nervous necrosis virus (SJNNV) in adult striped jack.

Fluorescent antibody technique (FAT) and polymerase chain reaction (PCR) method were used to localize striped jack nervous necrosis virus (SJNNV, a nodavirus) in adult striped jack Pseudocaranx dentex. One group of brood stocks (N = 4) consisted of 13-yr-old spawners whose reproductive fluids were SJNNV-positive by the PCR test. The other group (N = 4) consisted of 4-yr-old fish which had not previously spawned whose reproductive fluids were negative by the PCR test. Positive FAT reactions using an anti-SJNNV rabbit serum were observed in the gonad, intestine, stomach, kidney, and liver of the 13-yr-old fish but not in the corresponding organs of the 4-yr-old fish. In neither group were the viral antigens detected in the spinal cord, brain, or retina tissues, the target organs of the virus in striped jack larvae. The FAT results were consistent with PCR results for the detection of the SJNNV coat protein gene. The present results suggest that SJNNV originates in various organs of striped jack spawners and is shed from the intestine and gonad, which results in contamination of eggs

Diagnostic and preventive practices for WSSV in Japan

White spot syndrome (WSS), considered equivalent to PAV (penaeid acute viremia) in Japan, has become the most serious problem not only in the farming industry but also in hatcheries for sea ranching of kuruma prawn, Penaeus japonicus. The prevalence of WSSV (white spot syndrome virus), the causative agent of WSS, was examined in wild kuruma prawn broodstocks by nested PCR (polymerase chain reaction). As a result, WSSV was detected at the highest prevalence (10.1%) in the ovary of female prawn. This result indicates that spawners are sources of infection. In 1997, brooders were pre-screened using PCR to detect WSSV before these spawned. WSSV was noted to occur in postlarvae obtained from brooders caught between July and August. In 1998 and 1999, eggs were selected based on WSSV detection by PCR from receptaculum seminis of spawned broodstock. Consequently, WSSV did not occur in their offsprings in both years. These results strongly indicate that selection of eggs based on PCR results is a practical way of controlling WSSV in hatcheries.We express gratitude to Messrs. Toru Furusawa, Younosuke Mizuta and other members of JASFA for their encouragement in this study. We also thank Drs. Kiyokuni Muroga and Toyohiko Nishizawa of Hiroshima University for their valuable suggestions and technical assistance

Studies on technical development of brood stock management in striped jack and yellowtail

目次 緒論 / p1 第1章 シマアジの成熟および産卵に関する親魚養成技術 / p4 　第1節 採卵用親魚の養成 / p4 　　1. 親魚の時期別養成管理 / p4 　　2. 寄生虫の駆除 / p5 　第2節 養成親魚の産卵誘発 / p6 　　1. 加温処理 / p8 　　2. 加温とホルモンの併用処理 / p8 　　3. 水温上限制御処理 / p10 　　4. 無処理 / p10 　　5. その他 / p13 　第3節 採卵とふ化仔魚の活力 / p15 　　1. 採卵方法の比較 / p17 　　2. 卵管理条件 / p20 　　3. 卵比重の変化 / p24 　　4. ふ化仔魚の活力判定 / p27 　第4節 まとめ / p39 第2章 シマアジのVNNに関する防除対策 / p41 　第1節 間接ELISAによる親魚血漿抗体の検出 / p43 　第2節 仔魚の発病に対する親魚の抗体価および産卵飼育方法の影響 / p51 　第3節 PCR法を用いたウイルス遺伝子の検出による産卵親魚の選別 / p59 　第4節 ヨード剤を用いた卵消毒によるVNN防除の試み / p68 　第5節 まとめ / p77 第3章 ブリの成熟および産卵に関する親魚養成技術 / p80 　第1節 採卵用親魚の養成と採卵技術 / p80 　　1. 親魚の養成管理 / p80 　　2. ホルモン処理による産卵誘発 / p82 　　3. 採卵と卵管理 / p86 　　4. 卵比重の変化 / p87 　　5. ふ化仔魚の活力判定 / p89 　第2節 産卵に及ぼす親魚養成餌料の影響 / p98 　　1. モイストペレット給餌の効果 / p98 　　2. ドライペレット給餌の効果 / p108 　第3節 卵の最終成熟および産卵に及ぼす長日化処理の影響 / p112 　第4節 まとめ / p123 謝辞 / p125 要約 / p126 引用文献 / p130 SUMMARY / p139広島大学(Hiroshima University)博士(農学)Agriculturedoctora

Lowered Phagocytosis in the Blood of Eels Exposed to Copper

致死濃度以下の銅液(100,250μg-Cu/l)に浸潰したニホンウナギ血漿コルチコステロイド量は, 12時間銅処理魚において最高値を示した。血中の白血球数(リンパ球, 顆粒球)は24時間銅処理魚において最も減少した。白血球の Edwardsiella tarda に対する食作用を in vitro で調べたところ, 24時間処理魚の白血球の食菌率は対照区のそれの半分程度に低下していた。以上の結果から, 先に報告した銅処理によるウナギの E. tarda などに対する感受性の増大は, ストレスの3次反応であり, 主として白血球の食菌作用の低下に起因するものと考えられた。In a previous paper, the authors reported that the susceptibilities of Japanese eel (Anguilla japonica) to Edwardsiella tarda and Pseudomonas anguilliseptica were increased by exposure to sublethal concentrations of copper (100 or 250 μg-Cu/l) for 24 or 48 hours, and this was interpreted as a tertiary response to stress. In the present study, primary and secondary responses to stress caused by copper exposure were investigated. The apparent increase of corticosteroids was observed in eels exposed to copper for 12 hours. The numbers of lymphocytes and granulocytes in the 24 hour-exposed eels decreased to one third of those of control fish. It was also demonstrated by an in vitro test that phagocytic rate of leucocytes in the blood of the stressed eels lowered against E. tarda but not against Vibrio anguillarum. From these results, the increased susceptibility to the pathogens is interpreted as due to lowered phagocytosis

シマアジVNNの予防法 : PCR法を用いたSJNNV遺伝子の検出による産卵親魚の選別

PCR法によるシマアジ親魚(生殖巣)からのウイルス性神経壊死症(VNN)原因ウイルス(SJNNV)遺伝子の検出結果と仔魚でのVNN発生との関係を検討した。その結果, VNNはウイルス陰性親魚群からの仔魚には発生せず, ウイルス陽性魚を含む親魚群の仔魚に発生した。また後者の親魚群からウイルス陽性魚を除去して産卵させて得た仔魚にはVNNは発生しなかった。従って, PCR法によるウイルス遺伝子の検出はVNN防除のための親魚選別に有効であると考えられた。A preventive trial of viral nervous necrosis (VNN) in larval striped jack Pseudocaraux dentex was made by selecting virus-free spawners based on the detection of the causative virus (SJNNV) gene by polymerase chain reaction (PCR) method. PCR detection of SJNNV gene from fish was done by amplifying the target sequence (T4: 426 bp) of the coat protein gene (RNA2). Four spawner groups, each consisting of 12 to 16 fish, were examined for the presence of SJNNV in their gonads just before spawning at one month intervals. Their offsprings (eggs and larvae) were subjected to rearing experiments to observe the occurrence of VNN. The SJNNV gene was detected from some spawners of these groups at the late spawnings. VNN occurred in larvae from spawner groups including SJNNV gene-positive fish, but not in larvae obtained from spawner groups which consisted of SJNNV gene-negative fish. These results suggest that the selection of striped jack spawners based on the detection of SJNNV gene from gonads by PCR just before spawning is efficacious for the prevention of vertical transmission of SJNNV in seed production