Disease mechanisms of emaciation disease of tiger puffer

虎河豚消瘦病发病机制

• 批准号: 12460084
• 负责人: OGAWA Kazuo
• 金额: $ 8.77万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12460084/
• 关键词: myxosporean; tiger puffer; parasites; histopathology; osmotic regulation; aquaculture; Myxidium; Leptotheca; 浸透圧調節

1) Parasitological examinations of myxosporeans from the intestine of emaciated tiger puffer were conducted, and morphological characteristics and developmental processes of Myxidium fugu n. sp., Leptotheca fugu n. sp. and Myxidium sp. TP were described. Further, diagnostic procedures of the above myxosporeans were established based on Diff-Quik-stained intestine imprints and HE ＆ Uvitex2B-stained histological sections.2) Histopathological examinations indicated that heavy infections with Myxidium sp. TP or Leptotheca fugu caused exfoliation and degeneration of the intestinal epithelia of tiger puffer, while M. fugu caused no significant damage in the intestinal tissues.3) Myxidium sp. TP and M. fugu transmitted from fish to other fish by feeding the infected tissues, cohabitation with infected fish and exposure to effluent from a tank holding infected fish.4) Kinetics of Myxidium sp. TP were investigated in experimentally infected fish. Development of the parasites was found to be temperature-dependent : They developed at 20C and 25C, while they became "cryptic" at 15C. Experimentally infected fish with Myxidium sp. TP became anorexic from week 3 at 20C, and showed the typical sign of the from week 6 at 20C.5) Moisture absorbance ability of infected fish was significantly lower than that of uninfected fish, indicating that functions of osmotic regulation were hampered in diseased fish. Further, atrophy of the liver and reduced hepatic indicators (LDH, GOT and GPT) of infected fish suggested that emaciated fish had a functional disorder in the liver.6) The causative organisms of emaciation disease of tiger puffer were demonstrated to be the Intestinal myxosporeans, Myxidium sp. TP and Leptotheca fugu. Modes of transmission and developmental kinetics of the parasites were characterized. Heavy infections with the myxosporeans caused a significant disorder in osmotic regulations in the intestine, resulting in the emaciation disease.

1)对瘦弱老虎河豚肠道粘孢子虫进行了寄生虫学检查，描述了河豚粘孢子虫（Myxidium fugu n. sp.）、河豚细囊粘孢子虫（Leptotheca fugu n. sp.）和河豚粘孢子虫（Myxidium sp. TP .）的形态特征和发育过程。此外，根据diff - quick染色的肠印迹和HE & uvitex2b染色的组织学切片，建立了上述粘孢子菌的诊断方法。2)组织病理学检查表明，重度感染粘菌（Myxidium sp. TP）或河豚细囊菌（Leptotheca fugu）可引起河豚肠道上皮脱落变性，而河豚细囊菌对肠道组织无明显损伤。3) TP和河豚粘虫通过喂食受感染的组织、与受感染的鱼同居以及接触装有受感染鱼的水箱排出的污水从鱼传染给其他鱼。4)在实验感染的鱼体内研究了粘菌的动力学。研究发现，寄生虫的发育与温度有关：它们在20摄氏度和25摄氏度下发育，而在15摄氏度时变得“隐蔽”。实验感染粘菌TP的鱼在20C条件下从第3周开始出现厌食，并表现出第6周的典型症状。5)病鱼的吸湿能力显著低于未病鱼，说明病鱼的渗透调节功能受到阻碍。此外，受感染鱼的肝脏萎缩和肝脏指标（LDH、GOT和GPT）降低表明，瘦弱的鱼的肝脏功能紊乱。6)虎河豚消瘦病的病原微生物为肠粘孢子虫、粘孢子虫和河豚瘦毛虫。研究了寄生虫的传播方式和发育动力学。黏液孢子菌的严重感染引起肠道渗透调节的明显紊乱，导致消瘦病。