Neuropathology of brain myxosporean disease of fish

1.养殖鱼类骨骼畸形的病理学分析：马鲛的骨骼外部呈背腹弯曲。组织病理学检查显示脊柱弯曲是由一种脑粘孢子虫引起的。在嗅叶、视叶、视顶盖腔和第四脑室内发现粘孢子虫囊肿。2.自然感染亚临床野生鱼类的病理学分析：褐纹鲀（Canthigaster rivulata）和黄鳍虾虎鱼（Acanthogobius flavimanus）自然感染棘虎鱼，但未表现出任何骨骼异常。组织学观察显示，在视叶、延髓和小脑中发现大量囊肿。3.棘虎鱼PCR检测方法的建立--建立了以棘虎鱼SSU rDNA为靶点的PCR检测方法。应用巢式PCR技术对37种野生鱼类寄生虫进行了流行病学调查。结果表明，叉吻红娘鱼（阿拉塔）和赤鲷（日本Evynnis japonica）是棘虎鱼的寄主。此外，还对棘虎鱼可能的替代环节动物宿主进行了调查，但未获得放线孢子菌和PCR阳性反应。4.脑外科植入引起的鱼类异常行为实验：将直径约1 mm的玻璃珠植入金鱼的第四脑室，观察其游泳行为。结果表明，实验鱼表现出明显的身体弯曲和旋转行为。这表明脊椎弯曲是由位于第四脑室的外来颗粒的机械压力引起的。

1.Pathological analysis of skeletal deformity of cultured fish : Diseased Japanese mackerel (Scomber japonicus) exhibited dorso-ventral curvature externally. Histopathological examination revealed that the spinal curvature was caused by a brain myxosporean, Myxobolus acanthogobii. Myxosporean cysts were found in the olfactory lobe, optic lobe, the cavity of optic tectum and the fourth ventricle. However, the anatomical location of cysts responsible for the skeletal abnormalities could not be determined.2.Pathological analysis of naturally infected but subclinical wild fishes : Brown-lined puffer (Canthigaster rivulata) and yellowfin goby (Acanthogobius flavimanus) were found to be naturally infected with M.acanthogobii, but did not show any skeletal abnormalities. Histopathological observation showed that numerous cysts were found in the optic lobe, medulla oblongata and cerebellum.3.Development of PCR-based detection method for M.acanthogobii-A PCR method targeting SSU rDNA of M.acanthogobii was developed. Nested-PCR analysis was applied to epizootiological survey of the parasite in feral fishes (37 species). As a result, forksnout searobin (Lepidotrigla alata) and crimson seabream (Evynnis japonica) were found to be the hosts for M.acanthogobii. Further, surveys on possible alternate annelid hosts for M.acanthogobii were conducted, but actinosporeans and PCR-positive reactions were not obtained.4.Experimentally induced abnormal behavior of fish caused by implant by brain surgery : Glass beads (ca.1 mm in diameter) were implanted in the 4th ventricle of goldfish, and swimming behavior was observed. As a result, the experimental fish showed a notable body curvature and whirling behavior. This suggests that spinal curvature is caused by mechanical pressure of foreign particles localized in the 4th ventricle of fish brain.