Outbreaks of an infectious disease affecting cultured white sturgeon (Acipenser transmontanus) were investigated. Clinical signs included erratic swimming, arching of the back and mortality. Necropsy findings included poorly demarcated yellow to dark-red and friable lesions in the epaxial muscle, ulcerative skin lesions and haemorrhages in the swim bladder and coelomic wall. Histological evaluation revealed areas of necrotizing and heterophilic myositis with aggregates of bacterial cocci. The lumen of blood vessels in the dermis, under ulcerated areas, and in the posterior kidney, was occluded by fibrin thrombi. Aggregates of Gram-positive cocci were observed in the muscle lesions and within the fibrin thrombi in the dermis and kidney. Genetically homogeneous Streptococcus iniae strains were recovered from affected fish from different outbreaks. The isolates shared high degree of similarity at gene locus (gyrB) with previously characterized S. iniae from cultured fish in California, confirming the emergence of this particular strain of S. iniae in US aquaculture.

中文翻译：

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养殖的白色st鱼（Acipenser transmontanus L.）与猪链球菌相关的严重肌炎暴发。

调查了影响养殖白st（Acipenser transmontanus）的传染病暴发。临床体征包括游泳不规律，背部弯曲和死亡。尸检的结果包括：划定的黄色到深红色的边界较差，脊髓的易碎病灶，溃疡性皮肤病的病灶以及游泳膀胱和结肠壁的出血。组织学评估显示坏死性和嗜异性肌炎的区域有细菌球菌的聚集。纤维蛋白血栓阻塞了真皮，溃疡区域下方和肾后部的血管腔。在肌肉损伤以及真皮和肾脏的纤维蛋白血栓内观察到革兰氏阳性球菌的聚集。从不同暴发的受感染鱼中回收了遗传上均一的链球菌菌株。