One of the clinical manifestations of streptococcosis is swimming errors of the infected fish, which is likely caused by lesions in the brain. As most studies described brain histopathology in streptococcosis as meningitis, with a limited description of lesions in the whole brain, the aim of this study was therefore to explore histopathology of the whole brain of red tilapia experimentally infected with Streptococcus agalactiae serotype III. Transcripts relating to motoneuron functions and inflammatory responses were also investigated. In the S. agalactiae‐infected fish, the parenchyma of the whole brain and its associated meninx primitiva were found to be markedly infiltrated by mononuclear cells and Gram‐positive cocci. Hemorrhage, neuronal necrosis, and localized spongiform histopathology were observed, especially within the midbrain and the cerebellum. The lesion was observed in the medial longitudinal fasciculus and its nucleus. Expressions of the transcripts CD166, GAP43, SMN, and SV2B of the infected fish did not change, while those of IL‐1β and TNF‐α were significantly upregulated. It is likely that S. agalactiae cause extensive damage to the fish brain, especially in areas that control swimming activities, through both direct invasion of the bacteria and acute inflammatory responses of the brain resident macrophages, or microglia.

中文翻译：

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红罗非鱼Oreochromis sp。的脑组织病理学。实验上感染了无乳链球菌血清型III。

链球菌病的临床表现之一是被感染鱼的游泳失误，这很可能是由于脑部病变引起的。由于大多数研究将链球菌病的脑组织病理学描述为脑膜炎，对全脑病变的描述有限，因此，本研究的目的是探索实验性感染无乳链球菌血清型III的红色罗非鱼全脑的组织病理学。还研究了与运动神经元功能和炎症反应有关的转录本。在S中。无乳科发现被感染的鱼，全脑实质及其相关的Meninx primitiva被单核细胞和革兰氏阳性球菌明显浸润。观察到出血，神经元坏死和局部海绵状组织病理，特别是在中脑和小脑内。在内侧纵筋膜及其核中观察到病变。被感染鱼的CD166，GAP43，SMN和SV2B转录本的表达没有变化，而IL-1β和TNF-α的表达显着上调。S可能是。无乳科 通过细菌的直接入侵和脑部巨噬细胞或小胶质细胞的急性炎症反应，对鱼脑造成广泛损害，尤其是在控制游泳活动的区域。