In September 2016, a marine fish farm operator in Selangor, Malaysia, reported a disease outbreak affecting juvenile hybrid groupers (Camouflage Grouper Epinephelus polyphekadion × Tiger Grouper E. fuscoguttatus). The average daily mortality was 120 fish, resulting in a cumulative mortality rate of 29% within 10 d. The affected hybrid groupers displayed lethargy, excessive mucus production, rotten fins, congestion of livers and kidneys, and enlargement of spleens. Microscopically, general congestion of the brains and internal organs was evident. Vibrio harveyi and V. alginolyticus were successfully isolated from the diseased fish. The isolated pathogens were found to be sensitive to oxytetracycline and tetracycline, but resistant towards ampicillin and vancomycin. Experimental infections using the isolated V. harveyi (108 CFU/mL), V. alginolyticus (108 CFU/mL), and concurrent infection by V. harveyi (108 CFU/mL) and V. alginolyticus (108 CFU/mL) in juvenile Asian Seabass Lates calcarifer resulted in 60, 100, and 100% mortality, respectively, within 240 h postinfection. The experimentally infected Asian Seabass demonstrated similar clinical signs and histopathological changes as the naturally infected hybrid groupers. However, concurrently infected fish demonstrated severe clinical signs and histopathological changes compared with single infections. These results suggest that both isolates of Vibrio are pathogenic to fish and responsible for the disease outbreak. However, concurrent infection involving V. alginolyticus and V. harveyi leads to a more devastating impact to the cultured fish. This is the first report of concurrent Vibrio infection in cultured marine fish in Malaysia.

中文翻译：

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马来西亚养殖杂交石斑鱼中哈维弧菌和溶藻弧菌的自然并发感染

2016 年 9 月，马来西亚雪兰莪州的一家海水养鱼场经营者报告了一起影响幼年杂交石斑鱼（Camouflage Grouper Epinephelus polyphekadion × Tiger Grouper E. fuscoguttatus）的疾病爆发。平均每日死亡率为 120 条鱼，导致 10 d 内的累积死亡率为 29%。受影响的杂种石斑鱼表现出嗜睡、粘液分泌过多、鳍腐烂、肝肾充血以及脾脏肿大。显微镜下，大脑和内脏的普遍充血是明显的。从病鱼中成功分离出哈维弧菌和溶藻弧菌。发现分离的病原体对土霉素和四环素敏感，但对氨苄青霉素和万古霉素耐药。使用分离的 V. harveyi (108 CFU/mL)、V. 的实验感染。alginolyticus (108 CFU/mL) 以及同时感染 V. harveyi (108 CFU/mL) 和 V. alginolyticus (108 CFU/mL) 在幼年亚洲鲈鱼中分别导致 60%、100% 和 100% 的死亡率，感染后 240 小时内。实验感染的亚洲鲈鱼表现出与自然感染的杂交石斑鱼相似的临床症状和组织病理学变化。然而，与单一感染相比，同时感染的鱼表现出严重的临床症状和组织病理学变化。这些结果表明，两种弧菌分离物对鱼类都是致病的，是导致疾病爆发的原因。然而，涉及溶藻弧菌和哈维弧菌的并发感染会对养殖鱼造成更具破坏性的影响。