ABSTRACT: Freshwater farming of barramundi Lates calcarifer in Thailand is a growing sector in aquaculture, but mortalities due to infectious diseases are still a major threat to this industry. In 2018, an episode of severe mortality in juvenile barramundi was noted in a freshwater earth pond site. Fish presented with severe gill necrosis, as well as severe cutaneous hemorrhages, scale loss, and discoloration at the base of dorsal fin (saddleback lesions). Histopathology revealed extensive necrosis of skeletal muscle and gill filaments, as well as basophilic inclusion bodies and megalocytosis in muscle, gill, liver, and kidney. Scale drop disease virus (SDDV) infection was subsequently confirmed by virus-specific semi-nested PCR. Further, DNA sequences of the viral major capsid protein (MCP) and ATPase genes had a respective homology of 99.85 and 99.92% with sequences of SDDV infecting barramundi in saltwater culture. Gill necrosis and saddleback lesions are not typical lesions associated with scale drop syndrome. Their presence was explained by Flavobacterium columnare isolation from the gill, followed by positive F. columnare-specific PCR. To our knowledge, this is the first report of SDDV-associated mortality in freshwater-farmed barramundi. Furthermore, this mortality presented as a concurrent infection with SDDV and F. columnare, with typical lesions of both infections.

中文翻译：

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同时从病态淡水饲养的澳洲肺鱼鳞翅目检出鳞屑病病毒和黄杆菌。

摘要：澳洲肺鱼钙石的淡水养殖在泰国，水产养殖业正在增长，但是由于传染病造成的死亡仍然是该行业的主要威胁。在2018年，在淡水地球池塘中发现了澳洲肺鱼的严重死亡事件。鱼表现出严重的腮坏死，以及严重的皮肤出血，鳞屑流失和背鳍基部变色（鞍背病变）。组织病理学显示骨骼肌和腮丝细丝广泛坏死，嗜碱性包涵体和肌肉，腮，肝和肾中的巨噬细胞。随后通过病毒特异性半巢式PCR确认了鳞屑病病毒（SDDV）感染。此外，病毒主要衣壳蛋白（MCP）和ATPase基因的DNA序列分别具有99.85和99的同源性。在海水培养中，有92％的SDDV序列感染了肺鱼。ill坏死和鞍背病变不是伴有鳞屑下降综合征的典型病变。他们的存在是由解释柱状黄杆菌从鳃隔离，随后正F. columnare特异性PCR。据我们所知，这是淡水养殖的肺鱼中SDDV相关死亡率的首次报道。此外，这个死亡率呈现与SDDV和并发感染F. columnare，既感染的典型病变。