Infectious spleen and kidney necrosis virus (ISKNV) is a fish-pathogenic virus belonging to the genus Megalocytivirus of the family Iridoviridae. In 2018, disease occurrences (40-50% cumulative mortality) associated with ISKNV infection were reported in grown-out Asian sea bass (Lates calcarifer) cultured in an inland freshwater system in Thailand. Clinical samples were collected from seven distinct farms located in the eastern and central regions of Thailand. The moribund fish showed various abnormal signs, including lethargy, pale gills, darkened body, and skin hemorrhage, while hypertrophied basophilic cells were observed microscopically in gill, liver, and kidney tissue. ISKNV infection was confirmed on six out of seven farms using virus-specific semi-nested PCR. The MCP and ATPase genes showed 100% sequence identity among the virus isolates, and the virus was found to belong to the ISKNV genotype I clade. Koch’s postulates were later confirmed by challenge assay, and the mortality of the experimentally infected fish at 21 days post-challenge was 50-90%, depending on the challenge dose. The complete genome of two ISKNV isolates, namely KU1 and KU2, was recovered directly from the infected specimens using a shotgun metagenomics approach. The genome length of ISKNV KU1 and KU2 was 111,487 and 111,610 bp, respectively. In comparison to closely related ISKNV strains, KU1 and KU2 contained nine unique genes, including a caspase-recruitment-domain-containing protein that is potentially involved in inhibition of apoptosis. Collectively, this study indicated that inland cultured Asian sea bass are infected by homologous ISKNV strains. This indicates that ISKNV genotype I should be prioritized for future vaccine research.

传染性脾肾坏死病毒（ISKNV）是属鱼致病性病毒Megalocytivirus家庭的虹彩病毒科。2018 年，成年亚洲鲈鱼（Lates calcarifer) 在泰国的内陆淡水系统中养殖。从位于泰国东部和中部地区的七个不同农场收集临床样本。垂死的鱼表现出各种异常体征，包括嗜睡、鳃苍白、身体变黑和皮肤出血，而显微镜下观察到鳃、肝脏和肾脏组织中的肥大嗜碱性细胞。使用病毒特异性半巢式 PCR 在七个农场中的六个农场中确认了 ISKNV 感染。MCP 和 ATPase 基因在病毒分离株中表现出 100% 的序列同一性，发现该病毒属于 ISKNV 基因型 I 进化枝。Koch 的假设后来通过攻击试验得到证实，在攻击后 21 天，实验感染的鱼的死亡率为 50-90%，这取决于攻击剂量。两个 ISKNV 分离株的完整基因组，即 KU1 和 KU2，是使用鸟枪宏基因组学方法直接从受感染的标本中回收的。ISKNV KU1 和 KU2 的基因组长度分别为 111,487 和 111,610 bp。与密切相关的 ISKNV 菌株相比，KU1 和 KU2 包含九个独特的基因，包括可能参与抑制细胞凋亡的含有半胱天冬酶招募结构域的蛋白质。总的来说，这项研究表明内陆养殖的亚洲鲈鱼被同源 ISKNV 菌株感染。这表明 ISKNV 基因型 I 应优先用于未来的疫苗研究。KU1 和 KU2 包含九个独特的基因，包括一个包含半胱天冬酶募集结构域的蛋白质，可能参与抑制细胞凋亡。总的来说，这项研究表明内陆养殖的亚洲鲈鱼被同源 ISKNV 菌株感染。这表明 ISKNV 基因型 I 应优先用于未来的疫苗研究。KU1 和 KU2 包含九个独特的基因，包括一个包含半胱天冬酶募集结构域的蛋白质，可能参与抑制细胞凋亡。总的来说，这项研究表明内陆养殖的亚洲鲈鱼被同源 ISKNV 菌株感染。这表明 ISKNV 基因型 I 应优先用于未来的疫苗研究。