Botany and Microbiology Department, Faculty of Science, South Valley University, Qena, 83523, Egypt.
Applied and Environmental Microbiology Center, South Valley University, Qena, 83523, Egypt.
Int Microbiol. 2024 Apr;27(2):559-569. doi: 10.1007/s10123-023-00406-5. Epub 2023 Jul 29.
Nervous necrosis virus (NNV) is the causative agent of viral nervous necrosis in freshwater and marine fishes. In this study, NNV circulating among wild and farmed Nile tilapia (Oreochromis niloticus) was genetically and morphologically characterized using reverse transcription polymerase chain reaction (RT-PCR), sequencing analysis, and transmission electron microscopy (TEM). Brain, eye, and other organ (spleen, kidney, heart, and liver) specimens were collected from 87 wild (66) and farmed (21) Nile tilapia fish during their adult or juvenile stage at different localities in Qena and Sohag governorates in southern Egypt. Among them, 57/87 fish showed suspected NNV clinical signs, and 30/87 were healthy. The results revealed that NNV was detected in 66 out of 87 fish (58.62% in the wild and 17.24% in farmed Nile tilapia by RT-PCR), and the prevalence was higher among diseased (55.17%) than in healthy (20.69%) fish. NNV was detected in the brain, eye, and other organs. Using TEM, virion size variations based on the infected organs were observed. Nucleotide sequence similarity indicated that NNVs had a divergence of 75% from other fish nodaviruses sequenced in Egypt and worldwide. Phylogenetic analysis distinguished them from other NNV genotypes, revealing the emergence of a new NNV genotype in southern Egypt. In conclusion, NNV is circulating among diseased and healthy Nile tilapia, and a new NNV genotype has emerged in southern Egypt.
神经坏死病毒（NNV）是淡水和海水鱼类病毒性神经坏死病的病原体。在这项研究中，使用逆转录聚合酶链反应（RT-PCR）、测序分析和透射电子显微镜（TEM）对野生和养殖尼罗罗非鱼（Oreochromis niloticus）中循环的 NNV 进行了遗传和形态特征分析。从埃及南部 Qena 和 Sohag 省不同地点的成年或幼年阶段的 87 条野生（66 条）和养殖（21 条）尼罗罗非鱼的大脑、眼睛和其他器官（脾脏、肾脏、心脏和肝脏）采集了样本。其中，57/87 条鱼出现疑似 NNV 临床症状，30/87 条鱼健康。结果表明，通过 RT-PCR 在 87 条鱼中的 66 条（野生鱼中为 58.62%，养殖鱼中为 17.24%）中检测到了 NNV，且在患病鱼（55.17%）中的流行率高于健康鱼（20.69%）。NNV 检测到在大脑、眼睛和其他器官中。使用 TEM 观察到基于感染器官的病毒粒子大小变化。核苷酸序列相似性表明，埃及和全球范围内测序的其他鱼类诺达病毒与 NNV 有 75%的差异。系统进化分析将其与其他 NNV 基因型区分开来，表明在埃及南部出现了一种新的 NNV 基因型。总之，NNV 在患病和健康的尼罗罗非鱼中传播，并且在埃及南部出现了一种新的 NNV 基因型。
