Senapin Saengchan, Dong Ha Thanh, Meemetta Watcharachai, Gangnonngiw Warachin, Sangsuriya Pakakul, Vanichviriyakit Rapeepun, Sonthi Molruedee, Nuangsaeng Bunlung
Faculty of Science, Fish Health Platform, Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Mahidol University, Bangkok, Thailand.
National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani, Thailand.
J Fish Dis. 2019 Jan;42(1):119-127. doi: 10.1111/jfd.12915. Epub 2018 Nov 5.
In Southeast Asia, a new disease called scale drop disease (SDD) caused by a novel Megalocytivirus (SDDV) has emerged in farmed Asian sea bass (Lates calcarifer) in Singapore, Malaysia and Indonesia. We received samples from an Eastern Thai province that also showed gross signs of SDD (loss of scales). Clinical samples of 0.2-1.1 kg L. calcarifer collected between 2016 and 2018 were examined for evidence of SDDV infection. Histopathology was similar to that in the first report of SDDV from Singapore including necrosis, inflammation and nuclear pyknosis and karyorrhexis in the multiple organs. Intracytoplasmic inclusion bodies were also observed in the muscle tissue. In a density-gradient fraction from muscle extracts, TEM revealed enveloped, hexagonal megalocytiviral-like particles (~100-180 nm). By PCR using primers derived from the Singaporean SDDV genome sequence, four different genes were amplified and sequenced from the Thai isolate revealing 98.7%-99.9% identity between the two isolates. Since viral inclusions were rarely observed, clinical signs and histopathology could not be used to easily distinguish between SDD caused by bacteria or SDDV. We therefore recommend that PCR screening be used to monitor broodstock, fry and grow-out fish to estimate the current impact of SDDV in Southeast Asia and to prevent its spread.
在东南亚，一种由新型巨细胞病毒（SDDV）引起的名为鳞片脱落病（SDD）的新疾病已在新加坡、马来西亚和印度尼西亚的养殖亚洲海鲈（尖吻鲈）中出现。我们收到了来自泰国东部一个省份的样本，这些样本也显示出鳞片脱落病的明显症状（鳞片脱落）。对2016年至2018年间采集的体重为0.2 - 1.1千克的尖吻鲈临床样本进行了检查，以寻找SDDV感染的证据。组织病理学与新加坡首次报道的SDDV相似，包括多个器官出现坏死、炎症以及核固缩和核碎裂。在肌肉组织中也观察到了胞质内包涵体。在肌肉提取物的密度梯度组分中，透射电子显微镜（TEM）显示出有包膜的、六边形的类巨细胞病毒颗粒（约100 - 180纳米）。通过使用源自新加坡SDDV基因组序列的引物进行聚合酶链反应（PCR），从泰国分离株中扩增并测序了四个不同的基因，结果显示这两个分离株之间的同一性为98.7% - 99.9%。由于很少观察到病毒包涵体，临床症状和组织病理学无法轻易区分由细菌引起的鳞片脱落病和由SDDV引起的鳞片脱落病。因此，我们建议使用PCR筛查来监测亲鱼、鱼苗和成鱼，以评估SDDV目前在东南亚的影响，并防止其传播。
