Zrnčić Snježana, Brnić Dragan, Panzarin Valentina, Abbadi Miriam, Lojkić Ivana, Zupičić Ivana Giovanna, Oraić Dražen
Department of Pathology, Croatian Veterinary Institute, Savska cesta 143, 10000 Zagreb, Croatia.
Department of Virology, Croatian Veterinary Institute, Savska cesta 143, 10000 Zagreb, Croatia.
Pathogens. 2022 Mar 30;11(4):418. doi: 10.3390/pathogens11040418.
Due to the insufficient capacity of Croatian hatcheries, marine aquaculture depends on the importation of fry from different countries in the Mediterranean basin. Importation enables a risk of spreading pathogenic agents. Viral nervous necrosis (VNN), caused by betanodavirus is devastating for the farming of European sea bass. We described a VNN outbreak that occurred in Croatia in 2014. After the diagnosis of VNN in sea bass fry introduced from the same hatchery to five unconnected marine farms at the Adriatic Coast, we performed surveillance within one of the affected farms. It resulted in proven horizontal spreading of the virus within the farm and to feral fish around farm cages. Real-time RT-PCR tested samples showed the dependence of the virus' proliferation to the water temperature and the fish age. The highest mortality rates were noted during higher sea temperatures. Phylogenetic analysis of partial sequences of RNA1 and RNA2 supported the hypothesis that the virus was introduced to all studied farms from the same hatchery. Moreover, phylogenetic analysis of the whole genome sequences of infected farmed sea bass and thicklip mullet showed high similarity and it is unlikely that infection in Croatian sea bass farms has originated from wild reservoirs, as the first positive record in wild mullet was recorded after the disease outbreak.
由于克罗地亚孵化场的产能不足，海水养殖依赖于从地中海盆地不同国家进口鱼苗。进口带来了病原体传播的风险。由β-诺达病毒引起的病毒性神经坏死（VNN）对欧洲海鲈养殖具有毁灭性影响。我们描述了2014年在克罗地亚发生的一次VNN疫情。在诊断出从同一孵化场引入亚得里亚海沿岸五个不相连的海水养殖场的海鲈鱼苗感染VNN后，我们在其中一个受影响的养殖场内进行了监测。结果证实病毒在养殖场内以及向养殖网箱周围的野生鱼类水平传播。实时RT-PCR检测的样本显示病毒增殖对水温及鱼龄的依赖性。在海水温度较高时死亡率最高。对RNA1和RNA2部分序列的系统发育分析支持了该病毒从同一孵化场引入所有研究养殖场的假设。此外，对感染的养殖海鲈和厚唇鲻全基因组序列的系统发育分析显示高度相似，而且克罗地亚海鲈养殖场的感染不太可能源自野生宿主，因为野生鲻鱼的首次阳性记录是在疾病爆发之后。
