Palikova Miroslava, Balazova Alena, Pojezdal Lubomir, Papezikova Ivana, Mikulikova Ivana, Toulova Ivona, Motlova Jitka, Pikula Jiri
Department of Ecology and Diseases of Zoo Animals, Game, Fish and Bees, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Science Brno, Brno, Czechia.
Department of Zoology, Fisheries, Hydrobiology and Apiculture, Mendel University in Brno, Brno, Czechia.
Front Vet Sci. 2025 Feb 14;12:1532861. doi: 10.3389/fvets.2025.1532861. eCollection 2025.
Carp Edema Virus (CEV) has emerged as a viral threat to the sustainability of European pond fisheries, with water temperature and stress playing a crucial role in disease outbreaks. Here, we report on a natural CEV infection in overwintering common carp (; = 1,160) broodstock that began to manifest clinically at an unusually low water temperature. In the initial outbreak phase, young broodstock fish exhibited abnormal activity and shoaling at the pond edge. While the water temperature under a discontinuous thin ice layer was 2°C, no deaths were observed. The first fish examined, using standard molecular methods for virological diagnosis, tested negative for CEV. Despite showing clinical signs suggestive of CEV infection, there was no gross pathology except for an increased amount of gill mucus, suggesting that CEV molecular detection may be dependent on infection progression. A shift from a period of cold stress to warming pond water temperatures may have influenced the subsequent progression of the disease. Ongoing clinical signs affected a large part of the population, which remained lethargic and gathered close to the banks. Subsequent virological testing performed ca. 3 weeks after the outbreak and first observation of clinically diseased fish detected the CEV genogroup I agent. CEV-driven die-offs occurred gradually as water temperatures increased to 8°C, with mortalities continuing for ca. 1 month. Interestingly, Přerov scaly carp and Hungarian mirror carp M2 strains differed significantly in mortality rates, at 30 and 60%, respectively. We tested a novel virus detection method, based on loop-mediated isothermal amplification (LAMP) of primers targeting the CEV genogroup I gene, for applicability in the field. Samples from moribund fish, cadavers, and pond water all tested positive, with samples positive using LAMP subsequently confirmed by qPCR. To summarize, our data suggest it may be challenging to detect CEV DNA in both the first carp showing signs and surviving carp; scaly and scaleless carp show differential susceptibility to CEV infection; very low water temperatures of 2-4°C permit CEV infection in common carp; the LAMP method is applicable for rapid on-site CEV detection in clinical and environmental samples.
鲤鱼水肿病毒（CEV）已成为欧洲池塘渔业可持续发展的一种病毒威胁，水温及应激在疾病暴发中起着关键作用。在此，我们报告了在越冬的鲤鱼（；=1160尾）亲鱼中发生的自然CEV感染情况，该病在异常低温时开始出现临床症状。在最初的暴发阶段，幼龄亲鱼在池塘边缘表现出异常活动和聚集行为。当间断薄冰层下的水温为2℃时，未观察到死亡情况。使用标准分子方法进行病毒学诊断，对首批检测的鱼进行检测，结果CEV呈阴性。尽管这些鱼表现出提示CEV感染的临床症状，但除鳃黏液增多外，未发现明显病理变化，这表明CEV分子检测可能取决于感染进程。从冷应激期到池塘水温升高的转变可能影响了疾病的后续发展。持续的临床症状影响了大部分鱼群，它们仍行动迟缓并聚集在岸边。在疾病暴发及首次观察到临床患病鱼约3周后进行的后续病毒学检测，检测到了CEV基因组I型毒株。随着水温升至8℃，由CEV导致的死亡逐渐发生，死亡率持续约1个月。有趣的是，普热罗夫有鳞鲤鱼和匈牙利镜鲤M2品系的死亡率差异显著，分别为30%和60%。我们测试了一种基于针对CEV基因组I型基因的引物进行环介导等温扩增（LAMP）的新型病毒检测方法在现场的适用性。濒死鱼、尸体及池塘水样本检测均呈阳性，LAMP检测呈阳性的样本随后经qPCR确认。总之，我们的数据表明，在首批出现症状的鲤鱼及存活的鲤鱼中检测CEV DNA可能具有挑战性；有鳞和无鳞鲤鱼对CEV感染表现出不同的易感性；2 - 4℃的极低水温可使鲤鱼感染CEV；LAMP方法适用于临床和环境样本中CEV的快速现场检测。
