Fujioka Hiroya, Yamasaki Kenichi, Furusawa Keiki, Tamura Kazuki, Oguro Kazuki, Kurihara Sumire, Seki Shingo, Oshima Syun-ichirou, Imajoh Masayuki
Graduate School of Kuroshio Science, Kochi University, Nankoku, Kochi 783-8502, Japan.
Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
Vet Microbiol. 2015 Feb 25;175(2-4):362-8. doi: 10.1016/j.vetmic.2014.12.002. Epub 2014 Dec 11.
Cyprinid herpesvirus 3 (CyHV-3) causes lethal disease in common and koi carp. Mortality by CyHV-3 disease has not been reported since 2011 in Kochi Prefecture, Japan. Here, we detected and quantified CyHV-3 in common carp inhabiting three rivers in the prefecture to examine if the carp are carriers of CyHV-3 as a source of infection. CyHV-3 DNA was detected in 16.7% (12/72) of brain samples in Kagami River, 3.9% (3/76) of brain and 3.9% (3/76) of gill samples in Monobe River, and 5.1% (4/79) of brain and 1.3% (1/79) of gill samples in Wajiki River. CyHV-3 genotypes identified in the 23 samples were classified as the J genotype A1 that has been found in Japan. The CyHV-3 DNA load did not differ statistically between sampling months, indicating that CyHV-3 has been silent in common carp, unlike Lake Biwa where the annual reactivation occurs in spring. Taken together, our results represented definitive evidence that seasonal changes in water temperature do not affect CyHV-3 activity in carp. Considering that infectious virus was not isolated from CyHV-3 DNA-positive samples, it was suggested that CyHV-3 establishes a latent infection in carp populations inhabiting Kagami River, Monobe River and Wajiki River. Further, the presence of circular or concatameric CyHV-3 DNA was detected in five of 23 CyHV-3 DNA-positive samples. Common carp inhabiting Lake Biwa were reported previously to harbor linear but not circular CyHV-3 DNA. This difference suggested that the CyHV-3 genome may be circularized for long-term maintenance without active viral replication.
鲤疱疹病毒3型（CyHV - 3）可导致普通鲤鱼和锦鲤患上致命疾病。自2011年以来，日本高知县尚未有因CyHV - 3疾病导致的死亡报告。在此，我们对该县三条河流中的普通鲤鱼进行了CyHV - 3的检测和定量分析，以检查这些鲤鱼是否为CyHV - 3的感染源携带者。在镜川的脑样本中，16.7%（12/72）检测到CyHV - 3 DNA；在茂部川的脑样本中，3.9%（3/76）检测到CyHV - 3 DNA，鳃样本中3.9%（3/76）检测到；在胁木川的脑样本中，5.1%（4/79）检测到CyHV - 3 DNA，鳃样本中1.3%（1/79）检测到。在这23个样本中鉴定出的CyHV - 3基因型被归类为在日本发现的J基因型A1。CyHV - 3的DNA载量在不同采样月份之间没有统计学差异，这表明CyHV - 3在普通鲤鱼中处于潜伏状态，这与琵琶湖不同，琵琶湖每年春季会出现病毒再激活现象。综上所述，我们的结果明确证明水温的季节性变化不会影响鲤鱼体内CyHV - 3的活性。鉴于未从CyHV - 3 DNA阳性样本中分离出感染性病毒，提示CyHV - 3在栖息于镜川、茂部川和胁木川的鲤鱼种群中建立了潜伏感染。此外，在23个CyHV - 3 DNA阳性样本中的5个样本中检测到了环状或串联状的CyHV - 3 DNA。此前有报道称，栖息于琵琶湖的普通鲤鱼携带线性而非环状的CyHV - 3 DNA。这种差异表明，CyHV - 3基因组可能会环化以进行长期维持，而无需病毒的活跃复制。
