title: Prevalence and characteristics of Cyprinid herpesvirus 3 (CyHV-3) infection in common carp (Cyprinus carpio L.) inhabiting three rivers in Kochi Prefecture, Japan.
abstract: 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.
authors.affiliation: Graduate School of Kuroshio Science, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Hiroya
authors.initials: H
authors.lastname: Fujioka
authors.affiliation: Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yamasaki
authors.affiliation: Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Keiki
authors.initials: K
authors.lastname: Furusawa
authors.affiliation: Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Tamura
authors.affiliation: Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Oguro
authors.affiliation: Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Sumire
authors.initials: S
authors.lastname: Kurihara
authors.affiliation: Fish Ecology Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Seki
authors.affiliation: Graduate School of Kuroshio Science, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Syun-ichirou
authors.initials: S
authors.lastname: Oshima
authors.affiliation: Fish Disease Laboratory, Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan. Electronic address: m-imajoh@kochi-u.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Imajoh
mesh_terms: D000818:Animals; D002347:Carps; D005393:Fish Diseases / Q000453:epidemiology / Q000821:virology*; D006564:Herpesviridae / Q000302:isolation & purification*; D006566:Herpesviridae Infections / Q000662:veterinary* / Q000821:virology; D007564:Japan / Q000453:epidemiology; D015995:Prevalence; D045483:Rivers; D012621:Seasons; D013696:Temperature
keywords: Cyprinid herpesvirus 3; Genotyping; Japan; Virus detection; Virus quantification; Wild common carp