Identification of a novel cyprinid herpesvirus 3 genotype detected in koi from the East Asian and South‐East Asian Regions

Abstract

Cyprinid herpesvirus 3 (CyHV-3) is a highly contagious virus that causes significant morbidity and mortality in common carp Cyprinus carpio L. and considered to be one of the most important pathogens of koi and common carp worldwide. Cyprinid herpesvirus 3 infected consignments imported from East Asian and South-East Asian regions were identified during quarantine period in Singapore, and virus from a 2005 consignment was successfully isolated in koi fin cells. A combination of sequence analyses and duplex PCR were used to characterize 15 CyHV-3 isolates detected in koi consignments between 2005 and 2011. Sequence analyses of the enlarged 9/5, SphI-5 and TK gene regions identified both the Asian 1 (n = 11) and European 4 (n = 4) genotypes. Duplex PCR analysis of two variable marker regions between ORF29 and ORF30 (marker I) as well as ORF133 and its upstream region (marker II) revealed viruses of genotypes J (I II ), U/I (I II ), an intermediate genotype (I II ) and a novel genotype, I II , which was identified in viruses from seven different consignments. This novel genotype has a 13-bp deletion in marker II, while maintaining the I allele of marker I. The I II genotype may have emerged from East Asian and South-East Asian regions in recent years.

Whole-genome sequence of a novel Chinese cyprinid herpesvirus 3 isolate reveals the existence of a distinct European genotype in East Asia

“…During the revision of this study, a study in Singapore also detected E4-like CyHV3 on four early diseased koi samples that were imported from Malaysia in 2008 (Chen et al, 2014). However, attempts to isolate these E4-like CyHV3s from the early ice-stored samples by cell culture were unsuccessful because of the fragility of CyHV3 virions (Chen et al, 2014;Kim and Kwon, 2013).…”

Mass mortality associated with koi herpesvirus in common carp in Iraq

“…U/I strains are designated I −− II − as all three domains are absent in markers I and II, while the J strain is designated I ++ II + as all three domains are present [ 6 ]. Recently, a new genotype (I −+ II − ), which has one of the two marker I domains, was reported in the Netherlands, and, in Malaysia, another novel genotype with a deletion of 13 nucleotides in marker II (I ++ II +Δ ) was identified [ 7 , 8 ].…”

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Koi herpes virus disease (KHV)

“…However, no reliable estimates of mortality rates are available in outbreak sites in Europe and elsewhere, due to difficulties in determining the total host population size. In Taiwan, data from cultured carp outbreaks showed mortality of 70-100% (Chen et al, 2015). Data on cases in UK lakes supplied by the Centre for Environment, Fisheries and Aquaculture Science (Taylor, 2016) show total mortalities occurred when water temperatures were in excess of 16°C, and were highly variable between sites (ranging between 1 and > 2,000 in number).…”

“…In the case of natural infections in open water systems, although several studies suggest that mortality due to KHV (in lake and farm systems) can be high, knowledge gaps exist as due to difficulties in determining the total host population size, thus no reliable estimates of percentage mortality are available in case sites. In Taiwan, data from cultured carp outbreaks showed mortality of 70-100% (Chen et al, 2015); however, information on mortality rates in Europe is limited. Data on cases in the UK lakes supplied by Cefas (Taylor, 2016) show total mortalities to occur when water temperatures were in excess of 16°C, and to be highly variable between sites (ranging between 1 and > 2,000).…”