Cyprinid herpesvirus 3 (CyHV-3), also named koi herpesvirus (KHV), is a lethal pathogen of koi and common carp Cyprinus carpio. In the present study, we described a procedure to generate monoclonal antibodies (mAbs) against the envelope protein pORF132 of CyHV-3 and application of the mAb. Three recombinant plasmids targeting the expression of one complete pORF132 and two truncated pORF132 were constructed, respectively. After induction, a truncated pORF132 was successfully expressed in a soluble form and the purified recombinant protein was used in the preparation of mAbs. Two hybridoma cell clones, 4E11 and 4B11, were obtained and mAb 4E11 reacted to CyHV-3 infected cells and not to CyHV-2 (goldfish hematopoietic necrosis virus) and IcHV-1 (channel catfish virus) infected cells. An antigen-capture ELISA based on the pair of mAb 4E11 and anti-CyHV-3 IgY was primarily constructed. This antigen-capture ELISA could distinguish between the CyHV-3 infected and uninfected fish samples.
Kudoa septempunctata infecting the muscle of the olive flounder Paralichthys olivaceus has been recently demonstrated to cause food poisoning in humans who eat the raw flesh of flounder. In the present study, we assessed the effective treatments of a water supply to prevent K. septempunctata infection in a flounder hatchery where the parasite was enzootic. The prevalence of infection in a positive control fish group exposed to unfiltered seawater was 33% at 3 months post-exposure, whereas no infection was observed in the treated fish groups exposed to sand-filtered seawater, sand- and cartridge (5 μm)-filtered seawater or sand-filtered seawater followed by ultraviolet (UV) irradiation at a dose of 46 mJ/cm2. Additionally, treatment with UV irradiation alone was effective for the prevention of K. septempunctata infection. To ensure complete protection from K. septempunctata infection, we recommend double treatments of a water supply with sand filtration and UV irradiation in olive flounder hatcheries.
Cyprinid herpesvirus 3 (CyHV-3) is the causative agent of koi herpesvirus disease and poses a significant threat to common and koi carp. Since its first description, the virus has spread worldwide. In 2010 and 2011, mass mortality of common carp was reported in a hatchery and several ponds in northern Vietnam. CyHV-3 was detected in infected tissues by PCR, confirmed by sequencing of the thymidine kinase gene. Duplex PCR demonstrated that the virus belonged to the genetic lineage (I++/II-) previously described in Indonesia. This suggests CyHV-3 as the causative agent of the disease outbreak and constitute the first report of CyHV-3 in Vietnam.