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Koi herpesvirus (KHV; cyprinid herpesvirus‐3) and carp oedema virus (CEV) are important viruses of common and koi carp (Cyprinus carpio); however, the distribution of these viruses in wild common carp in North America is largely unknown. During the summers of 2017 and 2018, 27 mass mortalities of common carp were reported from four states in the USA (Minnesota, Iowa, Pennsylvania and Wisconsin), the majority of which were distributed across eight major watersheds in southern Minnesota. Samples from 22 of these mortality events and from five clinically healthy nearby carp populations were screened for KHV, CEV and SVCV using real‐time polymerase chain reaction (qPCR). KHV was confirmed in 13 mortality events, CEV in two mortality events and coinfections of KHV/CEV in four mortality events. Nucleotide sequence analysis revealed that the KHV and CEV detected here are closely related to European lineages of these viruses. While molecular detection alone cannot conclusively link either virus with disease, the cases described here expand the known range of two important viruses. This is also the first reported detection of KHV and CEV coinfections in wild carp populations.

Zinc is the second most abundant trace element in the animal body.It cannot be stored in the body (Zalewski et al., 2005) and can be consumed as regular dietary intake to meet the physiological need of the body. As a component of numerous enzymes and hormones, it is necessary for the proper physiological functioning (Prasad, 1991).Several important enzymatic activities like alcohol dehydrogenase, alkaline phosphatase (ALP), aldolase, lactate dehydrogenase (LDH), RNA and DNA polymerases, reverse transcriptase and superoxide dismutase (SOD) are dependent on this micronutrient. Zinc oxide nanoparticles have been stated to enhance growth performance, Abstract A 120-day feeding trial was conducted to assess the effects of dietary supplementation of zinc oxide (ZnO) and selenium (Se) nanoparticles (NPs) on growth, immunological and enzymatic profiles in rohu, Labeo rohita. Fishes were fed with basal diet incorporated with laboratory-synthesized nanoparticles, viz., zinc oxide nanoparticles-10 mg/kg and Se nanoparticles-0.3 mg/kg throughout the experimental period. At an interval of every 30 days, treated and control fishes were randomly collected and subjected to estimation of growth, non-specific immune parameters and serum enzyme assays. It was observed that there was significant (p < 0.05) increase in growth and non-specific immune parameters like respiratory burst, lysozyme and myeloperoxidase activities as compared to the control group (only basal diet). Serum enzymatic profiles such as lactate dehydrogenase and alkaline phosphatase activities down-regulated (p < 0.05) in treated group compared to control group, and superoxide dismutase and acetylcholine esterase activity up-regulated in treated group. The relative percentage survival (RPS) found to be significantly higher in treated groups (60.00 ± 8.82%) as compared to control group (45.00 ± 6.17%) while challenged with virulent bacterial strain Aeromonas hydrophila. These results indicated that dietary supplementation of zinc oxide (ZnO) and selenium (Se) nanoparticles stimulates immunity and enhances resistance to bacterial infection in L. rohita. K E Y W O R D SA. hydrophila, aquaculture, enzyme activities, growth performance, immune response, nanoparticles How to cite this article: Swain P, Das R, Das A, Padhi SK, Das KC, Mishra SS. Effects of dietary zinc oxide and selenium nanoparticles on growth performance, immune responses and enzyme activity in rohu, Labeo rohita (Hamilton). Aquacult Nutr. 2019;25:486-494. https://doi.

Cyprinid herpesvirus-3 (CyHV-3, syn. koi herpesvirus) is an important pathogen worldwide and a common cause of mass mortality events of wild common carp (Cyprinus carpio) in North America, however, reference strains and genomes obtained from wild carp are not available. Additionally, it is unclear if fishes in North America are susceptible to CyHV-3 infection due to incomplete susceptibility testing. Here we present the first North American type strain and whole-genome sequence of CyHV-3 isolated from wild carp collected from a lake with a history and recent incidence of carp mortality. Additionally, the strain was used in an in-vivo infection model to test the susceptibility of a common native minnow (Pimephales promelas) and goldfish (Carrasius auratus) which is invasive in North America. Detection of CyHV-3 DNA was confirmed in the tissues of a single fathead minnow but the same tissues were negative for CyHV-3 mRNA and samples from exposed fathead minnows were negative on cell culture. There was no detection of CyHV-3 DNA or mRNA in goldfish throughout the experiment. CyHV-3 DNA in carp tissues was reproducibly accompanied by the detection of CyHV-3 mRNA and isolation on cell culture. Additionally, environmental CyHV-3 DNA was detected on all tank filters during the study. These findings suggest that fathead minnows and goldfish are not susceptible to CyHV-3 infection and that detection of CyHV-3 DNA alone in host susceptibility trials should be interpreted with caution.