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ObjectiveTo analyze the levels of dioxin contamination in pork and pork liver from five provinces of China： A， B， C， D， and E， and evaluate the dietary exposure of the population， aiming to provide fundamental data for the future formulation of national limit standards of PCDD/Fs.MethodsA total of 146 pork and pork liver samples were collected during 2013 to 2019. According to the national standard method "Determination of Toxicity Equivalent of Dioxins and Analogues in Foods" （GB 5009.205-2013）， 17 polychlorinated dibenzo-p-dioxin/furans （PCDD/Fs） in food samples were detected by isotope dilution chromatography/high resolution dual-focusing magnetic mass spectrometry （HRGC/HRMS）. Based on the food consumption data， the dietary exposure via pork for the population was assessed.ResultsThe median TEQ concentration of dioxin in pork and pork liver samples was 0.106 pg/g·fat and 2.32 pg/g·fat， respectively. The concentration of PCDD/Fs in pork in various regions were sequentially decreased by A （0.859 pg/g·fat）>D（0.145 pg/g·fat）>C（0.097 4 pg/g·fat）>B（0.039 9 pg/g·fat）>E（0.023 pg/g·fat）， and the decreased order of PCDD/F levels in pork liver samples from various regions was A （3.616 pg/g·fat）>B （1.84 pg/g·fat）>D（1.313 pg/g·fat）>E（0.85 pg/g·fat）. The patterns for 17 congeners of PCDD/Fs in pork and pork liver samples were similar and OCDD was the dominant congener， accounting for 95% and 90% of the total mass concentrations， respectively. As for the TEQ concentrations， the congener patterns of PCDD/Fs in pork and pork liver samples were inconsistent. In addition， it also varied greatly in the congener patterns of PCDD/Fs for the same class of food samples from different regions. The median intakes of PCDD/Fs via pork for local residents in the five regions ranged from 0.192 to 2.054 pg/kg·bw/month， which were all lower than the PTMI value recommended by JECFA （70 pg/kg·bw/m）.ConclusionPCDD/Fs contamination in pork and pork liver existed in some areas of China. Spatial difference in PCDD/F levels was observed among the five areas and higher levels of PCDD/Fs for pork existed in developed areas . Residents showed low risk of dioxin exposure via pork intake overall. It is necessary to take long-term monitoring on the levels of PCDD/Fs in retailed food covered the larger area in China， and comprehensive exposure assessments of dioxins from various food categories should be further carried out to ensure the food safety of livestock and human health in the future.

Cyprinid herpesvirus 3 (CyHV‐3) is the main pathogen of koi herpesvirus disease (KHVD), which has caused serious damage to the ornamental and food‐producing carp industry. Effective and rapid on‐site detection methods are needed for early diagnosis of CyHV‐3. A lateral flow immuno‐chromatographic assay (LFIA) using two specific anti‐CyHV‐3 monoclonal antibodies has been developed and validated for on‐site detection of CyHV‐3. MAb 3C9 was used to bio‐conjugate CyHV‐3 antigen with colloidal gold, and MAb 2A8 was used to capture antigen bound colloidal gold on the test line. The control line was lined with goat anti‐mouse IgG to capture unbound colloidal gold to validate performance. The test results can be viewed within 10 min after putting the strip into CyHV‐3 virus infection fluid. The lowest limit of detection for the LFIA test was found to be 1.5 × 104 copies/μL and it showed no cross‐reactivity with other fish viral pathogens. The specificity of the strip was 100% when spleen and kidney tissues of CyHV‐3‐infected and healthy koi were validated at the field level. The LFIA strip will be an effective device for the early detection of CyHV‐3 in the future. [ABSTRACT FROM AUTHOR]

Cyprinid herpesvirus 2 (CyHV‐2) is a viral pathogen worldwide and causing high mortality on goldfish and silver crucian carp (Carassius auratus gibelio). In order to establish a stable and sensitive immunological diagnostic approach, the recombinant ORF121 protein encoded by the CyHV‐2 ORF121 gene, was selected as a capture antigen to identify cells and tissues infected with CyHV‐2 by immunological methods in this study. Firstly, the open reading frame of CyHV‐2 ORF121 was cloned into the PGEX‐4T‐3 vector and expressed in Escherichia coli. Purified recombinant ORF121 protein was then used as an antigen to prepare monoclonal antibodies, and an efficient hybridoma cell line was selected by dot‐blot assay. The resulting mAb‐3D9 was applied to detect CyHV‐2 in infected caudal fin of Carassius auratus gibelio (GiCF) cells and fish tissues by western blotting, immunofluorescence assays and immunohistological asays. The monoclonal antibody could specifically identify CyHV‐2 in infected GiCF cells and the gills, the kidney and the spleen tissues, and it could attenuate CPE by CyHV‐2 in vitro, suggesting it can be applied for CyHV‐2 detection in the crucian carp and ORF121 may be a candidate vaccine against CyHV‐2. [ABSTRACT FROM AUTHOR]