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To visually and rapidly detect a novel goose astrovirus (N-GoAstV) causing fatal gout in goslings, an isothermal detection method based on one-step reverse transcription loop-mediated isothermal amplification (one-step RT-LAMP) was established. The one-step RT-LAMP assay for N-GoAstV detection, using Bst 3.0 DNA polymerase with strong reverse transcription activity and primer sets targeting the opening reading frame 1b (ORF1b) of N-GoAstV, could be completed in 30 min using a water bath at 61°C; the detection results could be visually observed by adding a pH-sensitive dye containing phenol red and cresol red. The detection limit of the one-step RT-LAMP assay was 57.8 copies, which was similar to that of reverse transcription-quantitative polymerase chain reaction. The assay specifically detected N-GoAstV without any cross-reaction with other reference viruses, and this was further confirmed using enzyme digestion. These results indicated that the newly established RT-LAMP assay could accomplish reverse transcription, amplification, and visual result determination in one step, and the results obtained via this rapid and cost-effective method could be used to support disease control on farms in terms of N-GoAstV infection., (Copyright © 2020. Published by Elsevier Inc.)

Simple Summary: The duck hepatitis B virus (DHBV), owing to its high similarity to the human hepatitis B virus (HBV), is an ideal model for HBV research. In this study, 23 complete genomes of Chinese strains of DHBV were analyzed using phylogenetic methods, and their recombinant events were predicted and analyzed. These data aid in understanding the intergenotypic recombination of HBV and are expected to promote further research on the epidemiology and evolution of DHBV. In this study, we detected 12 duck and 11 goose flocks that were positive for duck hepatitis B virus (DHBV) using polymerase chain reaction and isolated 23 strains between 2020 and 2022 in China. The complete genomes of goose strains E200801 and E210501 shared the highest identity (99.9%), whereas those of strains Y220217 and E210526 shared the lowest identity (91.39%). The phylogenetic tree constructed based on the genome sequences of these strains and reference strains was classified into three major clusters: the Chinese branch DHBV-I, the Chinese branch DHBV-II, and the Western branch DHBV-III. Furthermore, the duck-origin strain Y200122 was clustered into a separate branch and was predicted to be a recombinant strain derived from DHBV-M32990 (belonging to the Chinese branch DHBV-I) and Y220201 (belonging to the Chinese branch DHBV-II). Additionally, preS protein analysis of the 23 DHBV strains revealed extensive mutation sites, almost half of which were of duck origin. All goose-origin DHBV contained the mutation site G133E, which is related to increased viral pathogenicity. These data are expected to promote further research on the epidemiology and evolution of DHBV. Continuing DHBV surveillance in poultry will enhance the understanding of the evolution of HBV. [ABSTRACT FROM AUTHOR]

Goose circovirus (GoCV) is a common pathogen that causes immunosuppression and promotes secondary infections with other infectious agents in geese worldwide. In the present study, we identified GoCV in 2 out of 93 duck flocks from China and successfully sequenced the complete genomes of 2 strains (AH22du and HN20du). The whole genome of the two strains shared a high identity of 90.5 to 98.63% with China GoCV reference, and low identity of 58.98% with DuCV reference, respectively. Phylogenetic tree constructed on the two and other genome sequences of GoCV revealed three main branches. Both strains sequenced in this study were distributed on different sub-branches with most other Chinese GoCV strains, and AH22du clustered into an independent sub-branch within the cluster. Recombination analysis predicted that HN20du might potentially recombine from the major parent of yk4 (Zhejiang Province, China, 2007) and minor parent of GD/YJ/g2 (Guangdong Province, China, 2020). To the best of our knowledge, this is the first report of GoCV in ducks from China. This broadened host spectrum of GoCVs requires attention from the waterfowl industry and researchers. [ABSTRACT FROM AUTHOR]