Highly Pathogenic Swine Getah Virus in Blue Foxes, Eastern China, 2017

Background: Duck circovirus (DuCV) is a potential immunosuppressive virus that causes feather disorders in young ducks. In this study, DuCV obtained from various species of ducks was investigated by polymerase chain reaction (PCR) in southern and southwestern China (Guangdong, Guangxi and Yunnan provinces) from 2018 to 2019. Results: A total of 848 bursa samples were collected from dead Mulard, Cherry Valley Pekin, Muscovy and Mallard ducks from duck farms. The positivity rate of DuCV in the total sample was approximately 36.91%. We found that the prevalence of DuCV in Yunnan (43.09%) was higher than those in Guangxi (34.38%) and Guangdong (34.4%). However, the positivity rates of DuCV in the four duck species were not significantly different (P > 0.05). Nineteen randomly selected complete viral genomes were sequenced. The complete genomes of the DuCV were 1987 to 1995 nt in length, and were 81.7–99.3% homologous to the other 57 sequences in GenBank. Phylogenetic analyses based on the complete genomes of 76 DuCVs showed that the 19 novel DuCV sequences from Guangdong and Guangxi provinces mainly belonged to the DuCV-1 and DuCV-2 genetic groups, respectively. However, the two genotype groups coexisted in Yunnan Province. In addition, recombination analysis showed putative recombination sites in 3 strains in Yunnan that originated from strains Guangdong and Guangxi. Interestingly, the epidemiological investigation showed that Mulard ducks, Cherry Valley Pekin ducks and Muscovy ducks more than 4 weeks old were more susceptible to infection with the novel DuCV than ducks less than 4 weeks old. Conclusions: These data provide insight into the molecular epidemiology and genetic diversity of DuCVs circulating in southern and southwestern China for the first time.

Introduction: Batai virus (BATV), a zoonotic pathogen transmitted by mosquitoes, infects vertebrates, including livestock, birds, and humans. Although BATV has been detected and isolated in mosquitoes in Yunnan Province, China, there have been no reports of livestock infection. Thus, we conducted a molecular and serological investigation of BATV in cattle and goat sera collected in spring and autumn from 2021 to 2022 in Honghe Prefecture, Yunnan Province, on the China-Vietnam border.Methods: We used indirect enzyme-linked immunosorbent assays and reverse transcription real-time PCR (RT-qPCR) to test 929 cattle and 973 goat serum samples.Results: BATV antibodies were detected in 262/929 (28.2%) cattle and 263/973 (27.0%) goat serum samples. RT-qPCR did not detect BATV RNA.Discussion: The positive rate of BATV serum antibodies in cattle and goats in Luxi County was higher compared with other areas, and it was also higher in autumn compared with spring, which may be related to climate, temperature, and mosquito density. Although our findings indicated the presence of BATV infection in livestock in the region, RT-qPCR did not detect BATV RNA. Therefore, BATV monitoring in cattle and goats should be heightened in autumn, and the scope of host monitoring should be expanded to clarify the hosts and vectors of BATV infection.

In this study, we analyzed 137 liver samples collected from deceased Muscovy ducks in Guangdong, China, between 2020 and 2023. The GD2407 strain was isolated from these samples. Genomic analysis revealed that the complete genome of GD2407 is 5067 bp in length, encoding both non-structural (NS) and structural proteins (VP). Identity analysis demonstrated that GD2407 shares 99.9% homology with the GDZJ1901 strain. Recombination analysis indicated that GD2407 originated from a recombination event between Muscovy duck parvovirus (MDPV) and goose parvovirus (GPV). Genetic evolution analysis showed that GD2407 is genetically closely related to GDZJ1901 but distinct from the pre-2020 prevalent GD201911 strain. These findings suggest that the circulation of MDPV in this region may contribute to illness and mortality in ducks.

Introduction: Bulbul coronavirus (BuCoV), a delta coronavirus recently identified in passerine birds, remains poorly characterized regarding its ecology and evolutionary dynamics. This study aimed to determine the prevalence of BuCoV in wild avifauna, clarify its evolutionary relationship with other delta coronaviruses, and identify genetic signatures potentially relevant to host adaptation and cross-species transmission in southern China. Methods: From 2023 to 2024, we conducted molecular surveillance across 12 regions in Guangdong Province, China. A total of 2,145 avian fecal samples were collected and screened for BuCoV using real-time quantitative PCR. The complete genomes of representative strains were obtained using next-generation sequencing. Subsequent analyses included phylogenetic reconstruction using maximum likelihood methods, recombination detection using RDP4 and SimPlot, and comparative amino acid analysis. Results: BuCoV was detected exclusively in Shenzhen (3/168, 1.78%), with all positive samples originating from bulbuls (Pycnonotus spp.). The Shenzhen strain GD2411 exhibited the highest nucleotide identity with BuCoV strains HKU11-796 (97.26%) and HKU11-934 (96.79%), but far lower similarity (78.9%–82.4%) to other delta coronaviruses. Phylogenetic analysis placed GD2411 in a monophyletic clade with HKU11 strains. Recombination analyses revealed mosaic structures within the spike (S) gene, involving multiple coronavirus lineages. Thirty-one amino acid substitutions were detected in the S protein, together with mutations in RdRp, 3CLpro, and nucleocapsid. Discussion: These findings suggest that BuCoV GD2411 emerged through inter-lineage recombination and is undergoing adaptive evolution, particularly in the spike protein. The detection of BuCoV exclusively in Shenzhen, a critical node in the East Asian-Australasian Flyway, suggests that migratory birds may facilitate viral dissemination. The identified mutations may affect viral replication, host adaptation, or immune evasion. These findings provide essential baseline genomic and epidemiological data critical for understanding BuCoV diversity and assessing potential zoonotic risks in southern China.