Shilong Chen

Isolation and characterization of a distinct duck-origin goose parvovirus causing an outbreak of duckling short beak and dwarfism syndrome in China

Many mule duck and Cherry Valley duck flocks in different duck-producing regions of China have shown signs of an apparently new disease designated “short beak and dwarfism syndrome” (SBDS) since 2015. The disease is characterized by dyspraxia, weight loss, a protruding tongue, and high morbidity and low mortality rates. In order to characterize the etiological agent, a virus designated SBDSV M15 was isolated from allantoic fluid of dead embryos following serial passage in duck embryos. This virus causes a cytopathic effect in duck embryo fibroblast (DEF) cells. Using monoclonal antibody diagnostic assays, the SBDSV M15 isolate was positive for the antigen of goose parvovirus but not Muscovy duck parvovirus. A 348-bp (2604-2951) VP1gene fragment was amplified, and its sequence indicated that the virus was most closely related to a Hungarian GPV strain that was also isolated from mule ducks with SBDS disease. A similar disease was reproduced by inoculating birds with SBDSV M15. Together, these data indicate that SBDSV M15 is a GPV-related parvovirus causing SBDS disease and that it is divergent from classical GPV isolates.

Evidence for natural recombination in the capsid gene VP2 of Taiwanese goose parvovirus

To investigate the possible role of recombination in the evolution of Muscovy duck parvovirus (MDPV) and goose parvovirus (GPV) in Taiwan, we analyzed a potentially significant recombination event that occurred only in GPV by comparing thirteen complete sequences of the capsid gene VP2 of GPV and MDPV. The recombination event occurred between GPV strain 06-0239 as the minor parent and strains 99-0808 as the major parent, which resulted in the GPV recombinant V325/TW03. GPV V325/TW03 is likely to represent a new genotype among the Taiwanese GPV strains. This represents the first evidence that intergenotype recombination within the VP2 gene cluster contributes to the genetic diversity of the VP2 genes of Taiwanese GPV field strains.

Phylogenetic analysis of VP1 gene sequences of waterfowl parvoviruses from the Mainland of China revealed genetic diversity and recombination.

To determine the origin and evolution of goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV) in the Mainland of China, phylogenetic and recombination analyses in the present study were performed on 32 complete VP1 gene sequences from China and other countries. Based on the phylogenetic analysis of the VP1 gene, GPV strains studied here from Mainland China (PRC) could be divided into three genotypes, namely PRC-I, PRC-II and PRC-III. Genotype PRC-I is indigenous to Mainland China. Only one GPV strain from Northeast China was of Genotype PRC-II and was thought to be imported from Europe. Genotype PRC-III, which was the most isolated genotype during 1999-2012, is related to GPVs in Taiwan and has been the predominant pathogen responsible for recent Derzys disease outbreaks in Mainland China. Current vaccine strains used in Mainland China belong to Genotype PRC-I that is evolutionary distant from Genotypes PRC-II and PRC-III. In comparison, MDPV strains herein from Mainland China are clustered in a single group which is closely related to Taiwanese MDPV strains, and the full-length sequences of the VP1 gene of China MDPVs are phylogenetic closely related to the VP1 sequence of a Hungarian MDPV strain. Moreover, We also found that homologous recombination within VP1 gene plays a role in generating genetic diversity in GPV evolution. The GPV GDFSh from Guangdong Province appears to be the evolutionary product of a recombination event between parental GPV strains GD and B, while the major parent B proved to be a reference strain for virulent European GPVs. Our findings provide valuable information on waterfowl parvoviral evolution in Mainland China.

The newly emerging duck-origin goose parvovirus in China exhibits a wide range of pathogenicity to main domesticated waterfowl

Short beak and dwarfism syndrome virus (SBDSV) is a newly emerging distinct duck-origin goose parvovirus that belongs to the genus Dependovirus. Our previous studies have found that SBDSV was highly pathogenic to Cherry Valley ducklings and mule ducklings. However, little is known about its pathogenicity to other waterfowls. In the present study, the pathogenicity of SBDSV was evaluated in domesticated waterfowl including Muscovy ducklings, Sheldrake ducklings and domestic goslings. All experimentally infected birds exhibited remarkable growth retardation, anorexia and diarrhea similar to naturally infected birds. Interestingly, atrophic beaks and protruded tongues were not observed in all infection groups. At necropsies, no diagnostic pathological lesions were observed. Viral antigens existed in most organ tissues such as heart, liver, spleen, kidney, pancreas and intestine. All ducks in Muscovy duckling and Sheldrake duckling infected groups and 70% goslings in infected groups were seropositive for goose parvovirus (GPV) antibodies at 21dpi with the average titers as 28.4, 26.9, 24.0, respectively. Muscovy ducklings were more prominent in viral load and weight loss with a higher GPV antibodies titer than Sheldrake ducklings and goslings. Taken together, SBDSV exhibits a wide range of pathogenicity to main domesticated waterfowl with variable symptoms and cause considerable economic losses in China.

Analysis of differentially expressed proteins in Muscovy duck embryo fibroblasts infected with virulent and attenuated Muscovy duck reovirus by two-dimensional polyacrylamide gel electrophoresis

Muscovy duck reovirus (MDRV) belongs to the Orthoreovirus genus of the Reoviridae family, which is a significant poultry pathogen leading to high morbidity and mortality in ducklings. However, the pathogenesis of the virus is not well understood. In the present study, two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE) combined with LC-MS-MS was used to identify differentially expressed proteins between Muscovy duck embryo fibroblasts (MDEF) infected with virulent (MV9710 strain) and attenuated (CA strain) MDRV and non-infected MDEFs. A total of 115 abundant protein spots were identified. Of these, 59 of differentially expressed proteins were detected, with functions in metabolism and utilization of carbohydrates and nucleotides, anti-stress, and regulation of immune and cellular process. GO analysis of the identified proteins showed that they belonged to the classes molecular function (141 proteins), cellular component (62 proteins), and biological process (146 proteins). The results were validated by qRT-PCR, which suggests that the analysis method of 2D PAGE combined with LC-MS-MS used in this study is reliable. This study lays a foundation for further investigation of the biology of MDRV infection in MDEF.