Molecular characteristics and phylogenetic analysis of novel goose parvovirus strains associated with short beak and dwarfism syndrome.

Short beak and dwarfism syndrome (SBDS) emerged in Cherry Valley duck flocks in China in 2015, and novel goose parvovirus (NGPV) was shown to be the etiological agent of SBDS. To date, it is not known whether SBDS-related NGPV isolates possess common molecular characteristics. In this study, three new NGPV strains (namely, SDHT16, SDJN19, and SDLC19) were isolated from diseased ducks showing typical signs of SBDS and successfully passaged in embryonated goose or Cherry Valley duck eggs. The complete genome sequences of these NGPV strains were 98.9%-99.7% identical to each other but showed slightly less similarity (95.2%-96.1% identity) to classical GPV strains. A total of 16 common amino acid substitutions were present in the VP1 proteins of six NGPV strains (SDHT16, SDJN19, SDLC19, QH, JS1, and SDLC01) compared with the classical Chinese GPV strains, nine of which were identical to those found in European GPV strain B. The non-structural protein Rep1 of the six NGPV strains had 12 common amino acid substitutions compared with the classical GPV strains. Phylogenetic analysis indicated that the Chinese NGPV strains clustered with the European SBDS-related NGPV strains, forming a separate branch that was distinct from the group formed by the classical GPV strains. The present study shows the common molecular characteristics of NGPV isolates and suggests that the Chinese NGPV isolates probably share a common ancestor with European SBDS-related NGPV strains.

Sole recombinant Muscovy duck parvovirus infection in Muscovy ducklings can form characteristic intestinal embolism.

Recombinant Muscovy duck parvovirus (rMDPV) has been recently identified as a novel pathogen circulating in Chinese Muscovy duck flocks in the past two decades. Different from classical MDPV, rMDPV infection can form embolism in the intestinal tract of deceased Muscovy ducklings. However, whether rMDPV acts as the sole causative agent involved in the formation of the characteristic embolism in Muscovy ducklings remains unclear. In this study, an infectious plasmid clone pZW containing the complete genome of strain ZW, a previously characterized rMDPV isolate, was constructed, and a single nucleotide mutation was then introduced in the VP1 gene within pZW as the genetic marker. Transfection of pZW in 11-day-old embryonated Muscovy duck eggs via the chorioallantoic membrane route resulted in the rescue of the infectious virus. The rescued virus exhibited similar biological characteristics to its parental strain ZW, as evaluated by the median embryo lethal dose and the replication kinetics in embryonated Muscovy duck eggs. Muscovy duckling infection tests showed that the rescued virus and parental strain can kill all Muscovy ducklings within 7 days post-infection. Postmortem examination revealed that embolism can be observed in the intestinal tracts of deceased ducklings in the rescued and parental virus infection groups. Collectively, the present study demonstrated that sole rMDPV infection of Muscovy ducklings, without participation of other pathogens, is enough to form characteristic embolism in the intestinal tract.

Retrospective investigation and molecular characteristics of the recombinant Muscovy duck parvovirus circulating in Muscovy duck flocks in China.

The recombinant Muscovy duck parvovirus (rMDPV) has been recently characterized and identified in China. However, whether other additional rMDPV field isolates exist, and whether these strains possess common molecular characteristics, remain to be explored. In this retrospective study, two new rMDPV isolates, namely, JH06 and JH10, were identified through genome sequencing and recombination analysis. JH06, JH10, and four previously characterized rMDPV strains (SAAS-SHNH, ZW, FJM3, and PT97) underwent the same recombination events in a 1.1-kb region in their VP3 genes and displayed highly consistent beginning and ending breakpoints. JH06, JH10, SAAS-SHNH, ZW, and FJM3, but not PT97, underwent recombination in their P9 promoter regions. In both recombination events, the classical MDPV strain YY acted as the major parent, whereas the virulent strain DY16 and the vaccine strain SYG61v of goose parvovirus (GPV) served as the minor parents. The sequence alignments of inverted terminal repeats (ITRs) revealed that rMDPV strains shared higher identities (96.0%-97.2%) with classical MDPV strains than with GPV and contained typical one-nucleotide-pair deletions in the palindromic stems of their ITRs. This work elucidated the common molecular characteristics and differences of six rMDPV strains. The results of this work will facilitate the preparation of an efficacious vaccine for the protection of Muscovy ducks against rMDPV infection.