Molecular characterization of a novel Muscovy duck parvovirus isolate: evidence of recombination between classical MDPV and goose parvovirus strains

Development and application of a novel recombinase polymerase amplification-Pyrococcus furiosus argonaute system for rapid detection of goose parvovirus

Rapid and accurate detection of goose parvovirus (GPV) is crucial for controlling outbreaks and mitigating their economic impact on the poultry industry. This study introduces recombinase polymerase amplification combined with the Pyrococcus furiosus argonaute (RPA-PfAgo) system, a novel diagnostic platform designed to address the limitations of traditional GPV detection methods. Capitalizing on the rapid DNA amplification of RPA and stringent nucleic acid cleavage by the PfAgo protein, the RPA-PfAgo system offers high specificity and sensitivity in detecting GPV. Our optimization efforts included primer and probe configurations, reaction parameters, and guided DNA selection, culminating in a detection threshold of 102 GPV DNA copies per microlitre. The specificity of the proposed method was rigorously validated against a spectrum of avian pathogens. Clinical application to lung tissues from GPV-infected geese yielded a detection concordance of 100%, surpassing that of qPCR and PCR in both rapidity and operational simplicity. The RPA-PfAgo system has emerged as a revolutionary diagnostic modality for managing this disease, as it is a promising rapid, economical, and onsite GPV detection method amenable to integration into broad-scale disease surveillance frameworks. Future explorations will extend the applicability of this method to diverse avian diseases and assess its field utility across various epidemiological landscapes.

Pathogenicity of duck circovirus and novel goose parvovirus co-infection in SPF ducks

Duck circovirus (DuCV) is one of the most prevalent infectious viruses in the duck industry in China. Although the clinical signs vary, it often causes immunosuppression in the host and leads to secondary infection with other pathogens. Novel goose parvovirus (NGPV) mainly infects ducks and causes short beak and dwarfism syndrome in ducks. However, the incidence of infection in ducks has increased in recent years, and the phenomenon of mixed infection with DuCV is common, resulting in more severe clinical morbidity. However, there are no systematic studies evaluating the presence of mixed infections. In order to investigate the synergistic pathogenicity of DuCV and NGPV co-infection in SPF ducks, a comparative experiment using DuCV and NGPV co-infection and mono-infection bird models was established. The results showed that the clinical signs of short beak, dwarfism and immunosuppression were more obvious in DuCV and NGPV co-infected ducks; the tissue damage of target organs was more serious, and the viral titre in organs and cloacal swabs were more significant compared with those of SPF ducks infected with only one virus. The results indicated that co-infection with DuCV and NGPV could promote viral replication and cause more severe tissue damage and immunosuppression than single virus infection. The present study reveals that the co-infection of NGPV and DuCV has a synergistic pathogenic effect from the aspect of pathogenicity, and the conclusions drawn not only clarify the direction of the subsequent research on the mechanism of co-infection of NGPV and DuCV, but also provide a scientific basis for the research on the co-infection of immunosuppressive pathogens and other pathogens.

Development and application of quadruplex real time quantitative PCR method for differentiation of Muscovy duck parvovirus, Goose parvovirus, Duck circovirus, and Duck adenovirus 3

Introduction

Muscovy duck parvovirus (MDPV), Goose parvovirus (GPV), Duck circovirus, (DuCV) and Duck adenovirus 3 (DAdV-3) are important pathogens that cause high morbidity and mortality in ducks, causing huge economic loss for the duck industry.

Methods

The present study, a quadruplex one-step real time quantitative PCR method for the detection of MDPV, GPV, DuCV, and DAdV-3 was developed.

Results

The results showed that assay had no cross-reactivity with other poultry pathogens [Duck plague virus (DPV), Duck tembusu virus (DTMUV), H6 avian influenza virus (H6 AIV), New duck reovirus (NDRV), Newcastle disease virus (NDV), H4 avian influenza virus (H4 AIV), Escherichia coli (E. coli), Muscovy duck reovirus (MDRV), Egg drop syndrome virus (EDSV), Pasteurella multocida (P. multocida)]. The sensitivity result showed that the limits of detection for MDPV, GPV, DuCV, and DAdV-3 were 10, 10, 1 and 10 copies/µl, respectively; The coefficients of variation intra- and inter-method was 1-2%; The range of linear (109 to 103 copies/µL) demonstrated the R2 values for MDPV, GPV, DuCV, and DAdV-3 as 0.9975, 0.998, 0.9964, and 0.996, respectively. The quadruplex real time quantitative PCR method efficiency was 90.30%, 101.10%, 90.72%, and 90.57% for MDPV, GPV, DuCV, and DAdV-3, respectively. 396 clinical specimens collected in some duck sausages from June 2022 to July 2023 were simultaneously detected using the established quadruplex real time quantitative PCR method and the reported assays. The detection rates for MDPV, GPV, DuCV, and DAdV-3 were 8.33% (33/396), 17.93% (71/396), 33.58% (133/396), and 29.04% (115/396), respectively. The agreement between these assays was greater than 99.56%.

Discussion

The developed quadruplex real-time quantitative PCR assay can accurately detect these four viruses infecting ducks, providing a rapid, sensitive, specific and accurate technique for clinical testing.

Molecular Characterization of the Chicken Parvovirus Based on VP1 Gene Circulating in Brazilian Chicken Flocks

Parvovirus infection affects several animal species, especially young animals. In birds, parvovirus infection has been described in Muscovy ducks, turkeys, and chickens, all of which had enteric diseases characterized by diarrhea. Chicken parvovirus (ChPV) has been detected in poultry around the world in animals affected by enteric problems, showing dwarfism, cloacal pasting, and diarrhea. In Brazil, ChPV was detected in chickens affected by diarrhea fifteen years ago. However, the genetic characteristics of ChPV circulating in chicken flocks were not determined. Therefore, the aim of the present investigation was to determine the genetic characteristics of the VP1 gene from ChPV detected in chickens affected by enteric diseases in Brazil. For this purpose, a molecular approach was used. Specific primers were designed to flank the complete VP1 gene of ChPV and amplify it using PCR. The amplified products from samples of chickens with enteric diseases were sequenced, and 22 complete CDs of the VP1 gene were obtained. These samples, compared to the ABU-P1 sequence, showed 17 sequences with high nucleotide (NT) similarity of 92.7-97.4% and amino acid (AA) similarity of 94.8-99.5% associated with Runting and Stunting syndrome (RSS); there were also five samples associated with hens with diarrhea with unusual jejunal dilatation (JD) that had less similarity than the RSS sequences (NT of 86.5% and AA of 93-93.1%). The phylogenetic analysis determined four groups. Group I had sequences from Korea. The second group included sequences from Korea, China, and Brazil (not included in this work). The third group had studied RSS sequences grouped with the ABU-P1 strain and sequences from China and the United States. Finally, the sequences from JD were clustered in a separate group with a bootstrap of 100%, a group that was denoted as group IV, and included sequences from China. RDP4 and SimPlot analysis showed one point of recombination with the sequences of group III ChPV in the JD sequences. Herein, we show that circulating strains of ChPV exhibit genetic differences in the VP1 gene in Brazilian chicken flocks. Nevertheless, more studies are needed to determine the probability of a new genetic group of ChPV based on the analysis of the complete genome.

Isolation and genetic characterization of waterfowl parvovirus in ducks in Northern Vietnam

Background and Aim

Short beak and dwarfism syndrome (SBDS), a highly contagious disease, has been reported in duck farms in Vietnam since 2019. In this study, we evaluated the virulence and characterized the virus obtained from SBDS cases in North Vietnam.

Materials and Methods

Polymerase chain reaction was used to detect waterfowl parvovirus in ducks, and the virus from positive samples was inoculated into 10-day-old duck-embryonated eggs to reproduce the disease in young ducklings to determine the virulence and subjected to phylogenetic analysis of non-structural (NS) and VP1 gene sequences.

Results and Discussion

Goose parvovirus (GPV) was isolated from ducks associated with SDBS in Vietnam. The virus Han-GPV2001 is highly virulent when inoculated into 10-day-old duck embryos and 3-day-old ducklings. The mortality rate of duck embryos was 94.35% within 6 days of virus inoculation. Inoculating 3-day-old ducks with the virus stock with 104.03 EID50 through intramuscular and neck intravenous administration resulted in 80% and 66.67% of clinical signs of SDBS, respectively, were shown. Phylogenetic analysis based on the partial NS and VP1 gene sequences revealed that the viral isolate obtained in this study belonged to novel GPV (NGPV) and was closely related to previous Vietnamese and Chinese strains.

Conclusion

A GPV strain, Han-GPV2001, has been successfully isolated and has virulence in duck-embryonated eggs as well as caused clinical signs of SBDS in ducks. Phylogenetic analyses of partial genes encoding NS and capsid proteins indicated that the obtained GPV isolate belongs to the NGPV group.

Bioinformatics analysis of Muscovy duck parvovirus REP and VP1 proteins

This article was aimed at analyzing the sequence, structure, and function of the two Muscovy duck parvovirus proteins, including REP and VP1. The antigenicity, physical and chemical properties, transmembrane regions, phosphorylation sites, glycosylation sites, three-dimensional structure, and linear epitope of VP1 and REP were predicted and analyzed through bioinformatics methods. A multi-epitope vaccine was also constructed based on the screened epitopes, and the vaccine was characterized, modeled, molecularly docked and molecularly cloned. The epitopes were screened according to the criteria of antigenicity, non-allergenicity and non-toxicity, and 12 epitope fragments were obtained. The B cell epitopes were analyzed according to four scales: β-turn, hydrophilicity, surface accessibility and antigenicity. Combined with the epitope prediction results based on structure, the final epitope prediction results were obtained. The multi-epitope vaccine used an EAAAK-linked adjuvant, a GPGPG-linked T-cell epitope, and a KK-linked B-cell epitope. The analysis showed that the vaccine was stable hydrophilic, antigenic, conserved and non-allergenic. Based on molecular docking it was shown that good interactions between the vaccine and the immune receptor were generated and were essential to generate an immune response. The final vaccine was reverse translated into cDNA and the DNA vaccine was designed by codon optimization and molecular cloning. Further trials are still needed to demonstrate the immunogenicity and other aspects of vaccine efficacy.Communicated by Ramaswamy H. Sarma.

A Novel Dependoparvovirus Identified in Cloacal Swabs of Monk Parakeet (Myiopsitta monachus) from Urban Areas of Spain

The introduction of invasive birds into new ecosystems frequently has negative consequences for the resident populations. Accordingly, the increasing population of monk parakeets (Myiopsitta monachus) in Europe may pose a threat because we have little knowledge of the viruses they can transmit to native naïve species. In this study, we describe a new dependoparvovirus detected by metagenomic analysis of cloacal samples from 28 apparently healthy individuals captured in urban areas of Madrid, Spain. The genomic characterization revealed that the genome encoded the NS and VP proteins typical of parvoviruses and was flanked by inverted terminal repeats. No recombination signal was detected. The phylogenetic analysis showed that it was closely related to a parvovirus isolated in a wild psittacid in China. Both viruses share 80% Rep protein sequence identity and only 64% with other dependoparvoviruses identified in Passeriformes, Anseriformes, and Piciformes and are included in a highly supported clade, which could be considered a new species. The prevalence was very low, and none of the additional 73 individuals tested positive by PCR. These results highlight the importance of exploring the viral genome in invasive species to prevent the emergence of novel viral pathogenic species.

Parvovirus dark matter in the cloaca of wild birds

With the development of viral metagenomics and next-generation sequencing technology, more and more novel parvoviruses have been identified in recent years, including even entirely new lineages. The Parvoviridae family includes a different group of viruses that can infect a wide variety of animals. In this study, systematic analysis was performed to identify the "dark matter" (datasets that cannot be easily attributed to known viruses) of parvoviruses and to explore their genetic diversity from wild birds' cloacal swab samples. We have tentatively defined this parvovirus "dark matter" as a highly divergent lineage in the Parvoviridae family. All parvoviruses showed several characteristics, including 2 major protein-coding genes and similar genome lengths. Moreover, we observed that the novel parvo-like viruses share similar genome organizations to most viruses in Parvoviridae but could not clustered with the established subfamilies in phylogenetic analysis. We also found some new members associated with the Bidnaviridae family, which may be derived from parvovirus. This suggests that systematic analysis of domestic and wild animal samples is necessary to explore the genetic diversity of parvoviruses and to mine for more of this potential dark matter.

Epidemiological Analysis and Genetic Characterization of Parvovirus in Ducks in Northern Vietnam Reveal Evidence of Recombination

In total, 130 tissue-pooled samples collected from ducks in some provinces/cities in north Vietnam were examined for waterfowl parvovirus genome identification. Twenty-six (20%) samples were positive for the parvovirus infection, based on polymerase chain reaction analysis. Of the 38 farms tested, 14 (36.84%) were positive for the waterfowl parvovirus genome. The rate of the parvovirus genome detection in ducks aged 2−4 weeks (37.04%) was significantly (p < 0.05) higher than that at ages <2 weeks (9.09%) and >4 weeks (16.30%). The positive rate on medium-scale farms (9.36%) was significantly (p < 0.05) lower than for small-scale (31.03%) and large-scale (29.73%) farms. The lengths of the four Vietnamese waterfowl parvovirus genomes identified were 4750 nucleotides. Among the four Vietnamese parvovirus genomes, nucleotide identities were from 99.29% to 99.87%. Phylogenetic analysis of the near-complete genomes indicated that the waterfowl circulating in northern Vietnam belonged to the novel goose parvovirus (NGPV) group. The Vietnamese NGPV group was closely related to the Chinese group. Recombination analysis suggested that the Vietnam/VNUA-26/2021 strain was generated by a recombination event. One positive selection site of the capsid protein was detected.

Development and application of a multiplex PCR method for simultaneous detection of waterfowl parvovirus, duck enteritis virus and goose astrovirus

Waterfowl parvovirus, duck enteritis virus and goose astrovirus have become serious pathogens in waterfowl farming. Co-infections occasionally occur, and as a result, it is much harder to rapidly and simultaneously identify several pathogens using conventional PCR. According to the characteristics of the goose parvovirus (GPV) and muscovy duck parvovirus (MDPV) genome sequences, a universal PCR primer was designed using Rep1 as the target gene. The specific detection primers were designed based on the specific conserved regions of UL54 of the duck enteritis virus (DEV) gene and ORF1a of the goose astrovirus (GAstV) gene. The PCR reaction system and conditions were optimized, and the optimal annealing temperature was found to be 56.2 ℃. The volume ratio of the GPV-MDPV, GAstV and DEV primers (20 μM) was 1:4:5. The established multiplex PCR detection method can simultaneously detect GPV, MDPV, DEV and GAstV within one reaction, and be negative for duck Tembusu virus, muscovy duck reovirus, duck hepatitis A virus type 3 and duck circovirus. The method with excellent sensitivity, specificity and repeatability was successfully applied to clinical samples, it is a useful platform for identifing co-infections of GPV, MDPV, DEV and GAstV in waterfowl.

Recombinant Muscovy Duck Parvovirus Led to Ileac Damage in Muscovy Ducklings

Waterfowl parvovirus (WPFs) has multiple effects on the intestinal tract, but the effects of recombinant Muscovy duck parvovirus (rMDPV) have not been elucidated. In this study, 48 one-day-old Muscovy ducklings were divided into an infected group and a control group. Plasma and ileal samples were collected from both groups at 2, 4, 6, and 8 days post-infection (dpi), both six ducklings at a time. Next, we analyzed the genomic sequence of the rMDPV strain. Results showed that the ileal villus structure was destroyed seriously at 4, 6, 8 dpi, and the expression of ZO-1, Occludin, and Claudin-1 decreased at 4, 6 dpi; 4, 6, 8 dpi; and 2, 6 dpi, respectively. Intestinal cytokines IFN-α, IL-1β and IL-6 increased at 6 dpi; 8 dpi; and 6, 8 dpi, respectively, whereas IL-2 decreased at 6, 8 dpi. The diversity of ileal flora increased significantly at 4 dpi and decreased at 8 dpi. The bacteria Ochrobactrum and Enterococcus increased and decreased at 4, 8 dpi; 2, 4 dpi, respectively. Plasma MDA increased at 2 dpi, SOD, CAT, and T-AOC decreased at 2, 4, 8 dpi; 4, 8 dpi; and 4, 6, 8 dpi, respectively. These results suggest that rMDPV infection led to early intestinal barrier dysfunction, inflammation, ileac microbiota disruption, and oxidative stress.

The Diversity of Parvovirus Telomeres

Parvoviridae are small viruses composed of a 4–6 kb linear single-stranded DNA protected by an icosahedral capsid. The viral genes coding non-structural (NS), capsid, and accessory proteins are flanked by intriguing sequences, namely the telomeres. Telomeres are essential for parvovirus genome replication, encapsidation, and integration. Similar (homotelomeric) or different (heterotelomeric) at the two ends, they all contain imperfect palindromes that fold into hairpin structures. Up to 550 nucleotides in length, they harbor a wide variety of motifs and structures known to be recognized by host cell factors. Our study aims to comprehensively analyze parvovirus ends to better understand the role of these particular sequences in the virus life cycle. Forty Parvoviridae terminal repeats (TR) were publicly available in databases. The folding and specific DNA secondary structures, such as G4 and triplex, were systematically analyzed. A principal component analysis was carried out from the prediction data to determine variables signing parvovirus groups. A special focus will be put on adeno-associated virus (AAV) inverted terminal repeats (ITR), a member of the genus Dependoparvovirus used as vectors for gene therapy. This chapter highlights the diversity of the Parvoviridae telomeres regarding shape and secondary structures, providing information that could be relevant for virus-host interactions studies.

Emergence and genomic analysis of a novel ostrich-origin GPV-related parvovirus in China

In recent years, ostrich disease characterized by paralysis and diarrhea has been circulating in some regions of China, causing huge economic losses to the ostrich breeding industry. In our study, clinical samples from diseased ostriches were collected, and only parvovirus was detected. The virus distribution analysis by histopathology and quantitative real-time PCR assays indicated that the virus had a wide range of tissue tropisms. The full-length genome of the ostrich parvovirus (OsPV) was sequenced and comprehensively analyzed. Interestingly, the phylogenetic and alignment results indicated that the OsPV and the goose parvovirus (GPV) form a separate branch. In contrast to GPV strains, OsPV showed 2 new 14 nucleotide deletions in the inverted terminal repeat (ITR) region. Furthermore, recombination analysis indicated that OsPV was a recombination strain between the vaccine strain SYG61v and the virulent strain B strain, with the major parent of OsPV as the SYG61v strain and the minor parent as the B strain. The 14 nucleotide deletions in the ITR region as well as recombination may be some of the reasons for the cross-species transmission of parvovirus from goose to ostrich. The above data will contribute to a better understanding of the molecular biology of the novel OsPV and help to develop the vaccine candidate strain.

Advances in research on genetic relationships of waterfowl parvoviruses

Derzsy’s disease and Muscovy duck parvovirus disease have become common diseases in waterfowl culture in the world and their potential to cause harm has risen. The causative agents are goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV), which can provoke similar clinical symptoms and high mortality and morbidity rates. In recent years, duck short beak and dwarfism syndrome has been prevalent in the Cherry Valley duck population in eastern China. It is characterised by the physical signs for which it is named. Although the mortality rate is low, it causes stunting and weight loss, which have caused serious economic losses to the waterfowl industry. The virus that causes this disease was named novel goose parvovirus (NGPV). This article summarises the latest research on the genetic relationships of the three parvoviruses, and reviews the aetiology, epidemiology, and necropsy characteristics in infected ducks, in order to facilitate further study.

Molecular Characterization and Pathogenicity of the Novel Recombinant Muscovy Duck Parvovirus Isolated from Geese

Simple Summary

Waterfowl parvoviruses are important pathogens that cause severe disease in young waterfowl. Waterfowl parvoviruses can be divided into goose parvovirus (GPV)- and Muscovy duck parvovirus (MDPV)-related groups. New variant strains can be generated from genomic recombination between different waterfowl parvoviruses and result in new epidemics. Recently, a novel recombinant MDPV (rMDPV) derived from recombination between GPVs and MDPV was reported. This virus caused high morbidity and mortality rates in ducklings and was circulating in waterfowl in mainland China. In this study, a novel rMDPV was isolated in Taiwan from a goose flock that experienced a high mortality. The complete genome of this goose-origin rMDPV was sequenced. Phylogenetic and recombination analyses were performed to elucidate its molecular characteristics. The virulence of this rMDPV was evaluated using experimental infection goose embryos and goslings. This study was the first report showing the pathogenicity of rMDPV in geese.

Abstract

Goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV) are the main agents associated with waterfowl parvovirus infections that caused great economic losses in the waterfowl industry. In 2020, a recombinant waterfowl parvovirus, 20-0910G, was isolated in a goose flock in Taiwan that experienced high morbidity and mortality. The whole genome of 20-0910G was sequenced to investigate the genomic characteristics of this isolate. Recombination analysis revealed that, like Chinese rMDPVs, 20-0910G had a classical MDPV genomic backbone and underwent two recombination events with classical GPVs at the P9 promoter and partial VP3 gene regions. Phylogenetic analysis of the genomic sequence found that this goose-origin parvovirus was highly similar to the circulating recombinant MDPVs (rMDPVs) isolated from duck flocks in China. The results of experimental challenge tests showed that 20-0910G caused 100% mortality in goose embryos and in 1-day-old goslings by 11 and 12 days post-inoculation, respectively. Taken together, the results indicated that this goose-origin rMDPV was closely related to the duck-origin rMDPVs and was highly pathogenic to young geese.

Phylogenetic and codon usage analysis for replicase and capsid genes of porcine circovirus 3

Porcine circovirus type 3 (PCV3) is a highly contagious virus belonging to the family Circoviridae that causes the severe dermatitis and nephropathy syndrome. To date, PCV3 has a worldwide distribution and bring huge economic losses to swine industry. Replicase (Rep) and capsid (Cap) are two major coded proteins of PCV3. Considering the large number of new PCV3 isolates were reported in the past few years and the research for the codon usage pattern of Rep and Cap genes was still a gap, phylogenetic and codon usage analysis of these two genes was performed. Phylogenetic analyses showed that Rep genes in PCV3a were dispersed with no clear clusters while corresponding sequences in PCV3b clustered into two groups and Cap genes clustered into distinct clades according to different genotypes. Relative synonymous codon usage (RSCU) analysis revealed that the codon usage bias existed and effective number of codon (ENC) analysis showed that the bias was slight low. ENC-GC3s plot indicated that mutational pressure and other factors both played a role in PCV3 codon usage and neutrality plot analysis showed that natural selection was the main force influencing the codon usage pattern. The results presented here provided the important basic data on codon usage pattern of Rep and Cap genes, and a better understanding of the evolution and potential origin of PCV3.

Molecular analysis of goose parvovirus field strains from a Derzsy's disease outbreak reveals local European-associated variants

Since its first recognition in the early 1960s, Derzsy's disease has caused significant economic losses in the goose meat industry through the world. Today, Derzsy's disease still maintains its importance for small-scale waterfowl farming, despite not having a significant impact on public health. In the present study, we investigated the distribution of goose parvovirus (GPV) and its potential variants from a 2019 outbreak in Turkey. Tissue samples were obtained from infected eggs and goslings that were raised in distinct farming areas of the various provinces. For this purpose, a novel primer set for amplification of a 630-bp region of VP3 was designed to confirm GPV infection by conventional PCR method. A 4709-base nucleotide sequence including the structural, non-structural, and 5' inverted terminal repeat regions was obtained from three samples from the Central Anatolian region. Multiple sequence comparisons and phylogenetic analysis demonstrated that the field strains clustered with European group 2 and contained a series of unique amino acid substitutions that might affect the virulence of the virus. These results confirmed that European-related field strains caused the outbreak in Asia Minor, and this might assist in understanding the circulation of GPV in Asia and Europe.

Isolation and characterization of a recombinant Muscovy duck parvovirus circulating in Muscovy ducks in South China

In 2019, flocks of Muscovy ducks presented with clinical signs typical of MDPV infection. The MDPV GD201911 strain was isolated by inoculating samples from positive birds into Muscovy duck embryos. Challenge with the isolate GD201911 caused typical MDPV disease symptoms and resulted in 25%-40% mortality, depending on the challenge dose, indicating the high pathogenicity of GD201911 for Muscovy ducks. Genome sequencing and phylogenetic analysis demonstrated that GD201911 clustered with recombinant MDPV strains, indicating that recombinant MDPV is circulating in China. Epidemiological monitoring should be performed continuously to assist with decision making for disease control.

Novel goose parvovirus in domestic Linwu sheldrakes with short beak and dwarfism syndrome, China

Recently, short beak and dwarfism syndrome (SBDS) had a sudden outbreak in Cherry Valley duck flocks, followed by Pekin ducks and mule ducks in various regions of mainland China. This widely spreading infectious disease was characterized by growth retardation, smaller beak and tarsus with high morbidity and low mortality rate. In this study, we identified and characterized virus from domestic Linwu sheldrakes (namely as HuN18) with SBDS. HuN18 isolates shared high nucleotide identity with novel goose parvovirus (N-GPV). A 5110-nucleotide full-length genome sequence of HuN18 was found with no deletion in ITR region. Alignment studies of HuN18 showed 96.8%-99.0% identity with other N-GPVs and 92.9%-96.3% identity with classic GPV. According to the recombination analysis, HuN18 showed the potential major parent was the N-GPV sdlc01 strain, the potential minor parent was the classical GPV Y strain, and the secondary potential minor parent was the SYG61v strain. To the best of our knowledge, this is the first report of N-GPV in domestic Linwu sheldrakes with SBDS; these data provide evidence that attenuated live viruses are involved in genetic recombination with prevailing wild parvoviruses, which contributes to the novel emerging variants of waterfowl parvoviruses.

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.

Development of a PCR assay for detection and differentiation of Muscovy duck and goose parvoviruses based on NS gene characterization

Muscovy duck parvovirus (MDPV) and goose parvovirus (GPV) have both been found to cause high mortality and morbidity in Muscovy ducklings. Specific detection is often rife with false positives due to high identity at the genomic nucleotide level and antigenic similarity between MDPVs and GPVs. In this study, significantly variable regions were found, via non-structural (NS) comparison, between MDPV and GPV NS genes; however, NS genes were conserved within the MDPV and GPV groups. A polymerase chain reaction (PCR) assay for detecting and differentiating MDPVs and GPVs was developed with more specificity based on the NS gene characterization. The assay detected as low as 10³ DNA copies of both the MDPV and GPV strains, along with 549 separate base pairs (bp). No bands of the same size from other duck pathogens, including duck circovirus, duck enteritis virus, egg drop syndrome virus, duck-origin goose hemorrhagic polyomavirus, Escherichia coli, Salmonella, Riemerella anatipestifer and Pasteurella multocida were amplified. This indicates that this method for performing PCR provides a useful and reliable alternative tool for more precise differentiation of MDPV and GPV infection in clinical samples.

Specific detection of Muscovy duck parvovirus infection by TaqMan-based real-time PCR assay

BACKGROUND

Muscovy duck parvovirus (MDPV) causes high mortality and morbidity in Muscovy ducks, with the pathogenesis of the virus still unknown in many respects. Specific MDPV detection is often rife with false positive results because of high identity at the genomic nucleotide level and antigenic similarity with goose parvovirus (GPV). The objective of this study was to develop a sensitive, highly specific, and repeatable TaqMan-based real-time PCR (qPCR) assay for facilitating the molecular detection of MDPV.

RESULTS

The specific primers and probe were designed based on the conserved regions within MDPVs, but there was a variation in GPVs of the nonstructural (NS) genes after genetic comparison. After the optimization of qPCR conditions, the detection limit of this qPCR assay was 29.7 copies/μl. The assay was highly specific for the detection of MDPV, and no cross-reactivity was observed with other non-targeted duck-derived pathogens. Intra- and inter-assay variability was less than 2.21%, means a high degree of repeatability. The diagnostic applicability of the qPCR assay was proven that MDPV-positive can be found in cloacal swabs samples, Muscovy duck embryos and newly hatched Muscovy ducklings.

CONCLUSIONS

Our data provided incidents that MDPV could be possible vertically transmitted from breeder Muscovy ducks to Muscovy ducklings. The developed qPCR assay in the study could be a reliable and specific tool for epidemiological surveillance and pathogenesis studies of MDPV.