Continuing evolution of canine parvovirus in China: Isolation of novel variants with an Ala5Gly mutation in the VP2 protein

Old and Novel Enteric Parvoviruses of Dogs

Parvovirus infections have been well known for around 100 years in domestic carnivores. However, the use of molecular assays and metagenomic approaches for virus discovery and characterization has led to the detection of novel parvovirus species and/or variants in dogs. Although some evidence suggests that these emerging canine parvoviruses may act as primary causative agents or as synergistic pathogens in the diseases of domestic carnivores, several aspects regarding epidemiology and virus-host interaction remain to be elucidated.

Detection of Selected Canine Viruses in Nigerian Free-Ranging Dogs Traded for Meat Consumption

Animal trade favors the spreading of emerging and re-emerging pathogens. Concerns have been previously expressed regarding the risks of dog trade in spreading zoonotic pathogens in Nigeria. However, the role of these dogs in disseminating highly pathogenic canine viruses has not yet been explored. The present study aimed to identify selected canine viruses in dogs traded for meat consumption in Nigeria. A total of 100 blood samples were screened for carnivore protoparvovirus-1 (CPPV-1), canine adenovirus 1/2 (CAdV-1/2), canine circovirus (CaCV), and canine distemper virus (CDV) by using real-time PCR and conventional PCR and/or sequencing. CPPV-1 DNA was identified in 83% of canine samples while CaCV DNA and CDV RNA were detected in 14% and 17% of the dog samples, respectively. None of the dogs tested positive for CAdV-1/2. The CaCVs identified in this study clustered along with other European, Asian, and American strains. Moreover, CDV strains identified in Nigeria clustered in a separate lineage with the closest genetic relatedness to the Europe-South America-1 clade. Further surveys prior to and after arrival of dogs at the slaughtering points are required to clarify the real virus burden in these animals.

Prevalence and Characteristics of Canine Parvovirus Type 2 in Henan Province, China

To investigate the epidemic profile and genetic diversity of canine parvovirus type 2 (CPV-2), a total of 111 clinical samples collected from dogs suspected of CPV-2 infection in 10 cities of Henan province of China during 2020 to 2021 were screened by PCR. The results showed a CPV-2-positive rate of 88.29% (98/111). Nearly full-length genomes of 98 CPV-2 strains were sequenced and analyzed. CPV-2c strains (91.84%, 90/98) were significantly higher than that of new CPV-2a strains (8.16%, 8/98) in Henan province without detecting other CPV genotypes, indicating that CPV-2c has become the dominant genotype in Henan province. A phylogenetic analysis of NS1 and VP2 amino acids grouped the strains in this study with Asian strains, which clustered into an identical branch. Based on the CPV-2 VP2 sequences in this study and available in the NCBI database, the adaptation analyses showed that 17 positive selection sites and 10 parallel evolution sites were identified in the VP2 protein of CPV-2, of which three sites (sites 5, 370, and 426) were both under positive selection pressure and parallel evolution. Interestingly, two amino acid mutations (A5G and Q370R) were also observed in the VP2 proteins of 82 CPV-2c strains in this study, which differed from the earlier CPV-2c strain (GU380303) in China. In addition, a unique mutation (I447M) was observed in the VP2 protein of five CPV-2c strains, which was first reported in China. This study provides powerful insight to further our understanding of the epidemic status and evolution of CPV-2 in China. IMPORTANCE CPV-2 was the original virus strain identified in dogs, which cause an acute and lethal disease in dogs. Subsequently, the original CPV-2 was replaced throughout the world by novel antigenic variants (e.g., CPV-2a, CPV-2b, new CPV-2a, new CPV-2b, and CPV-2c). Currently, the epidemiological characteristics of CPV-2 in Henan province of China is still unclear. In our study, a total of 98 nearly full-length genomes of CPV-2 strains were obtained to explore prevalence and genetic evolution of CPV-2 in Henan Province. Moreover, the epidemiological and genetic evolution of CPV-2 in China since its discovery was also investigated. The results of this study will provide valuable information regarding the evolution of CPV-2 strains in China.

Isolation and identification of a novel canine parvovirus type 2c strain in domestic cats in Dalian, China

Canine parvovirus (CPV) and feline panleukopenia virus (FPV) are highly contagious and cause severe enteric diseases, with high mortality rates in dogs and cats. In the present study, we isolated and identified a novel CPV-2c strain (FPV-DL04 strain) from 18 cats with gastroenteritis symptoms and a positive parvovirus PCR test result in Dalian, China. Molecular characterization, sequence analysis, and phylogeny determination were performed on the VP2 gene of this strain. The results showed that the FPV-DL04 strain had 99.4% homology with the CPV-2c CN/HN1708 strain, and both strains had S297A and A300G key mutation sites. Interestingly, we also found that the DL04 strain has a A5G mutation site, but no F267Y and Y324I mutation sites. This study provided new important findings regarding the evolution of parvovirus infection in domestic cats in China.

Prophylaxe der kaninen Parvovirose

Obwohl Impfstoffe gegen das canine Parvovirus (CPV) weltweit eingesetzt werden, tritt die Parvovirose vor allem bei jungen Hunden nach wie vor vergleichsweise häufig auf. Der vorliegende Übersichtsartikel konzentriert sich auf die Ursachen für ein Impfversagen. Hierfür kommen unterschiedlichste Faktoren in Betracht, die den Hund selbst oder seine Umwelt betreffen. So gibt es genetisch bedingt Hunde, die keine Antikörper (Non-Responder) oder nur sehr niedrige Konzentrationen an Antikörpern (Low-Responder) nach einer CPV-Impfung ausbilden. Der Impferfolg kann auch durch andere intrinsische Faktoren (z. B. Gewicht, Alter, Reproduktions- und Ernährungsstatus, Krankheiten) und/oder extrinsische Faktoren (z. B. Stress, Belastung, Medikamente) beeinträchtigt werden. Neben Ursachen, die den individuellen Hund betreffen, kann ein Impfversagen auch durch eine reduzierte immunisierende Eigenschaft des Impfstoffs bedingt sein; hierfür kommt eine Vielzahl verschiedener Faktoren in Betracht (z. B. Herstellung, Lagerung, Applikation).

Identification and Molecular Characterization of a Divergent Asian-like Canine Parvovirus Type 2b (CPV-2b) Strain in Southern Italy

Canine parvovirus type 2 (CPV-2) is an infectious agent relevant to domestic and wild carnivorans. Recent studies documented the introduction and spread of CPV-2c strains of Asian origin in the Italian canine population. We investigated tissue samples from a puppy collected during necropsy for the presence of viral enteropathogens and all samples tested positive only for CPV-2. The full coding sequence of a CPV-2b (VP2 426Asp) strain was obtained. This virus was related to CPV-2c strains of Asian origin and unrelated to European CPV-2b strains. The sequence had genetic signatures typical of Asian strains (NS1: 60Val, 545Val, 630Pro; VP2: 5Gly, 267Tyr, 324Ile) and mutations rarely reported in Asian CPV-2b strains (NS1: 588N; VP2: 370Arg). Phylogenetic analyses placed this strain in well-supported clades, including Asian CPV-2c-like strains, but always as a basal, single-sequence long branch. No recombination was observed for this strain, and we speculate that it could have originated from an Asian CPV-2c-like strain that acquired the 426Asp mutation. This study reports the first evidence of an Asian-like CPV-2b strain in Italy, confirming the occurrence of continuous changes in the global CPV-2 spread. Since positive convergent mutations complicate data interpretation, a combination of phylogenetic and mutation pattern analyses is crucial in studying the origin and evolution of CPV-2 strains.

Molecular characterization of carnivore protoparvovirus 1 circulating in domestic carnivores in Egypt

Canine parvovirus (CPV) and feline panleukopenia virus (FPV), now included in the unique species Carnivore protoparvovirus 1 (CPPV1), have been circulating in dogs and cats for several decades and are considered the causes of clinically important diseases, especially in young animals. While genetic evidence of the circulation of parvoviruses in Egyptian domestic carnivores has been provided since 2016, to date, all available data are based on partial fragments of the VP2 gene. This study reports the molecular characterization of CPPV strains from Egypt based on the full VP2 gene. Overall, 196 blood samples were collected from dogs and cats presented at veterinary clinics for routine medical assessment in 2019 in Egypt. DNA extracts were screened and characterized by real-time PCR. Positive samples were amplified by conventional PCR and then were sequenced. Nucleotide and amino acid changes in the sequences were investigated and phylogeny was inferred. Carnivore protoparvovirus DNA was detected in 18 out of 96 dogs (18.8%) and 7 of 100 cats (7%). Phylogenetic analyses based on the full VP2 gene revealed that 9 sequenced strains clustered with different CPV clades (5 with 2c, 2 with 2a, 1 with 2b, and 1 with 2) and 1 strain with the FPV clade. All three CPV variants were detected in dog and cat populations with a predominance of CPV-2c strains (7 of 18, 38.9%) in dog samples, thus mirroring the circulation of this variant in African, European, and Asian countries. Deduced amino acid sequence alignment revealed the presence of the previously unreported unique mutations S542L, H543Q, Q549H, and N557T in the Egyptian CPV-2c strains.

Concomitant Infections With Canine Parvovirus Type 2 and Intracellular Tick-Borne Pathogens in Two Puppy Dogs

In this report the concomitant infection with canine parvovirus type 2 (CPV-2), Hepatozoon canis and Ehrlichia canis in two puppy dogs from Southern Italy is described. Dogs were referred to a veterinary university hospital for the acute onset of lethargy and gastrointestinal signs. A complete clinical and clinicopathological evaluation was carried out and the multiple infection was confirmed by microscopic detection of inclusion bodies in peripheral blood smear, rapid immunoenzymatic tests, indirect fluorescent antibody tests, and molecular assays. Sequence analysis revealed that the CPV-2 identified belonged to the 2c variant and had amino acid residues in the predicted VP2 protein typical of “Asian-like” strains widespread in Asia and occasionally reported in Romania, Nigeria and Italy, particularly in the region of Sicily. Numerous monocytes were infected by both H. canis gamonts and E. canis morulae, suggesting that this co-infection is not accidental and that E. canis preferably infects those cells parasitized by H. canis. The clinical presentation of these animals was severe but supportive cares associated with early etiological therapy allowed a good prognosis. Movement of puppies from geographic areas where vector-borne pathogens are endemic must be carefully evaluated and core vaccinations and ectoparasite prevention treatments must be rigorously adopted.

Genetic characterization and evolutionary analysis of canine parvovirus in Tangshan, China

Canine parvovirus (CPV) is a major enteric virus of carnivores worldwide that poses a considerable threat to dogs. In this study, we investigated the genetic variation of CPV in Tangshan, China, and the relationships between CPV disease and the vaccination status, age, and gender of dogs. Seventy-seven fecal samples from dogs in Tangshan that tested positive for CPV were obtained for analysis. Twenty-two full-length VP2 gene sequences were successfully amplified. The 22 strains included 17 CPV-2c variants, four new CPV-2a variants, and one new CPV-2b variant. Phylogenetic analysis showed that all of the CPV-2c strains clustered together and were closely related to CPV-2c strains from Asia but distantly related to CPV-2c strains from Europe. Further amino acid sequence analysis showed that, relative to CPV-2c strains from Europe, most of the CPV-2c stains in this study had A5G, F267Y, Y324I, and Q370R mutations. These findings provide a more comprehensive understanding of the variants of CPV circulating in China.

Predominance and first complete genomic characterization of canine parvovirus 2b in Turkey

Viral enteritis is a significant threat to domestic dogs. The two primary pathogens that cause viral enteritis in dogs are canine coronavirus (CCoV) and canine parvovirus (CPV). In this study, we investigated the occurrence of CPV-2, CCoV, and canine circovirus coinfection by characterizing circulating subtypes of CPV-2 in faecal samples from symptomatic dogs admitted to veterinary clinics located in Ankara, Elazığ, Kayseri, and Kocaeli provinces of Turkey, between 2019 and 2022. Virus detection by PCR and RT-PCR revealed that CPV-2 was present in 48 (77.4%) samples, and no other agents were detected. Based on the occurrence of the codon GAT at positions 1276 to 1278 (coding for aspartate at residue 426) of VP2, all CPV-2 isolates were confirmed to be of the CPV-2b subtype. The complete genome sequences of two CPV-2b isolates showed a high degree of similarity to and phylogenetic clustering with Australian and East Asian strains/isolates. The predominant CPV strain circulating in the three different regions of Turkey was found to be a CPV-2b strain containing the amino acid substitutions at Y324I and T440A, which commonly contribute to immune escape. This is the first report of complete genomic analysis of CPV-2 isolates circulating in symptomatic domestic dogs in Turkey. The evolution of CPV-2 has raised questions about the efficacy of current vaccination regimes and highlights the importance of monitoring the emergence and spread of new CPV-2 variants.

Molecular characteristics and genetic evolutionary analyses of circulating parvoviruses derived from cats in Beijing

Background

Feline parvovirus (FPV) is a member of the family Parvoviridae, which is a major enteric pathogen of cats worldwide. This study aimed to investigate the prevalence of feline parvovirus in Beijing of China and analyze the genetic features of detected viruses.

Results

In this study, a total of 60 (8.5%) parvovirus-positive samples were detected from 702 cat fecal samples using parvovirus-specific PCR. The complete VP2 genes were amplified from all these samples. Among them, 55 (91.7%) sequences were characterized as FPV, and the other five (8.3%) were typed as canine parvovirus type 2 (CPV-2) variants, comprised of four CPV-2c and a new CPV-2b strain. In order to investigate the origin of CPV-2 variants in cats, we amplified full-length VP2 genes from seven fecal samples of dogs infected with CPV-2, which were further classified as CPV-2c. The sequences of new CPV-2b/MT270586 and CPV-2c/MT270587 detected from feline samples shared 100% identity with previous canine isolates KT156833 and MF467242 respectively, suggesting the CPV-2 variants circulating in cats might be derived from dogs. Sequence analysis indicated new mutations, Ala91Ser and Ser192Phe, in the FPV sequences, while obtained CPV-2c carried mutations reported in Asian CPV variants, showing they share a common evolutionary pattern with the Asian 2c strains. Interestingly, the FPV sequence (MT270571), displaying four CPV-specific residues, was found to be a putative recombinant sequence between CPV-2c and FPV. Phylogenetic analysis of the VP2 gene showed that amino acid and nucleotide mutations promoted the evolution of FPV and CPV lineages.

Conclusions

Our findings will be helpful to further understand the circulation and evolution of feline and canine parvovirus in Beijing.

Phylogenetic Characteristics of Canine Parvovirus Type 2c Variant Endemic in Shanghai, China

Canine parvovirus type 2 (CPV-2) has spread and mutated globally over the past 40 years. In the present study, 206 samples from dogs suspected of CPV-2 infection were collected from five veterinary clinics in Shanghai city, China. The average positive rate for CPV-2 was detected to be 40.78% using the PCR method. Using an F81 cell (feline kidney cell) culture, the isolates of three CPV-2c strains were obtained. The near full-length genome sequences of the isolates were determined and submitted to GenBank: CPV-SH2001 (MW650830), CPV-SH2002 (MW811188), and CPV-SH2003 (MW811189). By comparing the amino acid sequences of 12 CPV strains with those of 48 related strains retrieved from GenBank, all of the CPV strains from Shanghai were typed as belonging to a relatively new CPV-2c variant spreading in Asia, with typical amino acid residues (5Gly, 267Tyr, 324Ile, and 370Arg) in the VP2 protein. The divergence time of this new CPV-2c clade was estimated by the phylogenetic tree using the maximum likelihood and RelTime with Dated Tips (RTDT) approaches. Our results indicate that the 426 and 324 VP2 amino acid residues are under strong selection pressure with a posterior probability of 0.966 and 0.943, respectively. Therefore, this study provides insight into the phylogenetic characteristics of the current CPV-2c variant in Shanghai city, China.

Molecular diversity of the VP2 of Carnivore protoparvovirus 1 (CPV-2) of fecal samples from Bogotá

Background

Carnivore protoparvovirus 1, also known as canine parvovirus type 2 (CPV-2), is the main pathogen in hemorrhagic gastroenteritis in dogs, with a high mortality rate. Three subtypes (a, b, c) have been described based on VP2 residue 426, where 2a, 2b, and 2c have asparagine, aspartic acid, and glutamic acid, respectively.

Objectives

This study examined the presence of CPV-2 variants in the fecal samples of dogs diagnosed with canine parvovirus in Bogotá.

Methods

Fecal samples were collected from 54 puppies and young dogs (< 1 year) that tested positive for the CPV through rapid antigen test detection between 2014–2018. Molecular screening was developed for VP1 because primers 555 for VP2 do not amplify, it was necessary to design a primer set for VP2 amplification of 982 nt. All samples that were amplified were sequenced by Sanger. Phylogenetics and structural analysis was carried out, focusing on residue 426.

Results

As a result 47 out of 54 samples tested positive for VP1 screening, and 34/47 samples tested positive for VP2 980 primers as subtype 2a (n = 30) or 2b (n = 4); subtype 2c was not detected. All VP2 sequences had the amino acid, T, at 440, and most Colombian sequences showed an S514A substitution, which in the structural modeling is located in an antigenic region, together with the 426 residue.

Conclusions

The 2c variant was not detected, and these findings suggest that Colombian strains of CPV-2 might be under an antigenic drift.

Simultaneous detection of feline parvovirus and feline bocavirus using SYBR Green I-based duplex real-time polymerase chain reaction

Since both feline parvovirus (FPV) and feline bocavirus (FBoV) can cause diarrhea in cats, it is difficult to distinguish them clinically. This study aimed to develop a SYBR Green I-based duplex real-time polymerase chain reaction (PCR) assay for distinguishing FPV and FBoV-1 on the basis of the melting temperature of the PCR product. A total of 132 fecal samples from different domestic and feral cats were collected, and the results of SYBR Green I-based duplex real-time PCR assay were compared with those of the traditional PCR assay for a comprehensive evaluation. The melting temperatures were found to be 86 °C and 77.5 °C for FBoV-1 and FPV, respectively, and no specific melting peaks for other non-targeted feline viruses were observed. The data obtained from this assay had a good linear relationship; the detection limits of FPV and FBoV-1 were 2.907 × 10¹ copies/μL and 3.836 × 10¹ copies/μL, respectively. In addition, the experiment exhibited high reproducibility. The positive detection rates of the SYBR Green I-based duplex real-time PCR assay for FPV and FBoV-1 were 16.67% (22/132) and 6.82% (9/132), respectively, and the positive detection rate for co-infection with FPV and FBoV-1 was 3.03% (4/132). This result was much more sensitive than that of the traditional PCR method. Thus, the developed SYBR Green I-based assay is a sensitive, rapid, specific, and reliable method for the clinical diagnosis of FPV and FBoV-1 and can provide technical support for the simultaneous detection of co-infection with these viruses in the future.

Predominance of canine parvovirus 2b in Japan: an epidemiological study during 2014-2019

Canine parvovirus 2 (CPV-2) is an important pathogen of domestic dogs and wild canids. In Japan, CPV-2 infection is one of the most common infectious diseases of dogs. We analyzed samples collected between 2014 and 2019 to identify antigenic variants of CPV-2 in dogs in Japan. Our results demonstrated that the CPV-2b variant was predominant. The CPV-2c variant was not found among our samples. Our findings demonstrate that the distribution of CPV-2 antigenic variants in Japan was more similar to that in Australia than to that in neighboring countries in Asia.

The detection of canine parvovirus type 2c of Asian origin in dogs in Romania evidenced its progressive worldwide diffusion

Background

Canine parvovirus (CPV) is one of the most important pathogens of dogs. Despite vaccination, CPV infections are still ubiquitous in dogs, and the three antigenic variants 2a, 2b and 2c are variously distributed in the canine population worldwide. To date, no information is available on CPV variants circulating in some European countries. The aim of this study was to genetically characterise the CPV detected in ten dogs with clinical signs of acute gastroenteritis in Romania. The presence of Carnivore protoparvovirus 1 DNA was investigated in faecal samples using an end-point PCR targeting the complete VP2 gene and positive amplicons were sequenced and analysed.

Results

All ten dogs with acute gastroenteritis tested positive to Carnivore protoparvovirus 1 DNA in faecal samples. The identified viruses belonged to CPV-2c type, showed identical sequences of the VP2 gene and were characterised by distinctive amino acid residues in the deduced VP2 protein: 5-glicine (5Gly), 267-tirosine (267Tyr), 324-isoleucine (324Ile) and 370-arginine (370Arg). These distinctive amino acid residues have already been reported in CPV-2c widespread in Asia and occasionally detected in Italy and Nigeria.

Conclusions

Since CPV-2c with VP2 amino acid residues 5Gly, 267Tyr, 324Ile and 370Arg were never reported before 2013, it can be assumed that this virus is progressively expanding its spread in the world dog population. This study adds new data about the presence of this new virus in Europe and underline worrying questions about its potential impact on the health of the canine population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02918-6.

Molecular Characteristics of Carnivore protoparvovirus 1 with High Sequence Similarity between Wild and Domestic Carnivores in Taiwan

Carnivore protoparvovirus 1 (CPPV-1) is a DNA virus causing gastrointestinal disease and immunosuppression in various terrestrial carnivores. Domestic dogs and cats are considered the primary CPPV-1 reservoirs. The habitat overlap of wild carnivores and free-roaming dogs increases the threat of CPPV-1 transmission between them. This study explored the CPPV-1 distribution among wild carnivores in Taiwan through PCR screening and compared the partial capsid protein (VP2) gene sequences from wild and domestic carnivores. In total, 181 samples were collected from 32 masked palm civets (Paguma larvata), 63 Chinese ferret badgers (Melogale moschata), and 86 crab-eating mongooses (Herpestes urva), from 2015 to 2019 were screened for CPPV-1. The average prevalence of CPPV-1 was 17.7% (32/181), with the highest prevalence in masked palm civets (37.5%). In addition, a masked palm civet was coinfected with two CPPV-1 strains. Among the 33 partial VP2 gene sequences, 23 were identical to the sequences amplified from domestic dogs and cats in Asia, and the remaining 10 were identified for the first time. This study supported the circulation of CPPV-1 strains with the same genomic features as domestic carnivores that are also in wild carnivores from the same environment in Taiwan by molecular data. Therefore, further population control and health management of free-roaming domestic carnivores are recommended.

Molecular characterization of canine parvovirus from domestic dogs in Nigeria: Introduction and spread of a CPV-2c mutant and replacement of older CPV-2a by the "new CPV-2a" strain

Canine parvovirus (CPV) is a contagious and highly pathogenic virus of dogs. After its first report in 1978, the CPV original type (CPV-2) was rapidly and totally replaced by three antigenic variants named CPV-2a, CPV-2b and CPV-2c that circulate in various countries at different frequencies and recently reported in Nigeria. This study describes the molecular characterization of 28 CPV strains in dogs presenting with gastroenteritis in veterinary clinics at Lagos and Ibadan, Nigeria. The results show the predominance (92.8%) of CPV-2a, while CPV-2c was found only in two samples. Phylogenetic analyses revealed that the CPV Nigerian strains were closely related to Asian strains and 26 CPV-2a out of 28 CPV sequences fell into 2 different subclades consistent with predicted amino acid mutations at position 267, 321, 324 and 440. Lys321Asn was evident in all the Nigerian strains whilst Phe267Tyr and Tyr324Ile were observed in 96.4% of the sequences, respectively. Thr440Ala occurred in 89.3% of sequences from this study. The new CPV-2a was predominant and appears to have replaced other CPV-2a strains in South-western Nigeria whilst the CPV-2c strain which is identical to the isolate recently reported in Northern Nigeria, may have been introduced in this country at the time of this study. Monitoring virus epidemiology is important to better understand the dynamics of CPV evolution and the eventual need to change or improve existing vaccination strategies.

Molecular Epidemiological Survey of Canine Parvovirus Circulating in China from 2014 to 2019

The global distribution of canine parvovirus (CPV-2) derived from a closely related carnivore parvovirus poses a considerable threat to the dog population. The virus is continuously undergoing genetic evolution, giving rise to several variants. To investigate the prevalence of Chinese CPV-2 strains in recent years, a total of 30 CPV-2 strains were collected from 2018 to 2021 and the VP2 gene was sequenced and analyzed. Two variants, new CPV-2a (297Ala, 426Asn) and CPV-2c (426Glu), were identified. In contrast to previous reports, the CPV-2c variant has gained an epidemiological advantage over the new CPV-2a variant in China. To compensate for the relatively small sample size, 683 Chinese CPV-2 strains identified between 2014 and 2019 were retrieved from the GenBank database and previous publications, and analyses of these strains further supported our findings, which should be considered since the CPV-2c variant has been frequently associated with immune failure in adult dogs. VP2 protein sequence analysis revealed several amino acid substitutions, including Ala5Gly, Pro13Ser, Phe267Tyr, Tyr324Ile, Gln370Arg, Thr440Ala, and Lys570Arg. Phylogenetic analysis of full-length VP2 gene indicated a close relationship between Chinese strains and other Asian strains, suggesting mutual transmission between Asian countries. Furthermore, intercontinental transmission is a cause for concern. Surprisingly, two feline panleukopenia virus (FPV) strains with the Ile101Thr mutation in the VP2 protein were identified in canine fecal samples; FPV has been considered incapable of infecting dogs. This study clarified the epidemic characteristics of Chinese CPV-2 strains detected between 2014 and 2019, offering a reference for epidemic control. In addition, the detection of FPV in canine samples may provide information for future studies on the evolution of carnivore parvoviruses.

Canine parvovirus type 2c in Vietnam continues to produce distinct descendants with new mutations restricted to Vietnamese variants

Viral protein 2 (VP2) of canine parvovirus (CPV) exhibits a high degree of genetic and antigenic diversity. We analyzed 88 Vietnamese CPV-VP2 sequences (1755 bp), 34 from this study and 54 from previous studies, and discovered a new sublineage, "new var.", within the lineage CPV-2c-"new", characterized by the mutation 5G/447M, which is restricted to the Vietnamese isolates. These new mutants appear to have emerged in recent years, accounting for 65.5% of the total. With strong nodal support (98%), the distinct Vietnamese 2c-"new-var." sublineage (5G/426E/447M) was found to be separate from the 2c-"new" sublineage (5G/426E/447I) within the 2c-(Asia)/Asia-2c lineage. Amino acid changes in epitopes of VP2 might have led to the generation of subvariants and affected the antigenicity, immunogenicity, or virulence of the virus, resulting in vaccine failure worldwide.

Molecular epidemiology and genetic evolution of canine parvovirus in East China, during 2018-2020

Canine parvovirus type 2 (CPV-2) emerged in the late 1970s, which caused high rates of morbidity and mortality in dogs. In last decade, five genetic variants (CPV-2a, CPV-2b, CPV-2c, New CPV-2a, and New CPV-2b) were frequently reported in the dog population, and replaced the original CPV-2, rising widespread concerns. However, little is known about their recent genetic diversity and evolution. The aim of this study was to analyze the characteristics of the CPV-2 strains collected in East China from 2018 to 2020. The 57 CPV-2 strains were isolated from rectal swab samples (n=140). They belong to three different genotypes, based on VP2 protein amino acid sequence. The results revealed a high prevalence of CPV-2c (77.19%) compared to the New CPV-2a (5.26%) and New CPV-2b (17.54%) strains. Further analysis showed that nucleotide homology of the VP2 gene among the 57 CPV strains was 98.9%~100%, and the homology with 24 reference strains from different countries and regions was 98.1%~100%. The phylogenetic tree of VP2 gene sequence showed that 44 CPV-2c strains were distantly related to CPV-2, CPV-2a, CPV-2b, New CPV-2a, New CPV-2b and European/American CPV-2c strains, and were closely related to Asian CPV-2c strains. The results showed that these Asian CPV-2c strains had become the dominant strain, which renewed the knowledge of CPV-2 molecular epidemiology in East China.

A systematic literature review and meta-analysis of characterization of canine parvoviruses 2 prevalent in mainland China

Background

Canine parvovirus 2 (CPV-2) is a pathogenic virus that infects dogs, causing a highly infectious disease. Monitoring CPV-2 spread is an important part of prevention; however, the prevalence and epidemiological characteristics of CPV-2 have not been systematically evaluated and analyzed in mainland China. Therefore, a systematic review and meta-analysis were performed to assess prevalence and epidemiological characteristics of CPV-2 in domestic dogs in mainland China.

Methods

In this study, Chinese and English literature on CPV-2 epidemiology published between January 2006 and December 2019 was evaluated. Regarding meta-analysis, the random-effect model was employed by forest plot with 95% of confidence interval. The number of CPV-2 infections was identified and the pooled prevalence of infection, as well as the epidemiological characteristics, was calculated using meta-analysis.

Results

A total of 39 studies (data from 137,844 dogs) met the evaluation criteria and were used in our study. The pooled prevalence of CPV-2 infection in mainland China was 36%. CPV-2 infection were associated with age, breed, sampling season and immunization status, but not with gender, publication time and diagnostic methods.

Conclusions

Our results indicated that CPV-2 is prevalent among dogs in China. It is therefore necessary to carry out continuous surveillance and epidemiological studies of CPV-2. In addition, accordingly, effective measures should be taken to prevent the transmission and spread of CPV-2 among the Chinese dog population.

Detection and molecular epidemiology of canine parvovirus type 2 (CPV-2) circulating in Jilin Province, Northeast China

Canine parvovirus (CPV) is highly contagious and can cause haemorrhagic enteritis and myocarditis in dogs. To understand the current epidemic situation of CPV in Jilin Province, China, a total of 44 fecal or intestinal tissue samples of pet dogs suspected of being infected with CPV from February 2018 to November 2019 in Changchun and Liaoyuan City, Jilin Province were collected.All of the 44 collected samples were tested positive to CPV-2 by a PCR assay. The sequencing and analyzing of complete VP2 genes showed that CPV-2c was the most prevalent variant (n = 31;70.4 %), followed by new-CPV-2a (n = 8;18.2 %), new-CPV-2b (n = 4; 9.1 %) and CPV-2 (n = 1; 2.3 %). Phylogenetic analysis revealed that the 31 CPV-2c strains in our study are closely related to local CPV-2c isolates in cluster I. The VP2 protein of the acquired CPV 2c strains all possessed the substitutions Ala5Gly, Phe267Tyr, Tyr324Ile, and Gln370Arg only one with a novel Arg481Lys mutation. These findings demonstrate that CPV-2c was the most prominent type of CPV circulating in Jilin in 2018-2019, clustered in a separate group that is far from the vaccine strains and suggest that further and extensive epidemiological investigation among pet dogs are warranted to provide information for usage and research of current vaccines.

Genetic Characterisation and Local Genotypes of Canine Parvovirus Strains Collected from Pet Dogs in Central and Eastern China During 2018-2019

Introduction

Canine parvovirus type-2 (CPV-2) causes acute infectious diseases in puppies, which show high morbidity and mortality. Better effect of vaccination against these diseases could be achieved with deeper knowledge of CPV-2 genotype dissemination and mutation history. This study investigated CPV-2–positive samples collected recently over a wide region of China.

Material and Methods

A total of 118 faecal samples from dogs identified as CPV-positive were collected from veterinary clinics in central and eastern China. Overall, 16 strains collected from Anhui, 29 from Henan, and 16 from Zhejiang Province were sequenced to determine the genotypic composition of CPV-2 and mutational complexity of CPV-VP2.

Results

The CPV-2a, CPV-2b, and CPV-2c genotypes were detected in Anhui and Henan Provinces, while CPV-2c alone was detected in Zhejiang Province. Sequence analysis of all strains showed 98.5%–99.8%, 98.3%–99.9%, and 98.7%–99.8% identity among the 16 Anhui, 29 Henan, and 16 Zhejiang strains, respectively. Strains collected from Anhui and Henan Provinces showed lower identity (97.0%), suggesting greater genetic divergence in central China. The mutation rates of Henan and Anhui strains were lower than that of Zhejiang strains. Major amino acid mutations occurred at sites 5, 370, 426, and 440. Epitope and entropy analyses implied these sites’ likely conformance to the principles of mutation tendency, complexity, and diversity.

Conclusion

The findings for the evolutionary structure of CPV-2 strains collected from three provinces in central and eastern China advance trend monitoring of the genetic variation in canine parvovirus and point to its implications in the development of novel vaccines.

Genetic characterization of feline panleukopenia virus from dogs in Vietnam reveals a unique Thr101 mutation in VP2

Background

Canine parvovirus type 2 (CPV-2) and feline parvovirus (FPV) are known as the main causes of several serious diseases and have a severe impact on puppies and kittens, respectively. FPV and new CPV-2 variants are all able to infect cats, causing diseases indistinguishable from feline panleukopenia. However, FPV only replicates efficiently in feline cells in vitro and replicates in dogs in the thymus and bone marrow without being shed in feces. In our previous study, the genotypes of six parvoviral isolates were unable to be identified using a SimpleProbe^® real-time PCR assay.

Methods

In the present study, we characterized previously unidentified FPV-like viruses isolated from dogs in Vietnam. The six isolates were utilized to complete VP2 gene sequencing and to conduct phylogenetic analyses.

Results

Sequence analysis of the six parvoviral strains identified the species as being similar to FPV. Phylogenetic analysis demonstrated that the complete VP2 genes of the strains are similar to those of FPV. The FPV-like strains contain a Thr101 mutation in the VP2 protein, which is different from prototype FPV strains.

Discussion

Our data provide evidence for the existence of changes in the charge, protein contact potential and molecular surface of the core of the receptor-binding size with an Ile101 to Thr101 mutation. This is also the first study to provide reliable evidence that FPV may be a threat to the Vietnamese dog population.

The increasing prevalence of CPV-2c in domestic dogs in China

Background

Canine parvovirus type 2 (CPV-2), a serious pathogen, leads to high morbidity and mortality in dogs and several wild carnivore species. Although it is a DNA virus, it evolves particularly rapidly, with a genomic substitution rate of approximately 10⁻⁴ substitutions/site/year, close to that of some RNA viruses. Tracing the prevalence of CPV-2 in dogs is significant.

Methods

In this study, an aetiological survey was carried out from 2016 to 2019 in Guangdong Province, China, involving Guangzhou, Shenzhen and Dongguan. Furthermore, to systematically analyse the prevalence of CPV-2 in China, the VP2 gene sequences of all Chinese isolates were downloaded from the NCBI nucleotide database in December 2019, and changes in CPV-2 variants were examined.

Results

A total of 55.7% (34/61) of samples were CPV-2 positive by PCR detection and virus isolation. In addition to different variants circulating in dogs, coinfection with multiple variants was identified, as was coinfection with other canine enteric pathogens in some cases. Two previously reported amino acid sites, A5G and Q370R of CPV-2c mutants, reported in variants in China were assessed, and several CPV-2 isolates with P13S and K582N mutations were detected in this study. Finally, we speculate on the prevalence of different CPV-2 variants in China. According to the VP2 gene sequence obtained from the NCBI nucleotide database, the proportion of different variants in China has changed, and CPV-2c appears to be growing rapidly. In conclusion, this aetiology survey suggests that CPV-2 continues to be common in China and that the prevalence of CPV-2c is increasing.

Molecular and phylogenetic analysis of Vietnamese canine parvovirus 2C originated from dogs reveals a new Asia-IV clade

Canine parvovirus type 2 (CPV-2) is a small, single-stranded DNA virus causing fatal haemorrhagic enteritis in dogs. Currently, CPV-2 is classified into CPV-2a, CPV-2b and CPV-2c based on genetic variation in the VP2 gene. The CPV-2c variant has become ubiquitous worldwide and gained attention for monitoring parvoviral evolution. In this study, we characterized the full-length genome sequences of CPV-2c strains obtained from 59 dogs in Vietnam. Molecular analysis revealed that Vietnamese CPV-2c shared a common evolutionary pattern with the Asian CPV-2 clade, which is marked by genetic signature patterns in the structural and nonstructural proteins. In addition, these Vietnamese CPV-2c strains exhibited unique Thr112Ile and Ile447Met mutations in the VP1 and VP2 sequence, respectively. Interestingly, phylogenetic analysis indicated that the mutations of amino acid residues in both the structural and nonstructural genes have contributed to the emergence of a new clade, designated here as the Asia-IV clade. The substitution rates, estimated from a dataset containing 199 sequences over the last 42 years, confirmed that CPV-2 showed a high rate of nucleotide substitution, at about 2.49 × 10^-4 nucleotide substitutions per site per year (nt/s/y), with VP1/2 and NS1/2 estimates of 3.06 × 10^-4 and 3.16 × 10^-4 nt/s/y, respectively. Even though no evidence of genetic recombination in these Vietnamese CPV-2c strains was established, potential positive selection sites were observed in both the structural and nonstructural genes, suggesting the viral evolutionary process has occurred in both the structural and nonstructural proteins. Genetic and evolutionary analysis of the full-length genome sequence is necessary to gain evolutionary insight of CPV-2.

Analysis of canine parvoviruses circulating in Australia reveals predominance of variant 2b and identifies feline parvovirus-like mutations in the capsid proteins

Canine parvovirus (CPV) is a major enteric pathogen of dogs worldwide that emerged in the late 1970s from a feline parvovirus (FPV)-like ancestral virus. Shortly after its emergence, variant CPVs acquired amino acid (aa) mutations in key capsid residues, associated with biological and/or antigenic changes. This study aimed to identify and analyse CPV variants and their capsid mutations amongst Australian dogs, to gain insights into the evolution of CPV in Australia and to investigate relationships between the disease and vaccination status of dogs from which viruses were detected. CPV VP2 sequences were amplified from 79 faecal samples collected from dogs with parvoviral enteritis at 20 veterinary practices in five Australian states. The median age at diagnosis was 4 months (range 1-96 months). Only 3.7% of dogs with vaccination histories had completed recommended vaccination schedules, while 49% were incompletely vaccinated and 47.2% were unvaccinated. For the first time, CPV-2b has emerged as the dominant antigenic CPV variant circulating in dogs with parvoviral enteritis in Australia, comprising 54.4% of viruses, while CPV-2a and CPV-2 comprised 43.1% and 2.5%, respectively. The antigenic variant CPV-2c was not identified. Analysis of translated VP2 sequences revealed a vast repertoire of amino acid (aa) mutations. Several Australian CPV strains displayed signatures in the VP2 protein typical of Asian CPVs, suggesting possible introduction of CPV strains from Asia, and/or CPV circulation between Asia and Australia. Canine parvoviruses were identified containing aa residues typical of FPV at key capsid (VP2) positions, representing reverse mutations or residual mutations retained from CPV-2 during adaptation from an FPV-like ancestor, suggesting that evolutionary intermediates between CPV-2 and FPV are circulating in the field. Similarly, intermediates between CPV-2a-like viruses and CPV-2 were also identified. These findings help inform a better understanding of the evolution of CPV in dogs.

Phylogenetic and Geospatial Evidence of Canine Parvovirus Transmission between Wild Dogs and Domestic Dogs at the Urban Fringe in Australia

Canine parvovirus (CPV) is an important cause of disease in domestic dogs. Sporadic cases and outbreaks occur across Australia and worldwide and are associated with high morbidity and mortality. Whether transmission of CPV occurs between owned dogs and populations of wild dogs, including Canis familiaris, Canis lupus dingo and hybrids, is not known. To investigate the role of wild dogs in CPV epidemiology in Australia, PCR was used to detect CPV DNA in tissue from wild dogs culled in the peri-urban regions of two Australian states, between August 2012 and May 2015. CPV DNA was detected in 4.7% (8/170). There was a strong geospatial association between wild-dog CPV infections and domestic-dog CPV cases reported to a national disease surveillance system between 2009 and 2015. Postcodes in which wild dogs tested positive for CPV were 8.63 times more likely to also have domestic-dog cases reported than postcodes in which wild dogs tested negative (p = 0.0332). Phylogenetic analysis of CPV VP2 sequences from wild dogs showed they were all CPV-2a variants characterized by a novel amino acid mutation (21-Ala) recently identified in CPV isolates from owned dogs in Australia with parvoviral enteritis. Wild-dog CPV VP2 sequences were compared to those from owned domestic dogs in Australia. For one domestic-dog case located approximately 10 km from a wild-dog capture location, and reported 3.5 years after the nearest wild dog was sampled, the virus was demonstrated to have a closely related common ancestor. This study provides phylogenetic and geospatial evidence of CPV transmission between wild and domestic dogs in Australia.

Genetic characterization of canine parvovirus type 2c from domestic dogs in Korea

Canine parvovirus type 2 (CPV‐2) is an aetiological agent that causes acute haemorrhagic enteritis and fatal myocarditis in dogs. Since CPV‐2 first emerged in the late 1970s, its rapid evolution has resulted in three antigenic variants: CPV‐2a, CPV‐2b and CPV‐2c. Here, we report, for the first time in Korea, two cases of CPV‐2c infection in two dogs with severe diarrhoea. The complete open reading frame (4,269nt) of CPV‐2, encoding both non‐structural (NS) and structural (VP) proteins, was sequenced. Based on the amino acid Gln present at residue 426 of the VP2 gene, these strains were typed as CPV‐2c, and were named Korea CPV‐2c_1 and Korea CPV‐2c_2. These strains shared 99.48% reciprocal nucleotide sequence identity and had the highest nucleotide identity (99.77%–99.34%) with Asian CPV strains isolated in China, Italy (found in a dog imported from Thailand), and Vietnam from 2013 to 2017. Phylogenetic analysis based on the non‐structural (NS1) and capsid (VP2) genes revealed that Korean CPV‐2c strains clustered closely to Asian CPV strains, and separately from strains isolated in Europe, South America and North America. Amino acid changes never reported before were observed in NS1 (Thr70Pro, Cys287Tyr), VP1 (Lys17Arg, Phe33Leu) and VP2 (Gln365His, Ala516Val). Additional observed mutations, including Phe267Tyr, Tyr324Ile and Gln370Arg, have been previously reported in the recent CPV‐2c strains with Asian origins. These results suggest that the Korean CPV‐2c strains were potentially introduced via neighbouring Asian countries.

A Mini-Review on the Epidemiology of Canine Parvovirus in China

Canine viral diarrhea is a severe disease in dogs worldwide. The role of canine parvovirus (CPV) in canine viral diarrhea is a common health problem in dogs, attracting major concern from veterinarians and dog owners across China. In this mini-review, we summarize the CPV epidemiology in China, including its origin, prevalence, coinfection, and the genetic evolution of the virus. The review reveals the correlation between CPV-2 infection and seasonality, a dog's age/gender/breed/vaccination; that CPV-2 is the main causative agent of canine diarrhea in Northeast China and that coinfection with other pathogens is a common occurrence; the predominant CPV epidemic strains were the new CPV-2a, and CPV-2c has shown significant growth trends since 2010. This mini-review will provide valuable information for CPV infections across China and other countries.

Nearly full-length genome characterization of canine parvovirus strains circulating in Nigeria

Canine parvovirus type 2 (CPV‐2) emerged suddenly in the late 1970s as pathogen of dogs, causing a severe and often fatal gastroenteric disease. The original CPV‐2 was replaced by three antigenic variants, CPV‐2a, CPV‐2b and CPV‐2c, which to date have gained a worldwide distribution with different relative proportions. All previous studies conducted in Africa were based on partial VP2 gene sequences. The aim of this study was to provide a genome analysis to characterize the CPV strains collected in Nigeria, Africa. Rectal swab samples (n = 320) were collected in 2018 and tested by means of an immunochromatographic assay. Among the 144 positive samples, 59 were selected for further analyses using different molecular assays. The results revealed a high prevalence of CPV‐2c (91.5%) compared to the CPV‐2a variant (8.5%). The VP2 gene sequences showed a divergence from the strains analysed in 2010 in Nigeria and a closer connection with CPV strains of Asian origin. The non‐structural gene analysis evidenced amino acid changes never previously reported. The molecular analysis based on genomic sequences evidenced a geographical pattern of distribution of the analysed strains, suggesting a potential common evolutionary origin with CPV of Asian origin. This study represents the first CPV molecular characterization including all the encoding gene sequences conducted in the African continent and contributes to define the current geographical spread of the CPV variants worldwide.

Spreading of canine parvovirus type 2c mutants of Asian origin in southern Italy

Canine parvovirus type 2 (CPV‐2) emerged as dog pathogen in the late 1970s, causing severe and often fatal epizootics of gastroenteritis in the canine population worldwide. Although to date CPV‐2 is circulating in all continents, most of the current studies have analysed the amino acid changes accounted in the VP2 gene sequence, with limited information on virus introductions from other countries. The aim of this study was to analyse the genetic features of CPV‐2c strains currently spreading in Italy. Swabs and tissue samples were collected from dogs suspected of CPV infection. The nearly complete genome sequence from the CPV‐positive samples was obtained. The co‐circulation of two different but related CPV‐2c strains, with amino acid changes characteristic of CPV strains of Asian origin (NS1: 60V, 544F, 545F, 630P – NS2: 60V, 151N, 152V ‐ VP2: 5A/G, 267Y, 297A, 324I, 370R), were observed. The phylogenetic analyses inferred from the NS1 and VP2 gene sequences confirmed the relationship with Asian CPV‐2c strains. This study reports the spread of novel CPV‐2c mutants in Italy and supports further studies to evaluate the coexistence of genetically divergent CPV strains in the same geographical environment.

Simultaneous detection and differentiation of canine parvovirus and feline parvovirus by high resolution melting analysis

BACKGROUND

Canine parvovirus (CPV) and feline parvovirus (FPV) are causative agents of diarrhea in dogs and cats, which manifests as depression, vomiting, fever, loss of appetite, leucopenia, and diarrhea in young animals. CPV and FPV can single or mixed infect cats and cause disease. To diagnose sick animals effectively, an effective virus diagnostic and genome typing method with high sensitivity and specificity is required.

RESULTS

In this study, a conserved segment containing one SNP A4408C of parvovirus was used for real-time PCR amplification. Subsequently, data were auto-analyzed and plotted using Applied Biosystems® High Resolution Melt Software v3.1. Results showed that CPV and FPV can be detected simultaneously in a single PCR reaction. No cross-reactions were observed with canine adenovirus, canine coronavirus, and canine distemper virus. The assay had a detection limit of 4.2 genome copies of CPV and FPV. A total of 80 clinical samples were subjected to this assay, as well as to conventional PCR-sequence assay and virus isolation. Results showed that the percentage of agreement of the assay and other methods are high.

CONCLUSIONS

In short, we have developed a diagnostic test for the accurate detection and differentiation of CPV and FPV in fecal samples, which is also cost effective.

The first isolation and identification of canine parvovirus (CPV) type 2c variants during 2016-2018 genetic surveillance of dogs in Mongolia

Canine parvovirus type 2 (CPV-2) causes a highly contagious and fatal disease, developing into acute hemorrhagic enteritis and myocarditis, in dogs. CPV-2 has evolved, generating antigenic variants CPV-2a/2b/2c that are globally distributed. However, investigating molecular characterization of CPV-2 among dog populations in Mongolia has been limited. Herein, 42 stool samples were collected from dogs with clinical signs of infection, and conventional PCR assays were employed to detect CPV-2 in 23. Our results indicated that during 2016-2018, the new CPV-2a and 2c subtypes were detected in 34.7% of the samples, and the new CPV-2b subtype was detected in 30.4% of samples. VP2 protein sequence analysis and next-generation sequencing of the complete viral genome confirmed these antigenic types. However, sequence analysis indicated new and unreported mutations, Pro580Thr, and Tyr584His in the CPV-2c subtype. From a PCR-positive sample, CPV-2c was successfully isolated, and we performed an immunofluorescence assay for antigen detection. Additionally, we performed genetic characterization and phylogenetic analysis to investigate genetic diversity among isolates from the region, resulting in high CPV-2 genetic diversity in the Mongolian dog population. Striking similarities were also observed between sequences of the strains isolated from Mongolia and China over a similar time span.

Molecular epidemiology of canine parvovirus type 2 in Vietnam from November 2016 to February 2018

BACKGROUND

Canine parvovirus type 2 (CPV-2) was first identified in the late 1970s; it causes intestinal hemorrhage with severe bloody diarrhea in kennels and dog shelters worldwide. Since its emergence, CPV-2 has been replaced with new genetic variants (CPV-2a, CPV-2b, and CPV-2c). Currently, information about the genotype prevalence of CPV-2 in Vietnam is limited. In the present study, we investigated the genotype prevalence and distribution of CPV-2 in the three regions of Vietnam.

METHODS

Rectal swabs were collected from 260 dogs with suspected CPV-2 infection from northern, central, and southern Vietnam from November 2016 to February 2018. All samples were identified as parvovirus positive by real-time PCR, and further genotyping was performed using a SimpleProbe® real-time PCR assay.

RESULTS

Of the 260 Vietnamese CPV-2 isolates, 6 isolates (2.31%) were identified as CPV-2a, 251 isolates (96.54%) were identified as CPV-2c and 3 isolates (1.15%) were untypable using the SimpleProbe® real-time PCR assay. In northern Vietnam, the percentages of CPV-2a and CPV-2c were 2.97% (3/101) and 97.3% (98/101), respectively. In central Vietnam, the percentages of CPV-2a and CPV-2c were 1.11% (1/90) and 98.89% (89/90), respectively. In southern Vietnam, the percentages of CPV-2a and CPV-2c were 3.03% (2/66) and 96.97% (64/66), respectively. CPV-2b was not observed in this study. The VP2 genes of CPV-2c in Vietnam are more genetically similar to those of CPV-2c strains in China and Taiwan than to those of prototype CPV-2c strains (FJ222821) or the first Vietnamese CPV-2c (AB120727).

CONCLUSION

The present study provides evidence that CPV-2c is the most prevalent variant in Vietnam. Phylogenetic analysis demonstrated that the recent Vietnamese CPV-2c isolates share a common evolutionary origin with Asian CPV-2c strains.

Genome sequence characterization of canine parvoviruses prevalent in the Sichuan province of China

Canine parvovirus 2 (CPV-2) infection is responsible for large numbers of animal deaths worldwide and is one of the most dangerous infectious diseases in young puppies. Twenty-four rectal swabs were collected from dogs with clinical signs of vomiting and haemorrhagic diarrhoea and were initially verified to be infected with CPV-2 using colloidal gold test strips. From the 24 CPV-positive samples, complete genome of 5050-5054 nucleotides was sequenced with a next-generation sequencing platform. Characteristics of the Open Reading Frames from different CPV-2 strains detected in this study were analyzed. Several VP2 point mutations were discovered, and demonstrated the co-circulation of new CPV-2a, new CPV-2b and CPV-2c in Sichuan province of China. The analysis results of the Chinese CPV-2 retrieved from the NCBI nucleotide, showed that new CPV-2a has become the predominant variant in some provinces of China. Phylogenetic analysis of global VP2 and NS1 nucleotide sequences revealed certain correlations among geographical regions, types and circulating time, which lays the foundation for further research concerning the epidemiology, genetic variation, vaccination and molecular evolutionary relationships of the CPV-2 identified at different times and from different regions.

Naturally-occurring right terminal hairpin mutations in three genotypes of canine parvovirus (CPV-2a, CPV-2b and CPV-2c) have no effect on their growth characteristics

We have isolated 4 naturally-occurring strains of CPV in mainland China and have identified them as CPV-2, 2a, 2b and 2c genotypes according to their VP2 sequences which also revealed substitutions within their right terminal regions. To determine if these substitutions affected the growth characteristics of the 4 strains, we constructed plasmids based on their genomic sequences minus their right terminal sequences, with the latter replaced by a single right terminal region. Analysis of rescued recombinants showed that the substitutions within their natural right termini had no significant effect on their growth characteristics.

First genetic detection and characterization of canine parvovirus from diarrheic dogs in Zambia

Although canine parvovirus (CPV) causes severe gastroenteritis in dogs globally, information on the molecular epidemiology of the virus is lacking in many African countries. Here, 32 fecal samples collected from diarrheic dogs in Zambia were tested for CPV infection using molecular assays. CPV was detected in 23 samples (71.9%). Genetic characterization revealed the predominance of CPV-2c (91.3%). This finding differs from previous reports in Africa, which indicated that CPV-2a and CPV-2b were most prevalent. Phylogenetically, most Zambian CPVs formed a distinct cluster. This is the first report on the molecular characterization of CPV in Zambia.

Trigger factor assisted self-assembly of canine parvovirus VP2 protein into virus-like particles in Escherichia coli with high immunogenicity

Canine parvovirus (CPV) has been considered to be an important pathogen, which can cause acute infectious disease in canids. Although current vaccines are effective in preventing CPV infection, safety problems still remain unsolved. In this study, a subunit vaccine against CPV based on virus-like particles (VLPs) with good safety and immunogenicity is reported. Soluble CPV VP2 protein was produced by co-expression of chaperone trigger factor (Tf16) in Escherichia coli (E.coli), and assembled into CPV VLPs which could be affected by NaCl and pH. At 250 mM NaCl pH 8.0, the VLPs co-expressed with Tf16 had similar size (25 nm) and shape with the authentic virus capsid under the transmission electron microscopy (TEM), which is also in accordance with the dynamic light scattering (DLS) data. Immunization with these particles could induce high-titer hemagglutination inhibition (1:12288) and neutralizing antibodies (1:6144) in guinea pigs. Splenic cells of them could secrete IFN-γ and IL-4 after stimulation by CPV. Thus, the VLPs produced by the new approach with high yield and immunogenicity could be a potential candidate for CPV vaccine.

Loop-mediated Isothermal Amplification-Single Nucleotide Polymorphism Analysis for Detection and Differentiation of Wild-type and Vaccine Strains of Mink Enteritis Virus

Broad coverage of mink enteritis virus (MEV) vaccination program in northeast of China has provided effective protection from mink viral enteritis. Nevertheless, MEV vaccine failures were reported due to continually evolving and changing virulence of field variants or wild-type MEV. In this study, a combined loop-mediated isothermal amplification (LAMP) and single nucleotide polymorphism (SNP) method, named LAMP-SNP assay, was developed for detection and differentiation of wild-type and vaccine strains of MEV. Four primers in MEV-VP2-LAMP were used to detect both wild-type and vaccine strains of MEV in our previous publication, and other four primers in LAMP-SNP were designed to amplify the NS1 gene in wild-type MEV and only used to detect wild-type viruses. The LAMP-SNP assay was performed in a water bath held at a constant temperature of 65 °C for 60 min. LAMP-SNP amplification can be judged by both electrophoresis and visual assessment with the unaided eyes. In comparison with virus isolation as the gold standard in testing 171 mink samples, the percentage of agreement and relative sensitivity and specificity of the LAMP-SNP assay were 97.1, 100%, and 94.0%, respectively. There were no cross-reactions with other mink viruses. The LAMP-SNP assay was found to be a rapid, reliable and low-cost method to differentiate MEV vaccine and field variant strains.

Molecular epidemiological survey of canine parvovirus in domestic dogs in four provinces, China

Canine parvovirus (CPV) can cause severe disease in animals, especially in dogs, and continuously generates new variants. In this study, the complete VP2 genes of 59 CPV isolates from clinical diseased dogs between 2015 and 2016 in 4 Chinese provinces were sequenced and analyzed. The results showed that new CPV-2a was still the prominent CPV genotype, followed by CPV-2c and new CPV-2b. CPV-2c with Ala5Gly and Gln370Arg mutations was first detected in Henan, Guangxi and Jiangsu provinces in China. A phylogenetic tree based on VP2 sequences showed that all isolates in this study formed a close lineage which separated from foreign isolates. The above results indicated that point mutations in VP2 were constantly occurring along with the widespread of CPV in China.

A multiplex TaqMan real-time PCR for detection and differentiation of four antigenic types of canine parvovirus in China

Canine parvovirus (CPV) is an important pathogen in domestic dogs, and the original antigenic types CPV-2 and its variants, CPV-2a, 2b and 2c, are prevalent worldwide. A multiplex TaqMan real-time PCR method was developed for the detection and differentiation of four antigenic types of CPV. A set of primers and probes, CPV-305F/CPV-305R and CPV-2-305P (for CPV-2)/CPV-2a-305P (for CPV-2a, 2b and 2c), was able to differentiate CPV-2 and its variants (CPV-2a, 2b and 2c). Another set of primers and probes, CPV-426F/CPV-426R and CPV-2-426P (for CPV-2 and 2a)/CPV-2b-426P (for CPV-2b)/CPV-2c-426P (for CPV-2c), was able to differentiate CPV-2a (2), CPV-2b, and CPV-2c. With these primers and probes, the multiplex TaqMan real-time PCR assay detected effectively and differentiated CPV-2, 2a, 2b and 2c by two separate real-time PCRs. No cross reactivity was observed with canine distemper virus, canine adenovirus, and canine coronavirus. The detection limit of the assay is 10¹ genome copies/μL for CPV-2, CPV-2a, CPV-2b, and 10² copies/μL for CPV-2c. The multiplex real-time PCR has 100% agreement with DNA sequencing. We provide a sensitive assay that simultaneously detects and differentiate four antigenic types of CPV and the method was also used for quantification of CPVs viral genome.

•

The Multiplex TaqMan real-time PCR can simultaneously detect and differentiate four antigenic types of CPV.

•

The method is suit for using in detection of CPVs in China.

•

The method showed a high specificity and sensitivity.

•

The method was also used for quantification of CPVs viral genome.

Introduction of Asian canine parvovirus in Europe through dog importation

Canine parvovirus (CPV) is an important infectious agent of domestic and wild carnivores, responsible for severe and often fatal haemorrhagic gastroenteritis and leukopenia. This paper reports the genomic characterization of a CPV strain collected from a dog recently imported to Italy from Thailand. The virus was detected in all tissue samples collected. The whole genome encompassing the two open reading frames encoding for non‐structural (NS1/NS2) and structural (VP1/VP2) proteins was amplified and sequenced. On the basis of genetic analysis of the VP2 gene, the isolate was characterized as CPV‐2c, but it presented genetic signatures typical of Asian strains. Sequence analysis revealed the presence of amino acid changes never observed in European CPV‐2c strains (NS1: Ile60Val, Tyr544Phe, Glu545Val, Leu630Pro; VP2: Ala5Gly, Phe267Tyr, Tyr324Ile, Gln370Arg). By phylogenetic analysis of full‐length VP2 gene, the analysed strain clustered together with Asian viruses. Therefore, a possible introduction of the virus from Asia through the imported dog was suggested, thus confirming the important role of movement of dogs in the global spread of viruses. In addition, full‐length genome analysis could help better trace the spread of canine viruses through different continents.

Genetic characterization of the complete genome of a mutant canine parvovirus isolated in China

A field canine parvovirus (CPV) strain, CPV-SH14, was previously isolated from an outbreak of severe gastroenteritis in Shanghai in 2014. The complete genome of CPV-SH14 was determined by using PCR with modified primers. When compared to other CPV-2 strains, several insertions, deletions, and point mutations were identified in the 5' and 3' UTR, with key amino acid (aa) mutations (K19R, E572K in NS1 and F267Y, Y324I and T440A in VP2) also being observed in the coding regions of CPV-SH14. These results indicated that significant and unique genetic variations have occurred at key sites or residues in the genome of CPV-SH14, suggesting the presence of a novel genetic variant of new CPV-2a. Phylogenetic analysis of the VP2 gene revealed that CPV-SH14 may have the potential to spread worldwide. In conclusion, CPV-SH14 may be a novel genetic variant of new CPV-2a, potentially with a selective advantage over other strains.

A rapid method for establishment of a reverse genetics system for canine parvovirus

Canine parvovirus (CPV) is an important and highly prevalent pathogen of dogs that causes acute hemorrhagic enteritis disease. Here, we describe a rapid method for the construction and characterization of a full-length infectious clone (rCPV) of CPV. Feline kidney (F81) cells were transfected with rCPV incorporating an engineered EcoR I site that served as a genetic marker. The rescued virus was indistinguishable from that of wild-type virus in its biological properties.

Evolutionary and genetic analysis of the VP2 gene of canine parvovirus

BACKGROUND

Canine parvovirus (CPV) type 2 emerged in 1978 in the USA and quickly spread among dog populations all over the world with high morbidity. Although CPV is a DNA virus, its genomic substitution rate is similar to some RNA viruses. Therefore, it is important to trace the evolution of CPV to monitor the appearance of mutations that might affect vaccine effectiveness.

RESULTS

Our analysis shows that the VP2 genes of CPV isolated from 1979 to 2016 are divided into six groups: GI, GII, GIII, GIV, GV, and GVI. Amino acid mutation analysis revealed several undiscovered important mutation sites: F267Y, Y324I, and T440A. Of note, the evolutionary rate of the CPV VP2 gene from Asia and Europe decreased. Codon usage analysis showed that the VP2 gene of CPV exhibits high bias with an ENC ranging from 34.93 to 36.7. Furthermore, we demonstrate that natural selection plays a major role compared to mutation pressure driving CPV evolution.

CONCLUSIONS

There are few studies on the codon usage of CPV. Here, we comprehensively studied the genetic evolution, codon usage pattern, and evolutionary characterization of the VP2 gene of CPV. The novel findings revealing the evolutionary process of CPV will greatly serve future CPV research.

Occurrence of canine parvovirus in dogs from Henan province of China in 2009-2014

BACKGROUND

There is no information concerning the genotype of Canine parvovirus (CPV) currently circulating in Henan province, China. Therefore, the aim of the present study was to provide insights into the epidemiology and molecular characterization of CPV circulating in Henan province from 2009 to 2014.

RESULTS

Nineteen thousand nine hundred seven dogs from pet hospitals in the cities of Luoyang, Anyang, Jiaozuo, Sanmenxia, Xinxiang, Zhengzhou in Henan province between 2009 and 2014 were investigated. Over the 6-year period, 1169 CPV-positive cases were identified and the morbidity of CPV infection ranged from 4.16 to 8.06 %, although morbidity was not significant (P > 0.05) between 2009 and 2014. Factors associated with morbidity included sampling season, dog age, breed, vaccination status, and sex. CPV co-infection with coccidium (10.00 %), canine distemper virus (4.79 %), hookworm (2.40 %), canine coronavirus (1.11 %), roundworm (1.03 %), tapeworm (0.17 %) and Babesia spp. (0.09 %) were observed. The new CPV-2a variant was more prevalent than the new CPV-2b variant in Henan province. CPV 2c was not observed in this study.

CONCLUSIONS

The epidemiology of CPV infection and identification of the circulating genotypes in Henan province, China from 2009 to 2014 determined that the new CPV-2a variant was more prevalent.