Development of a SYBR Green real-time PCR assay with melting curve analysis for simultaneous detection and differentiation of canine adenovirus type 1 and type 2.

Canine adenovirus type 1 (CAdV-1) and canine adenovirus type 2 (CAdV-2) cause infectious canine hepatitis (ICH) and infectious tracheobronchitis (ITB) in dogs, respectively. Cases of ICH have been documented in recent years and recent surveys have demonstrated a wide percentage of asymptomatic CAdV-1 infection in the canine population. Since both CAdV types are detectable in the same biological matrices, and viral coinfection with CAdV-1 and CAdV-2 are reported with high frequency, it is urgent to have available a rapid, highly sensitive and specific assay for the diagnosis of CAdV infection and distinction between CAdV-1 and CAdV-2. In order to detect canine adenovirus in biological samples and to rapidly distinguish the two viral types, a SYBR Green real-time PCR assay was optimized to discriminate CAdV-1 and CAdV-2 via a melting curve analysis. The developed assay showed high sensitivity and reproducibility and was highly efficient and specific in discriminating the two CAdV types. This reliable and rapid technique may represent a simple, useful and economic option for simultaneous CAdV types detection, which would be feasible and attractive for all diagnostic laboratories, both for clinical purposes and for epidemiological investigations.

Development and application of a real-time PCR assay for the detection and quantitation of lymphocystis disease virus.

Lymphocystis disease virus (LCDV) is responsible for a chronic self-limiting disease that affects more than 125 teleosts. Viral isolation of LCDV is difficult, time-consuming and often ineffective; the development of a rapid and specific tool to detect and quantify LCDV is desirable for both diagnosis and pathogenic studies. In this study, a quantitative real-time PCR (qPCR) assay was developed using a Sybr-Green-based assay targeting a highly conserved region of the MCP gene. Primers were designed on a multiple alignment that included all known LCDV genotypes. The viral DNA segment was cloned within a plasmid to generate a standard curve. The limit of detection was as low as 2.6DNA copies/µl of plasmid and the qPCR was able to detect viral DNA from cell culture lysates and tissues at levels ten-times lower than conventional PCR. Both gilthead seabream and olive flounder LCDV has been amplified, and an in silico assay showed that LCDV of all genotypes can be amplified. LCDV was detected in target and non-target tissues of both diseased and asymptomatic fish. The LCDV qPCR assay developed in this study is highly sensitive, specific, reproducible and versatile for the detection and quantitation of Lymphocystivirus, and may also be used for asymptomatic carrier detection or pathogenesis studies of different LCDV strains.

Occurrence of different Canine distemper virus lineages in Italian dogs.

This study describes the sequence analysis of the H gene of 7 Canine distemper virus (CDV) strains identified in dogs in Italy between years 2002-2012. The phylogenetic analysis showed that the CDV strains belonged to 2 clusters: 6 viruses were identified as Arctic-like lineage and 1 as Europe 1 lineage. These data show a considerable prevalence of Arctic-like-CDVs in the analysed dogs. The dogs and the 3 viruses more recently identified showed 4 distinctive amino acid mutations compared to all other Arctic CDVs.

Severe, diffuse fibrinonecrotic pleuropneumonia in a cat affected by multiple viral infection.

This communication describes the coinfection with feline panleukopenia virus (FPV), feline herpesvirus 1 (FeHV-1), feline calicivirus (FCV) and feline coronavirus (FCoV) in a 1 year­old domestic cat living in a feline shelter. The cat was referred to veterinary hospital with clinical signs related to diffuse gastro-intestinal inflammation, it had developed a severe pneumopathy with fibrinous exudation in all body cavities and died 8 days after initial presentation. Pathological findings and biomolecular diagnostic test results were compatible with an initial FPV infection that, in consequence of the lymphoid depletion, has fostered coinfection or reactivation of chronic-latent infections with FeHV-1, FCV, and FCoV. In the reported case, the simultaneous presence of different viruses exacerbated the clinical status of the host, resulting in multiple organ damage and leading it to its death.

Co-infection with feline and canine parvovirus in a cat.

In this study we reported a case of co-infection with canine parvovirus (CPV) type 2a and feline panleukopenia virus (FPV) in a 3-month-old male kitten, with the presence of a parvovirus variant which is a true intermediate between CPV and FPV. The report of a viral variant which contained FPV- and CPV-specific epitopes stresses the importance of the mechanism of multistep mutation in the production of new variants and in the emergence of new viruses. This type of multistep adaptation has already been documented during the emergence of CPV and on the basis of our results, it was hypothesized that CPV had presumably started a new process of readaptation in the feline host, confirming the importance of viral host switching as a mechanism for the emergence of new viruses.

Molecular epidemiology of canine adenovirus type 1 and type 2 in free-ranging red foxes (Vulpes vulpes) in Italy.

To date, no studies exist regarding the presence of canine adenovirus (CAdV) infection in foxes in Italy. Furthermore, the majority of worldwide investigations regarding the presence of CAdV in foxes have been carried out using common serological assays which are unable to differentiate between CAdV type 1 and CAdV type 2. To assess the presence of viral infection in Italian red foxes (Vulpes vulpes), thirty-two subjects shot during the regular hunting season in the province of Pisa (Tuscany, Italy) were sampled and tested using a polymerase chain reaction (PCR) assay capable of distinguishing between CAdV type 1 and type 2. Two subjects were positive for CAdV-1 infection and one other for CAdV-2 infection. Sequence analysis of the two CAdV-1 viruses showed complete identity between them and a high genetic similarity with all reference strains sequenced in dogs in the last twenty years, indicating the presence of genetically stable CAdV-1 in red foxes in Italy which could easily be transmitted from the wild animal population to domestic dogs. Therefore, this is the first reliable identification of CAdV-2 in foxes, and cloning of the virus detected has revealed a possible coinfection involving two different CAdV-2 strains, raising new questions about the pathogenic role of CAdV-2 in wildlife. The presence of CAdV-1 and CAdV-2 infection in foxes could represent a problem for both wild animals and domestic dogs, and emphasises the central role of red foxes in maintaining these viruses in the territory.

A real-time PCR assay for bat SARS-like coronavirus detection and its application to Italian greater horseshoe bat faecal sample surveys.

Bats are source of coronaviruses closely related to the severe acute respiratory syndrome (SARS) virus. Numerous studies have been carried out to identify new bat viruses related to SARS-coronavirus (bat-SARS-like CoVs) using a reverse-transcribed-polymerase chain reaction assay. However, a qualitative PCR could underestimate the prevalence of infection, affecting the epidemiological evaluation of bats in viral ecology. In this work an SYBR Green-real time PCR assay was developed for diagnosing infection with SARS-related coronaviruses from bat guano and was applied as screening tool in a survey carried out on 45 greater horseshoe bats (Rhinolophus ferrumequinum) sampled in Italy in 2009. The assay showed high sensitivity and reproducibility. Its application on bats screening resulted in a prevalence of 42%. This method could be suitable as screening tool in epidemiological surveys about the presence of bat-SARS-like CoVs, consequently to obtain a more realistic scenario of the viral prevalence in the population.

The SARS-like coronaviruses: the role of bats and evolutionary relationships with SARS coronavirus.

Bats represent an order of great evolutionary success, with elevated geographical diffusion and species diversity. This order harbors viruses of high variability which have a great possibility of acquiring the capacity of infecting other animals,including humans. Bats are the natural reservoir for several viruses genetically closely related to the SARScoronavirus which is the etiological agent of severe acute respiratory syndrome (SARS), a human epidemic which emerged in China in 2002-2003. In the last few years, it has been discovered that the association between coronaviruses and bats is a worldwide phenomenon, and it has been hypothesised that all mammalian coronaviruses were derived from ancestral viruses residing in bats. This review analyzes the role of bats as a reservoir of zoonotic viruses focusing more extensively on SARS-related coronaviruses and taking into account the role of African and European strains in the evolutionary history of these viruses.

Genetic complexity and multiple infections with more Parvovirus species in naturally infected cats.

Parvoviruses of carnivores include three closely related autonomous parvoviruses: canine parvovirus (CPV), feline panleukopenia virus (FPV) and mink enteritis virus (MEV). These viruses cause a variety of serious diseases, especially in young patients, since they have a remarkable predilection for replication in rapidly dividing cells. FPV is not the only parvovirus species which infects cats; in addition to MEV, the new variants of canine parvovirus, CPV-2a, 2b and 2c have also penetrated the feline host-range, and they are able to infect and replicate in cats, causing diseases indistinguishable from feline panleukopenia. Furthermore, as cats are susceptible to both CPV-2 and FPV viruses, superinfection and co-infection with multiple parvovirus strains may occur, potentially facilitating recombination and high genetic heterogeneity. In the light of the importance of cats as a potential source of genetic diversity for parvoviruses and, since feline panleukopenia virus has re-emerged as a major cause of mortality in felines, the present study has explored the molecular characteristics of parvovirus strains circulating in cat populations. The most significant findings reported in this study were (a) the detection of mixed infection FPV/CPV with the presence of one parvovirus variant which is a true intermediate between FPV/CPV and (b) the quasispecies cloud size of one CPV sample variant 2c. In conclusion, this study provides new important results about the evolutionary dynamics of CPV infections in cats, showing that CPV has presumably started a new process of readaptation in feline hosts.

Sequence analysis of the nucleocapsid gene of feline coronaviruses circulating in Italy.

Molecular analysis of the N genes of feline coronaviruses (FCoV) strains detected in naturally infected cats were carried out to investigate the genetic diversity among these viruses. Phylogeny showed a general clustering trend on the basis of geographic origin rather than on virulence characteristics. The analysis of the pattern of nucleotide substitutions disclosed "hot spots" sites which may represent immunological domains. In conclusion, our results demonstrate that the N gene does not carry mutations associated with the pathotypical switch FECV --> FIPV. During persistent infection, the individual qualitative immune response might address the accumulations of mutations in the N gene and the development of FIP.

Genetic typing of bovine viral diarrhoea virus: evidence of an increasing number of variants in Italy.

Bovine Viral Diarrhoea Virus (BVDV) is responsible worldwide for severe economic losses on cattle farms. BVDV is an RNA virus with a high genome variability having practical consequences on epidemiology, diagnosis and disease control. Genetic monitoring was suggested as the first step in BVDV control. Thirty-seven Bovine Viral Diarrhoea Viruses were identified in persistently infected cattle, mucosal disease-affected animals and in bulk milk, and were characterised genetically. The 5'UTR region was amplified and sequenced, and a phylogenetic analysis was carried out comparing all the Italian sequences of BVDV available from the Genbank database. An unusual number of persistent infected animals was evidenced on more than one farm. Phylogenetic analysis attributed all our viruses to BVDV type I and distinguished four different subgroups inside this genotype. Analysis of old and new viruses revealed the circulation of viruses classified in subgroups BVDV Ia and Ij never reported in Italy.

High genetic diversity of the VP2 gene of a canine parvovirus strain detected in a domestic cat.

This study reports the detection of co-infection by multiple CPV variants and the high genetic complexity of a CPV-2 strain detected in a domestic cat. The CPV variants selected by cloning the VP2 gene were sequenced, and genetic diversity and selection pressure were investigated. Comparison of the nucleotide sequences has evidenced 10 different viral populations, and, in the same animal, more CPV variants coexist. Our analysis excludes the possibility that the recombination events took place during infection and that negative selection acted on the VP2 gene. These findings confirm that CPV-2 shows high genetic heterogeneity resembling the quasispecies found in RNA viruses.

In vitro activity of VEGF-E produced by orf virus strains isolated from classical and severe persistent contagious ecthyma.

Proliferative orf virus infections in adult sheep have increased in Italy in the past few years: these extreme cases are frequently fatal and difficult to differentiate from other infectious diseases of sheep such as blue tongue. A probable explanation for the proliferative and highly vascularized nature of the lesions was found in the expression of the VEGF-E gene encoded by the orf virus. To investigate a possible role of the viral VEGF in the pathogenesis of severe persistent orf virus lesions, the activity of four VEGF-E variants was compared by an angiogenesis in vitro model. Similar angiogenic activity was found between strains isolated from the classical and the proliferative forms of the disease, even if the latter was able to develop a higher number of vessels during the first 24 h of infection. Our in vitro findings seems to exclude that the VEGF variants encoded by the strain isolated from the atypical form of the disease could be the responsible for the histopathological aspect of the proliferative lesions.

Quasispecies composition and phylogenetic analysis of feline coronaviruses (FCoVs) in naturally infected cats.

Quasispecies composition and tissue distribution of feline coronaviruses (FCoVs) were studied in naturally infected cats. The genomic complexity of FCoVs was investigated using single-strand conformational polymorphism (SSCP) analysis of N and ORF7b amplicons, and the evolutionary process was investigated by sequence-based phylogenetic analysis. SSCP analysis showed high heterogeneity of the FCoV genome which was correlated with the seriousness of the clinical form. The two genomic regions analysed showed different levels of variation; the N region demonstrated significant heterogeneity as compared to ORF7b. Phylogenetic analysis of the nucleotide sequences showed the clear separation of sequences analysed on the basis of virulence and geographical origin. A maximum likelihood analysis of N and ORF7b data sets showed a situation of strong heterogeneity for the N region.

Genetic analysis of canine parvovirus isolates (CPV-2) from dogs in Italy.

Genetic and antigenic properties of 62 field isolates of canine parvovirus (CPV-2) collected from 1994 to 2001 in Italy were investigated. Antigenic characterisation was conducted using specific monoclonal antibodies (Mabs). The VP1\VP2 gene was amplified by PCR and characterised with restriction endonucleases to detect the 297 and 265 variant. The VP2 gene of 16 isolates was sequenced and molecular genetic analysis was conducted. The antigenic type prevalent among our isolates is type 2a as well as the 297 variant, which is also prevalent in the rest of Europe. Only the 9.7% of the isolates have the T265P mutation. The VP2 sequences of CPV-2 isolates were very similar to recent Asian isolates. In the threefold spike of CPV-699 a coding change was detected in the 440 residue where threonine was substituted by alanine: the same mutation has been found in two Asian CPV-2 isolates from leopard cats [Virology 278 (2000) 13]. Phylogenetic analysis revealed that the Italian CPV-2 strains followed the same evolution as observed in other countries and they gave no indication of a separate lineage.

Analysis of canine parvovirus sequences from wolves and dogs isolated in Italy.

The VP2 genes of Italian canine parvovirus (CPV) type 2 strains isolated from dogs and wolves were sequenced and a three-dimensional model of the VP2 capsid protein was constructed. Two mutations were detected in the VP2 sequences of the Italian strains: one at residue 297 and one at residue 265. Variant 297 is the predominant CPV isolate in Europe, whereas variant 265 has never been detected before. The mutation at residue 265 causes a disruption in a G strand of the beta-barrel in the VP2 protein. Data on strains isolated from wolves demonstrated that the same strain of CPV can circulate among domestic and wild canids; therefore, this result leads us to exclude the possibility that a separate parvovirus pool exists in wild populations.