Feline panleukopenia virus: its interesting evolution and current problems in immunoprophylaxis against a serious pathogen

Canine parvovirus type 2 (CPV-2) serological and molecular patterns in dogs with viral gastroenteritis from southern Brazil

Canine Parvovirus type 2 (CPV-2) is a highly contagious virus that can cause severe systemic disease with gastroenteric symptoms in dogs, particularly in young puppies. Originating from the feline parvovirus in the late 1970s, it swiftly propagated globally, instigating a pandemic in dogs. Despite vaccination advancements, CPV-2 remains a substantial challenge for veterinary professionals and pet owners. This study aimed to contribute knowledge about the current situation of CPV-2 among dogs in southern Brazil. In this study, the sera of 125 dogs (mostly with gastroenteritis symptoms) were screened for antibodies against CPV-2 and their faeces for the virus itself. The results showed that 40% (50/125) of dogs were infected with CPV-2. Most animals (65.5%) had previously been exposed to CPV-2 (with serotitres equal or above 1:40), and only 37.6% had protective antibody titres equal or above 1:80. The findings have also demonstrated that vaccination against CPV-2 significantly reduced the risk of infection, with positive cases decreasing from 56.9% (unvaccinated) to 2.0% (fully vaccinated). Furthermore, the prevalence of CPV-2 decreased as dogs aged, with younger dogs and those with an incomplete or non-existent vaccination history at the highest risk of infection. In conclusion, this study provides valuable insight into the prevalence and risk factors associated with CPV-2 infection in dogs in southern Brazil, thereby providing valuable knowledge for the improvement of veterinary care and pet health.

Complete genome sequence and phylogenetic analysis of feline panleukopenia virus from India

Parvoviruses are ubiquitous pathogens that cause fatal disease in cats. Feline panleukopenia virus (FPV) is a primitive virus reported first and canine parvovirus (CPV) evolved from FPV and was reported later. Both induce disease in cats and dogs with correlative signs. FPV in domestic cats is genetically diverse and some strains may differ from those used for vaccination. In this study, a virus of FPV strain, ABT/MVC/2022/FPV/001, was identified from a fecal sample of the suspected cat with severe haemorrhagic gastroenteritis. The phylogenetic analysis and complete genome sequence of the strain share 99.75% nucleotide identity with FPV variant MH559110 belonging to Tamil Nadu, India. The results also reveal similarities to strains isolated from Italy, Belgium, and China. The deduced amino acid sequence of isolated strain revealed specific amino acid substitution (Pro5Ala, Phe6Val, His7Gln, Asn9Asp, Lys16Arg, Lys19Arg, Asn52Lys, Gly58Trp, Thr66Ser, Lys67Arg, Leu70His, Asn373Asp and Ala390Thr) which differed from MH559110 and other strains. The complete genomic analysis revealed that the FPV strain circulating in India is evolving rapidly with unique antigenic variations between field FPV, CPV and vaccine strains which may be the major cause for vaccine failure in vaccinated cats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-023-00854-7.

China-origin G1 group isolate FPV072 exhibits higher infectivity and pathogenicity than G2 group isolate FPV027

Introduction

Feline parvovirus (FPV), a single-stranded DNA virus, is accountable for causing feline panleukopenia, a highly contagious and often lethal disease that primarily affects cats. The epidemiology prevalence and pathogenicity of FPV in certain regions of China, however, remains unclear. The aim of this research was to investigate the epidemiology of FPV in different regions of China in 2021 and compare its infectivity and pathogenicity.

Methods

In this research, a total of 36 FPV strains were obtained from diverse regions across China. Phylogenetic analysis was performed based on the VP2 and NS1 sequences, and two representative strains, FPV027 and FPV072, which belonged to different branches, were selected for comparative assessment of infectivity and pathogenicity.

Results and discussion

The results revealed that all strains were phylogenetically classified into two groups, G1 and G2, with a higher prevalence of G1 strains in China. Both in vitro and in vivo experiments demonstrated that FPV072 (G1 group) exhibited enhanced infectivity and pathogenicity compared to FPV027 (G2 Group). The structural alignment of the VP2 protein between the two viruses revealed mutations in residues 91, 232, and 300 that may contribute to differences in infectivity and pathogenicity. The findings from these observations will contribute significantly to the overall understanding of the molecular epidemiology of FPV in China and facilitate the development of an effective FPV vaccine.

Prevalence of Serum Antibody Titers against Core Vaccine Antigens in Italian Cats

Feline core vaccines strongly recommended for all cats are against Feline panleukopenia virus (FPV), Felid herpesvirus type 1 (FeHV-1), and Feline calicivirus (FCV), but cats can be classified as low- and high-risk based on their lifestyle. The aim of this study was to determine the actual seroprotection against FPV, FeHV-1, and FCV in a large cohort of Italian cats by using the VacciCheck test. A total of 740 cats (567 owned and 173 stray cats; 435 vaccinated and 305 unvaccinated) were analyzed for Protective Antibody Titers (PATs). Differences related to origin, sex, age, breed, FIV/FeLV status, health status, and time elapsed since last vaccination were evaluated. Less than half of the entire cohort (36.4%) had PATs for all three diseases simultaneously, increasing to 48.6% if weak positive values were also considered and 50.3% when considering only the 435 vaccinated cats. Particularly, antibodies were detected against FCV, FPV, and FeHV-1 at protective titers (PATs) in 78.6%, 68.1, and 49.1% of the cats, respectively. In general, owned, neutered, and adult FIV- and/or FeLV-negative cats were the most protected categories, even if not always for the three viruses. Most cats maintained high PATs for 3 years or longer after vaccination against FPV and FCV but not FeHV-1. Long-lasting protective immunity persisted for many years after the last vaccination (more than 18 years in the oldest cats). Nevertheless, since not all cats were protected after so many years and for all pathogens, checking protection via antibody titration could be the best choice to prevent immunity breakdowns. The discussion also focuses on the reliability of antibody titration for the two URTD (upper respiratory tract disease) viruses which, unlike for FPV, is not widely accepted as a valid index of protection.

Epidemiological and Molecular Approaches for a Fatal Feline Panleukopenia Virus Infection of Captive Siberian Tigers (Panthera tigris altaica) in the Republic of Korea

Feline panleukopenia virus (FPV), a member of the species Protoparvovirus carnivoran1, is one of the most fatal pathogens of domestic and wild carnivores. The virus endemically infects domestic carnivores worldwide and its cross-species transmission threatens endangered wild carnivores, including Siberian tigers. In this study, a fatal FPV infection in endangered Siberian tigers was investigated to trace the origin of the virus and elucidate the reason behind FPV's infection of the vaccinated tigers. Our genetic characterization and phylogenetic analysis revealed that the virus detected in the infected tigers, designated as the KTPV-2305 strain, was closely related to FPV strains circulating in Korean cats, suggesting that it might have been transmitted from stray cats wandering around the zoo. Compared with the prototype FPV reference strains, the KTPV-2305 strain carried three distinct amino acid (aa) mutations in the VP2 protein sequence (I101T, I232V, and L562V) in this study. These three mutations are commonly found in most global FPV strains, including Korean strains, indicating that these mutations are common evolutionary characteristics of currently circulating global FPVs. The reason why the vaccinated tigers were infected with FPV was most likely the insufficient protective immunity of the affected tigress or vaccine failure triggered by the interference of maternal-derived antibodies in the affected tiger cubs. These findings suggest that improved vaccination guidelines are urgently needed to save the lives of wild carnivores from this fatal virus.

Evaluation of the Inactivation Efficacy of Four Disinfectants for Feline Parvovirus Derived from Giant Panda

Feline panleukopenia (FPL) is a highly contagious acute infectious disease caused by feline parvovirus (FPV). FPV has also been found in giant pandas with clinical signs of vomiting and mild diarrhea, posing a threat to this vulnerable species. Cleaning and disinfection may be one of the most efficacious ways to prevent FPV spread in the habitat of giant pandas. This study evaluated the inactivation effect of peracetic acid (PAA), povidone-iodine (PVP-I), glutaral and deciquam solution (JM) and Virkon S. The tissue culture infective dose (TCID₅₀) assay indicated that the virus may be totally inactivated by JM, PAA and Virkon S. Meanwhile, the hemagglutination (HA) assay showed a high inactivation efficiency of PAA and Virkon S. The analysis of Western blot revealed that PAA, Virkon S and JM can inhibit the structural protein synthesis. Taken together, our findings demonstrated that PAA could rapidly and efficiently inactivate FPV, representing an efficacious disinfectant for FPV control.

Molecular characterization of carnivore protoparvovirus strains circulating in cats in Turkey

ABSTRACT: Cats are susceptible to feline panleukopenia virus (FPV) and canine parvovirus type 2 (CPV-2). Therefore, coinfection and superinfection with multiple parvovirus strains may occur, resulting in high heterogeneity and recombination. Considering the importance of cats as a potential source of genetic diversity for parvoviruses, we investigated the frequency of parvovirus infection in cats using their blood and fecal samples and performed molecular characterization of parvovirus strains circulating in cat populations. Accordingly, the fecal and blood samples of 60 cats with gastroenteritis symptoms were collected from Turkey’s Burdur, Isparta, and Izmit provinces. Of these 15 fecal samples tested as parvovirus-positive by PCR, 14 were confirmed to have been infected with true FPV strains by sequencing analysis. Through the phylogeny analysis, those were located in the FPV cluster, closely related to CPV-2, and one was discriminated in the CPV-2b cluster. Additionally, sequence analysis of the VP2 gene of CPV and FPV revealed that the FPV strains detected in Turkey and the vaccine strains were highly related to each other, with a nucleotide identity of 97.7- 100%. Furthermore, 13 variable positions were detected in VP2 of the field and reference FPV strains. Three synonymous mutations were determined in the VP2 gene. Some amino acid mutations in the VP2 protein-affected sites were considered responsible for the virus’s biological and antigenic properties. The partial sequence analysis of the VP2 gene revealed that four FPV strains detected in Turkey have a single nucleotide change from T to G at the amino acid position 384 between the nucleotides 3939-3941, which was reported for the first time. Therefore, these four isolates formed a different branch in the phylogenetic tree. The results suggest that both FPV and CPV-2b strains are circulating in domestic cats in Turkey and cats should be considered as potential sources of new parvovirus variants for cats, dogs and other animals.

SP1/miR-92a-1-5p/SOCS5: A novel regulatory axis in feline panleukopenia virus replication

MicroRNAs (miRNAs) are vital post-transcriptional regulators that participate in host-pathogen interactions by modulating the expression of cellular factors. Previous studies have demonstrated that feline panleukopenia virus (FPV) alters miRNA expression levels within host cells. However, the relationship between FPV replication and host miRNAs remains unclear. Here, we demonstrated that FPV infection significantly altered cellular miR-92a-1-5p expression in F81 cells by upregulating the expression of specificity protein 1 (SP1). Furthermore, we observed that miR-92a-1-5p enhanced interferon (IFN-α/β) expression by targeting the suppressors of cytokine signaling 5 (SOCS5) that negatively regulates NF-κB signaling and inhibits FPV replication in host cells. These findings revealed that miR-92a-1-5p plays a crucial role in host defense against FPV infection.

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.

Generation and Validation of Monoclonal Antibodies Suitable for Detecting and Monitoring Parvovirus Infections

For many applications it is necessary to detect target proteins in living cells. This is particularly the case when monitoring viral infections, in which the presence (or absence) of distinct target polypeptides potentially provides vital information about the pathology caused by the agent. To obtain suitable tools with which to monitor parvoviral infections, we thus generated monoclonal antibodies (mAbs) in order to detect the major non-structural protein NS1 in the intracellular environment and tested them for sensitivity and specificity, as well as for cross-reactivity towards related species. Using different immunogens and screening approaches based on indirect immunofluorescence, we describe here a panel of mAbs suitable for monitoring active infections with various parvovirus species by targeting the major non-structural protein NS1. In addition to mAbs detecting the NS1 of parvovirus H-1 (H-1PV) (belonging to the Rodent protoparvovirus 1 species, which is currently under validation as an anti-cancer agent), we generated tools with which to monitor infections by human cutavirus (CuV) and B19 virus (B19V) (belonging to the Primate protoparvovirus 3 and the Primate erythroparvovirus 1 species, respectively, which were both found to persistently infect human tissues). As well as mAbs able to detect NS1 from a broad range of parvoviruses, we obtained entities specific for either (distinct) members of the Rodent protoparvovirus 1 species, human CuV, or human B19V.

Genetic Insights into Feline Parvovirus: Evaluation of Viral Evolutionary Patterns and Association between Phylogeny and Clinical Variables

Feline panleukopenia is a severe disease of cats caused by feline parvovirus (FPV), and marginally canine parvovirus (CPV). Despite being less rapid than CPV, FPV evolution deserves attention, especially since outbreaks of particular severity are currently reported. This apparently different virulence needs monitoring from genetic and clinical points of view. This manuscript explored FPV molecular epidemiology at both Italian and international levels and the possible association between viral phylogeny and disease severity. Sequences from clinical cases of feline panleukopenia in Italy were obtained from 2011 to 2019, and the etiological agent was characterized, distinguishing FPV from CPV. Phylogenetic and phylodynamic analyses were conducted on Italian and international sequences. Moreover, the association between the viral sequence and clinical variables was evaluated on a group of highly characterized patients. After its origin in the 1920s, FPV showed a constant population size until a more recent expansion since 2000. Few long-distance introduction events characterized FPV spreading, however, most of its evolution occurred locally. Although without a strong statistical association, several clinical variables appeared influenced by viral phylogeny, suggesting a differential virulence potentially characterizing FPV strains. These results stress the importance of the continuous study of viral evolution and its repercussions on the disease clinical aspects.

Circulation of diverse protoparvoviruses in wild carnivores, Italy

Protoparvovirus is a monophyletic viral genus that includes the species Carnivore protoparvovirus-1 infecting domestic and wild carnivores. In this paper, the results of an epidemiological survey for Carnivore protoparvovirus-1 in wild carnivores in Italy are reported. Overall, 34 (11.4%) out of 297 tested animals were positive for Carnivore protoparvovirus-1, but the frequency of detection was much higher in intestine (54%) than in spleen samples (2.8%), thus suggesting that the intestine is the best sample to collect from wild animals for parvovirus detection. Feline panleukopenia virus (FPV) was detected in red foxes (Vulpes vulpes) (2.8%, 7/252) and Eurasian badgers (Meles meles) (10%, 1/10), whilst canine parvovirus (CPV) was found in wolves (54.3%, 19/35), Eurasian badgers (60%, 6/10) and one beech marten (Martes foina) (100%, 1/1), with more than one parvovirus type detected in some animals. Protoparvoviral DNA sequences from this study were found to be related to CPV/FPV strains detected in Asia and Europe, displaying some amino acid changes in the main capsid protein VP2 in comparison with other parvovirus strains from wildlife. In particular, the two most common mutations were Ile418Thr and Ala371Gly, which were observed in 6/12 (50%) and 5/12 (41.7%) of the CPV sequences from this study. Continuous surveillance for parvoviruses in wild carnivores and genetic analysis of the detected strains may help obtain new insight into the role of these animals in the evolution and epidemiology of carnivore parvoviruses.

Evaluation of an in-house indirect enzyme-linked immunosorbent assay of feline panleukopenia VP2 subunit antigen in comparison to hemagglutination inhibition assay to monitor tiger antibody levels by Bayesian approach

Background

Feline panleukopenia virus (FPV) is an etiologic pathogen of feline panleukopenia that infects all members of Felidae including tigers (Panthera tigris). Vaccinations against FPV among wild felid species have long been practiced in zoos worldwide. However, few studies have assessed the tiger immune response post-vaccination due to the absence of a serological diagnostic tool. To address these limitations, this study aimed to develop an in-house indirect enzyme-linked immunosorbent assay (ELISA) for the monitoring of tiger antibody levels against the feline panleukopenia vaccine by employing the synthesized subunit capsid protein VP2. An in-house horseradish peroxidase (HRP) conjugated rabbit anti-tiger immunoglobulin G (IgG) polyclonal antibody (HRP-anti-tiger IgG) was produced in this study and employed in the assay. It was then compared to a commercial HRP-conjugated goat anti-cat IgG (HRP-anti-cat IgG). Sensitivity and specificity were evaluated using the Bayesian model with preferential conditional dependence between HRP-conjugated antibody-based ELISAs and hemagglutination-inhibition (HI) tests.

Results

The posterior estimates for sensitivity and specificity of two indirect ELISA HRP-conjugated antibodies were higher than those of the HI test. The sensitivity and specificity of the indirect ELISA for HRP-anti-tiger IgG and HRP-anti-cat IgG were 86.5, 57.2 and 86.7%, 64.6%, respectively, while the results of the HI test were 79.1 and 54.1%. In applications, 89.6% (198/221) and 89.1% (197/221) of the tiger serum samples were determined to be seropositive by indirect ELISA testing against HRP-anti-tiger and HRP-anti-cat, respectively.

Conclusion

To the best of our knowledge, the specific serology assays for the detection of the tiger IgG antibody have not yet been established. The HRP-anti-tiger IgG has been produced for the purpose of developing the specific immunoassays for tigers. Remarkably, an in-house indirect ELISA based on VP2 subunit antigen has been successfully developed in this study, providing a potentially valuable serological tool for the effective detection of tiger antibodies.

Virome of a Feline Outbreak of Diarrhea and Vomiting Includes Bocaviruses and a Novel Chapparvovirus

An unexplained outbreak of feline diarrhea and vomiting, negative for common enteric viral and bacterial pathogens, was subjected to viral metagenomics and PCR. We characterized from fecal samples the genome of a novel chapparvovirus we named fechavirus that was shed by 8/17 affected cats and identified three different feline bocaviruses shed by 9/17 cats. Also detected were nucleic acids from attenuated vaccine viruses, members of the normal feline virome, viruses found in only one or two cases, and viruses likely derived from ingested food products. Epidemiological investigation of disease signs, time of onset, and transfers of affected cats between three facilities support a possible role for this new chapparvovirus in a highly contagious feline diarrhea and vomiting disease.

Feline Parvovirus Seroprevalence Is High in Domestic Cats from Disease Outbreak and Non-Outbreak Regions in Australia

Multiple, epizootic outbreaks of feline panleukopenia (FPL) caused by feline parvovirus (FPV) occurred in eastern Australia between 2014 and 2018. Most affected cats were unvaccinated. We hypothesised that low population immunity was a major driver of re-emergent FPL. The aim of this study was to (i) determine the prevalence and predictors of seroprotective titres to FPV among shelter-housed and owned cats, and (ii) compare the prevalence of seroprotection between a region affected and unaffected by FPL outbreaks. FPV antibodies were detected by haemagglutination inhibition assay on sera from 523 cats and titres ≥1:40 were considered protective. Socioeconomic indices based on postcode and census data were included in the risk factor analysis. The prevalence of protective FPV antibody titres was high overall (94.3%), even though only 42% of cats were known to be vaccinated, and was not significantly different between outbreak and non-outbreak regions. On multivariable logistic regression analysis vaccinated cats were 29.94 times more likely to have protective FPV titres than cats not known to be vaccinated. Cats from postcodes of relatively less socioeconomic disadvantage were 5.93 times more likely to have protective FPV titres. The predictors identified for FPV seroprotective titres indicate targeted vaccination strategies in regions of socioeconomic disadvantage would be beneficial to increase population immunity. The critical level of vaccine coverage required to halt FPV transmission and prevent FPL outbreaks should be determined.

Construction and Immunogenicity of Virus-Like Particles of Feline Parvovirus from the Tiger

Feline panleukopenia, caused by feline parvovirus (FPV), is a highly infectious disease characterized by leucopenia and hemorrhagic gastroenteritis that severely affects the health of large wild Felidae. In this study, tiger FPV virus-like particles (VLPs) were developed using the baculovirus expression system. The VP2 gene from an infected Siberian tiger (Panthera tigris altaica) was used as the target gene. The key amino acids of this gene were the same as those of FPV, whereas the 101st amino acid was the same as that of canine parvovirus. Indirect immunofluorescence assay (IFA) results demonstrated that the VP2 protein was successfully expressed. SDS-PAGE and Western blotting (WB) results showed that the target protein band was present at approximately 65 kDa. Electron micrograph analyses indicated that the tiger FPV VLPs were successfully assembled and were morphologically similar to natural parvovirus particles. The hemagglutination (HA) titer of the tiger FPV VLPs was as high as 1:2¹⁸. The necropsy and tissue sections at the cat injection site suggested that the tiger FPV VLPs vaccine was safe. Antibody production was induced in cats after subcutaneous immunization, with a >1:2¹⁰ hemagglutination inhibition (HI) titer that persisted for at least 12 months. These results demonstrate that tiger FPV VLPs might provide a vaccine to prevent FPV-associated disease in the tiger.

Regional adaptations and parallel mutations in Feline panleukopenia virus strains from China revealed by nearly-full length genome analysis

Protoparvoviruses, widespread among cats and wild animals, are responsible for leukopenia. Feline panleukopenia virus (FPLV) in domestic cats is genetically diverse and some strains may differ from those used for vaccination. The presence of FPLV in two domestic cats from Hebei Province in China was identified by polymerase chain reaction. Samples from these animals were used to isolate FPLV strains in CRFK cells for genome sequencing. Phylogenetic analysis was performed to compare our isolates with available sequences of FPLV, mink parvovirus (MEV) and canine parvovirus (CPV). The isolated strains were closely related to strains of FPLV/MEV isolated in the 1960s. Our analysis also revealed that the evolutionary history of FPLV and MEV is characterized by local adaptations in the Vp2 gene. Thus, it is likely that new FPLV strains are emerging to evade the anti-FPLV immune response.

Analysis of the microRNA expression profiles in feline kidney cell line infected with feline panleukopenia virus

MicroRNAs (miRNAs) play crucial roles in post-transcriptional regulation of gene expression in many biological processes. Feline panleukopenia virus (FPV) is a highly infectious pathogen that can cause severe disease in pets, economically important animals and wildlife. In this study, miRNAs associated with FPV infection were identified using high-throughput sequencing. Our results showed that 673 known miRNAs and 278 novel miRNAs were identified and 57 significantly differential expression miRNAs were found post-FPV infection in feline kidney cell line. Stem-loop qRT-PCR was applied to validate the expression of the randomly selected miRNAs; the results were consistent with the sequencing data. Furthermore, the target genes of differential expression miRNAs were analyzed and predicated by GO and KEGG pathway. Altogether, our analysis provides a potential link between miRNA expression and the pathogenesis of FPV infection.

Development of a recombinase polymerase amplification assay with lateral flow dipstick for rapid detection of feline parvovirus

Feline panleukopenia caused by feline parvovirus (FPV), a single-stranded DNA virus, is typically highly contagious and often presents with lethal syndrome. The broad spectrum of possible hosts suggests its potential for transmission from animal to person through close contact with pets. FPV thus serves as an example of the importance of new rapid point-of-care field diagnostic tools for the control and prevention of transmission, especially among rare wild animals and pet cats. Recombinase polymerase amplification (RPA), as a real-time and isothermal method, could be a more affordable alternative to PCR when combined with a lateral flow dipstick (LFD) indicator. In this study, we report a novel FPV lateral flow dipstick RPA (LFD-RPA) instant detection method capable of detecting a range of different FPV strains. The LFD-RPA assay consists of specific primers, probe, and nucleic acid strip. It is capable of detecting 10² copies of target nucleic acid per reaction, which is one order of magnitude higher than the sensitivity of traditional PCR. The most suitable reaction conditions for this assay are at 38 ℃ for 15 min. This paper develops an efficient visual detection system that can eliminate the need for professional staff and expensive and sophisticated equipment for field detection.

Lymphoplasmacytic Meningoencephalitis and Neuronal Necrosis Associated With Parvoviral Infection in Cats

Neurologic manifestations other than cerebellar hypoplasia are rarely associated with feline panleukopenia virus (FPV) infection in cats. Here the authors describe lymphoplasmacytic meningoencephalitis and neuronal necrosis in 2 cats autopsied after exhibiting ataxia and nystagmus. Gross changes consisted of cerebellar herniation through the foramen magnum, with flattening of cerebrocortical gyri and narrowing of sulci. Histologically, lymphoplasmacytic meningoencephalitis, extensive neuronal necrosis, and neuroaxonal degeneration with digestion chambers were present in the telencephalon and brain stem in both cats. Frozen brain tissue of both cats was positive for parvoviral antigen via fluorescent antibody testing, and formalin-fixed, paraffin-embedded tissue sections of brain were immunoreactive for parvovirus antigen and positive for parvoviral DNA on in situ hybridization. Frozen brain tissue from 1 case was positive for parvovirus NS1 and VP2 genes using conventional polymerase chain reaction, and subsequent DNA sequencing and phylogenetic analysis revealed that the viral strain was a FPV. Reverse transcription quantitative polymerase chain reaction on formalin-fixed, paraffin-embedded brain tissue revealed high levels of parvovirus in both cases, supporting an acute and active viral infection. Although rare, FPV infection should be considered in cases of lymphoplasmacytic meningoencephalitis and neuronal necrosis in cats.

Research on viral agents associated with feline reproductive problems reveals a high association with feline panleukopenia virus

Although reproductive failures (RF) such as abortion, stillbirth and neonatal mortality in cats are still under researched, it is known that many RF are caused by viral agents. This research surveyed the viral agent prevalence in queens with RF. Queens were excluded from the study if their RF was caused by issues other than infection, such as genetic, traumatic, hormonal or nutritional problems, or if they had a history of RF. Blood samples from 26 pregnant females with RF were collected for complete blood counts (BCC), renal/hepatic biochemistry and glycaemic analysis. Ultrasonography was performed to evaluate gestational age and foetal viability. When possible, placentas, humours and foetal tissues were collected. Blood samples were tested by PCR and qPCR for feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV), feline alphaherpesvirus 1 (FeHV-1) and carnivore protoparvovirus 1 (CPPV-1). All maternal samples were negative for FeLV, FIV and FeHV-1 and positive for CPPV-1. In addition, foetuses from one queen and three females were positive for CPPV-1 by qPCR and for feline panleukopenia virus (FPV) through DNA sequencing. The BCC and biochemistry results revealed significant neutrophilia, lymphopenia, monocytosis, and liver enzymes. These results provide the first description of an FPV agent causing only RF-related clinical signs in queens.

Role of transferrin receptor in hepatitis C viral infection

Hepatitis C virus (HCV) is the main pathogen causing chronic hepatitis and primary liver cancer. Various viral proteins and host cell molecules are involved in the HCV cell entry, but the mechanism of infection has not been completely elucidated. The transferrin receptor can act as a receptor for many viruses during cell entry. The transferrin receptor is not only closely related to HCV-induced iron metabolism disorders but also mediates the fusion of HCV with the host cell membrane as a specific receptor for CD81-dependent viral adhesion.

Efficacy of feline anti-parvovirus antibodies in the treatment of canine parvovirus infection

OBJECTIVE

This prospective, randomised, placebo-controlled, double-blinded study aimed to evaluate efficacy of commercially available feline anti-parvovirus antibodies in dogs with canine parvovirus infection.

METHODS

First, cross-protection of feline panleukopenia virus antibodies against canine parvovirus was evaluated in vitro. In the subsequent prospective clinical trial, 31 dogs with clinical signs of canine parvovirus infection and a positive faecal canine parvovirus polymerase chain reaction were randomly assigned to a group receiving feline panleukopenia virus antibodies (n=15) or placebo (n=16). All dogs received additional routine treatment. Clinical signs, blood parameters, time to clinical recovery and mortality were compared between the groups. Serum antibody titres and quantitative faecal polymerase chain reaction were compared on days 0, 3, 7, and 14.

RESULTS

In vitro, canine parvovirus was fully neutralised by feline panleukopenia virus antibodies. There were no detected significant differences in clinical signs, time to clinical recovery, blood parameters, mortality, faecal virus load, or viral shedding between groups. Dogs in the placebo group showed a significant increase of serum antibody titres and a significant decrease of faecal virus load between day 14 and day 0, which was not detectable in dogs treated with feline panleukopenia virus antibodies.

CLINICAL SIGNIFICANCE

No significant beneficial effect of passively transferred feline anti-parvovirus antibodies in the used dosage regimen on the treatment of canine parvovirus infection was demonstrated.

Feline Panleucopenia Virus NS2 Suppresses the Host IFN-β Induction by Disrupting the Interaction between TBK1 and STING

Feline panleucopenia virus (FPV) is a highly infectious pathogen that causes severe diseases in pets, economically important animals and wildlife in China. Although FPV was identified several years ago, little is known about how it overcomes the host innate immunity. In the present study, we demonstrated that infection with the FPV strain Philips-Roxane failed to activate the interferon β (IFN-β) pathway but could antagonize the induction of IFN stimulated by Sendai virus (SeV) in F81 cells. Subsequently, by screening FPV nonstructural and structural proteins, we found that only nonstructural protein 2 (NS2) significantly suppressed IFN expression. We demonstrated that the inhibition of SeV-induced IFN-β production by FPV NS2 depended on the obstruction of the IFN regulatory factor 3 (IRF3) signaling pathway. Further, we verified that NS2 was able to target the serine/threonine-protein kinase TBK1 and prevent it from being recruited by stimulator of interferon genes (STING) protein, which disrupted the phosphorylation of the downstream protein IRF3. Finally, we identified that the C-terminus plus the coiled coil domain are the key domains of NS2 that are required for inhibiting the IFN pathway. Our study has yielded strong evidence for the FPV mechanisms that counteract the host innate immunity.

Canine parvovirus in vaccinated dogs: a field study

The authors report a field study that investigated the canine parvovirus (CPV) strains present in dogs that developed the disease after being vaccinated. Faecal samples of 78 dogs that have been vaccinated against CPV and later presented with clinical signs suspected of parvovirus infection were used. Fifty (64.1 per cent) samples tested positive by PCR for CPV. No CPV vaccine type was detected. The disease by CPV-2b occurred in older and female dogs when compared with that by CPV-2c. The clinical signs presented by infected dogs were similar when any of both variants were involved. In most cases of disease, the resulting infection by field variants occurred shortly after CPV vaccination. Two dogs that had been subjected to a complete vaccination schedule and presented with clinical signs after 10 days of vaccination, had the CPV-2c variant associated. The phylogenetic studies showed a close relationship of the isolates in vaccinated dogs to European field strains. Despite the limited sample size in this study, the findings point to the significance of the continuous molecular typing of the virus as a tool to monitor the prevalent circulating CPV strains and access the efficacy of current vaccines. Adjustments on the vaccine types to be used may have to be evaluated again according to each epidemiological situation in order to achieve the dog's optimal immune protection against CPV.

Something old, something new: Update of the 2009 and 2013 ABCD guidelines on prevention and management of feline infectious diseases

OVERVIEW

The ABCD has published 34 guidelines in two Special Issues of the Journal of Feline Medicine and Surgery (JFMS): the first in July 2009 (Volume 11, Issue 7, pages 527-620) and the second in July 2013 (Volume 15, Issue 7, pages 528-652). The present article contains updates and new information on 18 of these (17 disease guidelines and one special article 'Prevention of infectious diseases in cat shelters'). For detailed information, readers are referred to the guidelines published in the above-mentioned JFMS Special Issues.

Faecal virome of cats in an animal shelter

We describe the metagenomics-derived feline enteric virome in the faeces of 25 cats from a single shelter in California. More than 90 % of the recognizable viral reads were related to mammalian viruses and the rest to bacterial viruses. Eight viral families were detected: Astroviridae, Coronaviridae, Parvoviridae, Circoviridae, Herpesviridae, Anelloviridae, Caliciviridae and Picobirnaviridae. Six previously known viruses were also identified: feline coronavirus type 1, felid herpes 1, feline calicivirus, feline norovirus, feline panleukopenia virus and picobirnavirus. Novel species of astroviruses and bocaviruses, and the first genome of a cyclovirus in a feline were characterized. The RNA-dependent RNA polymerase region from four highly divergent partial viral genomes in the order Picornavirales were sequenced. The detection of such a diverse collection of viruses shed within a single shelter suggested that such animals experience robust viral exposures. This study increases our understanding of the viral diversity in cats, facilitating future evaluation of their pathogenic and zoonotic potentials.

Parvoviruses: Small Does Not Mean Simple

Parvoviruses are small, rugged, nonenveloped protein particles containing a linear, nonpermuted, single-stranded DNA genome of ∼5 kb. Their limited coding potential requires optimal adaptation to the environment of particular host cells, where entry is mediated by a variable program of capsid dynamics, ultimately leading to genome ejection from intact particles within the host nucleus. Genomes are amplified by a continuous unidirectional strand-displacement mechanism, a linear adaptation of rolling circle replication that relies on the repeated folding and unfolding of small hairpin telomeres to reorient the advancing fork. Progeny genomes are propelled by the viral helicase into the preformed capsid via a pore at one of its icosahedral fivefold axes. Here we explore how the fine-tuning of this unique replication system and the mechanics that regulate opening and closing of the capsid fivefold portals have evolved in different viral lineages to create a remarkably complex spectrum of phenotypes.

Emerging animal viruses: real threats or simple bystanders?

The list of animal viruses has been frequently added of new members raising permanent concerns to virologists and veterinarians. The pathogenic potential and association with disease have been clearly demonstrated for some, but not for all of these emerging viruses. This review describes recent discoveries of animal viruses and their potential relevance for veterinary practice. Dogs were considered refractory to influenza viruses until 2004, when an influenza A virus subtype H3N8 was transmitted from horses and produced severe respiratory disease in racing greyhounds in Florida/USA. The novel virus, named canine influenza virus (CIV), is considered now a separate virus lineage and has spread among urban canine population in the USA. A new pestivirus (Flaviviridae), tentatively called HoBi-like pestivirus, was identified in 2004 in commercial fetal bovine serum from Brazil. Hobi-like viruses are genetically and antigenically related to bovine viral diarrhea virus (BVDV) and induce similar clinical manifestations. These novel viruses seem to be widespread in Brazilian herds and have also been detected in Southeast Asia and Europe. In 2011, a novel mosquito-borne orthobunyavirus, named Schmallenberg virus (SBV), was associated with fever, drop in milk production, abortion and newborn malformation in cattle and sheep in Germany. Subsequently, the virus disseminated over several European countries and currently represents a real treat for animal health. The origin of SBV is still a matter of debate but it may be a reassortant from previous known bunyaviruses Shamonda and Satuperi. Hepatitis E virus (HEV, family Hepeviridae) is a long known agent of human acute hepatitis and in 1997 was first identified in pigs. Current data indicates that swine HEV is spread worldwide, mainly associated with subclinical infection. Two of the four HEV genotypes are zoonotic and may be transmitted between swine and human by contaminated water and undercooked pork meat. The current distribution and impact of HEV infection in swine production are largely unknown. Avian gyrovirus type 2 (AGV2) is a newly described Gyrovirus, family Circoviridae, which was unexpectedly found in sera of poultry suspected to be infected with chicken anemia virus (CAV). AGV2 is closely related to CAV but displays sufficient genomic differences to be classified as a distinct species. AGV2 seems to be distributed in Brazil and also in other countries but its pathogenic role for chickens is still under investigation. Finally, the long time and intensive search for animal relatives of human hepatitis C virus (HCV) has led to the identification of novel hepaciviruses in dogs (canine hepacivirus [CHV]), horses (non-primate hepaciviruses [NPHV] or Theiler's disease associated virus [TDAV]) and rodents. For these, a clear and definitive association with disease is still lacking and only time and investigation will tell whether they are real disease agents or simple spectators.