Molecular epidemiology and phylogeny reveal complex spatial dynamics in areas where canine parvovirus is endemic

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.

Effect of Aging on the Immune Response to Core Vaccines in Senior and Geriatric Dogs

Elderly dogs are steadily increasing worldwide as well as veterinarians' and owners' interest in their health and wellness. Aging is not a disease, but a combination of changes negatively affecting the organism in general and the immune system in particular, resulting in a decline in protection over time. The aim of this study was to measure the specific serum antibody titers against the main dangerous and widespread viral diseases preventable by core vaccinations in senior and geriatric dogs using the in-practice test VacciCheck. A cohort of three hundred fifty elderly dogs was analyzed for Protective Antibody Titers (PATs) against CPV-2, CDV and CAdV-1. The age ranged from 5 to 19 years, with two hundred fifty-eight seniors (73.7%) and ninety-two geriatrics (26.3%), and 97.4% of them were vaccinated at least once in their lives. More than half of the entire study population (52.9%) had PATs simultaneously for all three diseases, with 80.5% seniors and 19.5% geriatrics. Specific PATs were found in 88.6% of aging dogs for CPV-2, 82.3% for CadV-1 and 66.0% for CDV, demonstrating that unprotected aging dogs represent a minority. Unexpectedly, the larger elderly dogs resulted as more protected than smaller ones for CPV-2. Protection then decreases over time, with geriatric dogs less protected than senior ones. Veterinary practitioners should therefore always consider whether to maintain core vaccinations in aging dogs as in adults on a three-year basis or opt instead for closer boosters (every 1 or 2 years). PATs for core vaccines could then represent a good biomarker of protection and their titration could become a standard of care, especially in such a sensitive period of the dogs' life.

[Parvovirus infections in cats in animal shelters]

Due to widespread vaccination programs against feline panleukopenia virus (FPV), the disease associated with this virus infection, feline panleukopenia, is rarely seen in privately owned cats in Germany. In contrast, the situation in animal shelters differs due to the constant intake of new cats that are often unprotected. In such facilities, panleukopenia outbreaks are common and often accompanied by a high number of fatalities. Due to the high contagiosity of the virus, some shelters do not accept cats with clinical signs suspicious for panleukopenia, since these animals can pose a risk to the shelter population. However, not only cats with panleukopenia shed parvovirus, but also healthy, asymptomatic cats can and thus contribute to risk of infection. Nevertheless, the risk for panleukopenia outbreaks in animal shelters can be reduced by rigorous outbreak management. This includes hygiene measures using correctly applied cleaning and disinfection protocols, quarantine measures, separate isolation units, as well as specific prophylactic measures, such as identification of infected animals and immunization of susceptible groups.

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

Canine vaccination is the main tool for preventing dangerous and widespread diseases. The strongly recommended (core) dog vaccines are against Canine Parvovirus type 2 (CPV-2), Canine Distemper Virus (CDV), and Canine Adenovirus (CAdV-1), but vaccination protocols should be tailored to dog lifestyles. Vaccination guidelines suggest vaccinating adult dogs no more frequently than every 3 years using modified live (attenuated) vaccines (MLV), thus obtaining a long-lasting (sometimes throughout life) specific protection in many but not all animals. The aim of this study was to determine the actual levels of seroprotection against CPV-2, CDV and CAdV-1 in a cohort of Italian dogs by using the in-practice test VacciCheck. A total of 1,027 dogs (951 vaccinated and 76 unvaccinated) were analyzed for Protective Antibody Titers (PATs) against CPV-2, CDV, and CAdV-1. Differences related to sex, age, breed size, health status, and time elapsed since last vaccination were evaluated. Half of the entire canine cohort (50.6%) had PATs for all three viruses (68.5% considering only vaccinated dogs). In particular, 90.8% of dogs were protected against CPV-2, 68.6% against CDV, and 79.8% against CAdV-1. Most dogs remained protected for 3 years after vaccination or longer. Revaccination on a 3-year basis can then be recommended for core MLV vaccines without altering individual's seroprotection or even herd immunity.

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.

Identification of novel recombinants and proposed standard reference genomes for phylogenetic classification of canine parvovirus-2 (CPV-2): Comprehensive analysis revealing global evolutionary trait

Sustained spread and continuous evolution of CPV-2 generate new genetic information; nevertheless, there is no adopted phylogenetic tool, and parvo virologists still refer to the three antigenic variants. Herein, this report attempted to review the evolutionary trait of CPV-2 and proposed standard reference genomes using the Maximum Likelihood-based phylogenetic analysis and Parsimony-Informative Sites. The analysis revealed three main evolutionary pathways where CPV-2 strains cluster into distinct clades depicted as GI, GII, or GIII, respectively. Furthermore, novel CPV-2 natural recombinants were detected, occurring only between the newly identified strains (2017–2020). Those findings provide unique insights into the evolutionary relatedness of CPV-2, clarify discrepancies between different geographic areas and will contribute to achieving a more reliable CPV-2 genetic and evolutionary genotyping classification.

Canine parvovirus is shed infrequently by cats without diarrhoea in multi-cat environments

Whether subclinical shedding of canine parvovirus (CPV) by cats might contribute to the epidemiology of canine CPV infections, particularly in facilities housing both cats and dogs, requires clarification. Conflicting results are reported to date. Using conventional PCR (cPCR) to amplify the VP2 gene, shedding of the CPV variants (CPV-2a, 2b, 2c) by healthy cats in multi-cat environments was reportedly common in Europe but rare in Australia. The aim of this study was to determine whether low-level faecal CPV shedding occurs in multi-cat environments in Australia and Italy using a TaqMan real-time PCR to detect Carnivore protoparvovirus 1 (CPV and feline parvovirus, FPV) DNA, and minor-groove binder probe real-time PCR assay to differentiate FPV and CPV types and to characterize CPV variants. In total, 741 non-diarrhoeic faecal samples from shelters in Australia (n = 263) and from shelters or cat colonies in Italy (n = 478) were tested. Overall, Carnivore protoparvovirus 1 DNA was detected in 49 of 741 (6.61 %) samples. Differentiation was possible for 31 positive samples. FPV was most common among positive samples (28/31, 90.3 %). CPV was detected in 4/31 samples (12.9 %) including CPV-2a in one sample, CPV-2b in another and co-infections of FPV/CPV-2b and CPV-2a/CPV-2b in the remaining two samples. A high rate of subclinical FPV infection was detected in one shelter during an outbreak of feline panleukopenia, during which 21 of 22 asymptomatic cats (95.5 %) sampled were shedding FPV. Faecal shedding of CPV by cats in multi-cat environments is uncommon suggesting that domestic cats are not significant reservoirs of CPV.

A virtual biobank for companion animals: A parvovirus pilot study

BACKGROUND

There is a lack of national population data concerning infectious disease in companion animals. Here, we piloted the feasibility of linking diagnostic laboratories, population surveillance and modern sequencing approaches to extract targeted diagnostic samples from laboratories before they were discarded, as a novel route to better understand national epidemiology of major small animal pathogens.

METHODS

Samples tested for canine or feline parvovirus were requested from a national veterinary diagnostic laboratory and analysed by Sanger or next generation sequencing. Samples were linked to electronic health data held in the SAVSNET database.

RESULTS

Sequences obtained from positive samples, together with associated metadata, provided new insights into the recent geographical distribution of parvovirus strains in circulation in the United Kingdom (UK).

CONCLUSIONS

This collaboration with industry represents a 'National Virtual Biobank' that can rapidly be called on, to efficiently add new layers of epidemiological information of relevance to animal, and potentially human, population health.

Molecular epidemiology of canine parvovirus type 2 in Italy from 1994 to 2017: recurrence of the CPV-2b variant

Background

Canine parvovirus type 2 (CPV-2) is the most important enteric virus infecting canids. It is a rapidly evolving virus; after its emergence in the 1970s, new antigenic variants (called CPV-2a, 2b and 2c) emerged and replaced the original antigenic type. The three antigenic variants are globally distributed with different frequencies and levels of genetic variability. This study focused on VP2 gene sequence analysis and the phylodynamics of CPV-2 which were detected in 123 dogs showing clinical signs of gastroenteritis collected in Italy from 1994 to 2017.

Results

For the most part, the sick dogs were young, and a third of them (32.5%) had been vaccinated. No statistical association was found between the CPV-2 antigenic variants, and sex, age, breed and vaccination status. Sequence analysis showed that all three antigenic types circulated in Italy; the CPV-2a type was the prominent genotype, followed by CPV-2c and CPV-2b, with notable differences regarding regional bases and significant fluctuations over time. Nucleotide sequence data showed high genetic heterogeneity with 67 nucleotide sequence types (ntSTs) identified, corresponding to 21 amino acid sequence types (aaSTs). The aaSTs and ntSTs obtained were distributed differently among the three CPV-2 antigenic variants: CPV-2a grouped 12/21 (57.1%) aaSTs and 41/67 (61.2%) ntSTs; CPV-2b grouped 5/21 (23.8%) aaSTs and 6/67 (8.9%) ntSTs, and CPV-2c grouped 4/21 (19.1%) aaSTs and 20/67 (29.9%) ntSTs. Canine parvovirus 2a was characterised by the highest genetic variability while CPV-2c was characterised by notable stability with a predominant amino acid profile during the entire sampling time. Canine parvovirus 2b re-emerged in recent years, showing a new and distinctive amino acid profile of the VP2 protein.

Conclusions

The findings of the present study provided new insights regarding the phylodynamics and evolution of CPV-2 in Italy, pointing out notable differences at the local level in the distribution of the CPV-2 variants and the selection of genetic subtypes. The evolution of CPV-2 has raised questions regarding the efficacy of vaccination; therefore, continuous monitoring regarding the evolution and spread of new CPV-2 variants should be a key aim of ongoing research.

Pharmaceutical Prescription in Canine Acute Diarrhoea: A Longitudinal Electronic Health Record Analysis of First Opinion Veterinary Practices

Canine acute diarrhoea is frequently observed in first opinion practice, though little is known about commonly used diagnostic or therapeutic management plans, including use of antimicrobials. This retrospective observational study utilised electronic health records augmented with practitioner-completed questionnaires from 3,189 cases (3,159 dogs) collected from 179 volunteer veterinary practices between April 2014 and January 2017. We used multivariable analysis to explore factors potentially associated with pharmaceutical agent prescription, and resolution of clinical signs by 10 days post-initial presentation. Use of bacteriological and/or parasitological diagnostic tests were uncommon (3.2% of cases, 95% confidence interval, CI, 2.4–4.0), though systemic antimicrobials were the most commonly prescribed pharmaceutical agents (49.7% of cases, 95% CI 46.1–53.2). Such prescription was associated with haemorrhagic diarrhoea (odds ratio, OR, 4.1; 95% CI 3.4–5.0), body temperature in excess of 39.0°C, or moderate/severe cases (OR 1.3, 95% CI 1.1–1.7). Gastrointestinal agents (e.g., antacids) were prescribed to 37.7% of cases (95% CI 35.4–39.9), and were most frequently prescribed to vomiting dogs regardless of presence (OR 46.4, 95% CI 19.4–110.8) or absence of blood (OR 17.1, 95% CI 13.4–21.9). Endoparasiticides/endectocides were prescribed to 7.8% of cases (95% CI 6.8–9.0), such prescription being less frequent for moderate/severe cases (OR 0.5, 95% CI 0.4–0.7), though more frequent when weight loss was recorded (OR 3.4, 95% CI 1.3–9.0). Gastrointestinal nutraceuticals (e.g., probiotics) were dispensed to 60.8% of cases (95% CI 57.1–64.6), these cases less frequently presenting with moderate/severe clinical signs (OR 0.6, 95% CI 0.5–0.8). Nearly a quarter of cases were judged lost to follow-up (n=754). Insured (OR 0.7, 95% CI 0.5–0.9); neutered (OR 0.4, 95% CI 0.3–0.5), or vaccinated dogs (OR 0.3, 95% CI 0.3–0.4) were less commonly lost to follow-up. Of remaining dogs, clinical signs were deemed resolved in 95.4% of cases (95% CI 94.6–96.2). Provision of dietary modification advice and gastrointestinal nutraceuticals alone were positively associated with resolution (OR 2.8, 95% CI 1.3–6.1); no such associations were found for pharmaceutical agents, including antimicrobials. Hence, this study supports the view that antimicrobials are largely unnecessary for acute diarrhoea cases; this being of particular importance when considering the global threat posed by antimicrobial resistance.

Feline Panleukopenia: A Re-emergent Disease

Feline panleukopenia (FPL) is caused by a Carnivore protoparvovirus infection. Feline parvovirus (FPV) causes most cases. When Canine parvovirus 2 (CPV-2) first emerged, it could not replicate in cats. All current CPV variants (CPV-2a-c) can infect cats to cause subclinical disease or FPL. Feline panleukopenia has re-emerged in Australia in shelter cats associated with failure to vaccinate. Parvoviruses can remain latent in mononuclear cells post-infection. Molecular methods such as polymerase chain reaction are used to determine the infecting strain. Current perspectives on causes, epidemiology, diagnosis, treatment, prognostic indicators, and management of outbreaks in shelters are reviewed.

New approaches to pharmacosurveillance for monitoring prescription frequency, diversity, and co-prescription in a large sentinel network of companion animal veterinary practices in the United Kingdom, 2014-2016

Pharmaceutical agents (PAs) are commonly prescribed in companion animal practice in the United Kingdom. However, little is known about PA prescription on a population-level, particularly with respect to PAs authorised for human use alone prescribed via the veterinary cascade; this raises important questions regarding the efficacy and safety of PAs prescribed to companion animals. This study explored new approaches for describing PA prescription, diversity and co-prescription in dogs, cats and rabbits utilising electronic health records (EHRs) from a sentinel network of 457 companion animal-treating veterinary sites throughout the UK over a 2-year period (2014-2016). A novel text mining-based identification and classification methodology was utilised to semi-automatically map practitioner-defined product descriptions recorded in 918,333 EHRs from 413,870 dogs encompassing 1,242,270 prescriptions; 352,730 EHRs from 200,541 cats encompassing 491,554 prescriptions, and 22,526 EHRS from 13,398 rabbits encompassing 18,490 prescriptions respectively. PA prescription as a percentage of booked consultations was 65.4% (95% confidence interval, CI, 64.6-66.3) in dogs; in cats it was 69.1% (95% CI, 67.9-70.2) and in rabbits, 56.3% (95% CI, 54.7-57.8). Vaccines were the most commonly prescribed PAs in all three species, with antibiotics, antimycotics, and parasiticides also commonly prescribed. PA prescription utilising products authorised for human use only (hence, 'human-authorised') comprised 5.1% (95% CI, 4.7-5.5) of total canine prescription events; in cats it was 2.8% (95% CI, 2.6-3.0), and in rabbits, 7.8% (95% CI, 6.5-9.0). The most commonly prescribed human-authorised PA in dogs was metronidazole (antibiotic); in cats and rabbits it was ranitidine (H2 histamine receptor antagonist). Using a new approach utilising the Simpson's Diversity Index (an ecological measure of relative animal, plant etc. species abundance), we identified differences in prescription based on presenting complaint and species, with rabbits generally exposed to a less diverse range of PAs than dogs or cats, potentially reflecting the paucity of authorised PAs for use in rabbits. Finally, through a novel application of network analysis, we demonstrated the existence of three major co-prescription groups (preventive health; treatment of disease, and euthanasia); a trend commonly observed in practice. This study represents the first time PA prescription has been described across all pharmaceutical families in a large population of companion animals, encompassing PAs authorised for both veterinary and human-only use. These data form a baseline against which future studies could be compared, and provides some useful tools for understanding PA comparative efficacy and risks when prescribed in the varied setting of clinical practice.

Molecular insight into Italian canine parvovirus heterogeneity and comparison with the worldwide scenario

Canine parvovirus is one of the most frequent pathogens of young dogs, causing severe clinical manifestations. Its phenotypic variability led to an antigenic-based classification into different variants, which have been reported worldwide. To update the Italian distribution of CPV, a molecular survey was performed on 100 geographically-annotated samples collected from 2008 to 2015 by full VP2 sequencing. All three antigenic variants (CPV-2a, 2b, 2c) were detected during the studied period, being CPV-2a the most prevalent (60%). Locally, CPV appeared widely distributed, without any regional or temporal clustering, demonstrating an outstanding and uncontrolled within-country viral spreading. The Italian sequences were also contextualized in the International scenario. The analysis of CPV worldwide molecular epidemiology highlighted the remarkable genetic heterogeneity of the circulating strains and their broad distribution. In fact, a frequent viral exchange among Countries, was proven both over short and long distances, involving haplotypes persisting through time. The reported information on viral dissemination patterns appears crucial for understanding the introduction routes of new variants or strains, which could complicate the epidemiological scenario, affect the disease patterns, show possible differential virulence and clinical relevance of emerging strains especially, and impair the vaccine efficacy.

Inter- and intracontinental migrations and local differentiation have shaped the contemporary epidemiological landscape of canine parvovirus in South America

Canine parvovirus (CPV) is a fast-evolving single-stranded DNA virus that causes one of the most significant infectious diseases of dogs. Although the virus dispersed over long distances in the past, current populations are considered to be spatially confined and with only a few instances of migration between specific localities. It is unclear whether these dynamics occur in South America where global studies have not been performed. The aim of this study is to analyze the patterns of genetic variability in South American CPV populations and explore their evolutionary relationships with global strains. Genomic sequences of sixty-three strains from South America and Europe were generated and analyzed using a phylodynamic approach. All the obtained strains belong to the CPV-2a lineage and associate with global strains in four monophyletic groups or clades. European and South American strains from all the countries here analyzed are representative of a widely distributed clade (Eur-I) that emerged in Southern Europe during 1990–98 to later spread to South America in the early 2000s. The emergence and spread of the Eur-I clade were correlated with a significant rise in the CPV effective population size in Europe and South America. The Asia-I clade includes strains from Asia and Uruguay. This clade originated in Asia during the late 1980s and evolved locally before spreading to South America during 2009–10. The third clade (Eur-II) comprises strains from Italy, Brazil, and Ecuador. This clade appears in South America as a consequence of an early introduction from Italy to Ecuador in the middle 1980s and has experienced extensive local genetic differentiation. Some strains from Argentina, Uruguay, and Brazil constitute an exclusive South American clade (SA-I) that emerged in Argentina in the 1990s. These results indicate that the current epidemiological scenario is a consequence of inter- and intracontinental migrations of strains with different geographic and temporal origins that set the conditions for competition and local differentiation of CPV populations. The coexistence and interaction of highly divergent strains are the main responsible for the drastic epidemiological changes observed in South America in the last two decades. This highlights the threat of invasion from external sources and the importance of whole-genome resolution to robustly infer the origin and spread of new CPV variants. From a taxonomic standpoint, the findings herein show that the classification system that uses a single amino acid to identify variants (2a, 2b, and 2c) within the CPV-2a lineage does not reflect phylogenetic relationships and is not suitable to analyze CPV evolution. In this regard, the identification of clades or sublineages within circulating CPV strains is the first step towards a genetic and evolutionary classification of the virus.

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.

Investigation of a Canine Parvovirus Outbreak using Next Generation Sequencing

Canine parvovirus (CPV) outbreaks can have a devastating effect in communities with dense dog populations. The interior region of Alaska experienced a CPV outbreak in the winter of 2016 leading to the further investigation of the virus due to reports of increased morbidity and mortality occurring at dog mushing kennels in the area. Twelve rectal-swab specimens from dogs displaying clinical signs consistent with parvoviral-associated disease were processed using next-generation sequencing (NGS) methodologies by targeting RNA transcripts, and therefore detecting only replicating virus. All twelve specimens demonstrated the presence of the CPV transcriptome, with read depths ranging from 2.2X – 12,381X, genome coverage ranging from 44.8–96.5%, and representation of CPV sequencing reads to those of the metagenome background ranging from 0.0015–6.7%. Using the data generated by NGS, the presence of newly evolved, yet known, strains of both CPV-2a and CPV-2b were identified and grouped geographically. Deep-sequencing data provided additional diagnostic information in terms of investigating novel CPV in this outbreak. NGS data in addition to limited serological data provided strong diagnostic evidence that this outbreak most likely arose from unvaccinated or under-vaccinated canines, not from a novel CPV strain incapable of being neutralized by current vaccination efforts.

Molecular characterization of canine parvovirus in Vientiane, Laos

The global emergence of canine parvovirus type 2c (CPV-2c) has been well documented. In the present study, 139 rectal swab samples collected from diarrheic dogs living in Vientiane, Laos, in 2016 were tested for the presence of the canine parvovirus (CPV) VP2 gene by PCR. The results showed that 82.73% (115/139) of dogs were CPV positive by PCR. The partial VP2 gene was sequenced in 94 of the positive samples; 91 samples belonged to CPV-2c (426Glu) subtype, while 3 samples belonged to the CPV-2a (426Asn) subtype. Notably, phylogenetic analysis of amino acid sequences revealed a close relationship between Laotian isolates and novel Chinese CPV-2c isolates. In Laotian CPV isolates, aligned protein sequences indicated a high rate of residue substitutions at positions 305, 324, 345, 370, 375, and 426 in the GH loop. The mutation at residue 370 (Q370R), a single mutation, was characterized as a unique mutant residue specific to the Laotian CPV-2c variant.

Canine parvovirus: the worldwide occurrence of antigenic variants

The most important enteric virus infecting canids is canine parvovirus type 2 (CPV-2). CPV is the aetiologic agent of a contagious disease, mainly characterized by clinical gastroenteritis signs in younger dogs. CPV-2 emerged as a new virus in the late 1970s, which could infect domestic dogs, and became distributed in the global dog population within 2 years. A few years later, the virus's original type was replaced by a new genetic and antigenic variant, called CPV-2a. Around 1984 and 2000, virus variants with the single change to Asp or Glu in the VP2 residue 426 were detected (sometimes termed CPV-2b and -2c). The genetic and antigenic changes in the variants have also been correlated with changes in their host range; in particular, in the ability to replicate in cats and also host range differences in canine and other tissue culture cells. CPV-2 variants have been circulating among wild carnivores and have been well-documented in several countries around the world. Here, we have reviewed and summarized the current information about the worldwide distribution and evolution of CPV-2 variants since they emerged, as well as the host ranges they are associated with.

Resurgence of canine parvovirus 2a strain in the domestic dog population from Argentina

Ninety-three rectal swab samples were taken, from dogs suspected of canine parvovirus (CPV) infection and analyzed by PCR. A fragment of the VP2 gene, was amplified in 41 (44%) of them, resulting CPV positive samples. Sequencing analysis of these PCR products showed that 37 samples (90.2%) belonged to the CPV2c type, whereas four samples (9.8%) were identified as CPV2a, which has not been found since 2008. It was also found that 24 out of 37 CPV2c samples (65%), carried the mutation Thr440Ala, whereas this mutation was absent in the four CPV2a strains reported herein. Using phylogenetic analysis of the full length VP2 gene, which was amplified by PCR in six local samples, it was seen that CPV2a Argentine strains reported in this study, were genetically closer to a previous local CPV2a isolate (year 2003) and to a South African CPV2a strain, than to any of the recently reported Uruguayan CPV2a strains. The results obtained in this work, together with those reported previously in Uruguay strongly suggest that, in spite of the geographical proximity, wild type CPV strains undergo different evolutive pathways in each country, resulting in the prevalence of different strains in related dog populations. Further extensive epidemiological studies are needed in order to improve the understanding of CPV evolution.

An insulated isothermal PCR method on a field-deployable device for rapid and sensitive detection of canine parvovirus type 2 at points of need

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A CPV 2 iiPCR method for on-site detection of all circulating CPV 2 strains was developed.

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Analytical sensitivity and specificity of CPV 2 iiPCR method in detecting CPV 2 DNA was examined.

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Performance of iiPCR agreed with that of a reference qPCR in detecting CPV 2 in clinical samples.

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The iiPCR method could provide rapid and accurate molecular detection of CPV at points of need.

Canine parvovirus type 2 (CPV-2), including subtypes 2a, 2b and 2c, causes an acute enteric disease in both domestic and wild animals. Rapid and sensitive diagnosis aids effective disease management at points of need (PON). A commercially available, field-deployable and user-friendly system, designed with insulated isothermal PCR (iiPCR) technology, displays excellent sensitivity and specificity for nucleic acid detection. An iiPCR method was developed for on-site detection of all circulating CPV-2 strains. Limit of detection was determined using plasmid DNA. CPV-2a, 2b and 2c strains, a feline panleukopenia virus (FPV) strain, and nine canine pathogens were tested to evaluate assay specificity. Reaction sensitivity and performance were compared with an in-house real-time PCR using serial dilutions of a CPV-2b strain and 100 canine fecal clinical samples collected from 2010 to 2014, respectively. The 95% limit of detection of the iiPCR method was 13 copies of standard DNA and detection limits for CPV-2b DNA were equivalent for iiPCR and real-time PCR. The iiPCR reaction detected CPV-2a, 2b and 2c and FPV. Non-targeted pathogens were not detected. Test results of real-time PCR and iiPCR from 99 fecal samples agreed with each other, while one real-time PCR-positive sample tested negative by iiPCR. Therefore, excellent agreement (k = 0.98) with sensitivity of 98.41% and specificity of 100% in detecting CPV-2 in feces was found between the two methods. In conclusion, the iiPCR system has potential to serve as a useful tool for rapid and accurate PON, molecular detection of CPV-2.

Isolation of Canine parvovirus with a view to identify the prevalent serotype on the basis of partial sequence analysis

Aim:

The aim of this study was to isolate Canine parvovirus (CPV) from suspected dogs on madin darby canine kidney (MDCK) cell line and its confirmation by polymerase chain reaction (PCR) and nested PCR (NPCR). Further, VP2 gene of the CPV isolates was amplified and sequenced to determine prevailing antigenic type.

Materials and Methods:

A total of 60 rectal swabs were collected from dogs showing signs of gastroenteritis, processed and subjected to isolation in MDCK cell line. The samples showing cytopathic effects (CPE) were confirmed by PCR and NPCR. These samples were subjected to PCR for amplification of VP2 gene of CPV, sequenced and analyzed to study the prevailing antigenic types of CPV.

Results:

Out of the 60 samples subjected to isolation in MDCK cell line five samples showed CPE in the form of rounding of cells, clumping of cells and finally detachment of the cells. When these samples and the two commercially available vaccines were subjected to PCR for amplification of VP2 gene, a 1710 bp product was amplified. The sequence analysis revealed that the vaccines belonged to the CPV-2 type and the samples were of CPV-2b type.

Conclusion:

It can be concluded from the present study that out of a total of 60 samples 5 samples exhibited CPE as observed in MDCK cell line. Sequence analysis of the VP2 gene among the samples and vaccine strains revealed that samples belonged to CPV-2b type and vaccines belonging to CPV-2.

Phylogenetic and genome-wide deep-sequencing analyses of canine parvovirus reveal co-infection with field variants and emergence of a recent recombinant strain

Canine parvovirus (CPV), a fast-evolving single-stranded DNA virus, comprises three antigenic variants (2a, 2b, and 2c) with different frequencies and genetic variability among countries. The contribution of co-infection and recombination to the genetic variability of CPV is far from being fully elucidated. Here we took advantage of a natural CPV population, recently formed by the convergence of divergent CPV-2c and CPV-2a strains, to study co-infection and recombination. Complete sequences of the viral coding region of CPV-2a and CPV-2c strains from 40 samples were generated and analyzed using phylogenetic tools. Two samples showed co-infection and were further analyzed by deep sequencing. The sequence profile of one of the samples revealed the presence of CPV-2c and CPV-2a strains that differed at 29 nucleotides. The other sample included a minor CPV-2a strain (13.3% of the viral population) and a major recombinant strain (86.7%). The recombinant strain arose from inter-genotypic recombination between CPV-2c and CPV-2a strains within the VP1/VP2 gene boundary. Our findings highlight the importance of deep-sequencing analysis to provide a better understanding of CPV molecular diversity.

Feline parvovirus infection and associated diseases

Feline panleukopenia, caused by the single-stranded DNA virus feline parvovirus (FPV), is a highly contagious and often lethal disease of cats and other Felidae. FPV, but also canine parvovirus (CPV) can be isolated from both healthy and diseased cats. In Germany, CPV was detected in only approximately 10% of feline samples, but in Southeast Asia, reports estimated that up to approximately 80% of diseased cats were infected with CPV. Infection spreads rapidly, especially in cells with high mitotic activity, such as bone marrow, lymphoid tissue and intestinal crypt cells. Anorexia, vomiting, diarrhoea, neutropenia and lymphopenia are common in clinically affected cases. In utero or neonatal infection can result in cerebellar hypoplasia. Depending on the severity of clinical signs, mortality ranges from 25 to 100%. Effective vaccination and thorough disinfection are of the utmost importance in the prevention of disease transmission in multi-cat households and animal shelters. If clinical signs develop, supportive treatment should be commenced. The efficacy of feline recombinant interferon and FPV antibodies has not been clearly demonstrated. Commercially available vaccines should induce protective immunity when administered according to current guidelines. Recent studies suggest that in some kittens, maternally derived antibodies (MDA) can persist for much longer than has been previously recognised. FPV serum antibody tests are available, but protection status needs to be interpreted with caution in kittens with MDA and a negative titre in adult cats does not necessarily denote lack of protection.

Canine parvovirus type 2c identified from an outbreak of severe gastroenteritis in a litter in Sweden

A litter of recently-vaccinated puppies in Sweden experienced signs of severe haemorrhagic gastroenteritis. Canine parvovirus (CPV) was suspected as the cause of this outbreak on the basis of the clinical signs and the presence of parvoviral antigen in the faeces from one of the affected pups - confirmed using a commercial in-clinic faecal antigen ELISA test kit. A concern was raised about whether the vaccine (which contained a live, attenuated strain of CPV) could have caused the disease and so further faecal samples from the affected pups were submitted for laboratory virus isolation and identification.

On cell culture, two out of four faecal samples were found to be virus-positive. This was confirmed as being canine parvovirus by immuno-staining with CPV specific monoclonal antibody. The virus was then tested using a series of PCR probes designed to confirm the identity of CPV and to distinguish the unique vaccine strain from field virus. This confirmed that the virus was indeed CPV but that it was not vaccine strain. The virus was then typed by sequencing the 426 amino acid region of the capsid gene which revealed this to be a type 2c virus.

Since its emergence in the late 1970s, canine parvovirus 2 (CPV2) has spread worldwide and is recognised as an important canine pathogen in all countries. The original CPV2 rapidly evolved into two antigenic variants, CPV2a and CPV2b, which progressively replaced the original CPV2. More recently a new antigenic variant, CPV2c, has appeared. To date this variant has been identified in many countries worldwide but there have been no reports yet of its presence in any Scandinavian countries. This case report therefore represents the first published evidence of the involvement of CPV2c in a severe outbreak of typical haemorrhagic gastroenteritis in a susceptible litter of pups in Scandinavia.

High local genetic diversity of canine parvovirus from Ecuador

Canine parvovirus (CPV) comprises three antigenic variants (2a, 2b, and 2c) that are distributed globally with different frequencies and levels of genetic variability. CPVs from central Ecuador were herein analyzed to characterize the strains and to provide new insights into local viral diversity, evolution, and pathogenicity. Variant prevalence was analyzed by PCR and partial sequencing for 53 CPV-positive samples collected during 2011 and 2012. The full-length VP2 gene was sequenced in 24 selected strains and a maximum-likelihood phylogenetic tree was constructed using both Ecuadorian and worldwide strains. Ecuadorian CPVs have a remarkable genetic diversity that includes the circulation of all three variants and the existence of different evolutionary groups or lineages. CPV-2c was the most prevalent variant (54.7%), confirming the spread of this variant in America. Ecuadorian CPV-2c strains clustered in two lineages, which represent the first evidence of polyphyletic CPV-2c circulating in South America. CPV-2a strains constituted 41.5% of the samples and clustered in a single lineage. The two detected CPV-2b strains (3.8%) were clearly polyphyletic and appeared related to Ecuadorian CPV-2a or foreign CPV-2b strains. Besides the substitution at residue 426 that is used to identify the variants, two amino acid changes occurred in Ecuadorian strains: Val139Iso and Thr440Ser. Ser(440) occurred in a biologically relevant domain of VP2 and is here described for the first time in CPV. The associations of Ecuadorian CPV-2c and CPV-2a with clinical symptoms indicate that dull mentation, hemorrhagic gastroenteritis and hypothermia occurred more frequently in infection with CPV-2c than with CPV-2a.

Identification of canine parvovirus with the Q370R point mutation in the VP2 gene from a giant panda (Ailuropoda melanoleuca)

Background

In this study, we sequenced and phylogenetic analyses of the VP2 genes from twelve canine parvovirus (CPV) strains obtained from eleven domestic dogs and a giant panda (Ailuropoda melanoleuca) in China. A novel canine parvovirus (CPV) was detected from the giant panda in China.

Results

Nucleotide and phylogenetic analysis of the capsid protein VP2 gene classified the CPV as a new CPV-2a type. Substitution of Gln for Arg at the conserved 370 residue in CPV presents an unusual variation in the new CPV-2a amino acid sequence of the giant panda and is further evidence for the continuing evolution of the virus.

Conclusions

These findings extend the knowledge on CPV molecular epidemiology of particular relevance to wild carnivores.

Evidence for natural recombination between mink enteritis virus and canine parvovirus

A virus was isolated from mink showing clinical and pathological signs of enteritis in China. This virus, designated MEV/LN-10, was identified as mink enteritis virus (MEV) based on its cytopathic effect in the feline F81 cell line, the hemagglutination (HA) and hemagglutination inhibition (HI) assay, electron microscopy (EM) and animal infection experiments. The complete viral genome was cloned and sequenced. Phylogenetic and recombination analyses on the complete MEV/LN-10 genome showed evidence of recombination between MEV and canine parvovirus (CPV). The genome was composed of the NS1 gene originating from CPV while the VP1 gene was of MEV origin. This is the first demonstration of recombination between a CPV and MEV in nature. Our findings not only provide valuable evidence indicating that recombination is an important genetic mechanism contributing to the variation and evolution of MEV, but also that heterogeneous recombination can occur in the feline parvovirus subspecies.

Canine parvovirus--a review of epidemiological and diagnostic aspects, with emphasis on type 2c

Canine parvovirus type 2 (CPV-2) emerged in late 1970s causing severe epizootics in kennels and dog shelters worldwide. Soon after its emergence, CPV-2 underwent genetic evolution giving rise consecutively to two antigenic variants, CPV-2a and CPV-2b that replaced progressively the original type. In 2000, a new antigenic variant, CPV-2c, was detected in Italy and rapidly spread to several countries. In comparison to the original type CPV-2, the antigenic variants display increased pathogenicity in dogs and extended host range, being able to infect and cause disease in cats. Epidemiological survey indicate that the newest type CPV-2c is becoming prevalent in different geographic regions and is often associated to severe disease in adult dogs and also in dogs that have completed the vaccination protocols. However, the primary cause of failure of CPV vaccination is interference by maternally derived immunity. Diagnosis of CPV infection by traditional methods has been shown to be poorly sensitive, especially in the late stages of infections. New diagnostic approaches based on molecular methods have been developed for sensitive detection of CPV in clinical samples and rapid characterisation of the viral type. Continuous surveillance will help assess whether there is a real need to update currently available vaccines and diagnostic tests.