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

Molecular Characterization of Feline Parvovirus from Domestic Cats in Henan Province, China from 2020 to 2022

Carnivore protoparvovirus-1, feline parvovirus (FPV), and canine parvovirus (CPV) continue to spread in companion animals all over the world. As a result, FPV and CPV underwent host-to-host transfer in carnivorous wild-animal hosts. Here, a total of 82 fecal samples of suspected cat FPV infections were collected from Henan Province from 2020 to 2022. The previously published full-length sequence primers of VP2 and NS1 genes were used to amplify the targeted genes of these samples, and the complete gene sequences of 11 VP2 and 21 NS1 samples were obtained and analyzed. Analysis showed that the amino acid homology of the VP2 and NS1 genes of these isolates was 96.1-100% and 97.6-100%, respectively. The phylogenetic results showed that the VP2 and NS1 genes of the local isolates were mainly concentrated in the G1 subgroup, while the vaccine strains were distributed in the G3 subgroup. Finally, F81 cells were inoculated with the local endemic isolate Luoyang-01 (FPV-LY strain for short) for virus amplification, purification, and titer determination, and the pathogenesis of FPV-LY was detected. After five generations of blind transmission in F81 cells, cells infected with FPV-LY displayed characteristic morphological changes, including a round, threadlike, and wrinkled appearance, indicative of viral infection. The virus titer associated with this cytopathic effect (CPE) was measured at 1.5 × 106 TCID50/mL. Subsequent animal regression tests confirmed that the virus titer of the PFV-LY isolate remained at 1.5 × 106 TCID50/mL, indicating its highly pathogenic nature. Cats exposed to the virus exhibited typical clinical symptoms and pathological changes, ultimately succumbing to the infection. These results suggest that the gene mutation rate of FPV is increasing, resulting in a complex pattern of gene evolution in terms of host preference, geographical selection, and novel genetic variants. The data also indicate that continuous molecular epidemiological surveillance is required to understand the genetic diversity of FPV isolates.

Establishment of RPA-Cas12a-Based Fluorescence Assay for Rapid Detection of Feline Parvovirus

Feline parvovirus (FPV) is highly infectious for cats and other Felidae and often causes severe damage to young kittens. In this study, we incorporated recombinase polymerase amplification (RPA) and Cas12a-mediated detection and developed an RPA-Cas12a-based real-time or end-point fluorescence detection method to identify the NS1 gene of FPV. The total time of RPA-Cas12a-based fluorescence assay is approximately 25 min. The assay presented a limit of detection (LOD) of 1 copies/μl (25 copies/per reaction), with no cross-reactivity with several feline pathogens. The clinical performance of the assay was examined using total genomic DNA purified from 60 clinical specimens and then compared to results obtained with qPCR detection of FPV with 93.3% positive predictive agreement and 100% negative predictive agreement. Together, the rapid reaction, cost-effectiveness, and high sensitivity make the RPA-Cas12a-based fluorescence assay a fascinating diagnostic tool that will help minimize infection spread through instant detection of FPV.

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.

Feline Parvovirus Lethal Outbreak in a Group of Adult Cohabiting Domestic Cats

Feline panleukopenia is a highly contagious and often fatal disease in cats. The virus, known as feline panleukopenia virus (FPV), primarily affects kittens and unvaccinated cats. It is transmitted through contact with infected cats or their bodily fluids, as well as contaminated objects and environments. The diagnosis of FPV infection can be confirmed through a combination of clinical signs, blood tests, and fecal testing. Prevention through vaccination is recommended for all cats. This case report describes an outbreak of feline panleukopenia in a group of unvaccinated domestic cats that resulted in acute mortality. The lesions were evaluated using histopathology, and the specific viral strain was characterized using molecular techniques. The clinical course of the outbreak was peracute, with a hemorrhagic pattern and 100% of lethality. The observed clinical-pathological pattern was unusual; nevertheless, molecular studies did not highlight peculiar genomic features of the parvovirus isolate. The outbreak affected 3 out of 12 cats in a very short time. However, the prompt application of biosecurity measures and vaccination resulted in an effective interruption of virus spread. In conclusion, we could assume that the virus found the ideal conditions to infect and replicate at high titers, resulting in a particularly aggressive outbreak.

Low Intrahost and Interhost Genetic Diversity of Carnivore Protoparvovirus 1 in Domestic Cats during a Feline Panleukopenia Outbreak

Feline panleukopenia (FPL), a highly contagious and frequently fatal disease of cats, is caused by Feline parvovirus (FPV) and Canine parvovirus (CPV). We characterised the diversity of these Carnivore protoparvovirus 1 variants in 18 faecal samples collected from domestic cats with FPL during an outbreak, using targeted parvoviral DNA metagenomics to a mean depth of >10,000 × coverage per site. All samples comprised FPV alone. Compared with the reference FPV genome, isolated in 1967, 44 mutations were detected. Ten of these were nonsynonymous, including 9 in nonstructural genes and one in VP1/VP2 (Val232Ile), which was the only one to exhibit interhost diversity, being present in five sequences. There were five other polymorphic nucleotide positions, all with synonymous mutations. Intrahost diversity at all polymorphic positions was low, with subconsensus variant frequencies (SVF) of <1% except for two positions (2108 and 3208) in two samples with SVF of 1.1−1.3%. Intrahost nucleotide diversity was measured across the whole genome (0.7−1.5%) and for each gene and was highest in the NS2 gene of four samples (1.2−1.9%). Overall, intrahost viral genetic diversity was limited and most mutations observed were synonymous, indicative of a low background mutation rate and strong selective constraints.

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.

Emerging Parvoviruses in Domestic Cats

Parvovirus infections in cats have been well known for around 100 years. Recently, the use of molecular assays and metagenomic approaches for virus discovery and characterization has led to the detection of novel parvovirus lineages and/or species infecting the feline host. However, the involvement of emerging parvoviruses in the onset of gastroenteritis or other feline diseases is still uncertain.

Genetic Characterization of Feline Parvovirus Isolate Fe-P2 in Korean Cat and Serological Evidence on Its Infection in Wild Leopard Cat and Asian Badger

Feline parvovirus (FPV) is a small, non-enveloped, single-stranded DNA virus that infects cats. We recently isolated a feline parvovirus Fe–P2 strain from a dead stray cat in Iksan, 2017. Its partial genomic sequence (4,643 bases) was obtained, and phylogenetic analysis based on the VP2 nucleotide sequence showed that the FPV Fe-P2 strain was closely related to the FPV isolate Gigucheon in cat, 2017 (MN400978). In addition, we performed a serum neutralization (SN) test with the FPV isolates in various mammalian sera. These were from raccoon dog, water deer, Eurasian otter, Korean hare, leopard cat, and Asian badger, which were kindly provided by Chungnam Wild Animal Rescue Center. Notably, serological evidence of its infection was found in Asian badger, Meles leucurus (2/2) and leopard cat, Prionailurus bengalensis (5/8) through SN tests, whereas there was no evidence in raccoon dog, water deer, Eurasian otter, and Korean hare based on the collected sera in this study. These findings might provide partial evidence for the possible circulation of FPV or its related viruses among wild leopard cat and Asian badger in Korea. There should be additional study to confirm this through direct detection of FPVs in the related animal samples.