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

Simple Summary: In this study, 82 fecal samples of suspected FPV infection were collected from different areas of Henan Province from 2020 to 2022 (small sample in 2023), viral DNA was extracted, and FPV identification primers were used to identify 25 FPV-positive cases. VP2 and NS1 primers were further used to amplify the above positive samples, and the whole gene sequences of 11 VP2 and 21 NS1 strains were obtained and analyzed. Homology analysis showed that the amino acid homology of the VP2/NS1 gene of the isolates was 96.1–100% and 97.6–100%, respectively, with that of domestic and foreign endemic strains. The phylogenetic tree results showed that VP2 and NS1 of the local strains were mainly concentrated in the G1 subgroup, while the vaccine strains were distributed in the G3 subgroup, and the two strains were far-related. F81 cells were inoculated with local endemic strain SNF-01 (FPV-LY strain for short) from the FPV G1 subgroup for virus amplification, purification, and titer determination, and the pathogenesis of SNF-01 was detected. After five generations of blind transmission of F81 cells, the cells of the FPV-LY strain were rounded, wire-drawn, and crumpled. After sucrose density gradient centrifugation, the virus titer was determined by the Reed–Muench method to be 1.5 × 10⁶ TCID₅₀/mL. Animal regression tests showed that the strain PFV-LY was highly pathogenic, and the cats showed typical clinical symptoms and pathological changes, and eventually died. 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. [ABSTRACT FROM AUTHOR]