INTRODUCTION

Feline parvovirus (FPV) and canine parvovirus (CPV) are among the most important viral pathogens affecting companion animals worldwide. Both viruses belong to the genus Protoparvovirus within the family Parvoviridae and primarily infect rapidly dividing cells of the intestinal epithelium, bone marrow, and lymphoid tissues. Infection commonly results in acute hemorrhagic enteritis, severe leukopenia, dehydration, and high mortality, particularly in young and unvaccinated animals [1, 2]. Although effective vaccines are available, parvoviral enteritis continues to occur globally due to incomplete vaccination, interference by maternally derived antibodies, vaccine failure, and the ongoing emergence of novel viral variants [2, 3].

FPV shares a high degree of genetic and antigenic similarity with CPV, which is believed to have originated from FPV through host-range mutations in the late 1970s [4]. Subsequent viral evolution resulted in the emergence of CPV-2a, CPV-2b, and CPV-2c variants, several of which have been identified in feline hosts and produce clinical manifestations indistinguishable from classical feline panleukopenia [5, 6]. Host adaptation is primarily associated with mutations in the VP2 capsid protein, which governs viral antigenicity, receptor binding, and host tropism [7, 8]. The VP2 gene remains the principal target for molecular epidemiological investigations because sequence variations can influence viral virulence, antigenic characteristics, host adaptation, and vaccine efficacy [9]. Molecular diagnostic techniques such as PCR, qPCR, and VP2 gene sequencing have therefore become indispensable tools for accurate diagnosis, differentiation of circulating variants, molecular surveillance, and monitoring of parvovirus evolution [10, 11].

Companion cats and dogs in India frequently coexist in households, shelters, rescue centers, breeding facilities, and free-roaming populations, creating favorable conditions for interspecies exposure and transmission of parvoviruses. Although several investigations have reported the occurrence of FPV and CPV infections in different regions of India, comprehensive molecular epidemiological information from Western India, particularly Gujarat, remains limited. Furthermore, previous studies have largely focused on either feline or canine populations, with relatively few studies simultaneously evaluating both host species to determine the extent of cross-species circulation. In addition, comparative assessments of the diagnostic performance of rapid antigen testing (RAT), conventional PCR, and qPCR under field conditions remain scarce. Information regarding the molecular characteristics of circulating VP2 variants, their phylogenetic relationships, and the emergence of novel CPV variants in this region is also insufficient. These knowledge gaps limit the understanding of regional viral evolution, transmission dynamics, diagnostic accuracy, and the effectiveness of existing surveillance and vaccination strategies. Therefore, updated molecular epidemiological data are essential to strengthen disease surveillance, improve diagnostic approaches, optimize vaccination programs, and support evidence-based control strategies for parvoviral infections in companion animals.

The present study aimed to determine the prevalence of FPV and CPV infections among companion cats and dogs in Gujarat, India, using molecular and immunological diagnostic approaches. Specifically, the study compared the diagnostic performance of RAT, conventional PCR, and probe-based qPCR for detecting parvoviral infections; characterized circulating viral variants through VP2 gene sequencing and phylogenetic analysis; investigated evidence of cross-species transmission between feline and canine hosts; evaluated the successful isolation of circulating viruses in cell culture; and assessed epidemiological characteristics associated with infection, including species, age, breed, vaccination status, and clinical presentation. Collectively, these findings were intended to provide updated regional molecular epidemiological data to support improved diagnosis, surveillance, and control of FPV and CPV infections in companion animals.