Isolation, Identification and Phylogenetic Analysis of Canine Parvovirus Type 2c in Two Regions of Iran

Canine parvovirus Type 2 (CPV-2) is a highly infectious canine virus that causes gastroenteritis in affected animals. As the virus emerged in the 1970s, it has undergone several mutations, resulting in three distinctive subtypes: CPV-2a, CPV-2b and CPV-2c. The distinction between these subtypes is based on mutations in the VP2 gene, which is the main structural protein of the virus.

This study aimed to identify the circulating CPV-2 strain in Iran through virus isolation and complete VP2 gene sequencing and to determine its phylogenetic relationship with strains reported globally.

Twenty-five rectal swabs were collected from dogs displaying clinical symptoms of CPV-2 infection. Samples were collected across the Alborz and Tehran Provinces of Iran during 2020 and 2021. Polymerase chain reaction (PCR) confirmed the presence of viral deoxyribonucleic acid (DNA) in the samples. The virus was isolated in the Crandell-Rees feline kidney (CRFK) cell line. The complete length of the VP2 gene of the isolated virus was amplified using PCR via five primer pairs. PCR products were purified, Sanger sequenced and assembled in BioEdit software. A phylogenetic tree was constructed in MEGA11 software using the maximum likelihood method with the Tamura 3-parameter model.

Glutamic acid at position 426 of the VP2 protein's amino acid sequence indicated that the isolate belonged to the CPV-2c subtype. Phylogenetic analysis showed a close relationship between this isolate and isolates from Asia and Africa which are more recent than South America and Europe. Several mutations were detected in our isolate: A5G, F267Y, Y324I, Q370R and L583I, with the latter being a novel mutation never reported before. A5G and Q370R mutations have been detected only in isolates reported since 2016, suggesting that this study's isolate belongs to a newly appeared group of CPV-2c viruses.

This study identified the circulating CPV-2 in Iran as the CPV-2c variant, featuring a distinct L583I mutation. Further studies involving a more significant number of samples from across the country are required to assess the presence of this mutation in the circulating CPV-2 population in Iran. Finding the possible impacts of this novel mutation on virus antigenicity is essential as it may affect the efficacy of CPV-2 available vaccines.