Molecular characterization of canine parvovirus-2 variants circulating in Tunisia

Canine parvovirus type 2 (CPV2) emerged in 1978 as a highly contagious and very serious disease in dogs. The characterization of CPV2 antigenic types is exclusively based on the identification of the amino acid residue at position 426 of the capsid protein VP2. Currently, three antigenic types CPV-2a (asparagine N(426)), CPV-2b (aspartic acid D(426)) and CPV-2c (glutamic acid E(426)) are circulating worldwide. In Tunisia, despite the fact that many clinical and few serological investigations clearly indicate that CPV is widespread and of major concerns in the local dog population, no molecular and antigenic type characterization of circulating variants has been carried out. This investigation showed that most of clinically presumed CPV infections were confirmed by classical or real-time PCR. When no real-time PCR facilities were affordable, classical PCR as reported here in association with restriction fragment length polymorphism (RFLP) with MboI and MboII can be very useful for screening and diagnosing CPV infections. A total of 50 variants were characterized by sequencing and an almost even representation of the different antigenic types, including CPV-2c and slightly more type 2b, were evidenced. Characterization of the Tunisian variants by MGB probe assays as reported was inefficient for most of CPV-2a variants because of their typical nucleotide mutation C(1269). Phylogenetic analysis showed that the Tunisian variants underwent evolution for a relatively long period of time inside the country. The analysis also showed some crossings of the different antigenic types, leaving both genotypic and phenotypic characteristic mutations.