3.1 High prevalence of the CPV-2c variant in Vietnam
All 59 sampled dogs were found to be CPV-2 PCR positive and confirmed by sequencing a partial fragment of the VP2 gene. There were no breed and sex predilections on the affected dogs, while their ages ranged from 2–9 month-old, with most (86.4%) being 2–5 months-old. Even though 11 (18.6%) dogs had been completely vaccinated against parvovirus, their samples were still positive in the CPV-2 PCR assay. In addition, almost all the dogs (58/59; 98.3%) showed a positive parvovirus infection with the rapid testkit, the single exception being a dog from Hanoi (HN-62) that was positive for both parvovirus and coronavirus (Supplementary Table S2).
Analysis of the deduced amino acid sequence of the VP-2 gene showed that the most of samples (58/59; 98.3%) carried residue 426Glu, and so were classified as CPV-2c variants. However, one sample, derived from a dog in Ho Chi Minh (HCM-16), showed amino acid residue 426Asn, and so was designated as a CPV-2a variant. No CPV-2b variant was detected in this study (Supplementary Table S2).