Background and Aim: Foot-and-mouth disease (FMD) is a dangerous infectious disease in livestock that rapidly spreads and causes economic losses for cattle farmers. However, the genetic characteristics of FMD virus (FMDV) strains that cause FMD in many provinces of the Mekong Delta, especially Tra Vinh province, remain unclear. Therefore, this study aimed to investigate the genotype of FMDV circulating in the Tra Vinh Province, Vietnam.

Materials and Methods: Forty-five probang samples from sick cows with clinical symptoms of FMD were collected and tested using reverse transcription-polymerase chain reaction (RT-PCR) to amplify the UTR (untranslated region) segment to determine FMDV. For the gene encoding VP1, four FMDV-positive samples with precise electrophoresis results were amplified and sequenced using the RT-PCR technique. A phylogenetic tree was established to analyze the relationship between the detected FMDV and GenBank sequences. Nucleotide and amino acid sequences were analyzed to identify mutation sites in the VP1 gene of the detected strains and GenBank sequences.

Results: Phylogenetic analysis showed that all four detected strains belonged to serotype O, topotype SEA/Mya-98. The results of VP1 gene analysis showed that the strains detected in Tra Vinh province belonged to serotype O and had a high nucleotide similarity rate with strain O/MYA/7/98 (93.83%–96.22%). These strains shared high homology with strains from Laos and Thailand but low homology with vaccine strain O/Manisa (DI431238.1). In addition, changes of 27 amino acids were discovered in the VP1 protein of the FMDV strains, several of which were significant FMDV neutralization-related antigenic determinants. These results imply that existing vaccination may not protect against the FMDV strains circulating in the Tra Vinh Province, Vietnam.

Conclusion: This study showed that these strains belong to serotype O, topotype SEA/Mya-98. In addition, mutations at 27 amino acid positions on the VP1 gene of these strains reduce the effectiveness of disease prevention with currently used vaccines.

Keywords: cattle, foot-and-mouth disease virus, polymerase chain reaction, Tra Vinh, Vietnam, VP1.