ABSTRACT
BACKGROUND: Porcine epidemic diarrhea (PED) is a highly contagious swine disease caused by the PED virus (PEDV), which is a member of the family Coronaviridae. Since the first outbreaks in Belgium and the United Kingdom were reported in 1971, PED has spread throughout many countries around the world and causing significant economic loss. This study was conducted to investigate the recent distribution of PEDV strains in Vietnam during the 2015-2016 seasons. METHODS: A total of 30 PED-specific PCR-positive intestinal and faecal samples were collected from unvaccinated piglets in Vietnam during the 2015-2016 seasons. The full length of the spike (S) gene of these PEDV strains were analysed to determine their phylogeny and genetic relationship with other available PEDV strains globally. RESULTS: Phylogenetic analysis of the complete S gene sequences revealed that the 28 Vietnamese PEDV strains collected in the northern and central regions clustered in the G2 group (both G2a and G2b sub-groups), while the other 2 PEDV strains (HUA-PED176 and HUA-PED254) collected in the southern region were clustered in the G1/G1b group/sub-group. The nucleotide (nt) and deduced amino acid (aa) analyses based on the complete S gene sequences showed that the Vietnamese PEDV strains were closely related to each other, sharing nt and aa homology of 93.2%-99.9% and 92.6%-99.9%, respectively. The N-glycosylation patterns and mutations in the antigenic region were observed in Vietnamese PEDV strains. CONCLUSIONS: This study provides, for the first time, up-to-date information on viral circulation and genetic distribution, as well as evidence to assist in the development of effective PEDV vaccines in Vietnam.