Use of Slaughterhouses as Sentinel Points for Genomic Surveillance of Foot-and-Mouth Disease Virus in Southern Vietnam.

The genetic diversity of foot-and-mouth disease virus (FMDV) poses a challenge to the successful control of the disease, and it is important to identify the emergence of different strains in endemic settings. The objective of this study was to evaluate the sampling of clinically healthy livestock at slaughterhouses as a strategy for genomic FMDV surveillance. Serum samples (n = 11,875) and oropharyngeal fluid (OPF) samples (n = 5045) were collected from clinically healthy cattle and buffalo on farms in eight provinces in southern and northern Vietnam (2015-2019) to characterize viral diversity. Outbreak sequences were collected between 2009 and 2019. In two slaughterhouses in southern Vietnam, 1200 serum and OPF samples were collected from clinically healthy cattle and buffalo (2017 to 2019) as a pilot study on the use of slaughterhouses as sentinel points in surveillance. FMDV VP1 sequences were analyzed using discriminant principal component analysis and time-scaled phylodynamic trees. Six of seven serotype-O and -A clusters circulating in southern Vietnam between 2017-2019 were detected at least once in slaughterhouses, sometimes pre-dating outbreak sequences associated with the same cluster by 4-6 months. Routine sampling at slaughterhouses may provide a timely and efficient strategy for genomic surveillance to identify circulating and emerging FMDV strains.

Novel Recombinant Foot-and-Mouth Disease Virus Circulating in Vietnam.

We report the genome sequences of 12 recombinant foot-and-mouth disease virus isolates from Vietnam. The recombinant strain has a capsid region from an A/Sea-97 strain and a nonstructural segment from an O/ME-SA/PanAsia strain. The isolates were obtained from two outbreak samples collected in June 2017 and 10 subclinical samples collected between 2017 and 2019.

Foot-and-Mouth Disease Virus Serotype O/CATHAY Genome Sequences from Five Outbreaks in Vietnam, 2017 to 2019.

We report the genomes of five foot-and-mouth disease viruses (FMDVs) from distinct provinces in Vietnam. All five viruses were grouped within the O/CATHAY topotype. Sequences contain the full polyprotein coding sequence and partial untranslated regions. These genomes provide critical data on the spread and evolution of FMDVs in the region.

First Genome Sequence of Foot-and-Mouth Disease Virus Serotype O Sublineage Ind2001e from Southern Vietnam.

We report the polyprotein coding sequence of the newly defined Ind2001e sublineage of foot-and-mouth disease virus (FMDV) serotype O, isolated from a bovine epithelial tissue sample collected in 2017 in Kon Tum Province, Vietnam. This discovery updates FMDV diversity in Vietnam, has implications for FMDV epidemiology, and influences future vaccine selections.

First Detection and Genome Sequence of Senecavirus A in Vietnam.

In 2018, senecavirus A was detected for the first time in Vietnam. This report contains the first complete genome of a senecavirus A isolate collected from pigs in Kon Tum Province, Vietnam. This novel incursion has substantial implications for regional control of vesicular transboundary diseases.

A traditional evolutionary history of foot-and-mouth disease viruses in Southeast Asia challenged by analyses of non-structural protein coding sequences.

Recombination of rapidly evolving RNA-viruses provides an important mechanism for diversification, spread, and emergence of new variants with enhanced fitness. Foot-and-mouth disease virus (FMDV) causes an important transboundary disease of livestock that is endemic to most countries in Asia and Africa. Maintenance and spread of FMDV are driven by periods of dominance of specific viral lineages. Current understanding of the molecular epidemiology of FMDV lineages is generally based on the phylogenetic relationship of the capsid-encoding genes, with less attention to the process of recombination and evolution of non-structural proteins. In this study, the putative recombination breakpoints of FMDVs endemic to Southeast Asia were determined using full-open reading frame sequences. Subsequently, the lineages' divergence times of recombination-free genome regions were estimated. These analyses revealed a close relationship between two of the earliest endemic viral lineages that appear unrelated when only considering the phylogeny of their capsid proteins. Contrastingly, one lineage, named O/CATHAY, known for having a particular host predilection (pigs) has evolved independently. Additionally, intra-lineage recombination occurred at different breakpoints compared to the inter-lineage process. These results provide new insights about FMDV recombination patterns and the evolutionary interdependence of FMDV serotypes and lineages.

First detection of foot-and-mouth disease virus O/Ind-2001d in Vietnam.

In recent years, foot-and-mouth disease virus (FMDV) serotype O, topotype Middle East-South Asia (ME-SA), lineage Ind-2001d has spread from the Indian subcontinent to the Middle East, North Africa, and Southeast Asia. In the current report, we describe the first detection of this lineage in Vietnam in May, 2015 in Dak Nông province. Three subsequent outbreaks caused by genetically related viruses occurred between May-October, 2015 after which the virus was not detected in clinical outbreaks for at least 15 subsequent months. The observed outbreaks affected (in chronological order): cattle in Dak Nông province, pigs in Dak Lak province and Dak Nông province, and cattle in Ninh Thuan province. The clinical syndromes associated with these outbreaks were consistent with typical FMD in the affected species. Overall attack rate on affected premises was 0.85 in pigs and 0.93 in cattle over the course of the outbreak. Amongst 378 pigs at risk on affected premises, 85 pigs died during the outbreaks; there were no deaths among cattle. The manner in which FMDV/O/ME-SA/Ind-2001d was introduced into Vietnam remains undetermined; however, movement of live cattle is the suspected route. This incursion has substantial implications for epidemiology and control of FMD in Southeast Asia.

Phylodynamics of foot-and-mouth disease virus O/PanAsia in Vietnam 2010-2014.

Foot-and-mouth disease virus (FMDV) is endemic in Vietnam, a country that plays an important role in livestock trade within Southeast Asia. The large populations of FMDV-susceptible species in Vietnam are important components of food production and of the national livelihood. In this study, we investigated the phylogeny of FMDV O/PanAsia in Vietnam, reconstructing the virus' ancestral host species (pig, cattle or buffalo), clinical stage (subclinical carrier or clinically affected) and geographical location. Phylogenetic divergence time estimation and character state reconstruction analyses suggest that movement of viruses between species differ. While inferred transmissions from cattle to buffalo and pigs and from pigs to cattle are well supported, transmission from buffalo to other species, and from pigs to buffalo may be less frequent. Geographical movements of FMDV O/PanAsia virus appears to occur in all directions within the country, with the South Central Coast and the Northeast regions playing a more important role in FMDV O/PanAsia spread. Genetic selection of variants with changes at specific sites within FMDV VP1 coding region was different depending on host groups analyzed. The overall ratio of non-synonymous to synonymous nucleotide changes was greater in pigs compared to cattle and buffalo, whereas a higher number of individual amino acid sites under positive selection were detected in persistently infected, subclinical animals compared to viruses collected from clinically diseased animals. These results provide novel insights to understand FMDV evolution and its association with viral spread within endemic countries. These findings may support animal health organizations in their endeavor to design animal disease control strategies in response to outbreaks.