Molecular surveillance of subclinical foot-and-mouth disease virus infection at slaughterhouses in Vietnam

Authors: GUNASEKERA, UMANGA - University Of Minnesota; Bertram, Miranda; DUNG, DO - Ministry Of Agriculture And Rural Development (MARD); HOANG, BUI - Ministry Of Agriculture And Rural Development (MARD); PHUONG, NGUYEN - Ministry Of Agriculture And Rural Development (MARD); HUNG, VO - Ministry Of Agriculture And Rural Development (MARD); DONG, PHAM - Ministry Of Agriculture And Rural Development (MARD); PEREZ, ANDRES - University Of Minnesota; VANDERWAAL, KIMBERLY - University Of Minnesota; Arzt, Jonathan; LONG, NGUYEN - Ministry Of Agriculture And Rural Development (MARD); PHAN, MINH - Ministry Of Agriculture And Rural Development (MARD); VU, LE - Ministry Of Agriculture And Rural Development (MARD)

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2021
Publication Date: 11/2/2021
Citation: Gunasekera, U., Bertram, M.R., Dung, D.H., Hoang, B.H., Phuong, N.T., Hung, V.V., Dong, P.V., Perez, A., Vanderwaal, K., Arzt, J., Long, N.V., Phan, M., Vu, L.T. 2021. Molecular surveillance of subclinical foot-and-mouth disease virus infection at slaughterhouses in Vietnam. Viruses. https://doi.org/10.3390/v13112203.
DOI: https://doi.org/10.3390/v13112203

Interpretive Summary: Foot-and-mouth disease (FMD), caused by FMD virus (FMDV), is an important livestock disease in many countries in Africa and Asia, including Vietnam. Many different strains of the virus exist in different countries, and it is important to know which strains are in a country to select appropriate vaccines. However, wide-scale testing for the virus on farms between outbreaks is impractical in most countries and it is difficult to control the disease by testing only sick animals during outbreaks. The purpose of this study was to evaluate whether testing for FMDV at slaughterhouses could be used to identify the different strains of FMDV circulating in Vietnam. The genetic diversity of FMDV strains collected at slaughterhouses was compared to the diversity of strains collected on farms between and during outbreaks using phylogenetic analysis. Seven distinct strains of FMDV were identified from farms and outbreaks, six of which were also found at slaughterhouses. This study suggests routine testing for FMDV at slaughterhouses can be a cost-effective surveillance method to identify the different FMDV strains present in an area, which will help to control the disease.

Technical Abstract: The genetic diversity of foot-and-mouth disease virus (FMDV) poses a substantial challenge to the successful control of the disease. In endemic settings such as Vietnam, it is important to identify the emergence and distribution of different strains promptly to implement timely control measures. The objective of this study was to evaluate sampling of clinically healthy livestock at slaughterhouses as a strategy for genomic surveillance of FMDV. We investigated the extent to which viruses recovered from slaughterhouses reflected the diversity in the source population, and whether they can serve as sentinels for the early detection of emerging outbreak strains. Serum samples (n = 11875) and oropharyngeal fluid (OPF) samples (n = 5045) were collected from asymptomatic cattle and buffalo on farms in eight provinces in southern and northern Vietnam from 2015 to 2019 to characterize the prevalence and diversity of FMDV circulating at the population-level. Outbreak sequences from clinical cases collected between 2009 and 2019 were also included for comparison in the study. In two slaughterhouses located in southern Vietnam, 1200 serum and OPF samples were collected from asymptomatic cattle and buffalo at bi-monthly intervals from 2017 to 2019 as a pilot study of the use of slaughterhouses as sentinel points of surveillance. To characterize viral diversity, sequences of the VP1 region were analyzed to identify clusters of closely related sequences. A phylogenetic cluster analysis was performed using discriminant principle component analysis (DAPC) and Bayesian time-scaled phylogenetic trees were created for serotypes O and A. For the seven serotype O and A clusters that were found to be circulating in southern Vietnam from 2017-19, six clusters were identified in at least one of the slaughterhouses. In some cases, sequences obtained from sub-clinical animals at slaughterhouses pre-dated the outbreak sequences associated with the same cluster by 4-6 months. Herein suggest Based that routine sampling at slaughterhouses may provide a timely and cost-effective strategy for genomic surveillance to identify circulating and emerging FMDV strains, ultimately aiding in the development of appropriate control measures in FMDV-endemic settings.