Use of Slaughterhouses as Sentinel Points for Genomic Surveillance of Subclinical Foot-and-mouth Disease Virus in 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 sampling of clinically healthy livestock at slaughterhouses as a strategy for genomic FMDV surveillance. 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 (2015 to 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 asymptomatic cattle and buffalo (2017 to 2019) as a pilot study on the use of slaughterhouses as sentinel points of surveil-lance. 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 from 2017-19 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 timely and cost-effective strategy for genomic surveillance to identify circulating and emerging FMDV strains.