Abstract
Foot and mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals with serious economic consequences. FMD is endemic in Southeast Asia (SEA) and East Asia (EA) with the circulation of multiple serotypes, posing a threat to Australia and other FMD-free countries. Although vaccination is one of the most important control measures to prevent FMD outbreaks, the available vaccines may not be able to provide enough cross-protection against the FMD viruses (FMDVs) circulating in these countries due to the incursion of new lineages and sub-lineages as experienced in South Korea during 2010, a FMD-free country, when a new lineage of serotype O FMDV (Mya-98) spread to the country, resulting in devastating economic consequences. In this study, a total of 62 serotype O (2013–2018) viruses selected from SEA and EA countries were antigenically characterized by virus neutralization tests using three existing (O/HKN/6/83, O/IND/R2/75 and O/PanAsia-2) and one putative (O/MYA/2009) vaccine strains and full capsid sequencing. The Capsid sequence analysis revealed three topotypes, Cathay, SEA and Middle East-South Asia (ME-SA) of FMDVs circulating in the region. The vaccines used in this study showed a good match with the SEA and ME-SA viruses. However, none of the recently circulating Cathay topotype viruses were protected by any of the vaccine strains, including the existing Cathay topotype vaccine (O/HKN/6/83), indicating an antigenic drift and, also the urgency to monitor this topotype in the region and develop a new vaccine strain if necessary, although currently the presence of this topotype is mainly restricted to China, Hong Kong, Taiwan and Vietnam. Further, the capsid sequences of these viruses were analyzed that identified several capsid amino acid substitutions involving neutralizing antigenic sites 1, 2 and 5, which either individually or together could underpin the observed antigenic drift.
Highlights
Foot and mouth disease (FMD) is an economically devastating and highly contagious vesicular disease affecting domestic and wild cloven-hoofed animals [1,2,3]
The vaccines used in this study showed a good match with the Southeast Asia (SEA) and Middle East-South Asia (ME-SA) viruses
We report the antigenic and genetic characteristics of serotype O FMD viruses (FMDVs) isolated over a six-year period (2013–2018) with the aim to study the antigenic nature of the viruses circulating in the region and/or detect the emergence of antigenic variants if any, as experienced previously in the Middle East necessitating the development of new vaccine strains for broad coverage [23]
Summary
Foot and mouth disease (FMD) is an economically devastating and highly contagious vesicular disease affecting domestic and wild cloven-hoofed animals [1,2,3]. The disease has been detected in more than 100 countries worldwide; most of Asia including Southeast. In South America, FMD is controlled by vaccination. The disease can cause a significant production loss in infected animals and results in trade barriers causing serious damage to the economy of countries by restricting the exports of livestock and livestock products. The causative agent, FMD virus (FMDV), is a non-enveloped single-stranded, positivesense RNA virus, belonging to the Family Picornaviridae in genus Aphthovirus. Due to the lack of the proof-reading activity of the RNA polymerase and the quasispecies nature of the virus, there is a greater chance of evolving new variants of FMDV, resulting in the existence of seven immunologically distinct serotypes of FMDV O, A, C, Asia 1, South
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