Evaluation of the Protective Efficacy of Foot-and-Mouth Disease Vaccines Against O/CATHAY Topotype Virus in Pigs

The world is divided into seven regional pools based on the serotype distribution and geographical spread of the foot-and-mouth disease (FMD) virus. The Republic of Korea (ROK) belongs to Pool 1, where serotypes O, A, and Asia1 are endemic. Recently, the risk of incursions by the O/CATHAY topotype has increased in Pool 1, raising concerns about its potential introduction into the ROK. To assess the protective effectiveness of three commercial FMD vaccine strains-O1/Manisa + O/3039, O/Primorsky, and O1/Campos-currently used in the ROK against this topotype, an animal challenge experiment was conducted. Three treatment groups (<i>n</i> = 4 in each) of pigs received a single 2 mL injection of one of the vaccines at 8-10 weeks of age, and the other group (<i>n</i> = 2) served as the control. All pigs were challenged with the O/HKN/5/2019 virus (O/CATHAY topotype) at 21 days post-vaccination. All vaccines conferred protective effects, with O1/Campos demonstrating the highest efficacy by inducing fewest clinical signs and significantly reducing virus shedding in the treated groups compared with those in the control group. These findings suggest O1/Campos may serve as an emergency measure; nevertheless, the development of a vaccine specifically targeting the O/CATHAY topotype is warranted.