Abstract
The African swine fever virus (ASFV) causes African swine fever (ASF), a highly lethal disease affecting domestic pigs and wild boars. Since its initial outbreak in October 2019 in Yeoncheon, Gyeonggi Province, ASF has continued to spread in South Korea. This study aimed to differentiate closely related ASFV strains through the analysis of the intergenic region (IGR) between I73R and I329L genes. In 2019, genetic analysis confirmed one IGR I type case and two IGR III type cases in Paju, followed by two more IGR III type cases in 2020. After a period of detecting only the IGR II type, IGR III type cases re-emerged in Pohang and Cheong-song in November and December 2023. Genetic analysis using B646L, CP204, B602L, and EP402R genes confirmed that the IGR III strains belong to genotype II and serogroup 8, similar to the Georgia/2007/1 strain but differing in IGR type. Since the first occurrence of ASF in wild boars in South Korea, we have continuously monitored the introduction and variation of ASFV. As a result, we reconfirmed the presence of the IGR III type ASFV in 2023, 3 years and 8 months later, in a different area from where it was last detected. This finding would not have been possible without the continuous monitoring of ASFV introduction and genetic variation. We emphasize the critical role of regular monitoring based on molecular markers and comprehensive genomic analysis in enhancing the effectiveness of ASFV control and prevention.