Novel method for sub-grouping of genotype II African swine fever viruses based on the intergenic region between the A179L and A137R genes

Background: African swine fever (ASF) is a highly contagious and deadly viral disease affecting domestic and wild pigs of all ages. African swine fever virus (ASFV) has spread rapidly through Eastern and Southeastern Asia first appearing in Vietnam in 2019. Objectives: Molecular typing of African swine fever virus (ASFV) in Vietnam has identified two principal variants circulating based on the sequencing of the intergenic region (IRG) between the I73R and I329L genes. Identification of additional genetic markers would enable higher resolution tracing of outbreaks within the country. Methods: Sequence analysis suggested the IRG between the A179L and A137R genes may also exhibit variability, PCR primers were designed and samples from Vietnam were subject to Sanger sequencing. Results: We developed a novel method for sub-grouping of ASFV based on the IRG between the A179L and A137R genes of ASFV. Our results demonstrated that the finding of the insertion or deletion of an 11- nucleotide sequence (GATACAATTGT) between the A179L-A137R genes. Conclusions: The sub-grouping method may provide useful insights into the evolution of genotype II ASFV as well as providing evidence of a relationship between geographically separated outbreaks.