Introduction
African swine fever (ASF) is a highly contagious disease occurring in
domestic pigs and wild suids, and leads to serious haemorrhage and
nearly 100% mortality. ASF is caused by infection with African swine
fever virus (ASFV; family: Asfarviridae , genus: Asfivirus )
(Dixon et al., 2020). Since its original description in the 1920s in
Kenya, this viral disease has been highly prevalent in African and
European countries. In Asia, ASF was first reported in a farm neat
Shenyang City in Liaoning province in China, in August 2018 (Zhou at
al., 2018). Thereafter, it quickly spread to other countries in
Southeast Asia including Myanmar, Laos, Vietnam, and the Philippines, as
well as nearly all provinces in mainland China, in 2019 (Lu et al.,
2020). ASF outbreaks have also been described in North and South Koreas
in the same year (Kim H. J. et al., 2020; Kim S. H. et al., 2020).
Despite the high mortality rates and socio-economic impacts of ASF, no
vaccines or therapeutic agents are available for controlling its
outbreak or its effective treatment (Dixon et al., 2020). Therefore,
studies on the routes and patterns of ASF transmission as well as its
early detection are urgently needed. Molecular epidemiology approaches
using polymorphic DNA sequences can provide insight into the
spatiotemporal patterns of disease transmission throughout the areas in
which ASF is prevalent. The
genomic DNA of ASFV shows a low evolution rate. Nevertheless, multiple
sites show inter-genomic polymorphisms, particularly those containing
short tandem repeats (STRs), which can be selected as informative
markers in epidemiological investigations (Goller et al, 2015; Nix et
al, 2006).
After ASFV was first isolated from a wild boar in October 2, 2019 in
South Korea (Kim S. H. et al., 2020), we conducted a surveillance
programme for wild boars in the relevant areas by the National Institute
of Environmental Research (NIER). Genotypes of ASFV DNAs obtained during
these surveys were investigated via polymerase chain reaction (PCR) and
nucleotide sequencing to trace viral transmission in the wild boar
population and monitor the probable emergence of viral variants.