Abstract
African Swine Fever (ASF) remains a severe threat to the global swine industry, particularly in Southeast Asia where smallholder farming dominates. This study investigated the transmission dynamics of African Swine Fever Virus (ASFV) in smallholder pig farms across five provinces in Northern Vietnam between January 2022 and June 2023. We integrated molecular phylogenetics with spatial analysis to map disease hotspots and trace evolutionary lineages. Diagnostic real-time PCR confirmed ASFV in 84 clinical samples. Phylogenetic analysis of the B646L (p72) gene confirmed that all isolates belonged to Genotype II, sharing high homology with the Georgia 2007/1 reference strain. However, sequence analysis of the I73R/I329L intergenic region and the EP402R (CD2v) gene revealed localized micro-diversification, including a novel tandem repeat sequence variant. Spatial analyses using Kernel Density Estimation and Nearest Neighbor Hierarchical Clustering identified three significant transmission hotspots clustered along major national highways and regional livestock markets. Spatial regression models indicated that proximity to transport corridors, high local farm density, and swill-feeding practices were significantly associated with outbreak clusters (p < 0.01). These findings demonstrate that transport infrastructure and biosecurity gaps drive ASFV dissemination in Northern Vietnam. Combining spatial statistics and genomic surveillance provides a powerful framework for designing targeted, risk-based veterinary interventions to control ASF in endemic smallholder settings.
