Cell-Free Genomic DNA Release into Serum of Wild Boar and Domestic Pigs Infected with Highly Virulent African Swine Fever Virus

African swine fever virus (ASFV) is the cause of a severe hemorrhagic disease in domestic pigs and wild boar. Currently, a highly virulent genotype II ASFV is causing massive pig mortality worldwide. In its acute form, the disease is characterized by high fever, a range of non-specific clinical signs and cell death. In this study, we demonstrate a greatly elevated level (>1000-fold) of cell-free DNA (cfDNA), more specifically, fragmented host genomic DNA (gDNA), in serum from both wild boar and domestic pigs infected with a highly virulent genotype II ASFV. Increases were also observed, to a lesser extent, in the serum levels of mitochondrial DNA (between 4- to >500-fold). For comparison, release of the cytoplasmic enzyme, lactate dehydrogenase, which is a commonly used marker for cellular damage, was also found to be elevated in some animals, but with less consistency. These results indicate that gDNA in serum (i.e., cfDNA) can be a useful marker for cell death during infection with highly virulent variants of the virus, and could be a promising biomarker to elucidate the pathogenesis of ASFV infection in both domestic pigs and wild boar in future studies.