Comparative evaluation of histopathological lesions and viral antigen distribution in domestic pigs and wild boar inoculated intranasally with the highly virulent ASFV genotype II strain "Armenia 2007".

African swine fever (ASF) is a devastating viral disease that affects domestic pigs (Sus scrofa domesticus) and European wild boar (Sus scrofa scrofa). A previous study indicated that wild boar were more susceptible to ASF than pigs, with shorter incubation periods and earlier onset of the disease. This follow-up study aims to compare the pathogenesis and progression of the disease between the two subspecies during the early and late stages of infection following intranasal inoculation with the highly virulent genotype II strain 'Armenia 2007'. Histopathological changes and viral antigen distribution by immunohistochemistry (IHC) were assessed over time following intranasal inoculation. Viral antigen and histological changes were detected earlier in wild boar than in pigs. In wild boar, the medial retropharyngeal (MRPLN) and submandibular lymph nodes were among the earliest sites of virus replication from 3 days post-infection (dpi), with widespread dissemination occurring by 5 dpi. In pigs, the viral antigen was first detected in the MRPLN at 5 dpi. At the humane endpoint, which occurred at 6 dpi in wild boar and 9 dpi in pigs, virus antigen and histopathological scores were lower in wild boar than in pigs, even though the appearance and increase of viral antigen in tissues, onset and development of lesions and humane endpoint occurred earlier in the former. The lower severity and lesser extent of lesions in wild boar suggest lower tolerance of tissue damage prior to reaching the humane endpoint, demonstrating their greater susceptibility to and lower resistance against ASFV.