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Pathogenesis of highly virulent African swine fever virus in domesic pigs exposed via intraoropharyngeal, intranasopharyngeal, and intramuscular inoculation, and by direct contact with infected pigs

Howey, Erin B., O'Donnell, Vivian, de Carvalho Ferreira, Helena C., Borca, Manuel V., Arzt, Jonathan
ARS USDA Submissions 2013 v.178 pp. 328
African swine fever, African swine fever virus, animal disease models, death, direct contact, disease course, drug delivery systems, nasal cavity, pathogenesis, swine, tonsils, vaccine development, viral shedding, viremia
In order to optimize novel systems for African Swine Fever Virus (ASFV) vaccine development, domestic pigs were challenged with the highly virulent ASFV-Malawi strain via intraoropharyngeal (IOP), intranasopharyngeal (INP), intramuscular (IM), and direct contact (DC) routes. Direct challenge doses ranged from 10^2 – 10^6 50 percent hemadsorbing doses (HAD^50) whereas contact challenge varied from 24 – 72h of comingling with previously infected pigs. All challenge routes resulted in clinical progression and postmortem lesions similar to those previously described in association with experimental and natural infection. Onset of clinical signs occurred between 1-7 days post inoculation (dpi) characterized by pyrexia and obtundation with variable progression to hematochezia, melena, moribundity and death. Viremia was first detected between 4-5 dpi in all inoculation groups whereas ASFV shedding from the nasal cavity and tonsil was first detected at 3-9 dpi. Overall, IM and DC were the most consistent manners of challenge as reflected by a 100 percent incidence of infection under all exposure doses and times; however these routes suffer from unnatural challenge route (IM) and inability to control dose and timing of challenge (DC). INP inoculation resulted in a consistent progression of disease across a wide range of doses whilst preserving simulation of natural exposure and is therefore considered to be a superior system for pathogenesis and vaccine efficacy investigation.