Assessing Virus Survival in African Swine Fever Virus Contaminated Materials—Implications for Indirect Virus Transmission

Introduction: of African swine fever virus (ASFV) into pig herds can occur via virus-contaminated feed or other objects. Knowledge about ASFV survival in different matrices and under different conditions is required to understand indirect virus transmission. Maintenance of ASFV infectivity occurs for extended periods outside pigs but depends on the contaminated material and environmental factors. Current assays detecting ASFV have inherent disadvantages. Cell culture-based assays are labor-intensive and sensitive to contaminants. Methods, using qPCR, detect ASFV DNA with high sensitivity and specificity but this may not correspond to infectious virus. Here, we combined these assays to assess replication of ASFV within cells, and determined the effect of pig feces, straw, wood shavings and mixed feed on ASFV infectivity. In porcine serum, infectious ASFV survived for at least 60 days at 4 °C, 22 °C and 37 °C, for two days at 50 °C, one day at 60 °C and ≤5 min. at 70 °C. In the presence of feed, straw or wood shavings, the survival of the virus was markedly shortened. Samples remained positive in the qPCR assay despite loss of virus infectivity. Thus, it was possible to distinguish between the presence of ASFV DNA and survival of infectious virus.