Inactivation of African swine fever virus inoculated in liquid plasma by spray drying and storage for 14 days at 4°C or 20°C

Abstract

African swine fever virus (ASFV) is a dsDNA virus that can cause high mortality in pigs of all ages. Spray-dried porcine plasma (SDPP) is a highly digestible ingredient used in feed because it benefits performance, gut function and immunity. The objectives were to test if the spray-drying (SD) conditions along with post-drying storage of product for 14 days can inactivate ASFV inoculated in liquid plasma. Fresh liquid porcine plasma was inoculated with ASFV (BA71V) to a final concentration of 105.18 ±0.08 TCID50/mL of liquid plasma. Triplicate 2-L samples of spiked plasma were SD in a lab drier set at an outlet temperature of 80°C or 71°C. The final dried samples were stored at 4°C or 20°C for 14 d. Liquid and SD samples were analyzed for ASFV infectivity in two mirror 24-well plaques containing VERO cells monolayers. Wells were inoculated with different dilutions of SDPP dissolved 1:9 in PBS. One plaque was immediately frozen at -80°C and the other was incubated at 37°C for 3 d. Each dilution was replicated 9 times. After incubation both plaques were analyzed for ASFV by qRT-PCR. Results indicated that the SD process inactivated between 3.2 to 4.2 Logs ASFV TCID50/mL and 2.53 to 2.75 Logs TCID50/mL when the outlet temperature were 80°C and 71°C respectively. All SD samples stored at 4°C or 20°C for 14 d were absent of infectious ASFV. The combination of SD and post drying storage at both temperatures for 14 d was able to inactive >5.18 ±0.08 Log10 of ASFV inoculated in liquid porcine plasma, demonstrating that the manufacturing process for SDPP can be considered safe regarding ASFV.