Survival and mitigation strategies of porcine epidemic diarrhea virus (PEDV) in complete feed

Abstract Text: Infection with PEDV causes severe diarrhea, vomiting, enteritis, and high mortality in young pigs and is a serious problem for the US swine industry. Contaminated feed can be a source of PEDV transmission and may be affected by feed storage time and chemical composition. Combinations of organic acids have been used to control pathogens such as Salmonella. However, there are no data measuring kinetics of virus survival and the effect of organic acids on PEDV survival in complete feed. The objectives of this study were to 1) measure wild virus survival kinetics in complete feed and 2) determine if organic acids are effective in reducing infectivity of cell culture adapted virus. In Exp. 1, jejunal mucosa scrapings of PEDV infected pigs were diluted in 0.5mL of PBS and utilized to infect 5g of feed. Infected feed was stored for 0, 7, 14, and 28d at 22°C. At the end of each storage time, 10d old pigs were inoculated with an extract of the contaminated feed. Results demonstrated that PEDV was capable of infecting naïve pigs in wet feed stored for 28d, but only 7d in dry feed. In Exp. 2, 5g of feed were weighed into vials and mixed with either 15mg Nutriad’s Ultracid P (orthophosphoric, citric, fumaric, and malic acid), 20mg Novus’ Activate DA (organic acids and 2-hydroxy-4-methylthio butanoic acid), 10mg Kemin Agrifoods’ KEM-GEST (phosphoric, fumaric, lactic, and citric acid), or 10mg AgriNutrition’s Acid Booster (phosphoric, citric, and lactic acid). We modified the concentration of sugar (20mg) and salt (20mg) in additional vials as methods of modifying the composition and water activity of the diets. A paired control sample was incubated without additives. We added 1mL of PEDV (3.2 x 10⁴ TCID₅₀/mL) to each vial and vortexed. Vials were stored at 22°C for 0, 1, 3, 5, 7, 14, and 21d. Virus was eluted and inoculated in Vero-81 cells to calculate TCID₅₀/mL. Virus inactivation kinetics were tested with log-linear or Weibull models. Data fitted the Weibull model better. There were no differences in the inactivation kinetics (Delta, d) of PEDv between the control samples and the samples treated with Nutriad (18.9) or salt (14.6). The acidifiers that produced the faster inactivation kinetics were Novus (0.4) followed by Kemin (1.8). Addition of some organic acids can reduce the survivability of PEDV in feed, but complete inactivation took up to 14d. 

Keywords: Feed Additives, Inactivation kinetics, Porcine Epidemic Diarrhea Virus