PSII-16 - Evaluation of formaldehyde on complete feed when inoculated with porcine epidemic diarrhea virus, porcine reproductive and respiratory syndrome virus, and Seneca Valley virus 1

Abstract: Chemical mitigants have been found to decrease virus concentrations in feed. Continued research is needed to identify the appropriate inclusion levels and application time for different viruses in this matrix. Therefore, the objective was to evaluate different inclusion levels of formaldehyde when applied either before virus inoculation (pre-inoculation) or after inoculation (post-inoculation) of porcine epidemic diarrhea virus (PEDV), porcine reproductive and respiratory syndrome virus (PRRSV) and Seneca Valley virus 1 (SVV1) to complete feed. The experiment was designed in a 2×2 factorial with a formaldehyde-based product (Termin-8, Anitox Corp. Lawrenceville, GA) applied either pre- or post-inoculation at either a 2 or 3 kg/MT. On d0, samples of swine feed were weighed in 50 g aliquots and added to 500 mL bottles. Chemical mitigants were applied to the pre-inoculation samples at their respective inclusion levels and 50 µL each of 1×10⁷ TCID₅₀/mL PEDV, 1×10⁸ TCID₅₀/mL PRRSV, and 1×10⁸ TCID₅₀/mL SVV1 were added to the post-inoculation samples. All bottles were shaken and allowed to sit at room temperature for 24 hours. On d1, virus was added to the pre-inoculation samples and chemical mitigants were added to the post-inoculation bottles. Half of the samples were immediately processed (0 hr) and the other half were incubated at room temperature for an additional 24 hours (24 hr). Samples were processed and aliquots were analyzed via a triplex RT-PCR at Kansas State University Veterinary Diagnostic Laboratory. Cycle threshold and proportion of PCR positive were analyzed using SAS GLIMMIX v 9.4 (SAS, Inc., Cary, NC) with each virus individually. An application time × inclusion level interaction was observed for PEDV at 0 hr and SVV1 and PEDV at 24 hr in feed, where less viral RNA (P < 0.05) was detected in the post-inoculation samples at either inclusion level as compared to the positive controls. An application time effect was noticed where less RNA was detected in the post-inoculation samples at 0 hr (P < 0.05) compared to the pre-inoculation samples and the control, and at 24 hr, both the pre- and post-inoculation samples had less detectable RNA (P < 0.05) than the control. Both the 2 and 3 kg/MT had less detectable PEDV, PRRSV, and SVV1 RNA (P < 0.05) than the control at 24 h. The quantity of detectable RNA detectable RNA decreased (P < 0.05) as the incubation time increased. Formaldehyde can reduce detectable RNA immediately in contaminated swine feed, with greater decreases observed as mitigant contact time continues.