67 Decontamination of a feed manufacturing environment following inoculation of porcine epidemic diarrhea virus, porcine reproductive and respiratory virus, and Seneca Valley virus 1

Abstract

Abstract Feed mill decontamination is difficult because equipment is not designed to be cleaned with water. Alternate strategies may improve the ability of a mill to decontaminate in the event of viral contamination. The objective was to evaluate different decontamination strategies within a mill following the inoculation of porcine epidemic diarrhea virus (PEDV), porcine reproductive and respiratory syndrome virus (PRRSV), and Seneca Valley virus 1 (SVV1) contaminated feed. A batch of feed was inoculated with PEDV, PRRSV, and SVV1 and ran through a mixer, bucket elevator, corn cleaner, screw conveyor, distributor head, and spout. Following mill inoculation, decontamination strategies were implemented with environmental samples collected after each decontamination step. Decontamination strategies included: 1) complete facility decontamination including organic matter removal with hot water power washing, disinfection with 1% peroxygen (Virkon S, Lanxess, Germany) followed by a rinse, and a second disinfection with 5% sodium hypochlorite (Clorox, Oakland, CA) followed by a heating period for 48 h once the facility reached 60°C; 2) chlorine dioxide application (ProOxine AH, Bio-Cide International, Inc., Norman, OK); 3) organic matter removal using vacuums (Ridge Tool Company, Elyria, OH) and chlorine dioxide application; 4) heat up with portable electric heaters for exactly 48 h; and 5) organic matter removal and heat up with portable heaters for exactly 48 h. Samples were analyzed via triplex PCR. Cycle threshold and proportion PCR positive were analyzed using SAS GLIMMIX v 9.4 (SAS, Inc., Cary, NC). A swine bioassay was completed to determine the infectivity of samples following the final decontamination step of each treatment. A treatment × decontamination step × location interaction was observed (P < 0.05) for SVV1, where less RNA was detected post-treatment compared with pre-treatment following complete facility decontamination on surfaces including the mixer, corn cleaner, screw conveyor, and floor around the feed discharge (P < 0.05). There was no statistical difference between pre- and post-treatment samples for other combinations of decontamination treatment and location (P > 0.05), although numerical increases in Ct were generally observed following treatment. Across all treatments, the act of decontamination reduced detectable PEDV (P < 0.05) and PRRSV (P < 0.05) RNA when compared with samples immediately following inoculation, but complete facility decontamination was the only treatment where PEDV and PRRSV was non-detectable in all locations. Pigs given samples post-treatment showed no evidence of SVV1 or PEDV infection. Although PRRSV RNA was rarely found via PCR from samples collected within the mill, PRRSV infection was observed in pigs given the chlorine dioxide with and without organic matter removal treatments and the organic matter removal plus heat treatment. Overall, all treatments reduced detectable RNA for all viruses between the inoculation step and the final decontamination step; however, PRRSV particles remained infectious following decontamination regardless of PCR results in a swine bioassay.