Characterizing the rapid spread of porcine epidemic diarrhea virus (PEDV) through an animal food manufacturing facility

Abstract

New regulatory and consumer demands highlight the importance of animal feed as a part of our national food safety system. Porcine epidemic diarrhea virus (PEDV) is the first viral pathogen confirmed to be widely transmissible in animal food. Because the potential for viral contamination in animal food is not well characterized, the objectives of this study were to 1) observe the magnitude of virus contamination in an animal food manufacturing facility, and 2) investigate a proposed method, feed sequencing, to decrease virus decontamination on animal food-contact surfaces. A U.S. virulent PEDV isolate was used to inoculate 50 kg swine feed, which was mixed, conveyed, and discharged into bags using pilot-scale feed manufacturing equipment. Surfaces were swabbed and analyzed for the presence of PEDV RNA by quantitative real-time polymerase chain reaction (qPCR). Environmental swabs indicated complete contamination of animal food-contact surfaces (0/40 vs. 48/48, positive baseline samples/total baseline samples, positive subsequent samples/total subsequent samples, respectively; P < 0.05) and near complete contamination of non-animal food-contact surfaces (0/24 vs. 16/18, positive baseline samples/total baseline samples, positive subsequent samples/total subsequent samples, respectively; P < 0.05). Flushing animal food-contact surfaces with low-risk feed is commonly used to reduce cross-contamination in animal feed manufacturing. Thus, four subsequent 50 kg batches of virus-free swine feed were manufactured using the same system to test its impact on decontaminating animal food-contact surfaces. Even after 4 subsequent sequences, animal food-contact surfaces retained viral RNA (28/33 positive samples/total samples), with conveying system being more contaminated than the mixer. A bioassay to test infectivity of dust from animal food-contact surfaces failed to produce infectivity. This study demonstrates the potential widespread viral contamination of surfaces in an animal food manufacturing facility and the difficulty of removing contamination using conventional feed sequencing, which underscores the importance for preventing viruses from entering and contaminating such facilities.

Evaluation of the effects of flushing feed manufacturing equipment with chemically treated rice hulls on porcine epidemic diarrhea virus cross-contamination during feed manufacturing1

“…Rice hulls were also verified to be devoid of detectable PEDV and PDCoV genetic material. The production scale mixer used was a 0.113-m 3 electric paddle mixer (H.C. Davis Sons Manufacturing, model # SS-L1; Bonner Springs, KS) with a mix time of 5 min as described previously ( Schumacher et al, 2017 ). Feed was discharged at a rate of approximately 4.5 kg/min into a bucket elevator (Universal Industries, Cedar Falls, IA) fitted with 74 buckets (114 cm 3 each), and then discharged through a 25.4-cm diameter discharge spout and collected in plastic biohazard bags.…”

“…Feed manufacturing equipment has been shown to be a potential source of porcine epidemic diarrhea virus ( PEDV ) cross-contamination ( Schumacher et al, 2017 ). Wet disinfection has been found to be the most effective feed mill equipment surface decontamination method ( Muckey, 2016 ).…”

“…Other research has assessed sequencing batches of PEDV-negative feed following an inoculated batch of feed to assess the effectiveness of reducing the risk of viral transmission ( Schumacher et al, 2016a ). Although this may be a practical mitigation technique for feed mills to implement, there remains a significant quantity of viral particles on feed-contact surfaces including dust production and distribution throughout the facility ( Schumacher et al, 2017 ). This dust may pose a risk for contamination of subsequent diets.…”

A review of strategies to impact swine feed biosecurity

“…Formaldehyde-based products and an MCFA blend have been shown to reduce the presence of PEDV on these surfaces when used in conjunction with a rice hull flush. Similarly, MCFA blends have been found to be effective at reducing S. enterica serovar Typhimurium on Schumacher et al (2017) reported the role of PEDV cross-contamination in feed mills. Initially, a PEDV-negative swine diet was manufactured, followed by a diet that included an ingredient that had been spiked with infectious PEDV, then four subsequent PEDV-negative diets in an attempt to 'flush' contamination from the manufacturing surfaces.…”

Current status of porcine epidemic diarrhoea (PED) in European pigs

“…Until the introduction of PEDV to the USA, feed for animals was not considered to be a vector in the spread of the virus. Recent studies have shown, however, that feed can be a potential vector for PEDV transmission and contaminated feed can be a source of disease (27). It is widely acknowledged that the most important risk factors for spreading the disease are contaminated vehicles (5,28).…”