An evaluation of a liquid antimicrobial (Sal CURB®) for reducing the risk of porcine epidemic diarrhea virus infection of naïve pigs during consumption of contaminated feed

Abstract

BackgroundSince its initial detection in May 2013, porcine epidemic diarrhea virus (PEDV) has spread rapidly throughout the US swine industry. Recently, contaminated feed was confirmed as a vehicle for PEDV infection of naïve piglets. This research provides in vivo data supporting the ability of a liquid antimicrobial product to reduce this risk.ResultsSal CURB® (Kemin Industries, Des Moines, IA, USA) is a FDA-approved liquid antimicrobial used to control Salmonella contamination in poultry and swine diets. To test its effect against PEDV, Sal CURB®-treated feed was spiked with a stock isolate of PEDV (Ct = 25.22), which PEDV-naïve piglets were allowed to ingest via natural feeding behavior (ad libitum) for a 14-day period. For the purpose of a positive control, a separate group of piglets was allowed to ingest non-treated (Sal CURB®-free) feed also spiked with stock PEDV (Ct = 25.22). A negative control group received PEDV-free feed. Clinical signs of PEDV infection (vomiting and diarrhea) and viral shedding in feces were observed in the positive control group 2–3 days post-consumption of non-treated feed. In contrast, no evidence of infection was observed in pigs fed Sal CURB®-treated feed or in the negative controls throughout the 14-day study period. In addition, the Sal CURB®-treated feed samples had higher (p < 0.0001) mean PEDV Ct values than samples from the positive control group.ConclusionsThese data provide proof of concept that feed treated with Sal CURB® can serve as a means to reduce the risk of PEDV infection through contaminated feed. Furthermore, the results from the positive control group provide additional proof of concept regarding the ability of contaminated feed to serve as a risk factor for PEDV infection of naïve piglets.

An evaluation of porcine epidemic diarrhea virus survival in individual feed ingredients in the presence or absence of a liquid antimicrobial

“…Finally, in regards to the management of “high risk” ingredients, under the conditions of this study, the formaldehyde-based liquid antimicrobial successfully reduced viral load and inactivated PEDV, independent of ingredient. These data confirm previously published reports of the efficacy of liquid antimicrobial biosecurity of PEDV-contaminated complete feed [10]. …”

“…This quantity of PEDV was selected in an effort to provide a final mean Ct value in feed ingredient of approximately 25 (range = 19–30) following mixing, based on data from actual field cases of PEDV-contaminated feed (S. Dee, unpublished observations, 2014–2015), a challenge level used in published studies [7, 10]. Once prepared, samples were stored outdoors in large plastic covered totes (Rubbermaid Cleverstore, 92.5 l capacity, Newell Rubbermaid, Atlanta, GA, USA) with one tote containing LA treated samples and the other the non-treated samples.…”

“…Animals ( n  = 24, 5–7 day old piglets) were sourced from a PEDV-naïve herd and were tested on arrival to the ARW via blood sampling and collection of rectal swabs from each pig. Prior to animal arrival, all rooms (walls, ceilings, floors and drains) were monitored for the presence of PEDV by PCR using sampling procedures previously described [8, 10]. Piglets were housed in one of 6 stainless steel gnotobiotic units measuring 0.6 m W x 1.2 m L x 0.6 m H. Units were divided into 4 semi-isolated housing units, allowing for 4 piglets per unit with individual feeding arrangements.…”

“…Following inoculation, the PEDV status of each group of piglets was monitored [8, 10]. On a daily basis, ARW personnel inspected animals for clinical signs of PED and collected rectal swabs (Dacron swabs, Fisher Scientific, Franklin Lakes, NJ, USA) from each pig, starting with the negative control unit.…”

“…Recently, a liquid antimicrobial (LA) product containing formaldehyde and propionic acid has been proposed as a means to mitigate risk (SalCURB®, Kemin Industries, Des Moines, IA, USA) [10]. This study demonstrated the ability to prevent PEDV infection in pigs consuming contaminated complete feed treated with LA [10]. However, information is not currently available regarding PEDV survival in other ingredients in swine diets or whether LA treatment can inactivate PEDV at the ingredient level.…”