Evidence of viral survival in representative volumes of feed and feed ingredients during long-distance commercial transport across the continental United States

Abstract

The hypothesis that feed ingredients could serve as vehicles for the transport and transmission of viral pathogens was first validated under laboratory conditions. To bridge the gap from the laboratory to the field, this current project tested whether three significant viruses of swine could survive in feed ingredients during long-distance commercial transport across the continental US. One-metric ton totes of soybean meal (organic and conventional) and complete feed were spiked with a 10 mL mixture of PRRSV 174, PEDV, and SVA and transported for 23 days in a commercial semi-trailer truck, crossing 29 states, and 10,183 km. Samples were tested for the presence of viral RNA by PCR, and for viable virus in soy-based samples by swine bioassay and in complete feed samples by natural feeding. Viable PRRSV, PEDV, and SVA were detected in both soy products and viable PEDV and SVA in complete feed. These results provide the first evidence that viral pathogens of pigs can survive in representative volumes of feed and feed ingredients during long-distance commercial transport across the continental US.

Survival of a surrogate African swine fever virus-like algal virus in feed matrices using a 23-day commercial United States truck transport model

“…In their recent 23-days bulk transport study, Dee et al (2021) found that RNA viruses (PEDV, SVA, and PRRSV) were present in one tonne totes of conventional soybean meal (average Ct values of 34.6, 35.7, and 34.9, respectively) and organic soybean meal (average Ct values of 37.6, 35.3 and 34.1, respectively) using real time RT-PCR. When evaluating totes with complete feed, SVA was recovered in only one tote (Ct value of 35.5), with no detectable PEDV or PRRSV found in inoculated totes using the same real time RT-PCR methodology.…”

“…When evaluating totes with complete feed, SVA was recovered in only one tote (Ct value of 35.5), with no detectable PEDV or PRRSV found in inoculated totes using the same real time RT-PCR methodology. However, when pigs were fed contaminated complete feed, they developed a positive PEDV infection, but were negative for PRRSV, suggesting that PEDV remained infectious in a feed matrix after a trans-continental journey, while PRRSV did not (Dee et al, 2021). These observations are not surprising because of the lack of adequate sensitivity of commonly used diagnostic assays to characterize the quantity of viable virus capable of causing infection (Shurson et al, 2021).…”

“…Although a sampling protocol has been developed for the detection of PEDV in soybean meal (Jones et al, 2019), it has not been validated for other viruses and feed ingredients (Shurson et al, 2021). Unfortunately, Dee et al (2021) only reported mean Ct values for SVA, PEDV, and PRRSV which makes it impossible to determine if inadequate sampling or uneven virus distribution within the bulk feed mass contributed to this contradictory result. It must also be noted that the limitations with animal-based experiments and the consequent subsampling of animal products are overcome by using the V-qPCR method.…”

“…The route covered various regions of the United States including 29 states in the Midwest, Rocky Mountains, Southwest, Gulf Coast, Eastern Seaboard, New England region, and the Great Lakes region (Figure 1). The temperature and humidity were recorded every 15 min during transport and were reported by Dee et al (2021). The commercial truck did not encounter any unexpected stops or accidents.…”

“…The goal of this route was to cover several regions of the United States and expose the feed ingredients and viruses to a wide variety of environmental conditions. The temperature ranged for 1-17.5°C within the feed with the relative humidity ranging from 20 to 68% (Dee et al, 2021). Upon completion of the journey, samples were removed from the truck and stored at −20°C until analysis.…”