Today we bring you a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
University of Minnesota researchers Lucas Ferreira, Mark Schwartz, Marie Culhane, and Cesar A. Corzo share preliminary results from their ongoing study examining trailer contamination at the harvest facility during unloading.
Key Points:
- PEDV can be detected on market hog trailers frequently.
- Biosecurity to and from the slaughterhouse should be a priority for producers.
Introduction
Porcine Epidemic Diarrhea Virus (PEDV) was first detected in the USA in 2013 and has been responsible for significant economic losses over the years by causing symptoms such as diarrhea, vomiting, dehydration, and mortality. Due to the high concentration of viral particles shed in feces, contamination of farm personnel, clothing, materials, and transport vehicles represents a significant factor in viral dissemination as pigs are moved between sites and ultimately reach the harvest facility. Lowe et al. (2014) demonstrated the role of unloading at harvest facility in PEDV trailer contamination during the early stages of the epidemic; however, there is no information available of the current trailer contamination risk. Therefore, determining the current risk is critical for informing biosecurity measures aimed at mitigating, controlling, and ultimately eliminating PEDV from swine production systems.
Methods
Fifteen environmental samples from harvest plant docks and trailers (before- and after-unloading) are being collected biweekly since calendar week 47 of 2024. Metadata on trailer origin, sanitation practices, destination and driver/plant employee behavior during unloading is also being recorded. Environmental samples are being submitted to the University of Minnesota Veterinary Diagnostic Laboratory for PEDV RT-PCR.
Results
The study is ongoing, and as of this writing, 65.2% of the samples have been collected, yielding 254 samples from docks and trailers. At the dock, PEDV was detected in 70.4% of the samples with a Ct value ranging between 25.55 and 37.91. Before market hogs were unloaded, PEDV was detected in 33% of the trailers, and when tested after unloading, the percentage of contaminated trailers increased to 59%. The increase in contaminated trailers was consistently observed across all tested weeks (Figure 1). The mean, minimum, and maximum PEDV RT-PCR of the samples after unloading market hogs were 33.73, 26.62, and 37.99, respectively. Of the 66.9% trailers that arrived PEDV negative to the harvest plant, 43.5% became contaminated. Preliminary results from the obtained metadata show that 81.5% of the trailers would visit the truck wash after unloading pigs, while 17.8% did not intend to wash their trailer after unloading pigs and 0.7% of the drivers did not know what their next steps would be regarding trailer sanitation and visiting farms.
Discussion
Preliminary results indicate that a significant proportion of trailers arriving at the harvest plant are already contaminated, suggesting PEDV transmission in the later stages of production or the possibility of trailers not being washed in between loads.
The percentage of contaminated docks is usually higher than the percentage of contaminated trailers arriving at the plant (pre-unloading), and the percentage of contaminated trailers after unloading is similar to the percentage of contaminated docks, suggesting that trailer contamination most likely occurs during the unloading process.
These findings underscore the critical importance of implementing effective biosecurity measures during the unloading process and ensuring market hog trailers are washed after every load.
This study is funded by the Swine Health Information Center (SHIC), the University of Minnesota Swine Disease Eradication Center (SDEC) and the American Association of Swine Veterinarians (AASV) Foundation.