or nearly two years, Lucas Ferreira has visited two swine harvest plant facilities biweekly, collecting samples and studying how often market hog transportation trailers get contaminated during unloading and what risk factors are associated with it.
“We know those trailers are going to the farms and getting the pigs to bring them to facilities,” he explains. “But nobody knew if those trailers leaving the facility were contaminated, how often it was happening, or the type of factors that might be related to it. The reality is there was no data —not just in the United States, but internationally.”
Currently a PhD student at the University of Minnesota College of Veterinary Medicine, Ferreira has been working with his advisor Cesar A. Corzo, Leman Chair in Swine Health & Productivity, to focus his research on swine health, looking into viral diseases such as porcine reproductive and respiratory syndrome (PRRS), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and Seneca Valley virus / Senecavirus A (SAV).
These viruses not only make animals sick but also cause economic losses in the swine industry (PRRS alone is estimated to cause more than $1 billion in losses per year for the U.S. pork industry) by causing respiratory disease and reproductive failure, severe diarrhea and vesicular lesions.
“We want to understand the pathogens that we know are circulating in the U.S., how often trailer contamination at the harvest facilities occurs, and also, in the scenario of a foreign animal disease that might enter the country, the industry will be better prepared by understanding how often contamination happens,” he says.
Ferreira conducted his research at two harvest facilities in the Midwest, surveying truck drivers on their trailer-washing protocols and collecting three environmental samples—one from the facility’s dock area and two from inside the trailer before and after the pigs are unloaded.
“We found that the trailers are leaving more contaminated than when they arrive,” he says. “Both in number of trailers, but also in number of pathogens. Sometimes the trailer will arrive with just PRRS, and then the trailer will leave with PRRS, SVA and PDCoV.”
According to the study he led, SVA can be detected on market hog trailers year-round, and the percentage of contaminated trailers after unloading is usually similar to the percentage of contaminated docks, suggesting trailer contamination most likely occurs during unloading. He also found contamination rates are higher during fall and summer than in winter and spring, and that after leaving the harvest plant, SVA-contaminated trailers often go unwashed.
“We were expecting contamination to occur, but the numbers are so high,” he says. “The amount of trailers leaving the plants contaminated was really significant.”
Ferreira says these findings are important for implementing effective biosecurity measures during unloading and ensuring market hog trailers are washed after every load. He hopes the findings raise industry awareness and prompt ways to prevent viruses from spreading.
“At the end of the day, we want to decrease the level of contamination that is currently being observed,” says Ferreira, who adds that more research is needed on cleaning and disinfection protocols for trailers and the plants. “We want to make sure that the pigs are healthy, that the trucks are not getting contaminated at current levels, and that the swine industry is better prepared to deal with different pathogens. Because if something happens and foreign animal diseases get into the country, what happens if those pathogens end up in the harvest plant facilities? We now know contamination is happening at alarming levels, and we want to avoid that.”
The Swine Health Information Center (SHIC), the University of Minnesota Swine Disease Eradication Center (SDEC), and the American Association of Swine Veterinarians (AASV) Foundation funded the study.