Researchers at Kansas State University simulated transpacific shipment to test which feed ingredients allowed for the survival of classical swine fever and pseudorabies
By Jackie Clark
Scientists from the College of Veterinary Medicine at Kansas State University have found that both classical swine fever (CSF) and pseudorabies are able to survive in feed ingredients over 37-day simulated transpacific shipment. These findings have implications for feed biosecurity and disease mitigation strategies.
CSF and pseudorabies “were historically endemic in swine herds in the U.S. The government then implemented these eradication programs which took many years and millions of dollars to eradicate the two diseases,” Megan Niederwerder, lead researcher and assistant professor of diagnostic medicine and pathobiology at Kansas State University, told Farms.com.
That eradication was a major accomplishment, but recent changes in geographical and viral patterns of the diseases may indicate a potentially increased threat.
CSF “has recently been reintroduced in places where it was not present for many years,” such as Japan, Niederwerder explained.
Additionally, in 2011 officials in China identified a variant strain of pseudorabies “associated with increased mortality and morbidity in older-aged animals,” including causing disease in vaccinated herds, she said.
“Any time a virus changes with the ability to cause disease,” the U.S. has to consider how they may be vulnerable to the virus, and how they can respond to protect their herds, Niederwerder explained.
Feed ingredients are a potential vector for infection.
“When we think about feed and feed ingredients as a risk factor for disease, we really didn’t appreciate that until PED (porcine epidemic diarrhea) virus,” Niederwerder said. Epidemiological investigations identified feed as a risk factor for spread of the disease.
So, researchers at Kansas State University sought to investigate how viruses survive in feed.
Feed ingredients can be contaminated through practices such as open-air drying of grain, Niederwerder said.
The scientists had to consider “the risk factor of those feed ingredients to become contaminated, which has a lot to do with the processing and manufacturing in the country of origin, but then also (the ability of) the virus to survive in that ingredient” she explained.
They hypothesized “that there are certain characteristics of the feed ingredients – maybe it’s the protein or moisture content – but some of those characteristics promote viral stability more than other feed ingredients,” she added.
To conduct the experiment “we take the feed ingredients and inoculate them with the virus, and then we put them into an environmental chamber,” Niederwerder said.
The researchers can then set the temperature and humidity to fluctuate daily for 37 days to simulate transpacific shipment “based on historical meteorological data,” she explained.
Their findings confirmed that feed ingredients can promote viral stability.
“Both CSF and pseudorabies were capable of surviving the 37-day model in feed,” Niederwerder said. “The pseudorabies virus was more stable and survived in a higher percentage of ingredients that we tested.”
The study was able to identify some higher-risk ingredients.
“There are several feed ingredients that have now been identified as having an ability to promote the stability of several viruses,” including pork sausage casing and conventional soybean meal, Niederwerder said.
To identify “feed ingredients we want to focus more mitigation strategies on, we can think about what feed ingredients promoted stability of more viruses,” she explained.
“We don’t know what the next disease is going to be,” she added. So detecting ingredients that provide stability for several virus types is a key finding of this research.
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