Simulation of overseas shipment revealed the deadly hog virus can survive in soybean meal for several weeks
BANFF, Alta. — The virus that causes deadly porcine epidemic diarrhea virus is proving to be a pesky survivor that can cross the ocean and remain viable in feed.
PED has killed millions of piglets in the United States since 2013 and has also infected more than 100 barns in Canada, primarily in Ontario and Quebec.
The U.S. infection is suspected to have originated in feed from China, although that has not been proven.
Even so, researchers decided to test the survival of PED virus by simulating a trip from China to Des Moines, Iowa, in which the virus was put into various feedstuffs commonly imported from China.
Dr. Scott Dee, a hog veterinarian and researcher for Minnesota-based Pipestone Applied Research, found that the virus survived a 37-day simulated land and ocean trek from Beijing, China, through San Francisco to Des Moines.
It was still viable and capable of infection when carried in non-treated samples of conventional and organic soybean meal, vitamin D, lysine hydrochloride and choline chloride.
“These results demonstrate the ability of PEDv to survive in a subset of feed ingredients using a model simulating shipment from China to the U.S.,” said Dee in his brief on the study.
“This is proof of concept suggesting that contaminated feed ingredients could serve as transboundary risk factors for PEDv, along with the identification of effective mitigation options.”
The samples in the test were put in an environmentally controlled chamber at South Dakota State University and subjected to the same temperature, humidity and time that would have been experienced on a trip from Beijing to Shanghai to San Francisco to Des Moines, using known conditions from December 2012 to January 2013, Dee told those at the Banff Pork Seminar Jan. 12.
As a control, a sample of the virus alone and not inoculated in feed ingredients was subjected to the same conditions and did not re-main viable. The study also in-volved use of two feed treatments, SalCURB and MCFA, which both worked against the virus. SalCURB is a blend of formaldehyde and organic acids. MCFA stands for medium chain fatty acids, which can be used to treat feed.
Dee said the study provided the first objective data showing that some feed ingredients can be vehicles for disease transmission between countries.
The findings have implications for imported hog feed and might indicate that greater consideration should be given to animal health status rather than price, he added.
In addition to testing the survival of PED, Dee and his team have tested the survival rates of other diseases using actual disease inoculum or surrogate diseases that are similar to the more dangerous ones.
For example, to test the survival rates of foot-and-mouth disease, they used Seneca Valley Virus inoculum.
They also tested or used surrogates for classical swine fever, pseudorabies, vesicular exanthema of swine, nipah virus, swine vesicular disease, vesticular stomatitis, circovirus, PRRS and African swine fever.
Dee said he and his team now have results from tests on four of those viruses.
They show that foot-and-mouth, or at least Seneca Valley Virus, can survive in a wide variety of feeds throughout a simulated trip from China.
In contrast, classical swine fever did not survive in any feed. Results varied with the other two viruses, depending on the type of feed. Soybean products appear to be particularly supportive of virus viability.
Further study will involve the other viruses and methods to mitigate their spread via imported feed, said Dee.