Several viruses deadly to swine may survive overseas trips in feed, pet food, or sausage casings, according to recent study results.
Relatives of pathogens—including the foot-and-mouth disease virus—also survived simulated shipping conditions.
In the article, published online in March (PLOS One 2018;13:e0194509), the authors describe their study on survival of 11 viruses pathogenic to livestock, using surrogates from the same families for viruses too dangerous for their laboratory. The authors simulated environmental conditions for trans-Pacific and trans-Atlantic shipments.
Seven remained viable in some of the ingredients: porcine reproductive and respiratory syndrome virus, African swine fever virus, porcine circovirus type 2, and relatives of the viruses that cause foot-and-mouth disease, vesicular exanthema of swine, pseudorabies, and swine vesicular disease. Four were not viable: vesicular stomatitis virus, influenza A viruses that cause swine influenza, and relatives of classical swine fever and Nipah viruses.
The article notes that prior research has indicated porcine epidemic diarrhea virus may have come to the U.S. in 2013 through contaminated feed from China. The Department of Agriculture has reported, since at least 2015, that the viruses in the U.S. likely came from China.
PED has killed millions of neonatal pigs and remains deadly on farms.
In the recent study, the researchers used a trans-Pacific model to estimate shipping conditions for 10 viruses endemic to China in the types of feed ingredients exported to the U.S. They used a trans-Atlantic model for African swine fever virus, which is endemic in the Caucasus, Eastern Europe, and the Baltic.
The study involved ingredients for livestock feed and pet foods as well as pork sausage casings. All were irradiated before virus inoculation.
Dr. Scott Dee, lead author and the director of research for Pipestone Veterinary Services in Minnesota, said he hopes the article helps veterinarians learn that feed can carry viable viruses around the world. He is among researchers now trying to develop mitigation strategies to protect livestock.
That research involves evaluating 10 feed additives that are safe for livestock to eat and that may reduce virus survival to manageable rates.
Related JAVMA content:
Herd sizes, trade risk pig health (May 1, 2017)
After porcine epidemic diarrhea, preparing for other diseases (May 1, 2015)
PED virus reinfecting U.S. herds (July 15, 2014)