Deadly US Swine Virus Traced back to China

A virus deadly to piglets that has been spreading across the US since May has its origins in the Chinese province of Anhui, according to Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech.

Molecular virology professor X.J. Meng used strains of the emergent porcine epidemic diarrhea virus (PEDV) isolated in Minnesota and Iowa to trace the virus' origins back to China.

"The virus typically only affects nursery pigs and has many similarities with transmissible gastroenteritis virus of swine," Meng said. "There is currently no vaccine against porcine epidemic diarrhea virus in the United States. Although some vaccines are in use in Asia, we do not know whether they would work against the U.S. strains of the virus."

Meng and his colleagues, writing in American Academy of Microbiology's journal, mBio, report that the US strains of PEDV diverged from a particularly strong strain of the virus that was documented in China within the last three years.

US strains of PEDV share 99.5 percent of their genetic code with the Chinese variants, but it is unclear where the US strains of the virus diverged in China or the US.

Regardless of its origins, the researchers say PEDV, which is a type of coronavirus, has caused economic and public health concerns across the US.

"The ongoing outbreaks of Middle East respiratory syndrome coronavirus in humans from countries in or near the Arabian Peninsula and the historical deadly nature of the 2002 outbreaks of severe acute respiratory syndrome coronavirus create further anxiety about the emergency of PEDV in the United States due to the lack of scientific information about the origin and evolution of this emerging coronavirus," said Yao-Wei Huang, the first author of the paper.

There is no evidence that PEDV can spread to humans or affect food safety. However, the researchers have found similarities in PEDV and a coronavirus found in bat populations, which suggests the virus may be capable of transferring between species.

Symptoms of PEDV include acute vomiting, anorexia and watery diarrhea with high mortality rates in pigs less than 10 days old, the researchers said.

"Veterinarians need to recognize the symptoms of the disease, and with the lack of a vaccine in the United States, practicing strict biosecurity and good sanitation procedures on the farm are important for prevention and control of this deadly disease," Meng added.