Japanese Encephalitis Virus Could Happen in U.S. Swine Herds

A disease that is endemic in Asia and the Pacific is being evaluated to determine if it could potentially attack herds in the U.S., where quick detection is vital to enacting a quick response to control spread.

Japanese encephalitis virus (JEV) has not been found in U.S. swine herds and it’s important to keep it out because the effects would be devastating.

“If JEV infects a naïve herd, the mortality rate of infected piglets is close to 100%,” reports the Swine Health Information Center (SHIC). “In addition 50% to 70% of sows experience reproductive failure.”

Researchers at the Kansas State Biosecurity Research Institute (KSBRI) are studying if the virus would be sustainable and detectable in the North American pork industry. The work is partially funded by SHIC.

It Could Happen Here
“In this first-of-its-kind study, the KSBRI team showed from Culex mosquitos to domestic pig susceptibility, North America has all the components for JEV to circulate and survive if introduced,” SHIC reports. “Thanks to SHIC’s contribution to this research, an oral fluids PCR test for JEV infection in swine has now been developed for U.S. veterinary diagnostic labs.”

“A Different Flavor of Flavivirus”
According to SHIC, JEV is a different flavor of flavivirus.

“Pigs, alongside viremic birds, are considered the main amplifying host capable of infecting Culex mosquitoes that can carry the virus,” the organization reports in its most recent newsletter. “It was originally thought JEV needed mosquitoes to move virus from pig to pig. However, oronasal pig-to-pig transmission was shown in laboratory pigs in 2016 and in domestic pigs in 2017. And this most recent K-State study also showed viral RNA present in tonsils at 28 days post infection demonstrates the possibility of persistent infection in swine.”

Monitoring the Virus
SHIC notes that JEV has not entered the U.S., but the K-State researchers recommend “increased international and possibly local surveillance of the virus through diagnostic methods.” Swine veterinarians should check out the JEV Fact Sheet for infection presentation and signals.

“Keep it in mind in those difficult cases with high piglet mortality or reproductive failure,” says the Information Center.