SHIC-Funded Research Discovers Novel Way to Monitor and Diagnose Japanese Encephalitis Virus

January 16, 2018 — Paul Sundberg

When Japanese Encephalitis Virus (JEV) infects a naïve herd, the mortality rate of infected piglets is close to 100 percent; and 50 to 70 percent of sows experience reproductive failure. While JEV is endemic in Asia and the Pacific, many countries like the United States don't have and don't want this disease. New research has uncovered the ability of the virus to be spread between pigs by direct contact so the Swine Health Information Center (SHIC) has sponsored a novel and convenient means to monitor for and detect JEV in saliva via rope testing.

When Porcine Epidemic Diarrhea (PED) hit the US in 2013, the US diagnostic lab system did not have a means to diagnose the disease at a high throughput quickly and routinely. The need for reagents and high-throughput tests for new or emerging diseases became apparent. The US pork industry is starting to reap the benefits of this urgent, targeted work.

JEV, a flavivirus related to West Nile and dengue fever, is a zoonotic disease classically thought to be persisting in nature through a cycle of transmission involving Culex mosquitoes, some domestic and wild birds, domestic and feral pigs, and humans. According to the World Health Organization, every year close to 68,000 humans are infected with JEV via mosquito vectors in affected Asian countries. The resulting viral encephalitis causes a 30 percent mortality rate in infected humans; and 30 to 50 percent of those infected have permanent neurologic or psychiatric sequelae. Humans are a dead end for the virus as we do not amplify it enough to infect mosquitoes. Pigs, however, are considered the main amplifying host capable of infecting mosquitoes that vector the virus.

It was originally assumed that JEV needed mosquitoes to transmit the virus from pig to pig. However, in laboratory hogs in 2016 and in domestic hogs in 2017, it was discovered pig oronasal contact could lead to direct pig-to-pig transmission. SHIC monitored this research and sponsored a team at Kansas State University College of Veterinary Medicine to investigate a novel way to diagnose and monitor for JEV. These successful efforts recently demonstrated the feasibility of using oral fluid as a diagnostic sample of JEV infection in swine species.

When SHIC was established in 2015, part of its mission was, and still is, to be ready to diagnose endemic and foreign diseases at high risk of causing problems in the US. This began with identifying unwanted diseases that are at greatest risk to enter or emerge in the US, which are listed on the Swine Disease Matrix. Prioritized diseases, like JEV, have been a focus. With SHIC funding, disease fact sheets have also been created to help inform veterinarians and producers (JEV Fact Sheet).

Funded by America's pork producers to protect and enhance the health of the US swine herd, the Swine Health Information Center focuses its efforts on prevention, preparedness, and response. As a conduit of information and research, SHIC encourages sharing of its publications and research for the benefit of swine health. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Paul Sundberg at psundberg@swinehealth.org.

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Paul Sundberg, Executive Director, Swine Health Information Center