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K-State studies the role of pigs and mosquito in spreading Japanese encephalitis virus

nechaev-kon/GettyImages/Istock Mosquito Bite Macro Photo
While an introductory event involving Japanese encephalitis virus has yet to happen in the U.S., the virus may have the potential to become endemic in the U.S. similar to the recent emergence of West Nile virus.

Source: Kansas State University

North American domestic pigs could be susceptible to Japanese encephalitis virus infections according to a study by Kansas State University College of Veterinary Medicine researchers. The study is believed to be the first of its kind in the United States.

"Collectively, our study demonstrates for the first time that North American domestic pigs can contribute to the Japanese encephalitis virus transmission cycle as amplifying hosts," says So Lee Park, a third-year veterinary student and concurrent doctoral student in pathobiology who was first author of the study.

Japanese encephalitis virus (JEV) is a mosquito-transmitted flavivirus that has human and veterinary health significance. It can cause encephalitic diseases in children. While humans can succumb to severe disease, the transmission cycle is maintained by viremic birds and pigs in endemic regions.

Pigs to human connection

According to the Centers for Disease Control and Prevention, the virus is transmitted through the bite of a mosquito and is the leading cause of vaccine-preventable encephalitis in Asia and the western Pacific. Currently, the endemic region of JEV is mainly restricted in the Asia-Pacific region, covering from Southeastern Russia to Japan, Eastern China, Southeastern Asia, India, and Northern Australia, where an estimated 68,000 JEV cases occur each year.

While most human infections are mild, a small percentage of people develop encephalitis — an infection of the brain — that can include a headache, high fever, tremors, coma and more. The CDC says about 1 in 4 cases of Japanese encephalitis are fatal.

The virus in swine can cause encephalitis in piglets and reproductive diseases in mature adult pigs.

The Kansas State University study suggests that JEV may have the potential to become endemic in the U.S. after an introductory event like the recent emergence of West Nile virus, a closely related flavivirus, says Dana Vanlandingham, associate professor of diagnostic medicine and pathobiology and corresponding author.

Previous studies have identified mosquitoes and susceptible avian species in North America that can sustain the enzootic transmission of JEV, designating the pathogen as a significant health threat.  JEV can be also maintained in a cycle between mosquitoes and vertebrates, mainly pigs and wading birds.

Earlier research at Kansas State University found that some North American mosquitoes can transmit the virus. 

"This means that all components of the transmission cycle are present in the U.S.," explains Scott Huang, assistant research professor of diagnostic medicine and pathobiology.

While an introductory event involving Japanese encephalitis virus has yet to happen in the U.S., the Kansas State University researchers recommend increased international and possibly local surveillance of the virus through diagnostic methods. They said that Japanese encephalitis virus is both a significant swine and human pathogen that cannot be ignored.

The researchers' study was published recently in Scientific Reports.

The research was conducted at Kansas State University's Biosecurity Research Institute. Support for the research was provided in part through a National Bio and Agro-defense Facility, or NBAF, transition grant from the state of Kansas. Japanese encephalitis virus is a priority pathogen that will be studied at NBAF, a federal facility that is under construction adjacent to the university's Manhattan campus. NBAF will be the nation's foremost animal disease facility.

Other Kansas State University contributors to the study included Amy Lyons, research assistant in diagnostic medicine and pathobiology and a master's student in biomedical science; Victoria Ayers, doctoral student in pathobiology; Susan Hettenbach, research assistant at the Biosecurity Research Institute; Kenneth Burton, program director of the National Agricultural Biosecurity Center at Kansas State University; Stephen Higgs, director of the Biosecurity Research Institute and professor of diagnostic medicine and pathobiology; and Scott McVey, a U.S. Department of Agriculture collaborator and director of the Center for Grain and Animal Health Research in Manhattan.


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