National Reference Laboratory for Japanese encephalitis virus (JEV)
Institute for Novel and Emerging Infectious Diseases
Martin H. Groschup and Ute Ziegler
The Japanese encephalitis virus (JEV), like Dengue-Virus, Yellow fever virus or West Nile fever virus, belongs to the family of Flaviviruses. The genome consists of a single-stranded plus-strand RNA with a size of 11 kb (kilobases). The RNA encodes for 3 structural proteins (capsid-, membrane- and envelope protein) and 7 non-structural proteins (enzymes). The virus can be found in Japan, but also in all temperate and tropical zones of south-east Asiawhere 30.000 to 50.000 human cases are reported each year. Main focuses are rural regions with rice production and pig-breeding, but there are also infections in urban regions of developed Asian countries. Like most arboviruses, Japanese encephalitis is spread by infected mosquitoes. However, a direct transmission between humans is not possible. Domestic animals like horses, pigs and dogs can be infected by the virus, too. More than 95 per cent of human infections proceed without any clinical symptoms, 5 per cent of the cases develop encephalitis (very often with late neurological sequelae). 0, 5 per cent of these cases end fatal.
The NRL could get serum from 6 horses which have been vaccinated with an inactivated JEV-vaccine because of their participation at the Olympic Games in 2008. Firstly, this reference material serves for serological testing of specificity with other Flaviviruses (for example West Nile virus). In future, the material will also be tested for the existence of JEV-antibodies with appropriate serological methods. Moreover, a quantitative real-time RT-PCR assay has been established at the NRL.