Encephalitis and retarded growth of chicks caused by Sitiawan virus, a newisolate belonging to the genus Flavivirus

A new virus named Sitiawan virus (SV) was isolated from sick broiler chicks in chicken embryos. The virus replicated well with cytopathogenic effect ( CPE) in the chicken B-lymphocyte cell line LSCC-BK3. The virus was an envel oped RNA virus of approximately 41 nm in size with hemagglutinating activit y (HA) to goose erythrocytes. It was cross-reactive with Japanese encephali tis virus (JEV), a member of flaviviruses by HA inhibition tests but not by cross-virus neutralization tests. The cDNA fragment of NS5 gene was amplif ied with primers corresponding to NS5 gene of flaviviruses. The nucleotide sequences were 92% homologous to Tembusu virus, a member of the mosquito-bo rne virus cluster of the genus Flavivirus. In cross-neutralization tests wi th Tembusu virus, antiserum to SV did not neutralize Tembusu virus, and ant iserum to Tembusu virus neutralized more weakly to SV than against homologo us virus. These results indicate that SV is a new virus which can be differ entiated serologically from Tembusu virus but is otherwise similar with res pect to nucleotide sequence. The virus causes encephalitis, growth retardat ion, and increased blood glucose levels in inoculated chicks.