Abstract:
Japanese encephalitis virus (JEV), the most important etiology of encephalitis, is a
zoonotic disease transmitted by mosquitoes to domestic and wild animals in most countries,
from eastern Asia to India. The main vectors in Thailand are Cx. tritaeniorhynchus, Cx.
gelidus and Cx. fuscocephala. The domestic pig is an effective amplifying host. There are 4
distinct genotypes of JEV; genetic variations occur among strains from different time periods
in the same region.
The purpose of study was to perform JEV strain and transmission surveillance from
mosquito vectors, domestic pigs and potential hosts from different regions in Thailand in the
years 2002-4. The JEV isolates obtained were sequenced on prM and envelope protein region
for their genetic relationships. Recently isolated JEV strains were used to evaluate their
immunology properties against sera of child vaccinees immunized with licensed inactivated
mouse brain derived JE vaccine.
One JEV isolate from Cx. quinquefasciatus in Phuket Province was a new scientific
finding. A blood meal study done with Cx. quinquefasciatus showed a preference for humans.
This mosquito could be a potential vector for human. Another isolate another JEV strain was
also isolated from Cx. tritaeniorhynchus in Ratchaburi province.
Using a pig sentinel, 10 JEV strains were isolated from Nakhon Pathom (N = 2), Khon
Kaen (N = 5) and Chumphon Province (N= 3).
An amplification host in lizard, was also include investigated.
Twelve JEV were analyzed at the prM and envelope protein region, all belonged to
genotype I as reported in Thailand from 1972 to 1993.
Evaluation of the neutralizing antibody characteristics of sera obtained from vaccinees
immunized with inactivated mouse brain derived JE vaccine revealed 63% seroconversion rate.