Mere than one thousand cases of Japanese encephalitis has broken out in a year since 1947 except last 2 years.
The fact that encephalitis appears during only summer when the mosquitoes crowd in Korea which has severe cold winter gives us a question where the virus exists during other seasons especially in winter. It is easy to understand cycle between animal and mosquito in the tropic zone where we can find active mosquito action all year around. But in Korea and Japan without complete understanding of overwintering mechanism of the virus the question of the reservoir of the, virus the temperate zone will not be solved.
Results of experiments on the overwintering mechanism of Japanese encephalitis virus in Korea from 1964 to 1970 are as follows.
1. JE virus isolation from mosquitoes other than C. tritaeniorhychus: C. tritaeniorhynchus is the main vector of Japanese encephalitis in Korea like in other countries of Asia. We have repeatedly isolated JE virus from C. tritaeniorhynchus during epidemic seasons. However, we have isolated one strain of JE virus from A vexans in 1965, two strains in 1967, and two strains from A.vexans in 1968 during epidemic seasons. This is the first report on isolation of the virus from mosquitoes other than C. tritaeniorhynchus in Korea.
2. Overwintering mosquitoes: During past 6 years we. tried to collect the overwintering mosquitoes by various methods and collected about 50,499, especially much attention was paid to collect the C. tritaeiorhynchus, the main vector of encephalitis. virus but in vain. There has been two strains of Japanese encephalitis virus isolated from´ the overwintering mosquitoes up to now. One is from Culex pipiens caught in December of 1964 and the other is also Culex pipiens cellected in February of 1965.
3. Experiments With hibernating bats: Up to now we-have collected 202 bats in 1965 and 1966, 379 in 1967, 616 in 1968 and 381 in 1969 (Total 1, 578). Virus. isolation was failed but about 12% of them were proven to have neutralizing antibody to JE virus.
4. JE virus isolation from cold-blooded animals: As. a result of examining 2, 051 snakes from 1965 to 1970 HI antibody to the virus was detected in 40´ per cent of snakes and neutralizing antibody in. 2~3 per cent. It should be noted that encephalitis. virus were isolated from two snakes (E. rufodorsata). One was caught on the 19th of October, 1966 and the other on the 16th of July, 1967.
5. Study on migratory birds: In the springs of 1968, 284 and 1969, 83 numbers of migratory birds were collected but failed to isolate the virus. About 7per cent of them had neutralizing antibody to JE virus. Hypothesis on the reservoir of Japanese encephalitis virus and overwintering mechanism. in Korea based on to our experiments were discussed.
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