Japanese encephalitis (JE), has been known in Korea for many years. The first case was said to be reported in 1935. There were epidemics in 1949 and. During the years -1958-1960, there were about 10,000 reported cases and over 3000 deaths.
JE virus was isolated for the first time from human cases in Korea in 1949, and from mosquitos (Culex tritaeniorhynchus) in 1958.
JE is prevalent throughout Korea. The highest endemic area is in Cholla Pukdo Province which is a plain area where the land is under cultivation-and is therefore suitable for the breeding of C. tritaeniorhynchus. It was also said that in this area there are large numbers of domestic animals which may act as amplifying hosts. In Korea C. tritaeniorhynchus has been regarded as the main, if not the only, vector of JE. Culex pipiens was suspected to -be responsible in urban areas. Anopheles. sinensis was also suspected. Little knowledge on. the bionomics of C. tritaeniorhynchus is available in Korea. For the control of JE, progress in the artificial immunization of the human population against this disease is in its infancy. At present, vector control. seem´ to be the choice. Aerial spraying of insecticides has been. undertaken in Seoul and certain other big cities in Korea for some years. It is doubtful. that any desirable effects could be obtained by this method because adult resting places cannot be covered by aerial spraying and the lush growth of rice during -the mosquito season prevents most of the insecticides from reaching the water. The methods of vector control must therefore be based on a fundamental understanding of the bionomics of the vector species. Certain studies on the vector´s bionomics have been undertaken in Japan- tnd Taiwan and are summarized as follows:
Breeding habitats-mainly in ricefields and marshes, also in swamps, creeks and paddles.
Life cycle-eggs hatch in one day, after being laid; larval stage, 1st: 1 day, 2nd: 1 day. 3rd:. 1-2 days, 4th: 2-3 days pupal stage: 1-2 days
Seasonal. prevalence: peak in- July-August.
Mating-Swarming of males occurs both in mornings and evenings; mating occurs as the` females. fly into the swarm; mating-takes place before or after feeding; some females mate repeatedly as observed in the laboratory.
Oviposition: The majority lay eggs dizri ig 1700 - 0800 hours, with a peak during 2300 - 0100´hours; an average of 200 eggs per egg raft.
Longevity: As observed in the laboratory ´ certain males are able to live -as long. as 29 ´days and females 107 days.
Resting habits: In the daytime a certain number of the´ mosquitos -are found in cowsheds, some in pig styes, but rarely in houses.
Feeding habits: As observed´ with ox bait, the greatest number of the mosquitos feed during the first hour after sunset; more mosquitos ´ are caught from an ox outdoors than from an ox ´ within the cattle shed.
Hibernation: In the adult stage, specimens can be found in caves, wood piles, bamboo piles and chicken houses,
Insecticide susceptibility: LC50 (p. p. m.) : DDT - 0.0036, dieldrin-0.0126, lindane 0.006, malathion - 0.0316.
As mentioned above, little study has been done on the vector aid its bionomics in Korea. It is suggested that investigations may be carried out at Kunsan
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