|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1998 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1997 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1996 : ¥700,000 (Direct Cost : ¥700,000)
1. Mosquito survey were made on Osaka Pref, Okayama Pref., Kanagawa Pref., Thttori Pref, Tohoku District of Japan and Ussuriisk, USSR from 1996 to 1998.
2. The decrease of incidence of malaria and Japanese encephalitis in recent years is mainly due to the decrease of the vector mosquitoes (Anopheles sinensis and Culex Iritaeniorhynchus), which is a secondary result of modernization of the agricultural style. Nowadays. ricefields have small amounts of water due to technology which controls the management of intermittent water supply, new varieties of rice have been deveIoped to shorten the period of cultivation, and pesticides are extensively used. Thes facts have transformed the ricefields into inadequate places for mosquito breeding.
3. At present the phenomena of retrocession of the northern species and northing of the southern species are not remarkable.
4. The tolerance to temperature was tested with Stegomyia mosquitoes at 15- 30 ﾟC (10L : 14D) in laboratory. They showed appreciable tolerance to low temperature. These findings suggest the possibility of the distribution of vector mosquito of dengu fever in wide areas in Japan in the near future.