Epidemio-entomological survey of Japanese encephalitis in Korea

, Baik, D H; , Joo, C Y

doi:1991.29.1.67

Korean J Parasito > Volume 29(1):1991 > Article

Original Article


Korean J Parasitol. 1991 Mar;29(1):67-85. English. Published online Mar 20, 1994. http://dx.doi.org/10.3347/kjp.1991.29.1.67
Copyright © 1991 by The Korean Society for Parasitology


Epidemio-entomological survey of Japanese encephalitis in Korea
D H Baik and C Y Joo
Department of Parasitology, School of Medicine, Keimyung University, Taegu 700-310, Korea.


Abstract
In order to determine the seasonal prevalence and population dynamics of Culex tritaeniorhynchus in relation to the epidemics of Japanese encephalitis, and ecology of these vector mosquito in Kyungpook Province, Korea, studies were conducted during the period of 7 years from 1984 to 1990. Cx. tritaeniorhynchus first collected in June between 4th and 28th, and trapped in large numbers during the period from mid-August to early September, showed a simple sharply pointed one-peaked curve. There was a gradual decrease from mid-September, with a very small number of them collected until early October in every year. The average number of Cx. tritaeniorhynchus rapidly decreased after 1985, and the number became particularly low in 1989. The highest population density, which was observed in August during the initial three years, was found to be delayed in the following years, accompanied by a decrease in the number of mosquitoes. In the trend of nocturnal activity of Cx. tritaeniorhynchus, with oncoming darkness they become very active, gradually decreasing in activity toward mid night, but slightly increasing toward dawn. The immature stages of Cx. tritaeniorhynchus were first found in rice fields contributing to peak adult densities in mid-July. The highest average densities of Cx. tritaeniorhynchus was 14,900 per m² on mid-August 19th. The larval Cx. tritaeniorhynchus showed high resistance levels and resistance ratios against 5 organophosphorus compounds. In the adult horizontal life table characteristics of Kyungsan colonies of Cx. tritaeniorhynchus under insectary conditions, life expectancy was 28.3 days for males and 59.8 days for females. The net reproductive rate was 7.8 and generation time was 25.6 days.

Figures


	Fig. 1 Surveyed areas (•) in Kyungpook Province, Korea.


	Fig. 2 Annual prevalence of Culex tritaeniorhynchus as shown in MPI calculated from the data or mosquito collection at 3 stations.

Tables


	Table 1 Monthly maximum and minimum temperature, relative humidity, and total precipitation reported by regional Meteorological Center in Taegu, Korea during 1984 and 1990


	Table 2 Seven Years' observation of the earliest date when Cx. tritaeniorhynchus appeared in Kyungsan county, Kyungpook rovince, together with meteorological data


	Table 3 Date of peak population of Cx. tritaeniorhynchus and meteorological data at that time


	Table 4 Date of disapearance of Cx. tritaeniorhynchus and meteorological data


	Table 5 Seasonal prevalence of Cx. tritaeniorhynchus by the average numbers collected in each trap during seven years in Kyungsan county, Kyungpook Province


	Table 6 Decrease of Cx. tritaeniorhynchus population in successive years after 1984 in correlation with the incidence of Japanese encephalitis


	Table 7 The results of overnight Cx. tritaeniorhynchus collection by light trap in a pigsty and on human bait (1990)


	Table 8 Comparison of total and engorged number of Cx. tritaeniorhynchus collected by light traps at three locations


	Table 9 Monthly fluctuation of total and engorged number of Culex tritaeniorhynchus collected by light traps


	Table 10 Age structures of immature stages of Cx. tritaeniorhynchus in the study area (1990)


	Table 11 Resistance levels and resistance ratios of larval Cx. tritaeniorhynchus exposed to 5 organophosphorus compounds for 24 hours


	Table 12 Effects of mating, association and/or egg deposit on lifespan of Cx. tritaeniorhynchus (1990)


	Table 13 Biological and life tabel characteristics of Kyungsan strain of Cx. tritaeniorhynchus (1990)


	Table 14 The reported average number per trap-night of Cx. tritaeniorhynchus by month in Korea

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