Affiliations :
      * Division of Medical Entomology, Department of Medical Sciences
      **Nagasaki University, Japan

Source:
      Ministry of Public Health Journal 1995; 14(7-9): 70-81

Language:
      Thai with English abstract

Abstract:
      Epidemic of Japanese encephalitis (JE) has occurred yearly in Thailand since 1969 with greatly different incidences of human cases in various regions. The present study on the dynamics of JE-vector mosquitoes is aimed principally at the elucidation of the reason for different incidences of human cases in various regions of Thailand. The surveys by light traps were carried out every month during January 1992 - December 1994 in 6 provinces from 4 regions of Thailand, which JE incidences were different. The results showed that Culex tritaeniorhynchus,   the principle JE vector was the dominant spicies in the high JE incidence areas (Chiangrai, Uttaradit), the maximum density of vector was 20,453 No./trap-night and had peak of density in the third quarter of the year (July-September). The pattern of population dynamics showed the same seasonal fluctuation as the incidence of encephalitis. In moderate JE incidence areas (Ayutthaya, Suratthani), Culex gelidus,   the secondary JE vector was the dominant species. The maximum density of vector was 19,029 No./trap-night and had a peak in the third and forth quarter of the year (July-December). In low JE incidence areas (Khonkaen, Chumphon), Culex tritaeniorhynchus   was the same dominant species as the high incidence areas but the pattern of population dynamics was irregular and maximum density was rather low, 7,786 No./trap-night. During the study the number of JE vector had decreased in most areas (p<0.1) especially in Chiangrai.