Kanojia P C, Shetty P S, Geevarghese G
National Institute of Virology (ICMR), Pune, India.
Indian J Med Res. 2003 Mar;117:104-10.
BACKGROUND & OBJECTIVES: Japanese encephalitis (JE) virus is an important cause of viral encephalitis in Gorakhpur district, UP. The area has been experiencing outbreaks of JE since 1978. No in-depth longitudinal studies have been carried out on the mosquito species, particularly JE vectors prevailing in the area. Entomological studies were carried out in the district in order to determine the species composition, relative abundance and seasonal prevalence of mosquitoes in relation to the incidence of JE.
Three JE affected villages were selected as study sites. Weekly visits were made to each village and mosquito collections were made in and around the pig enclosures and cattle sheds with the help of mouth aspirators, aided by flash lights at dusk.
The overall mosquito population showed a bimodal pattern with short and tall peaks during March and September respectively. Based on the elevated density and infection with JE virus, Culex tritaeniorhynchus has been considered responsible for causing epidemics in the area. Cx. pseudovishnui, Cx. whitmorei, Cx. gelidus, Cx. epidesmus, Anopheles subpictus, An. peditaeniatus and Mansonia uniformis are suspected to have played some role in the epidemiology of JE in the region. JE cases were reported between August and November with the peak in October when the vectors population, particularly Cx. tritaeniorhynchus was on the decline.
INTERPRETATION & CONCLUSION: The results of the study indicate that Cx. tritaeniorhynchus, the most likely vector of JE together with other known vector species remained more active during the period of paddy cultivation. Integrated antilarval measures before the beginning of paddy irrigation may check the breeding of JE vectors in the paddy fields. It may prove beneficial in reducing the vector population during the JE transmission season.
日本脑炎（JE）病毒是印度北方邦戈勒克布尔地区病毒性脑炎的一个重要病因。自1978年以来，该地区一直有日本脑炎疫情爆发。尚未对该地区流行的蚊种，尤其是日本脑炎传播媒介进行深入的纵向研究。为了确定与日本脑炎发病率相关的蚊虫种类组成、相对丰度和季节流行情况，在该地区开展了昆虫学研究。
选择三个受日本脑炎影响的村庄作为研究地点。每周走访每个村庄，在黄昏时借助手电筒，用吸蚊器在猪圈和牛棚内外采集蚊子。
总体蚊虫数量呈现双峰模式，分别在3月和9月出现短峰和高峰。基于日本脑炎病毒的高感染密度，三带喙库蚊被认为是该地区疫情的传播媒介。伪杂鳞库蚊、惠氏库蚊、环带库蚊、骚扰库蚊、伪威氏按蚊、多斑按蚊和棕尾库蚊被怀疑在该地区日本脑炎的流行病学中发挥了一定作用。日本脑炎病例报告于8月至11月之间，10月达到高峰，此时传播媒介数量，尤其是三带喙库蚊数量正在下降。
研究结果表明，三带喙库蚊作为日本脑炎最可能的传播媒介，与其他已知传播媒介物种在水稻种植期间仍较为活跃。在水稻灌溉开始前采取综合灭幼虫措施，可能会抑制稻田中日本脑炎传播媒介的繁殖。这可能有助于在日本脑炎传播季节减少传播媒介数量。
