苑柚位于开封东南,海拔72.5米,地下水位高程约70米,多为沙质土地;袁寨村位于开封与兰考之间,距苑柚40华里,地势低洼,属盐碱洼地,易遭内涝.两处多以水井灌溉,灌溉井棋布在村周围的田野内.1963年秋季,该地曾因连降大雨引起疟疾暴发流行。笔者在进行流行病学调查时,发现灌溉井内有中华按蚊幼虫的孳生,为了 Court grapefruit is located in Kaifeng southeast, 72.5 meters above sea level, the elevation of about 70 meters of groundwater level, mostly sandy land; Yuan Zhaicui is located between Kaifeng and Lankao, 40 miles from the garden pomelo, low lying, is salinization depression, vulnerable to waterlogging Two more were irrigated with wells, and the well was drained into the fields around the village. In the autumn of 1963, the area was hit by heavy rains causing a malaria outbreak. During the epidemiological investigation, I found that there is breeding of larvae of Anopheles sinensis in irrigation wells. In order to