昆山市玉山镇原是血吸虫病流行较严重的水网型疫区。1976年达到了基本消灭标准后，坚持反复查灭，已多年未查到钉螺。1991年4月，在监测查螺中在大公村查到有螺条块33个，有螺面积18317m’，钉螺最高密度达25O只／框（每框0．11m勺。该螺区范围广，环境复杂，分布干渠道18条、 Yushan Town, Kunshan City, the original epidemic of schistosomiasis is more serious water network-type epidemic area. After reaching the basic elimination standard in 1976, it insisted on repeatedly checking and extinguishing it and had not detected the snail for many years. In April 1991, a total of 33 snail strips were found in Dagang Village, with a snail area of ​​18317m ’and a maximum density of 25O snails per box (0.11m spoon per box) Complex environment, distribution of dry channel 18,