Abstract: Objective To understand the changes of Paragonimus metacercaria infection rates of freshwater crabs in Para? gonimus endemic areas and explore the causes in Yongjia County，Zhejiang Province，China. Methods A field investigation was carried out. The freshwater crabs were collected and the metacercaria were separated from the crabs. The infection rates， infectiosi? ties and infection indexes were calculated and the results were vertically compared with the historical findings. The causes of the changes were discussed. Results Compared with those in 1980，the average infection rate in original endemic areas decreased from 59.71% to 21.50%（P < 0.05），while the infection density decreased from 1.09/g to 0.23/g（P < 0.05） . The infection index decreased obviously. In Hesheng Village，it decreased from 4.05 to 0.01 （P < 0.01）， in Wuchi Village，it was from 37.90 to 2.91 （P <0.01）， and in Daruoyan Scinic area， it was from 5.85 to 0.03 （P < 0.01） . Two endemic areas disappeared but two new endemic areas（Sihai Village and Sunshan Village）were found，and in Sunshan Village，the metacercaria infection rate was 100%，the in? fection density and infection index were 21.30/g and 3 402.68 respectively，which meant it was a super high endemic focus. Con? clusion The Paragonimus metacercaria infection rate in crabs is lower than before in Yongjia County，but some super high epi? demic focus of paragonimiasis still exists. Therefore， we still should strengthen the control measures.

Key words: Paragonimus； Metacercaria；Fresh water crab； Yongjia County

摘要： 目的 目的 了解永嘉县各流行区淡水溪蟹卫氏并殖吸虫囊蚴感染率的变化并探讨其原因。方法 方法 实地考察永嘉县 各卫氏并殖吸虫病流行区， 采集淡水溪蟹进行囊蚴分离， 计算囊蚴感染率、 感染度和感染指数， 并与历史调查结果进行纵 向比较， 分析引起变化的原因。结果 结果 与1980年比较， 老流行区平均囊蚴感染率由59.71%下降至21.50%， 感染度由1.09 个/g下降至0.23个/g， 两者均有大幅度下降 （P均< 0.05）。感染指数 （i） 明显下降， 其中鹤盛村由4.05降为0.01， 五尺村由 37.90降为2.91， 大若岩风景区由5.85降为0.03 （P均< 0.01）。消失流行区2个， 新增四海山和大岙乡孙山村2个流行区。其 中大岙乡孙山村囊蚴感染率为100%， 感染度21.30个/g， 感染指数为3 402.68， 为超高度疫源地。结论 结论 永嘉县淡水溪蟹卫 氏并殖吸虫囊蚴感染率已明显下降， 但仍有新发超高度疫源地的存在， 需引起警惕， 防止卫氏并殖吸虫病在局部地区复 燃。

关键词: 卫氏并殖吸虫； 囊蚴； 淡水溪蟹； 永嘉县