Epidemiology and Control of Filariasis in Sri Lanka

1.微丝虫病（mf）阳性率和mf密度在Matara的6个村庄开展了检测微丝虫病的血液调查，覆盖约5000人。厚涂片法Mf阳性率分别为：Matotagama州7.03%、Hamugewatta州7.74%、Walgama北部3.27%、Walgama中部4.53%、Walgama南部4.77%，平均阳性率为5.02%。Mf密度约为30.2 / 60ml。丝虫病循环抗原500份血清标本丝虫病抗原筛选结果显示，抗原阳性率比mf阳性率高近2倍。有抗原而无mf的人是一个重要的人群，其流行病学意义有待明确。临床研究象皮病患病率为3.2%。在55岁及以上的人群中，这一比例为6-10%。这种症状是该研究地区迄今为止最大的公共卫生问题。收集临床病例的血清样本进行免疫学研究。部分村庄已开始使用乙基卡马嗪治疗，迄今已有117名mf阳性患者得到治疗。蚊虫研究在该地区采集的18种蚊虫中，致倦库蚊为班氏丝虫病的传播媒介。该蚊近10个月最丰富，室外捕获蚊丝蚴感染率为0.2 ~ 3.3%，室内捕获蚊丝蚴感染率为1.0 ~ 4.2%。比较了氯氰菊酯、高效氯氰菊酯和苯虫威对致倦库蚊的防治效果。药效持续22周，前两种药剂的药效强于恶虫威。

1.Microfilaria (mf) positive rate and mf densityBlood surveys for detecting microfilaraemia were carried out in 6 villages in Matara, covering about 5,000 people. Mf positive rates using the thick smearmethod were 7.03% in Matotagama, 7.74% in Hamugewatta, 3.27% in Walgama North, 5.14% in Walgama, 4.53% in Walgama Central and 4.77% in Walgama South, with the average rate of 5.02%. Mf density/60mul of blood was about 30.2.Filarial circulating antigenScreening of 500 serum samples for the filarial antigen revealed that the antigen positive rate was nearly twice higher than mf positive rate. Those with antigen and without mf constitute an important group of people whose epidemiological significance has to be clarified.3.Clinical studiesThe prevalence of elephantiasis was 3.2%. The rate was 6-10% at age 55 years and upward. The symptom is by far the biggest public health problem in the study area. Serum samples were collected from clinical cases for immunological studies. Treatment with diethylcarbamazine has been started in parts of the villages and so far 117 mf positives have been treated.4.Mosquito studiesOut of 18 species of mosquitoes collected in the area, Culex quinquefasciatus was confirmed as the vector of bancroftian filariasis. This mosquito was most abundant in the past 10 months, and filaria infection rates were 0.2-3.3% for mosquitoes caught outdoor and 1.0-4.2% for those caught indoor.5.Insecticide impregnated curtainsThe efficacy of permethrin, lambdacyhalothrin and bendiocarb against Culex quinquefasciatus was compared. They were effective for 22 weeks, and the former two chemicals showed stronger effect than bendiocarb.