Loke S R, Andy-Tan W A, Benjamin S, Lee H L, Sofian-Azirun M
Institute of Biological Sciences, Faculty of Science, Universiti Malaya, 50603 Kuala Lumpur, Malaysia.
Trop Biomed. 2010 Dec;27(3):493-503.
The susceptibility status of field-collected Aedes aegypti (L.) from a dengue endemic area to Bacillus thuringiensis israelensis (Bti) and temephos was determined. Since August 2007, biweekly ovitrap surveillance (OS) was conducted for 12 mo in 2 sites, A & B, in Shah Alam, Selangor. Site A was treated with a Bti formulation, VectoBac® WG at 500 g/ha, from December 2007 - June 2008 while Site B was subjected to routine dengue vector control activities conducted by the local municipality. Aedes aegypti larvae collected from OS in both sites were bred until F3 and evaluated for their susceptibility. The larvae were pooled according to 3 time periods, which corresponded to Bti treatment phases in site A: August - November 2007 (Bti pre-treatment phase); December 2007 - June 2008 (Bti treatment phase); and July - September 2008 (Bti post-treatment phase). Larvae were bioassayed against Bti or temephos in accordance with WHO standard methods. Larvae collected from Site A was resistant to temephos, while incipient temephos resistant was detected in Site B throughout the study using WHO diagnostic dosage of 0.02 mg/L. The LC50 of temephos ranged between 0.007040 - 0.03799 mg/L throughout the year in both sites. Resistance ratios (LC50) indicated that temephos resistance increased with time, from 1.2 - 6.7 folds. The LC50 of Ae. aegypti larvae to Bti ranged between 0.08890 - 0.1814 mg/L throughout the year in both sites, showing uniform susceptibility of field larvae to Bti, in spite of Site A receiving 18 Bti treatments over a period of 7 mo. No cross-resistance of Ae. aegypti larvae from temephos to Bti was detected.
测定了从登革热流行地区野外采集的埃及伊蚊对以色列芽孢杆菌（Bti）和双硫磷的易感性状况。自2007年8月起，在雪兰莪州莎阿南的A和B两个地点进行了为期12个月的双周诱蚊产卵器监测（OS）。2007年12月至2008年6月，A地点用500克/公顷的Bti制剂VectoBac® WG进行处理，而B地点则由当地市政当局开展常规登革热媒介控制活动。从两个地点的诱蚊产卵器监测中收集的埃及伊蚊幼虫饲养至F3代，并评估其易感性。幼虫根据3个时间段进行合并，这与A地点的Bti处理阶段相对应：2007年8月至11月（Bti预处理阶段）；2007年12月至2008年6月（Bti处理阶段）；以及2008年7月至9月（Bti处理后阶段）。按照世界卫生组织的标准方法对幼虫进行Bti或双硫磷生物测定。从A地点收集的幼虫对双硫磷具有抗性，而在整个研究过程中，使用世界卫生组织诊断剂量0.02毫克/升，在B地点检测到初期双硫磷抗性。两个地点全年双硫磷的半数致死浓度（LC50）介于0.007040 - 0.03799毫克/升之间。抗性比率（LC50）表明双硫磷抗性随时间增加，为1.2 - 6.7倍。两个地点全年埃及伊蚊幼虫对Bti的LC50介于0.08890 - 0.1814毫克/升之间，表明野外幼虫对Bti具有一致的易感性，尽管A地点在7个月内接受了18次Bti处理。未检测到埃及伊蚊幼虫对双硫磷和Bti的交叉抗性。
