Mashauri Fabian M, Manjurano Alphaxard, Kinung'hi Safari, Martine Jackline, Lyimo Eric, Kishamawe Coleman, Ndege Chacha, Ramsan Mahdi M, Chan Adeline, Mwalimu Charles D, Changalucha John, Magesa Stephen
National Institute for Medical Research, Mwanza Centre, Mwanza, Tanzania.
Research Triangle Institute (RTI) International, Dar es salaam, Tanzania.
PLoS One. 2017 May 10;12(5):e0176982. doi: 10.1371/journal.pone.0176982. eCollection 2017.
The indoor residual spraying programme for malaria vectors control was implemented in four districts of the Lake Victoria basin of Tanzania namely Ukerewe, Sengerema, Rorya andSerengeti. Entomological monitoring activities were implemented in one sentinel village in each district to evaluate the efficacy of pirimiphos-methyl 300 CS sprayed on different wall surfaces and its impact against malaria vectors post-IRS intervention.
The residual decay rate of p-methyl 300 CS applied at a target dosage of 1g a.i./m2 on thesprayed wall surfaces was monitored for a period of 43 weeks post-IRSusing the WHO cone wall bioassay method. The bioassays were performed by exposing 2-5 days old unfed susceptible female Anopheles gambiae s.s. (Kisumu strain) to sprayed wall surfaces for a period of 30 minutes. In each sentinel village, mosquito collection was carried out by trained community mosquito collectors. Monthly mosquito collections were carried out from 6.00pm to 6.00am using CDC light traps and clay pot methods for indoors host seekingand outdoors resting mosquitoes respectively. Six traps (2 CDC light traps and 4 clay pots) were set per sentinel village per night for28 consecutive days in a moon. PCR and ELISA were used for mosquito species identification and sporozoite detection, respectively.
Based on the WHOPES recommendation, insecticides should have a minimum efficacy of ≥ 80% mosquito mortality at 24 hours post exposure on the sprayed wall surfaces to be considered effective. In this study, p-methyl 300 CS was demonstrated to have a long residual efficacy of 21-43 weeks post-IRS on mud, cement, painted and wood wall surfaces. Numberof anopheline mosquitoes decreased post-IRS interventions in all sentinel villages. The highest numbers ofanopheline mosquitoes were collected in November-December, 38-43 weeks post-IRS. A total of 270 female anopheline mosquitoes were analyzed by PCR; out of which 236 (87.4%) were An. gambiae s.l. and 34 (12.6%) were An. funestus group. Of the 236 An. gambiae s.l.identified 12.6% (n = 34) were An. gambiae s.s. and 68.6% (n = 162) were An. arabiensis. Ofthe 34 An. funestus group indentified 91.2% (n = 31) were An. parensis and 8.8% (n = 3) were An. rivulorum. The overall Plasmodium falciparum sporozoite rate was 0.7% (n = 2,098).
Pirimiphos-methyl 300 CS was found to be effective for IRS in the Lake Victoria basin,Tanzania. P-methyl 300 CShas a long residual efficacy on sprayed wall surfaces and therefore it is effective in controlling principal malaria vectors of An. gambiae s.l and An. funestus which rest on wall surfaces after and before feeding.
坦桑尼亚维多利亚湖盆地的四个区，即乌克雷韦、森盖雷马、罗里亚和塞伦盖蒂实施了室内滞留喷洒疟疾媒介控制项目。在每个区的一个哨点村开展了昆虫学监测活动，以评估喷洒在不同墙面的300克/升甲基嘧啶磷乳油的效果及其在室内滞留喷洒干预后对疟疾媒介的影响。
使用世卫组织锥形墙生物测定法，在室内滞留喷洒后43周内，监测以1克有效成分/平方米的目标剂量施用于喷洒墙面的300克/升甲基嘧啶磷乳油的残留衰减率。生物测定通过将2至5日龄未进食的易感冈比亚按蚊（基苏木品系）雌蚊暴露于喷洒墙面30分钟来进行。在每个哨点村，由经过培训的社区蚊虫采集人员进行蚊虫采集。每月从下午6点至上午6点进行蚊虫采集，分别使用疾控中心诱蚊灯和陶罐法采集室内寻找宿主的蚊虫和室外栖息的蚊虫。每个哨点村每晚设置6个诱捕器（2个疾控中心诱蚊灯和4个陶罐），连续28天。分别使用聚合酶链反应（PCR）和酶联免疫吸附测定（ELISA）进行蚊虫种类鉴定和子孢子检测。
根据世卫组织疟疾防治专家组（WHOPES）的建议，杀虫剂在暴露于喷洒墙面24小时后的蚊虫死亡率应至少达到≥80%，才能被视为有效。在本研究中，300克/升甲基嘧啶磷乳油在室内滞留喷洒后在泥土、水泥、涂漆和木质墙面上显示出21至43周的长期残留效果。在所有哨点村，室内滞留喷洒干预后按蚊数量减少。按蚊数量最多的采集时间为室内滞留喷洒后38至43周的11月至12月。共对270只雌性按蚊进行了PCR分析；其中236只（87.4%）为冈比亚按蚊复合组，34只（12.6%）为嗜人按蚊种群。在鉴定出的236只冈比亚按蚊复合组中，12.6%（n = 34）为冈比亚按蚊指名亚种，68.6%（n = 162）为阿拉伯按蚊。在鉴定出的34只嗜人按蚊种群中，91.2%（n = 31）为帕氏按蚊，8.8%（n = 3）为溪流按蚊。恶性疟原虫子孢子总体感染率为0.7%（n = 2098）。
发现300克/升甲基嘧啶磷乳油对坦桑尼亚维多利亚湖盆地的室内滞留喷洒有效。300克/升甲基嘧啶磷乳油在喷洒墙面上具有长期残留效果，因此对控制在进食前后停歇在墙面的主要疟疾媒介冈比亚按蚊复合组和嗜人按蚊有效。
