Institut Pierre Richet (IPR), Bouaké, Côte d'Ivoire.
MIVEGEC, IRD, CNRS, Université de Montpellier, Montpellier, France.
Malar J. 2019 Feb 26;18(1):55. doi: 10.1186/s12936-019-2687-0.
Biotic and abiotic factors have been reported to affect the larvicidal efficacy of Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus (Bs), although the extent to which they are affected has been poorly documented. This paper studies the effect of sunlight exposure on the efficacy of a new larvicide formulation based on both Bti and Bs, herein after referred to as BTBSWAX, applied against two different larval stages.
The emergence of inhibition exhibited by BTBSWAX at three different dosages (1 g/m, 1.5 g/m, and 2 g/m) was monitored under semi-field conditions using a total of 32 containers comprising 16 that were covered and 16 that were uncovered. Two experiments were conducted using first- and second-instar larvae of Anopheles gambiae, respectively.
BTBSWAX at 2 g/m in covered containers exhibited high emergence inhibition (> 80%) when larvae were exposed from 1st instar on day-6 post-treatment, whereas the emergence inhibition was only 28% in uncovered containers. For larvae exposed from 1st instar on day-12 post-treatment, the emergence inhibition was moderate (70%) in covered containers but was low (< 20%) in uncovered containers. For larvae exposed from 2nd instar on day-10 post-treatment, the emergence inhibition was moderate (31%) in covered containers but was very low (< 10%) in uncovered containers. Moreover, the residual efficacy of BTBSWAX was markedly affected by environmental stresses, including sunlight exposure (Hazard ratio (HR) = 0.12, p < 0.001 and HR = 0.63, p = 0.033 for BTBSWAX at 2 g/m against 1st and 2nd instar larvae, respectively).
These findings emphasize the impact of environmental variables (e.g., sunlight exposure) on the residual efficacy of Bti and Bs biolarvicides in the field. They hence highlight the need to take these factors into account for larvicide formulation development processes. Moreover, studies of the ecology of Anopheles larvae in targeted areas are also crucial for the integration of larval control strategies into malaria transmission plans devised by national malaria control programmes of endemic countries.
生物和非生物因素已被报道会影响苏云金芽孢杆菌以色列亚种（Bti）和球形芽孢杆菌（Bs）的杀幼虫效果，尽管它们受影响的程度记录不佳。本文研究了阳光照射对一种新型基于 Bti 和 Bs 的杀幼虫剂制剂效力的影响，该制剂以下简称 BTBSWAX，应用于两种不同的幼虫阶段。
在半野外条件下，使用总共 32 个容器（其中 16 个有盖，16 个无盖）监测 BTBSWAX 在三个不同剂量（1 g/m、1.5 g/m 和 2 g/m）下的抑制效果。使用按蚊的一龄和二龄幼虫分别进行了两项实验。
在有盖容器中，当幼虫从第 1 龄开始在处理后第 6 天暴露时，BTBSWAX 在 2 g/m 的浓度下表现出高的出蛹抑制率（>80%），而在无盖容器中的出蛹抑制率仅为 28%。对于从第 1 龄开始在处理后第 12 天暴露的幼虫，在有盖容器中的出蛹抑制率为中等（70%），但在无盖容器中则很低（<20%）。对于从第 2 龄开始在处理后第 10 天暴露的幼虫，在有盖容器中的出蛹抑制率为中等（31%），但在无盖容器中则非常低（<10%）。此外，BTBSWAX 的残留效果明显受到环境压力的影响，包括阳光照射（BTBSWAX 在 2 g/m 时对一龄和二龄幼虫的危害比（HR）分别为 0.12，p<0.001 和 HR=0.63，p=0.033）。
这些发现强调了环境变量（例如阳光照射）对田间 Bti 和 Bs 生物杀幼虫剂残留效果的影响。因此，它们强调了在杀幼虫剂制剂开发过程中需要考虑这些因素。此外，在目标地区对按蚊幼虫生态学的研究对于将幼虫控制策略纳入疟疾流行国家国家疟疾控制规划制定的疟疾传播计划也至关重要。
