Yalla Nick O, Kosgei Jackline, Mechan Frank, McDermott Daniel P, Polo Brian, Omondi Seline, Omukunda Elizabeth, Ochomo Eric
Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
Department of Biological Sciences, Masinde Muliro University of Science and Technology, Kakamega, Kenya.
PLoS One. 2025 Jul 3;20(7):e0315472. doi: 10.1371/journal.pone.0315472. eCollection 2025.
Attractive Targeted Sugar Baits (ATSBs) effectively target Anopheles mosquitoes in semi-arid, low-humidity climates. However, high humidity encourages mould growth on ATSB surfaces, and its effect on the efficacy of ATSBs against malaria vectors is yet to be determined. This study explored how mould growth affects the performance of ATSB version 1.2 by comparing mouldy stations from exposed environments to non-mouldy stations from protected settings through laboratory bioassays on the local malaria vector, Anopheles arabiensis.
One hundred ATSB stations were deployed in Asembo, Rarieda-Subcounty, Siaya County Six samples, consisting of three mouldy from exposed locations and three non-mouldy from protected locations were collected monthly for laboratory bioassays. These were tested alongside three new laboratory-kept ATSBs and two negative controls (water only and 77% sugar solution with water) to assess mosquito feeding and mortality over 48 hours.
This study found that after 12 months of outdoor exposure, the mouldiest ATSBs from exposed locations showed a non-significant reduction in Anopheles arabiensis feeding rates compared to the least mouldy ATSBs from protected locations 57.42% (95% CI: 45.64-68.85) vs. 74.40% (95% CI: 64.56-82.50), (P = 0.062) respectively. Mosquito mortality significantly declined on mouldy ATSBs compared to laboratory controls 95.35% (95% CI: 92.23-97.48) vs. 98.70% (95% CI: 97.87-99.30), (P = 0.002) respectively. In contrast, protected (non-mouldy) ATSBs showed only a slight reduction in mortality compared to controls 95.94% (95% CI: 90.42-97.46) vs. 98.91% (95% CI: 97.67-99.60) respectively (P = 0.009).
This study provides evidence that environmental exposure post-deployment slightly reduced the efficacy of ATSBs in controlling Anopheles arabiensis, particularly beyond the recommended 6-month period. Although mould may have contributed to this reduction over 12 months, no significant difference was found between mouldy and non-mouldy ATSBs. However, mould invasion and community concerns highlight the need to replace mouldy stations to maintain effectiveness and safety.
有吸引力的靶向糖饵（ATSBs）在半干旱、低湿度气候条件下能有效靶向按蚊。然而，高湿度会促使ATSBs表面滋生霉菌，其对ATSBs对抗疟疾媒介效果的影响尚待确定。本研究通过对当地疟疾媒介阿拉伯按蚊进行实验室生物测定，比较暴露环境中的发霉站点与受保护环境中的未发霉站点，探讨霉菌生长如何影响1.2版ATSBs的性能。
在西阿亚县拉里埃达次县的阿森博部署了100个ATSB站点。每月收集六个样本，包括三个来自暴露地点的发霉样本和三个来自受保护地点的未发霉样本，用于实验室生物测定。将这些样本与三个新的实验室保存的ATSBs以及两个阴性对照（仅水和含77%糖的水溶液）一起进行测试，以评估48小时内蚊子的取食和死亡率。
本研究发现，在户外暴露12个月后，与受保护地点霉菌最少的ATSBs相比，暴露地点霉菌最严重的ATSBs上阿拉伯按蚊的取食率下降不显著，分别为57.42%（95%置信区间：45.64 - 68.85）和74.40%（95%置信区间：64.56 - 82.50），（P = 0.062）。与实验室对照相比，发霉的ATSBs上蚊子的死亡率显著下降，分别为95.35%（95%置信区间：92.23 - 97.48）和98.70%（95%置信区间：97.87 - 99.30），（P = 0.002）。相比之下，受保护（未发霉）的ATSBs与对照相比死亡率仅略有下降，分别为95.94%（95%置信区间：90.42 - 97.46）和98.91%（95%置信区间：97.67 - 99.60）（P = 0.009）。
本研究提供的证据表明，部署后环境暴露会略微降低ATSBs控制阿拉伯按蚊的效果，尤其是超过推荐的6个月期限后。虽然霉菌可能在12个月内导致了这种效果下降，但发霉和未发霉的ATSBs之间未发现显著差异。然而，霉菌入侵和社区担忧凸显了更换发霉站点以维持有效性和安全性的必要性。
