Kimutai Albert, Ngeiywa Moses, Mulaa Margaret, Njagi Peter G N, Ingonga Johnstone, Nyamwamu Lydia B, Ombati Cyprian, Ngumbi Philip
Department of Biological Sciences, University of Kabianga, P.O. Box 2030-20200, Kericho, Kenya.
University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya.
BMC Res Notes. 2017 Feb 15;10(1):98. doi: 10.1186/s13104-017-2396-0.
The sandfly, Phlebotomus duboscqi is a vector of zoonotic cutaneous leishmaniasis (ZCL) that is an important public health problem in Eastern Africa. Repellents have been used for protection of humans against vectors of ZCL and other vectors that transmit killer diseases including malaria, Rift Valley fever, dengue, and yellow fever. The repellent effects of different doses of the essential oils from the lemon grass, Cymbopogon citratus and Mexican marigold, Tagetes minuta were evaluated in a two-chamber bioassay against 3- to 7-day-old unfed females of P. duboscqi in the laboratory. The results were compared with those that were obtained when test animals were treated with an equivalent dose of diethyl-3-methylbenzamide, which is a repellent that is commonly used as a positive control.
Overall, percentage repellency increased with increasing doses of the essential oils while biting rates decreased with increasing concentrations of the oils. Further, the oil of C. citratus was more potent than that of T. minuta with regard to protection time and biting deterrence. The effective doses at 50% (ED) and at 90% (ED) for the oil of C. citratus, were 0.04 and 0.79 mg/ml, respectively. Those of the oil of T. minuta were 0.10 and 12.58 mg/ml. In addition, the percentage repellency of 1 mg/ml of the essential oils of C. citratus and T. minuta against sandflies was 100% and 88.89%, respectively. A lower dose of 0.5 mg/ml of the oils, elicited 89.13% repellency for C. citratus and 52.22% for T. minuta.
The laboratory tests showed that the essential oils of the two plants were highly repellent to adult sand flies, P. duboscqi. Thus, the two essential oils are candidate natural repellents that can be used against P. duboscqi due to their high efficacy at very low doses, hence, the envisaged safety in their use over chemical repellents. It remains to carry out clinical studies on human subjects with appropriate formulations of the oils prior to recommending their adoption for use against the sandflies.
白蛉（Phlebotomus duboscqi）是动物源性皮肤利什曼病（ZCL）的传播媒介，而ZCL是东非一个重要的公共卫生问题。驱虫剂已被用于保护人类免受ZCL传播媒介以及其他传播致命疾病（包括疟疾、裂谷热、登革热和黄热病）的媒介的侵害。在实验室的双室生物测定中，评估了不同剂量的柠檬草（Cymbopogon citratus）和墨西哥万寿菊（Tagetes minuta）精油对3至7日龄未进食的雌性杜氏白蛉的驱避效果。将结果与用等量的二乙-3-甲基苯甲酰胺处理试验动物时获得的结果进行比较，二乙-3-甲基苯甲酰胺是一种常用作阳性对照的驱虫剂。
总体而言，随着精油剂量的增加，驱避率百分比上升，而叮咬率随着精油浓度的增加而下降。此外，就保护时间和叮咬威慑力而言，柠檬草精油比墨西哥万寿菊精油更有效。柠檬草精油的50%有效剂量（ED50）和90%有效剂量（ED90）分别为0.04和0.79毫克/毫升。墨西哥万寿菊精油的ED50和ED90分别为0.10和12.58毫克/毫升。此外，1毫克/毫升的柠檬草和墨西哥万寿菊精油对沙蝇的驱避率分别为100%和88.89%。较低剂量的0.5毫克/毫升精油，柠檬草的驱避率为89.13%，墨西哥万寿菊为52.22%。
实验室测试表明，这两种植物的精油对成年杜氏白蛉具有高度驱避作用。因此，这两种精油是候选天然驱虫剂，由于它们在极低剂量下具有高效性，因此可用于对抗杜氏白蛉，从而在使用中比化学驱虫剂更具安全性。在推荐将其用于对抗沙蝇之前，仍需对人类受试者使用适当配方的精油进行临床研究。
