Efficacy of volatile oils from some medicinal plants on Culex quinquefasciatus repellency
Bandid Mangkit¹ Vichit Pipigool¹ Watcharee Khunkitti² Weerayutt Daenseekaew¹

Department of Parasitology, Faculty of Medicine, KKU¹. , Department of Phamarceutical Technology, Faculty of Phamarceutical Science, KKU.²

Abstact

Background : Few studies on the repellency effect of volatile oils from medicinal plants on Cx. quinquefasciatus, a night-biting mosquito have been carried out. In this study, we investigated the effect repellent of the volatile oils from medicinal plants on repellency of Culex.

Objective : To study efficacy of volatile oils from 3 medicinal plants : Zingiber officinalle (Ginger), Citrus hystrix (Kaffir lime) and Ocimum americanum (Hairy basil).

Design : Experimental laboratory research.

Setting : Cx. quinquefasciatus were bred in the laboratory of Department of Parasitology, Faculty of Medicine, KKU. The volatile oils of 3 medicinal plants were obtained by Steam distillation, from the Department of Phamarceutical Technology, Faculty of Phamarceutical Science, KKU.

Outcome measurement : The method recommended by The Thai Industrial Standards Institute, Ministry of Industry, Thailand (2529) was used in this study. The Culex repellent efficacy was expressed as protection time on human bait. The repellent effects on oil concentrations as well as the oils obtained from 3 medicinal plants were investigated.

Results : At 100%, 50%, 25% and 10 % concentration of Ginger oil could protect for 5.13, 3.75, 3.58 and 2.38 hrs., respectively. Kaffir lime oil could protect Culex for 2.67, 2.33, 1.75 and 1.25 hrs., respectively and Hairy basil oil could protect for 4.5, 4.21, 2.96 and 2.04 hrs., respectively.

Conclusions : Except at 10% and 25% of Kaffir lime oil, the studied oils at all concentrations were able to protect mosquito bites more than 2 hrs. with dose dependence . Ginger oil appears to be the most effective Culex repellent.