Pilot Study on Newly Developed Botanical Larvicides and Repellents against Aedes Mosquitoes in Myanmar

Abstract

Dengue Haemorrhagic Fever (DHF) is one of the major public health problems in Myanmar. There are no effective vaccine and specific drug for DHF and its containment is totally based on vector Aedes mosquito control. Thus the present study was conducted with the general objective of developing innovative environment-friendly vector control tools mainly focusing on the plant sources. The test plants – Caesalpinia pulcherrima Linn. And Ervatamia coronaria (Jacq) Stapf. were locally searched in Magway – central Myanmar, extracted, screened and tested against Ae. Aegypti larvae and adults under the laboratory conditions, and in field trials preceded by animal acute toxicity and skin irritation tests in line with standard procedures and guidelines of WHO and OECD from August through September, 2015. Indepth interviews were undertaken among local residents to evaluate the public acceptance on new control tools. Test plant leaves contained some phytochemicals with larvicidal and repellent properties. LC50 values (95% FCI) of crude ethyl acetate leaf extract larvicides of C. pulcherrima and E. coronaria against Ae. aegypti larvae were 3.21 (2.95 – 3.48) and 4.46 (3.16 – 6.05) mg/l respectively. Their repellent ED50 values (95% FCI) against Ae. aegypti adults were 0.02 (0.01 – 0.03) and 0.01 (0.005 – 0.02) mg/cm2 respectively. Their repellent percentage protection (mean ± SD) was 88.4±13.3 (dose, 1.6 mg/cm2) and 82.1± 6.4 (dose, 0.4 mg/cm2) at 90 min post application respectively. The results of animal acute toxicity and skin irritation tests using test extract/repellents showed the safe use of new control tools by human. In field trials it was found that larval mortality was 100% in minor water containers treated with C. pulcherrima larvicide (dose, 7.2 - 14.4 mg/l) and E. coronaria larvicide (dose, 12.7 – 25.4 mg/l) separately in 24 hr. Their repellent percentage protection (mean ± SD) was 98.3±1.4 (dose, 1.6 mg/cm2) and 97.8± 2.3 (dose, 0.4 mg/cm2) in 90 min respectively. T