- UY
Introduction : Malaria is a serious health problem in many African countries despite all the efforts already made against this disease. This is due in particular to the repeated use of synthetic insecticides which promotes the rapid expansion of insecticide resistance in mosquitoes there by limiting the effectiveness of vector control interventions against malaria. An alternative approach of mosquito control using plant-based products is vivaciously encouraged. It is in this scope that the insecticidal effect of the essential oil of Piper nigrum on the eggs, larvae and nymphs of Anopheles gambiae was evaluated in laboratory’s conditions.
Methodology : The essential oil of P. nigrum seeds was obtained by hydrodistillation and analyzed by gas phase chromatography (CPG)-mass spectrometry(CPG/SM), then eggs, larvae and pupae of An. gambiae were exposed to the plant oil following the WHO protocol.
Results: The major constituent of the plant oil included caryophylene (19.12%), limonene (9.74%), camphène (8.44%), β-pinene (8.00%), 3-carène (7.04%) and α-pinene (6.32 %). Essential oil of Piper nigrum tested at dose of 3% significant inhibited mosquito eggs hatching in which 2, 3 and 5% mosquito egg hatches were recorded after 24, 48 and 72 h post-exposure. Applied at 0.5%, 100% mortality of 1st and 2nd instar larvae was registered while total mortality of 3rd and 4th instar larvae were recorded at concentration of 0.7% and 0.9%, respectively. LC50 values registered for 1st, 2nd, 3rd, and 4th instar larvae were respectively 0.37, 0.38, 0.40 and 0.42% after 24 h and 0.29, 0.29, 0.35 and 0.25% after 48 hours. Tested at the concentration of 3%, a very low adult emergence (only 3%) from pupae was observed after 72 h post-exposure.
Conclusion: From these results, it appears that the essential oil of Piper nigrum seeds has ovicidal, larvicidal and “nymphocidal” properties on the aquatic stages of Anopheles gambiae and should be tested on field strains of An. gambiae to gain a real insight into its effectiveness.
Keywords: Malaria, essential oil, insecticide, Piper nigrum, Anopheles gambiae.
