O-65 Evaluation of the acute and subacute toxicity of Myristica fragrans essential oil against Aedes aegypti mosquitoes

Methods: The hydro-distilled essential oil of M. fragrans was evaluated against adult Aedes aegypti (Rockefeller) mosquitoes using blood-feeding and Centers for Disease Control and Prevention (CDC) bottle bioassays. Adult survival was assessed in both assays following exposure to varying concentrations of the oil. The sublethal effects of the oil were examined by exposing third instar (L3) larvae to the LC10 (1.58 ppm) and LC50 (7.179 ppm) concentrations of the essential oil and subsequently monitoring larval survival, pupation, adult emergence and adult longevity. Mortality and survival outcomes were recorded at defined time points using modified standard protocols. Survival curves were compared using the log-rank (Mantel-Cox) test and bar charts analyzed by one-way ANOVA followed by Dunnett’s test.

Results: Myristica fragrans essential oil reduced adult survival to 68.3% and 53.3% at 100 and 1000 ppm, respectively in the blood feeding assay. In the CDC bioassay, 100% knockdown of mosquitoes was achieved within 60 minutes at most of the tested concentrations. However, the 24-hour mortality only reached a maximum of 64.4% at the highest tested concentration of 1000 ppm, indicating an incomplete progression from knockdown to death. Sublethal exposure at the LC50 (7.179 ppm) concentration caused a significant decrease in larval survival at 24 hours but did not have any significant effect on pupation or adult emergence among surviving individuals. Notable, adult survival was significantly reduced to 58.8% in mosquitoes originating from LC50 treated L3 larvae (p<0.0004).

Conclusion: Jamaican M. fragrans essential oil possesses promising acute toxicity as well as subacute toxic effects against Ae. aegypti Rockefeller mosquitoes. However, further investigations using field Ae. aegypti and mechanistic studies are needed to determine the suitability of the oil as a potential control agent.