AB071. Larvicidal activity of Annona squamosa (Atis) leaves extract on Aedes aegypti

Background: Vector-borne diseases (VBDs), particularly mosquito-borne diseases, pose a substantial threat to the population in the world. Mosquito vector control measures are crucial for preventing dengue by stopping the spread of mosquito populations and enhancing environmental sanitation to improve public health services, but no successful preventive measures have been recorded for dengue vector control. Hence, possible alternatives to chemical larvicides have been explored, including plant alcoholic extracts. The general objective of this study is to determine the larvicidal efficacy of Annona squamosa ethanolic leaf extracts against third instar larvae of Aedes aegypti and the specific were the following: to determine mortality rates of Aedes aegypti larvae, at 2-hour intervals for a total duration of 24 hours, to measure the mean difference in mortality rates of the Aedes aegypti larvae across several Annona squamosa ethanolic leaf extract concentrations versus the positive and negative controls; and to determine the lethal dose 50% (LD₅₀) of Annona squamosa ethanolic leaf extract against Aedes aegypti larvae.

Methods: Three replicates of varying concentrations of Annona squamosa ethanolic extract (i.e., 10%, 40%, and 70%) versus positive (novaluron) and negative controls (tap water) were used to determine larval mortality.

Results: Greatest larval mortality was noted using the 70% concentration (i.e., 24% versus the observed values of 20% and 8%, respectively, for the 40% and 10% ethanolic concentrations). Relative to the controls, the mean differences in the mortality rates of the Aedes aegypti larvae across the leaf ethanolic concentrations were statistically significant (i.e., P value <0.05). There was an increasing trend in larval mortality over time, but LD₅₀ was not achieved.

Conclusions: This epidemiologic experiment showed a significant difference using the experimental intervention and controls, as it displayed the mean difference in mortality across the various ethanolic leaf extract concentrations, compared to positive and negative controls. The proportion of Aedes aegypti larval death at 2-hour intervals over 24 hours showed that the mortality rate of larvae generally increased over time. Although the study did not reach the LD₅₀ due to the short period of observation (i.e., 24 hours only), Annona squamosa leaf extract still had 24% larval death in the study. Hence, the different Annona squamosa ethanolic leaf extracts could be used as alternative botanical larvicides against Aedes species.

Keywords: Aedes aegypti mosquito; Annona squamosa; larvicidal activity