Residual effect of Bacillus thuringiensis var israelensis in the control of Aedes aegypti in Honduras

Abstract

Introduction: Aedes aegypti is the main vector responsible for the transmission of dengue fever, chikungunya fever and Zika. Honduras has a high morbidity burden secondary to these arboviruses. The bacteria from soil Bacillus thuringiensis var israelensis (Bti) has been used to control Ae. Aegypti. Studies are needed to describe and monitor those variables that influence its effectiveness. The study aim was to determine the impact of water renewal on the residual effect of Bti on the control of Aedes aegypti in Tegucigalpa, Honduras in 2015. Methods: An experimental study was conducted. The units of analysis were larvae of stages III and IV of Aedes aegypti, collected in Tegucigalpa from February to April of 2015. Two different doses of Bti (2.5 mg / L and 5 mg / L) were analyzed in containers with three types of water change (no change, every 2 days and every 7 days). Four replicates were made with Bti and 4 controls for each dose analyzed in the bioassays during a period of 64 days. Results: The higher the water renewal, the lower the Bti residual effect. Mortality remained above 90% for 13 days for all different doses and frequency of replacement. Conclusion: Our data reinforce that water exchange, such as occurs in domestic scenarios, has a negative influence on the residual effect of Bti. It is important to keep in mind this evidence when using Bti as a vector control strategy.