Evaluation of an ivermectin-based attractive targeted sugar bait (ATSB) against Aedes aegypti in Tanzania.

Abstract

Background The control of vector borne arboviral diseases such as Dengue is mainly achieved by reducing human-vector contact and controlling the vectors through source reduction and environmental management. These measures are constrained by labour intensity, insecticide resistance and pro-active community participation. The current study intended to develop and test an ivermectin-based attractive-targeted sugar bait (ATSB) against <i>Aedes aegypti</i>. Methods The 48hour lethal concentration (LC90) of ivermectin against <i>Ae. aegypti</i> was determined through serial dilution experiment where five 30cm x 30cm x 30cm cages were set; into each, a 10% sugar solution treated with ivermectin were introduced. 40 <i>Ae. aegypti</i> were released into each cage and observed for mortality after 4, 8, 24 and 48 hours. The ivermectin-based ATSB was evaluated in a semi field system where ATSB and attractive sugar bait (ASB) were deployed into each compartment of the semi field and 100 female <i>Ae. aegypti</i> were released every day and recaptured the next day through human land catch and Bio-gent sentinel trap. The developed and semi-field tested ATSB was further tested in the field by deploying them in garages. Results The ivermectin 48hr LC90 of male and female <i>Ae. aegypti</i> was found to be 0.03% w/v. In the semi field system, the ATSB significantly reduced a free-flying population of <i>Ae. aegypti</i> within 24 hours (incidence rate ratio (IRR) = 0.62; [95% confidence interval (95%CI); 0.54-0.70] and p-value < 0.001). However, in the field, the ATSBs required the addition of yeast as a carbon dioxide source to efficiently attract <i>Ae. aegypti</i> mosquitoes to feed. Conclusion Ivermectin is an active ingredient that can be used in an ATSB for <i>Ae. aegypti</i> depopulation. However, further research is needed to improve the developed and tested ATSB to compete with natural sources of sugar in a natural environment.