Comparison of effective dose with protection time for three botanicals by using multi-chamber-blood feeding system against Aedes aegypti

Abstract

The testing of repellents has typically been performed on shaven animals, such as rabbits, dogs, guinea pigs, chickens, and sheep as alternative subjects to humans. However, these techniques often raise queries concerning the ethical treatment of animals and/or humans, as well as practical aspects that sometimes cause the results of repellent tests to be misconstrued. In this study, a test system has been developed and improved method for the evaluation of mosquito deterrence time. This multi chamber blood feeding method was designed to require fewer test mosquitoes than conventional cages and also to reduce the risk of contamination with repellents, to evaluate effective dose and deterrent time. DEET and three botanical oils were used for this test against Aedes aegypti. Absolute ethanol was used as a positive control. Method involved placing treated netting of different repellent concentrations over a cup containing test mosquitoes for 5 minutes. The time, in minutes, between placement of the net over the test cup until first mosquito bite, was recorded as deterrence time. Results showed that citronella had the highest deterrent time of 240 minutes at 50% concentration, while 100% lemon eucalyptus oil and lavender oil deterrence times were lower, at 150 and 120 min, respectively. The control group experienced a higher biting rate than the treatment groups. The effective dose (ED50) of the tested repellents, in ascending order, were DEET (0.50%), citronella (10%), lemon eucalyptus (33.11%), and lavender (33.88%), to deter 50% of the tested mosquito population. The data were analyzed using the Kruskal Wallis test to compare the groups for effective dose and plot (log dose and % inhibition). It is suggested that this method is effective for repellent testing and may also be used for testing mosquito susceptibility/resistance to insecticides. The method used circumvents the need to use humans or animals, and therefore overcomes historical ethical challenges.