A push-pull system to reduce house entry of malaria mosquitoes

Abstract

Background: Mosquitoes are the dominant vectors of pathogens that cause infectious diseases such as malaria, dengue, yellow fever and filariasis. Current vector control strategies often rely on the use of pyrethroids against which mosquitoes are increasingly developing resistance. Here, a push-pull system is presented, that operates by the simultaneous use of repellent and attractive volatile odorants.

Method/results: Experiments were carried out in a semi-field set-up: a traditional house which was constructed inside a screenhouse. The release of different repellent compounds, para-menthane-3,8-diol (PMD), catnip oil e.o. and delta-undecalactone, from the four corners of the house resulted in significant reductions of 45% to 81.5% in house entry of host-seeking malaria mosquitoes. The highest reductions in house entry (up to 95.5%), were achieved by simultaneously repelling mosquitoes from the house (push) and removing them from the experimental set-up using attractant-baited traps (pull).

Conclusions: The outcome of this study suggests that a push-pull system based on attractive and repellent volatiles may successfully be employed to target mosquito vectors of human disease. Reductions in house entry of malaria vectors, of the magnitude that was achieved in these experiments, would likely affect malaria transmission. The repellents used are non-toxic and can be used safely in a human environment. Delta-undecalactone is a novel repellent that showed higher effectiveness than the established repellent PMD. These results encourage further development of the system for practical implementation in the field.

Figure 1

The MalariaSphere; a screenhouse with a traditional house constructed inside (image copied from [23])

Figure 2

Experimental set-up of experiment 1. Green represents an MMX trap baited with attractant, red represents an MMX trap dispersing the repellent. Asterisks indicate the mosquito release points. Numbers indicate the treatments at which the trap or dispenser was present (see also Table 1).

Figure 3

Experimental set-up of experiment 2. Green represents an MMX trap baited with attractant, red represents an MMX trap dispersing the repellent. The asterisk indicates the mosquito release point. Numbers indicate the treatments at which the trap or dispenser was present (see also Table 2).

Figure 4

Mean number of mosquitoes trapped inside and, when applicable, outside the experimental house. For all treatments n = 8, error bars indicate the standard error of the mean. Bars not sharing the same character are significantly different at α = 0.05 with Bonferroni post-hoc tests.

Figure 5

Mean number of mosquitoes trapped inside and, when applicable, outside the experimental house. For all treatments n = 6, error bars indicate the standard error of the mean. Bars not sharing the same character are significantly different at α = 0.05 with Games-Howell post-hoc tests. (d): p = 0.05081 for the comparison between the push-only dUDL treatment and the push-pull dUDL treatment.