Sugar-fermenting yeast as an organic source of carbon dioxide to attract the malaria mosquito Anopheles gambiae s.s.

Background

Carbon dioxide (CO₂) plays an important role in the host-seeking process of opportunistic, zoophilic and anthropophilic mosquito species and is therefore commonly added to mosquito sampling tools. The African malaria vector Anopheles gambiae Giles sensu stricto is attracted to human volatiles augmented by CO₂. We investigated whether CO₂, usually supplied from gas cylinders acquired from commercial industry, could be replaced by CO₂ derived from fermenting yeast (yeast-produced CO₂).

Methods

Trapping experiments were conducted in the laboratory, semi-field and field, with An. gambiae s.s. as the target species. MM-X traps were baited with volatiles produced by yeast-sugar solutions, prepared in bottles. Catches were compared with traps baited with industrial CO₂. The additional effect of human odours was also examined.

Results

Traps baited with yeast-produced CO₂ caught significantly more mosquitoes than unbaited traps and also significantly more than traps baited with industrial CO₂, both in the laboratory and semi-field. Adding yeast-produced CO₂ to traps baited with human odour significantly increased trap catches. During the field trials, traps baited with yeast-produced CO₂ caught similar numbers of An. arabiensis Patton as traps baited with industrial CO₂. Addition of human odour increased trap catches.

Conclusions

We conclude that yeast-produced CO₂ can effectively replace industrial CO₂ for sampling of An. gambiae s.s.. This will significantly reduce costs and allow sustainable mass application of odour-baited devices for mosquito sampling in remote areas.