Malaria, a tropical disease caused by Plasmodium falciparum, is transmitted by the haematophagous mated female Anopheles gambiae. The P. falciparum is reported as the most prevalent malaria parasite responsible for severe morbidity, mortality, and worldwide economic burden.
This calls for novel approaches targeting the vector to intervene malaria endemic. Natural and artificial sounds have been used in the study of phonotactic responses in mosquitoes and other insects. Studies have shown negative phonotactic response in mosquitoes for sounds from electronic mosquito repellent (EMR) (40-55 kHz), Odorrana tormota (35-60 kHz) and winded-EMR that yielding 68.99%, 45.88% and 60.70% efficacy respectively. Little has been reported on phonotaxis studies involving use of animal mimicking synthetic sounds generated from natural sounds formants and mated female Anopheles gambiae.
Therefore this study established the effect of 35-60 kHz synthetic sounds of Odorrana tormota, Delphinapterus leucas, and male Anopheles gambiae on evoked Spatial Activity Index (SAI) and Protection Index (PI) in tropical mated female Anopheles gambiae. The synthetic ultrasounds of O. tormota, mixed male A. gambiae and O. tormota, and mixed male A. gambiae, O. tormota and D. leucas were generated using Avisoft SASLab Pro version 5.2 and Raven Pro 1.6 from respective natural sounds evoking optimal repellency.
Fifty starved mated female A. gambiae were allowed into the fighto-Y bioassay cage containing blood meal and treated with 35-60 kHz sound of O. tormota, mixed male A. gambiae and O. tormota, and mixed male A. gambiae, O. tormota and D. leucas at a time with each bioassay lasting 1,200 s. The number of female A. gambiae that were responsive and landed were determined. The mean SAI in female A. gambie evoked by synthetic sound of O. tormota, mixed sound of the male A. gambiae and O. tormota, and mixed sound of the male A. gambiae, O. tormota, and D. leucas were 0.144, 0.078 and 0.14, respectively.
The overall PI evoked by synthetic sound of O. tormota, mixed sound of male A. gambiae and O. tormota, mixed sound of the male A. gambiae, O. tormota, and D. leucas were 46.35%, 39.55%, and 43.20% respectively, which were 33.71%, 40.51% and 36.86 % less than the PI of the 35-60 kHz natural sounds of O. tormota. The 35-60 kHz synthetic sound of O. tormota recorded the greatest PI and SAI processing superior acoustic propagation parameters. Synthesizing sounds of optimal PI does not improve the efficacy in repellency of the mated female A. gambiae.
Keywords: Synthesis, Mixed Sounds, Protection index; Spatial Activity Index; Phonotaxis
