Harnessing insect-derived oils for enhanced efficacy of plant-based repellents against disease-transmitting mosquitoes

Mosquito-borne diseases such as malaria, dengue, chikungunya, Zika, and yellow fever pose a growing global health threat, worsened by resistance to synthetic pesticides. This study evaluated insect oils from Schistocerca gregaria, Ruspolia differens, and Macrotermes spp. as adjuvants in plant-based mosquito repellents. The formulations were tested for complete protection time (CPT) against Anopheles gambiae, Aedes aegypti, and Culex quinquefasciatus, and volatile organic compounds (VOCs) emitted from treated volunteers were analyzed. Incorporating insect oils doubled CPT compared to essential oils alone. The most effective blend of Macrotermes oil with Cymbopogon nardus (1:1) achieved CPTs of 3.50 h for An. gambiae, 2.56 h for Ae.aegypti, and 2.81 h for Cx. quinquefasciatus, showing repellency comparable to 20% DEET during the first 3.5 h. Blends retained three times more VOCs than plant oils alone, prolonging repellent activity. Key compounds such as geranyl acetate, citronellyl acetate, and geranyl propanoate persisted on skin for over 180 min. These findings highlight the potential of insect oils, particularly from Macrotermes spp., to enhance the efficacy and longevity of plant-based mosquito repellents, offering a sustainable, eco-friendly alternative amid growing pesticide resistance.