Insecticidal activity of Leptodactylus knudseni and Phyllomedusa vaillantii crude skin secretions against the mosquitoes Anopheles darlingi and Aedes aegypti

Abstract

Background: Mosquitoes are important vectors of several diseases, including malaria and dengue, and control measures are mostly performed using chemical insecticides. Unfortunately, mosquito resistance to commonly applied insecticides is widespread. Therefore, a prospection for new molecules with insecticidal activity based on Amazon biodiversity using the anuransLeptodactylus knudseniandPhyllomedusa vaillantiiwas performed against the mosquito speciesAnopheles darlingiandAedes aegypti.Methods: The granular secretion from anuran skin was obtained by manual stimulation, and lethal concentrations (LCs) for larvicidal and adulticidal tests were calculated using concentrations from 1-100 ppm. The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species.Results: The skin secretions from the anuran species tested caused significant mortality within the first 24 hours on adults and larvae, but differed within the mosquito species. The calculated LC 50 ofL. knudseniskin secretions againstAn. darlingiwas 0.15 and 0.2 ppm for adults and larvae, respectively, but much higher forAe. aegypti, i.e., 19 and 38 ppm, respectively. Interestingly, the calculated LCs 50 ofP. vaillantiiagainst both mosquito species in adults were similar, 1.8 and 2.1 ppm, respectively, but the LC 50 forAn. darlingilarvae was much lower (0.4 ppm) than forAe aegypti(2.1 ppm).Conclusions: The present experiments indicate that skin secretions fromL. knudseniandP. vaillantiicontain bioactive molecules with potent insecticide activity. The isolation and characterization of skin secretions components will provide new insights for potential insecticidal molecules.