Karine da Silva Carvalho

Bacillus thuringiensis svar. israelensis (Bti) larvicides are effective in controlling Aedes aegypti; however, the effects of long-term exposure need to be properly evaluated. We established an Ae. aegypti strain that has been treated with Bti for 30 generations (RecBti) and is still susceptible to Bti, but females exhibited increased susceptibility to Zika virus (ZIKV). This study compared the RecBti strain to a reference strain regarding: first, the relative transcription of selected immune genes in ZIKV-challenged females (F₃₀) with increased susceptibility detected in a previous study; then, the whole transcriptomic profile using unchallenged females (F₃₅). Among the genes compared by RT-qPCR in the ZIKV-infected and uninfected females from RecBti (F₃₀) and the reference strain, hop, domeless, relish 1, defensin A, cecropin D, and gambicin showed a trend of repression in RecBti infected females. The transcriptome of RecBti (F₃₅) unchallenged females, compared with a reference strain by RNA-seq, showed a similar profile and only 59 differentially expressed genes were found among 9202 genes analyzed. Our dataset showed that the long-term Bti exposure of the RecBti strain was associated with an alteration of the expression of genes potentially involved in the response to ZIKV infection in challenged females, which is an important feature found under this condition.

Internacional de Saúde Única (Interface Mundial) (978-65-5941-608-0) - Avaliação Da Atividade Larvicida Dos Extratos Etanólicos De Caules E Folhas De Clusia Fluminensis (Clusiaceae) Sobre Aedes Aegypti (Diptera: Culicidae).

Internacional de Saúde Única (Interface Mundial) (978-65-5941-608-0) - Avaliação Da Atividade Larvicida De Extratos Aquosos De Caule De Clusia Fluminensis Planch. & Triana (Clusiaceae) Sobre Aedes Aegypti (Diptera: Culicidae)

Plant-derived essential oils can be used as insecticides for vector control. However, to establish their safety, it is necessary to perform toxicological studies. Herein, we evaluated the chemical composition and insecticidal activity of the essential oil from the leaves of Croton argyrophyllus on the third- and fourth-instar larvae and adult Aedes aegypti (L., 1762). We also evaluated the acute toxicity of the essential oil in adult female Mus musculus. The lethal concentration 50 (LC₅₀) and 90 (LC₉₀) of C. argyrophyllus essential oil on larvae of Ae. aegypti were 0.31 and 0.70 mg ml⁻¹, respectively, and 5.92 and 8.94 mg ml⁻¹, respectively, on Ae. aegypti adults. The major components of the essential oil were spathulenol (22.80%), (E)-caryophyllene (15.41%), α-pinene (14.07%), and bicyclogermacrene (10.43%). It also displayed acute toxicity in adults of Mus musculus; the intraperitoneal and oral lethal dose 50 (LD₅₀) were 2,000 mg kg⁻¹ and 2,500 mg kg⁻¹, respectively. The results showed that the essential oil from C. argyrophyllus leaves has insecticidal activity on Ae. aegypti larvae and adults at an average lethal concentration below the median lethal dose needed to cause acute toxicity in the common mouse.

For control of Aedes aegypti, the main vector of dengue, botanical insecticides can be a viable alternative. Herein, we evaluated the chemical composition and insecticidal activity of the essential oils of the leaves of Croton tetradenius on Ae. aegypti larvae and adults. We also evaluated the acute toxicity in Mus musculus. The essential oil chemical analysis was performed using chromatography coupled with mass spectrometry and flame ionization detection. Female mice were used for assessing toxicity according to the Organization for Economic Cooperation and Development’s Test Guideline 423/2001. Doses administered to mice orally and intraperitoneally were 5, 50, 300, and 2000 mg kg⁻¹. There was a greater toxic effect on larvae (LC₅₀ = 0.152 mg mL⁻¹ and LC₉₀ = 0.297 mg mL⁻¹) and on adults (LC₅₀ = 1.842 mg mL⁻¹ and LC₉₀ = 3.156 mg mL⁻¹) of Ae. aegypti after 24 h of exposure, when compared to other periods of exposure. Chemical analysis revealed 26 components, with camphor (25.49 %) as the major component. The acute toxicity via the intraperitoneal route identified an LD₅₀ = 200 mg kg⁻¹ and by the oral route an LD₅₀ = 500 mg kg⁻¹. Thus, the essential oil of C. tetradenius presents insecticidal potential for Ae. aegypti and has high safety threshold at the concentrations evaluated in this study.