Devi Shankar Suman

Background: Anopheles stephensi (Diptera: Culicidae) is a primary urban malaria vector in India and neighbouring countries. Spatial repellents are a novel tool for personal protection against bites and curbing malaria transmission. The current study assessed the spatial repellency of thymol (T), oleic acid (O) phytocompounds and naphthalene (N) individually and in blends against adult An. stephensi to estimate the spatial activity index (SAI) and dose-response relationship. In silico interactions of these phytochemicals with 11 target proteins and their associated active toxicity sites were assessed. Results: The SAI values ranged from 0 to 0.675 for T, O, and N individually, and from − 0.025 to 0.55 for the blends, indicating promising repellency. The lowest ED ₅₀ (0.052%) and ED ₉₀ (0.485%) were recorded for both thymol and naphthalene. Among the blends, 1T:1O:2 N showed the lowest ED ₅₀ and ED ₉₀ . The lowest binding energies (Kcal/mol) of thymol, oleic acid and naphthalene were observed with the Odorant binding protein (-7.1), M2 muscarine receptors (-7.0) and odorant receptors (-7.5), respectively. Hydrogen bond interactions were stronger between thymol and the odorant binding protein, and between oleic acid and the M2 muscarine receptor. Molecular dynamics simulation plots, including deformability, B-factor, eigenvalue, variance, covariance and elastic network models, showed conformational changes at the atomic level. Toxicity prediction scores of these compounds supported the SAI scores. Conclusion: Thymol and naphthalene were the most promising spatial repellents for An. stephensi . Molecular docking studies confirmed protein interactions and bioactivity of these compounds. These spatial repellents can be a potential tool in the management of malaria transmission.

Background: Aedes aegypti and Aedes albopictus are crucial vectors of dengue, chikungunya and Zika viruses in India and globally. Insecticide resistance in these mosquitoes suggests the exploration of alternative control strategies. The present study assessed the larvicidal efficacy of eucalyptus oil and in silico analysis of 16 phytocompounds to predict molecular docking with acetylcholinesterase (AChE) protein, ADME and toxicity analysis. Temephos was the positive control for bioassay and in silico studies. Results: The results showed that the 50% (LC ₅₀ ) and 90% mortalities (LC ₉₀ ) with eucalyptus oil were found at 14.8 mg/l and 50.7 mg/l for Ae. aegypti and 16.9 mg/l and 42.4 mg/l for Ae. albopictus , respectively. Temephos showed 50% (LC ₅₀ ) and 90% mortalities (LC ₉₀ ) at 0.0004 and 0.028 mg/l for Ae. aegypti , and 0.0004 and 0.031 mg/l for Ae. albopictus , respectively. The 3-carene was the most abundant compound in eucalyptus oil. The AChE docking score ranged from − 5.2 (α-thujene) to − 6.5 Kcal/mol (longifolene-V4) in comparison to − 5.2 Kcal/mol of temephos. The AChE showed 3 to 6 amino acid interactions with ligands, along with single (Terpinen-4-ol) and double ( l -α-Terpineol) hydrogen bonds. The toxicity prediction suggests that the majority of phytocompounds are safe for various classes of toxicity, except for blood-brain barrier and ecotoxicity targets and Cytochrome CYP2C9 classes. The (−)-trans-pinene and longifolene (V4) may be the most effective and least hazardous larvicides. Conclusion: The findings suggest that eucalyptus oil showed moderate larvicidal efficacy but significantly lower toxicity than temephos. Also, many phytocompounds of eucalyptus oil may be potential candidates in designing new, effective and eco-friendly larvicides for Aedes and other mosquitoes.

The Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae), is a global vector of dengue, chikungunya and zika viruses. With extreme adaptability of survival as diapause eggs, this mosquito has invaded and established in temperate climatic zones. The diapause eggs are specially programmed to overcome the harsh winter conditions in temperate habitats. In the laboratory, diapausing females are reared from early larval instars under short‐day conditions (21°C and 16D:8 L photoperiods). Aedes albopictus is normally fed on Guinea pigs for the rearing of diapause mosquitoes which requires ethical approval from the animal use committee and costly arrangements. Therefore, the present study was conducted to find whether bovine serum albumin protein (10%) with sucrose (5%) solution (SAP‐10) offered through a membrane‐free feeding system would result in an alternative diet for the production of diapause eggs in comparison to blood‐feeding. This feeding system shows a considerable rate of engorgement of diapausing females under short‐day conditions and produced 30.8 diapause eggs/female in comparison to blood‐feeding on a guinea pig (40.9 eggs/female). The diapause rate of viable eggs for the SAP‐10 diet (95.28%) was similar to the blood‐feeding (96.32%). The findings suggest that the present diet feeding system is a promising tool for the rearing of diapause Ae. albopictus mosquitoes under short‐day conditions. Further studies are suggested to evaluate the physiological and developmental aspects of mosquitoes reared on the diet.

The ecological variation in biological and adult life‐table attributes of two populations of Aedes aegypti (Diptera: Culicidae) from the desert (Jodhpur) and coastal (Kolkata) regions of India are assessed to understand the reproductive and survival strategies. The results showed that females lived longer than males in both strains. The desert strain was more r‐strategist because of its higher intrinsic rate of increase ( r _m = 0.23), finite rate of increase ( λ = 1.25), lower life expectancy of males (7.9 days) and females (14.4 days), mean generation time ( T = 19.2 days) and doubling time (DT = 3.0 days). However, there was no difference in net reproductive rate ( R ₀ ) between the desert and coastal strains. The coastal strain showed a longer female life expectancy (22.0 days) than the desert strain (14.4 days). However, the fecundity (eggs/female/day) was lower in the coastal strain (11.4) than in the desert strain (15.1). Conclusively, the desert (Jodhpur) strain is adapted to a better r‐strategy than the coastal (Kolkata) strain of Ae. aegypti , which might be helpful to flourish in harsh environmental conditions. This study may provide accurate predictions of Ae. aegypti population dynamics for vector management.