Comparative study of three herbal formulations against dengue vectors Aedes aegypti

Abstract

The efficacy of three formulations (i.e., natural lavender crude, essential oil, and gel) extracted from Lavender angustifolia was tested against vectors of the epidemic dengue virus, Aedesaegypti, to evaluate their larvicidal activity effect. The ethanolic extract of the lavender crude was prepared using a rotary evaporator, while the other extracts, such as essential oil and gel, were obtained from iHerb, a supplier of medicinal herbs in the US. The mortality rate of larvae was evaluated 24 h after exposure. Larvicidal activity of the lavender crude was 91% mortality at 150 ppm, 94% for essential oil at a concentration of 3000 ppm, and 97% for lavender gel at a 1000 ppm. Natural lavender crude was one of the most promising extracts tested against Ae.aegypti larvae, with lethal concentrations at LC₅₀ and LC₉₀ of 76.4 and 174.5 ppm post-treatment. The essential oil had the least effect on mosquito larvae, with LC₅₀ and LC₉₀ reaching 1814.8 and 3381.9 ppm, respectively. The lavender gel was moderately effective against Ae. aegypti larvae, with LC₅₀ and LC₉₀ values reaching 416.3 and 987.7 ppm after exposure. The occurrence of morphological abnormalities in the larvae treated with the three compounds, in turn, resulted in an incomplete life cycle. Therefore, our results indicated that natural lavender crude displayed the highest larvicidal activity against larvae, followed by gel and essential oil. Thus, this study concluded that lavender crude is an effective, eco-friendly compound that can be used as an alternative to chemical products to control vector-borne epidemic diseases.

Keywords: Dengue; Jeddah; Larvicidal activity; Lavender; Lavender gel; Oil essential.

Fig. 1

Mortality rate of Ae.aegypti larvae after exposure to five different concentrations of plant extract (L. angustifolia) for 24 h of treatment.

Fig. 2

Mortality rate of Ae. aegypti larvae after exposure to five different concentrations of essential oil extracted from L. angustifolia for 24 h of treatment.

Fig. 3

Mortality rate of Ae. aegypti larvae after exposure to five different concentrations of gel extracted from L. angustifolia for 24 h of treatment.

Fig. 4

Toxicity-Probit line (Ldp) of plant extract (L. angustifolia) on Ae. aegypti larvae after 24 h PT.

Fig. 5

Toxicity-Probit line (Ldp) of essential oil extract (L. angustifolia) on Ae. aegypti larvae after 24 h PT.

Fig. 6

Toxicity-Probit line (Ldp) of gel) L. angustifolia) on Ae. aegypti larvae after 24 h PT.

Fig. 7

Toxicity-Probit line (Ldp) of plant extract, essential oil, and gel of L. angustifolia on Ae. aegypti larvae after 24 h PT.

Fig. 8

Microscopic images of larvae and pupae of Ae. aegypti treated with lavender extracts. Control (a-d) not showing morphological changes (normal larva and pupa). Treatment with extract at different concentrations ppm after 24 h PT (e-p). Morphological abnormalities of the larvae and pupae of the Ae. aegypti mosquito: e-f: (2) Larval neck elongation. g: (6) Pigmentation, (7) Appendages. h: (3) Deformed head, (5) Breakup abdomen. i: (9) Antennae. j: (4) Deformed thorax, (8) Deformed siphon, (10) Deformed cuticles. k: (6) Pigmentation. l: (11) shrinkage of the larvae. m: (3) Deformed head, (4) Deformed thorax, (9) Antennae, (11) shrinkage of the larvae, (13) Failed to develop into a pupa. n: (12 An intermediate stage, (14) Albino pupa. o: An intermediate stage, (14) Albino pupa. p: (13) Failed to develop into a pupa, (14) Albino pupa.