Entomotoxic Effects of Clerodendrum Infortunatum: Analysis of Larval Midgut Histology and Digestive Enzymes of Culex Quinquefasciatus Say (Diptera: Culicidae)

Abstract

Introduction: Mosquitoes are medically important vectors globally transmitting diseases such as dengue, malaria and filariasis. Among mosquito species, Culex quinquefasciatus is a major vector responsible for lymphatic filariasis. For the control of mosquitoes, natural and man-made insecticides are used. Increased use of chemical insecticides causes insecticidal resistance and adverse effects on the environment. Therefore, safer alternatives are necessary, which are eco-friendly and cost-effective.  Phytochemicals are a promising source of botanical insecticides. Clerodendrum infortunatum belongs to the family Lamiaceae.

Objectives: The present study investigates the insecticidal potential of Clerodendrum infortunatum against fourth instar larvae of Culex quinquefasciatus, emphasising its effect on histology and the activity of digestive enzymes α – amylase and protease in the treated larvae compared to control ones.

Methods: The histopathological effect of the acetone extract of Clerodendrum infortunatum against fourth instar larvae of Culex quinquefasciatus was examined using Hematoxylin-eosin staining. The activity of α- amylase and protease was estimated to understand the effect of plant extract on the larval digestive system.

Results: Fourth instar larvae of Culex quinquefasciatus were monitored after 24 h treatment with the acetone extract of Clerodendrum infortunatum. Several histological aberrations were observed in treated larvae. The midgut showed damage, causing cell wall protrusion and vacuolisation. The digestive enzymes α-Amylase and Protease were decreased compared to the control. The observed histo-enzymological disruptions collectively contribute to impaired larval development and subsequent mortality.

Conclusions: The study provides insight into the effect of the acetone extract of Clerodendrum infortunatum against fourth instar larvae of Culex quinquefasciatus. Clerodendrum infortunatum can be used as a promising botanical larvicide with different modes of action. Further studies are necessary for identifying the active components of the plant extract.