Toxicological and ultrastructural effects of chitin synthesis inhibitors (lufenuron and chlorfluazuron) on third larval instars integument of Chrysomya albiceps (Diptera: Calliphoridae)

Abstract

Background: Chrysomya albiceps is of medical and veterinary importance as larvae cause cutaneous myiasis in both man and animals. Chitin synthesis inhibitors (CSI) are commonly used in control of dipterous flies causing myiasis. Several compounds are utilized to interfere with chitin deposition and molting processes during development. Objectives: In comparison to chlorfluazuron (CF), the current study aims to investigate the toxicological and ultrastructural effects of the CSI, lufenuron (LF) on the biological parameters of the third larval instar (L3) of C. albiceps. Material and Methods: Early L3 of C. albiceps were fed on diets mixed with four concentrations of LF and CF. Average larval mortality rates were subjected to probit model analysis for calculating LC25, LC50, and LC90. Larval deformation and mortality, percent pupation, adult emergence and chitinase enzyme activity were recorded. Using transmission electron microscope (TEM), ultrastructural study was carried out on non-treated and treated L3 to evaluate LF effects on the integument and muscle layer. Results: By recording LC50 values for LF and CF (146 and 194 ppm, respectively), LF showed more toxic effects on L3 than CF, and at a lower concentration. Reduction in pupation percentage, complete cessation of adult emergence from pupae and decrease in chitinase activity were observed after treatment with all concentrations of both compounds. Ultrastructural changes after treatment with LC50 of LF indicated tegumental, nuclear and mitochondria! toxicological effects, and muscle fibers disorganization. Conclusion: LF proved to be a successful CSI in controlling myiasis causing C. albiceps L3.