Effect of physicochemical factors of breeding sites on larval density and detoxification enzymes activities of Culex pipiens (l.) (Diptera: Culicidae) in qalyubia governorate, Egypt

There is limited evidence on the effects of physicochemical factors of breeding sites on the density of Culex pipiens (L.) (Diptera: Culicidae) larvae in Qalyubia Governorate. Therefore, the aim of this study was to investigate C. pipiens larval density and the response of their detoxification enzymes to levels of various physicochemical environmental factors present in their breeding sites. Larvae were collected from three different zones (domestic, agriculture and petrochemical) from March-June 2020. Water samples were collected during larval collection and levels of 10 physicochemical parameters (temperature, pH, conductivity, turbidity, total dissolved solids, phosphates, sulphates, nitrates, oil and grease) were measured. Activities of the three major detoxification enzymes, P450, GST and α & β-esterases were determined on the sampled larvae. Data were assessed by One-way ANOVA followed by Tukey's post-hoc test and Pearson Correlation analysis. Results showed significant difference in the mean larval density of C. pipiens within the three study zones with the residential zone having the highest mean larval density. The activities of the detoxification enzymes were higher in the agricultural and petrochemical zones, which recorded higher levels of the physicochemical factors. There was a significant negative correlation between the density of C. pipiens larvae and temperature, pH, turbidity, phosphates, sulphates, nitrates, oil and grease levels, whereas conductivity and total dissolved solids had no significant correlation with larval density. The concentrations of oil and grease which were significantly higher in petrochemical zone were strongly positively correlated with P450 activities. While, phosphate, sulphate and nitrate which were significantly higher in agricultural zone were associated with GST and α & β-esterase activities. The correlations observed between the physicochemical factors and larval density as well as the inductive impact on detoxification enzymes can confirm the effect of these factors on mosquito breeding activity and these observations could have a significant effect on the environmental management and approach to mosquito control in Qalyubia Governorate.