Ali Lamari

Resistance to pyrethroid insecticides in Culex pipiens pipiens (Diptera: Culicidae) from Tunisia

Resistance toward 2 pyrethroïd insecticides (permethrin and deltamethrin), and an organochloric one (DDT) was analyzed in 18 samples of Culex pipiens pipiens common mosquitoes collected from different Tunisian areas between March 2002 and November 2005. Bioassays were performed over different larvae samples. The recorded mortalities, after 24h exposure to increased doses of insecticides, were compared to those obtained on a susceptible reference strain (S-LAB). All samples were resistant to permethrin. However, a large variation in the tolerance to this insecticide was observed between samples. Resistance ratio levels at LC50 (RR50) for the analyzed samples were ranged from 1.5 to 9092 folds. For deltamethrin, 14 among 17 studied samples were resistant. RR50, in the resistant samples, were ranged from 3 to 453 folds. Resistance to the two tested pyrethroids and DDT were correlated. The use of synergists showed that the cytochrome P450-dependent monooxygenases had a major contribution to the permethrin and deltamethrin resistance and that the esterases (and/or glutathione-S-transferases) had only a minor contribution. Results were discussed in relation to resistance mechanisms and mosquitos control.

Evaluation of Chlorpyrifos Resistance and Biochemical Mechanisms of Culex pipiens in Five Localities of Grand Tunis Area, Northeast Tunisia

Five Culex pipiens samples were collected at preimaginal stages from breeding sites in 5 localities of Grand Tunis area, Northeast Tunisia, between March 2002 and November 2005. Larvae were used for bioassays using ethanol solutions of chlorpyrifos and propoxur insecticides. All samples were resistant to chlorpyrifos (RR>1, p 1,000-fold) were recorded in samples # 2, 4, and 5. Our synergist study showed that the increased detoxification by EST (and/or GST) had only a minor role in the chlorpyrifos resistance, although several overproduced esterases, known to be involved in the OPs resistance, were detected in all the resistant field samples. The mortality due to propoxur was significantly correlated with the LC50 of chlorpyrifos and indicated an insensitive AChE.

Chemical Composition and Insecticidal Activity of Essential Oil of Salvia officinalis L. Cultivated in Tunisia

This study was conducted to elucidate the chemical composition of essential oil of Salvia officinalis L. cultivated in Tunisia and to evaluate the insecticidal activity of this oil. The essential oil was extracted by hydrodistillation from fresh aerial part and analysed by gas chromatography and gas chromatographymass spectrometry. The major components were αthujone (21 %), camphor (16.58 %), 1,8-cineole (14.57 %), viridiflorol (7.47 %), β-thujone (6.76 %), manool (5.34 %), and camphene (4.51 %). Insecticidal assays showed that the essential oil is active against Culex pipiens pipiens larvae. The LC50 (the 50 % lethal concentration) and LC90 (the 90 % lethal concentration) were 58.91 and 113 µg/ml, respectively. This study showed that S. officinalis L. has also an insecticidal potential through its essential oil content.

Temephos Resistance in Three Populations of Culex pipiens Collected from Three Districts of Southern Tunisia and its Significance for the Resistance Mechanism

Objectives: The aim of this study was to investigate the resistance to temephos (OP) in three populations of Culex pipiens collected from three districts of Southern Tunisia and its significance for the resistance mechanism. Methods: Resistance to temephos insecticide was studied on Culex pipiens mosquitoes collected in three localities of Southern Tunisia. Larvae were used for different bioassays and adults were stored in -80°C for esterases identification. Results: Bioassays revealed the susceptibility of sample # 3. The weakest resistance was recorded in sample # 3 (RR50 = 0.68) and the strongest resistance for the sample # 2 (RR50 = 3.6). At LC95, two samples (# 1, and 3) were susceptible. The use of synergists showed the non-involvement of resistance mechanisms inhibited by DEF and Pb. Our investigation reported that temephos resistance could be explained by the two most common mechanisms of resistance to OP (overproduced esterases and AChE 1 mutation). Conclusion: Both detoxification mechanisms and target site alteration were involved in the resistance to temephos as reported in our study. These results are very important for the implementation and development of vector control strategies

Investigation of Pirimiphos-Methyl Resistance Status of Culex Pipiens (Diptera : Culicidae) Populations in Northern Tunisia

This article reports Pirimiphos-methyl resistance status of Culex pipiens populations harvested in four breeding sites in Northern Tunisia. Our results showed the resistance of all samples to Pirimiphos-methyl. The RR50 ranged from 3.3 1 to 62.1. The sample collected from Tazarka had the highest resistance among all studied populations. This status could be explained by its frequency of mortality caused by propoxur (0%) and also by its frequency of detected esterases (85%). Authors confirmed the implications of insensitive acetylcholinesterase and esterases enzymes in the resistance of Culex pipiens populations to Pirimiphos-methyl. It is the first investigation of Pirimiphos-methyl resistance status of Culex pipiens populations from Tunisia and it is very important for the implementation and development of vector control strategies. To cite this article [Tabbabi, A., Daaboub, J., Lamari, A., Ben Jha, I., & Ben Cheikh, H. (2017). Investigation of Pirimiphos-methyl Resistance Status of Culex pipiens (Diptera: Culicidae) Populations in Northern Tunisia. The Journal of Middle East and North Africa Sciences, 3(7), 1-5]. (P-ISSN 24129763) (e-ISSN 2412-8937). www.jomenas.org. 1

Temephos Resistance and Esterase Activity in Selected Laboratory Population of Culex Pipiens from Tunisia

Selection for resistance to temephos (an organophosphorus insecticide) was performed by exposing larvae of the field-collection population of Culex pipiens to increasing doses of temephos for four generations. Mosquito larval specimens were captured in Northwestern Tunisia and identified using morphological keys. Two insecticides including temephos and propoxur were used evaluating the susceptibility status of the selected population. Bioassays results showed high resistance to temephos and no esterase activity. A new esterase was first detected in one sample among 60 tested. This result will help to elucidate resistance mechanisms, which is essential for the planning of future insecticide resistance management programs. To cite this article [Tabbabi, A., Lamari, A., Daaboub, J., Ben Jha, I., & Ben Cheikh, H. (2017). Temephos resistance and esterase activity in selected laboratory population of Culex pipiens from Tunisia. The Journal of Middle East and North Africa Sciences, 3(4), 14-17]. (P-ISSN 24129763) (e-ISSN 2412-8937). www.jomenas.org. 3

Development of Resistance to Chlorpyrifos in Culex Pipiens (Diptera : Culicidae) Population under Temephos Selection Pressures

Development of resistance to chlorpyrifos in Culex pipiens population from Tunisia under temephos selection pressures was investigated. The objective of this study was to follow the evolution of resistance responses in Culex pipiens larvae under laboratory conditions. The selection to temephos caused a significant increase of resistance to chlorpyrifos levels. Indeed, the LD50 resistance rate increased from 75.90 in the natural population to approximately 6620.66 in the 4th generation of selection. This resistance dropped sharply in the 5th generation (1686.35) to increase again in the last generation of selection reaching 3929.36. The reason for this unstable variation is unknown and effects related to uncontrolled environmental parameters and/or inter-strain genetic variability is probably involved. Our results showed the involvement of insensitive acetylcholinesterase (AChE), which is a common target for temephos and chlorpyrifos insecticides, in the recorded resistance. The potential to develop resistance to the chlorpyrifos is very clear in this species. To cite this article [Tabbabi, A., Lamari, A., & Ben Cheikh, H. (2017). Development of Resistance to Chlorpyrifos in Culex pipiens (Diptera: Culicidae) Population under Temephos Selection Pressures. The Journal of Middle East and North Africa Sciences, 3(5), 14]. (P-ISSN 24129763) (e-ISSN 2412-8937). www.jomenas.org. 1

Cross-Resistance to Pyrethroid and Organophosphorus Insecticides Induced by Selection with Temephos in the Potential Mosquito Vector of West Nile Virus ( Culex Pipiens ) from Tunisia

A sample of Culex pipiens from Northwestern Tunisia, North Africa, with a high level of temephos resistance, was subjected to temephos selection to evaluate the utility of this organophosphate insecticide for mosquito control. High resistance developed after three generations of selection (52x). High cross-resistance was observed for the pyrethroid permethrin (32x). Synergism tests showed the implication of cytochrome P450 monooxygenases but not of esterase in temephos and permethrin resistance. Pyrethroid resistance could be associated with a cytochrome P450 monooxygenases and/or glutathione-S-transferase mechanism but not the esterases. The cross-resistance to permethrin from temephos selection could limit the use of both insecticides for Culex pipiens control. To cite this article [Tabbabi, A, Lamari, A., Daaboub, J., Ben Jha I., & Ben Cheikh, H. (2017). Cross-Resistance to Pyrethroid and Organophosphorus Insecticides Induced by Selection with Temephos in the Potential Mosquito Vector of West Nile virus (Culex Pipiens) from Tunisia. The Journal of Middle East and North Africa Sciences, 3(3), 25-29]. (P-ISSN 24129763) (e-ISSN 2412-8937). www.jomenas.org. 4

Insecticide Resistance Development in Culex Pipiens Population under Selection Pressures with Temephos

A collection of Culex pipiens from Boussalem, Northwestern Tunisia, with a low level of temephos resistance (14.90 at LD95) was selected to higher resistance with temephos in the laboratory. After 6 generations of pressure, the temephos resistance ratio increased to 103.95 at LD95. Synergism tests showed that temephos resistance was not associated with monooxygenase and esterases or (GST); however, evidence of insensitive acetylcholinesterase was found. It is evident that this important vector species, Culex pipiens, has the potential to develop resistance to temephos. To cite this article [Tabbabi, A., Ben Jha, I., Lamari, A., & Ben Cheikh, H. (2017). Insecticide Resistance Development in Culex pipiens Population under Selection Pressures with Temephos. The Journal of Middle East and North Africa Sciences, 3(5), 16-19]. (PISSN 24129763) (e-ISSN 2412-8937). www.jomenas.org. 4

Chlorpyrifos Resistance Characteristics of Culex pipiens (Diptera: Culicidae) from Northern Tunisia

We collected four field populations of Culex pipiens larvae from Northern Tunisia to study their chlorpyrifos resistance characteristics. Assays were performed using ethanol solutions of chlorpyrifos and data were analyzed using a log-probit program. All samples were resistant to chlorpyrifos (RR>1, p<0.05) and a large variation in the tolerance to this insecticide was observed. The sample 3 (Northeast) was the most resistant with a level higher than 10,000-fold (RR50=43,174). The level of resistance was lower, not exceeding 5-fold in samples 1 (North West). CYP450, EST and/or GST enzymes accounted for only a small part of the observed resistances. Synergists tests confirmed biochemical study where four esterases were detected in studied samples with low and average frequencies (0.03%-0.68%). Moreover, the mortality due to propoxur was significantly correlated with the LC50 of chlorpyrifos (P<0.01) indicated an insensitive AChE 1.