First studies showing high temephos resistance in Anopheles labranchiae (Diptera: Culicidae) from Tunisia

Background: Despite the public health importance of Anopheles (An.) labranchiae, their resistance status to temephos insecticide has not, to our knowledge, been explored.Objectives: The present study was carried out to determine the temephos resistance status of field populations of An. labranchiae from Tunisia.Methods: Six field populations of An. labranchiae were collected as larvae from breeding sites of Northern and Central Tunisia. All the tests were carried out according to the WHO method.Results: Results reported that the majority of field populations showed low and medium resistance ratios (6.2<RR50< 29.8) to temephos insecticide tested except for the strain # 1 which had interestingly a very high resistance with RR50 of 624 never detected in Tunisia and North Africa even on other species of mosquitoes.Conclusion: The resistance ratios of this species were higher than recorded in other countries. Biochemical and molecular studies would be of great importance to identify the mechanisms involved in the recorded resistance to temephos.Keywords: Anopheles labranchiae, temephos insecticide, Tunisia

First studies showing high temephos resistance in Anopheles labranchiae (Diptera: Culicidae) from Tunisia

Background: Despite the public health importance of Anopheles (An.) labranchiae, their resistance status to temephos insecticide has not, to our knowledge, been explored. Objectives: The present study was carried out to determine the temephos resistance status of field populations of An. labranchiae from Tunisia. Methods: Six field populations of An. labranchiae were collected as larvae from breeding sites of Northern and Central Tunisia. All the tests were carried out according to the WHO method. Results: Results reported that the majority of field populations showed low and medium resistance ratios (6.2<RR50< 29.8) to temephos insecticide tested except for the strain # 1 which had interestingly a very high resistance with RR50 of 624 never detected in Tunisia and North Africa even on other species of mosquitoes Conclusion: The resistance ratios of this species were higher than recorded in other countries. Biochemical and molecular studies would be of great importance to identify the mechanisms involved in the recorded resistance to temephos

First study of susceptibility and resistance status to pyrethroids insecticides in Anopheles (Cellia) sergentii (Theobald, 1907) from Southern Tunisia

Background: Insecticide resistance is an important threat to malaria control. Anopheles (An.) sergentii proved to be the number one vector in the oases and may be of a particular interest in projection of the future trends of the disease in Tunisia. Objectives: Resistance status to pyrethroids insecticides in An. sergentii was evaluated for the first time in Tunisia. Methods: Diagnostic resistance tests to pyrethroids insecticides were conducted on late third and early fourth larvae of An. sergentii collected in Southern Tunisia. Results: The level of resistance to permethrin and deltamethrin varied from 1.9 to 5.77 and from 2.75 to 4.63, respectively. The highest resistance was recorded in sample # 3 to the two used insecticides. Synergists showed that esterases and glutathione-S-transferase were not involved in the resistance to any of the evaluated insecticides. In contrast, cytochrome-P450 monooxygenases played a role in the detoxification of two among three studied samples. Positive correlations between larval tolerance to both Permethrin/DDT and Deltamethrin/DDT were recorded indicated target site insensitivity. Conclusion: Continued monitoring of insecticide susceptibility and generating complementary data on mechanisms of resistance using molecular and biochemical methods is essential to ensure early detection of insecticide resistance in potential malaria vectors in Tunisia

Resistance development and insecticide susceptibility in Culex pipiens pipiens, an important vector of human diseases, against selection pressure of temephos and its relationship to cross-resistance towards organophosphates and pyrethroids insecticides

Background: Culex pipiens pipiens is an important vector of human diseases. Objective: To determine the insecticide resistance development in Culex pipiens pipiens against selection pressure of temephos.. Methods: A field population of Culex pipiens pipiens was collected from Northwestern Tunisia with a medium level of temephos resistance (LC50 = 0.0069). It was subjected to six generations of temephos pressure selection to evaluate its relationship to cross-resistance towards organophosphates (OPs) and pyrethroids (PYR) insecticides. Results: The selection was initiated at the dose 0.0266, 0.0748 and 0.0069 which were increased during successive generations up to 0.1488, 3.8747 and 0.0086 after sixth generation for temephos, chlorpyrifos and permethrin insecticides, respectively. It is important to noted that high cross-resistance to chlorpyrifos insecticide (OP) was detected (51.88 7). However, little or no cross-resistance to the pyrethroid permethrin (PYR) was recorded (1.24 7). Contrary to metabolic resistance, it seemed that acetylcholinesterases AChE 1 was fixed under pressure selection. Conclusion: The high cross-resistance to temephos and chlorpyrifos is reasonable because they belong to the same class of insecticide (OP). However, the little cross-resistance to the pyrethroid permethrin could support its use alternately for Culex pipiens pipiens control

Evaluation of resistance to temephos insecticide in Culex pipiens pipiens larvae collected from three districts of Tunisia

Background: Mosquitoes are considered as the main groups of arthropods that cause nuisance and public health problems. Objectives: Evaluation of resistance to temephos insecticide in Culex pipiens pipiens larvae collected from three districts of Tunisia. Methods: Late third and early fourth instars larvae of Culex pipiens pipiens were collected in three localities of Northern and Southern Tunisia. Field collected populations were tested against temephos insecticide and compared to bioassays of a susceptible reference strain. The cross-resistance between temephos and propoxur, and the polymorphism of over-produced esterases and AChE 1 were investigated. Results: Studied populations exhibited tolerance to temephos with low and high levels of resistance. The resistance ratio (RR50) values of temephos ranged from 1.34 to 114. Synergists and starch electrophoresis showed that the metabolic resistances were involved in the recorded resistance. Likewise, the resistant target site (acetyl cholinesterase: AChE 1) was responsible for the recorded resistance to temephos compound in Culex pipiens pipiens. Conclusion: The low and high resistance recorded to temephos insecticides is particularly interesting, because it leaves a range of tools useable by vector control services. However, further studies are needed to determine its spread and anticipate vector control failure where these insecticides are used. DOI: https://dx.doi.org/10.4314/ahs.v19i1.8 Cite as: Tabbabi A, Daaboub J, Laamari A, Cheikh RB, Feriani M, Boubaker C, Jha IB, Cheikh HB. Evaluation of resistance to temephos insecticide in Culex pipiens pipiens (Diptera: Culicidae) larvae collected from three districts of Tunisia. Afri Health Sci. 2019;19(1): 1361-1367. https://dx.doi.org/10.4314/ahs.v19i1.

Resistance status to deltamethrin pyrethroid of Culex pipiens pipiens (Diptera: Culicidae) collected from three districts of Tunisia

Objectives: The aim of the present study was to determine the susceptibility status of Culex pipiens pipiens populations against deltamehtrin insecticide. Methods: Larvae of Culex pipiens pipiens were collected from three breeding places in Northern and Southern Tunisia between 2003 and 2005. Early third and late fourth instars were tested against deltamethrin pyrethroid insecticide. Cross-resistance with DDT resistance was evaluated in studied samples to estimate the role of target site insensitivity and two synergists including piperonyl butoxide (Pb) and S,S,S-tributyl phosphorotrithioate (DEF) were used to estimate the role of detoxification enzymes. Results: Our results revealed that the level of deltamehtrin resistance ranged from 0.67 to 31.4. We also showed the non-involvement of kdr resistance in pyrethroid resistance and no cross-resistance with DDT resistance was detected in all studied populations including the most resistant one. Synergists study on the resistant population (sample # 1) showed the involvement of CYP450 in the recorded resistance to the deltamethrin insecticide. Conclusion: The results obtained from this study should be considered in the current control programs to combat mosquitoes in Tunisia

Culex pipiens, an Experimental Efficient Vector of West Nile and Rift Valley Fever Viruses in the Maghreb Region

West Nile fever (WNF) and Rift Valley fever (RVF) are emerging diseases causing epidemics outside their natural range of distribution. West Nile virus (WNV) circulates widely and harmlessly in the old world among birds as amplifying hosts, and horses and humans as accidental dead-end hosts. Rift Valley fever virus (RVFV) re-emerges periodically in Africa causing massive outbreaks. In the Maghreb, eco-climatic and entomologic conditions are favourable for WNV and RVFV emergence. Both viruses are transmitted by mosquitoes belonging to the Culex pipiens complex. We evaluated the ability of different populations of Cx. pipiens from North Africa to transmit WNV and the avirulent RVFV Clone 13 strain. Mosquitoes collected in Algeria, Morocco, and Tunisia during the summer 2010 were experimentally infected with WNV and RVFV Clone 13 strain at titers of 107.8 and 108.5 plaque forming units/mL, respectively. Disseminated infection and transmission rates were estimated 14–21 days following the exposure to the infectious blood-meal. We show that 14 days after exposure to WNV, all mosquito st developed a high disseminated infection and were able to excrete infectious saliva. However, only 69.2% of mosquito strains developed a disseminated infection with RVFV Clone 13 strain, and among them, 77.8% were able to deliver virus through saliva. Thus, Cx. pipiens from the Maghreb are efficient experimental vectors to transmit WNV and to a lesser extent, RVFV Clone 13 strain. The epidemiologic importance of our findings should be considered in the light of other parameters related to mosquito ecology and biology

Implementation of the One Health approach to fight arbovirus infections in the Mediterranean and Black Sea Region: Assessing integrated surveillance in Serbia, Tunisia and Georgia

Background In the Mediterranean and Black Sea Region, arbovirus infections are emerging infectious diseases. Their surveillance can benefit from one health inter-sectoral collaboration; however, no standardized methodology exists to study One Health surveillance. Methods We designed a situation analysis study to document how integration of laboratory/clinical human, animal and entomological surveillance of arboviruses was being implemented in the Region. We applied a framework designed to assess three levels of integration: policy/institutional, data collection/data analysis and dissemination. We tested the use of Business Process Modelling Notation (BPMN) to graphically present evidence of inter-sectoral integration. Results Serbia, Tunisia and Georgia participated in the study. West Nile Virus surveillance was analysed in Serbia and Tunisia, Crimea-Congo Haemorrhagic Fever surveillance in Georgia. Our framework enabled a standardized analysis of One Health surveillance integration, and BPMN was easily understandable and conducive to detailed discussions among different actors/institutions. In all countries, we observed integration across sectors and levels except in data collection and data analysis. Data collection was interoperable only in Georgia without integrated analysis. In all countries, surveillance was mainly oriented towards outbreak response, triggered by an index human case. Discussion The three surveillance systems we observed prove that integrated surveillance can be operationalized with a diverse spectrum of options. However, in all countries, the integrated use of data for early warning and inter-sectoral priority setting is pioneeristic. We also noted that early warning before human case occurrence is recurrently not operationally prioritized

Fitness cost in field Anopheles labranchiae populations associated with resistance to the insecticide deltamethrin

We evaluated in the present study the effect of deltamethrin resistance on the fitness cost of the filed populations of Anopheles labranchiae. A susceptible population was used as reference to do different comparisons. We selected the most resistant larvae population collected from northern Tunisia. Eggs were used for study of life history traits including developmental time, larvae mortality, fertility, hatchability and adult sex-ratio. Our results showed that deltamethrin resistance affected negatively (p < 0.05) the developmental time with the median range of 70 h, mortality with the rate of 7 folds in resistant population and hatchability which are lower than in susceptible population. Whereas, no significant differences were detected in adult sex-ratio and fertility of the two studied populations. Our results could help to determine the evolution of population dynamics of the resistant studied population in the areas where insecticide resistance is reported and resistance management is needed. Keywords: deltamethrin, Insecticide resistance, Fitness cost, Anopheles labranchiae, Malaria vector, Tunisi

First investigation of deltamethrin pyrethroid susceptibility and resistance status of Anopheles labranchiae (Falleroni, 1926), potential malaria vector in Tunisia

Objective: To evaluate the deltamethrin pyrethroid insecticides against Anopheles labranchiae, potential malaria vector in Tunisia. Methods: Six field populations of Anopheles labranchiae mosquitoes were collected from six localities in Northern and Central Tunisia between October and November 2016. Different bioassays were performed to estimate the level of resistance in each collected population. Two synergists were used to estimate the involvement of detoxification enzymes in insecticide resistance. Results: All studied strains were resistant and the RR50 ranged from 12.5 in sample #1 to 72.5 in sample #6. Synergist tests using piperonyl butoxide indicated the involvement of monoxygenases enzymes in the recorded resistance. In contrast, the increase of deltamethrin mortality was not significant in presence of S,S,sributyl phosphorothioate (0.8 < SR < 1.2), suggesting no role of esterases (and/or GST) in the resistance phenotype. The correlation recorded between mortality due to DDT and the LC50 of deltamethrin insecticide indicated an insensitive sodium channel affected by Kdr mutation (Spearman rank correlation, r = â0.59, P < 0.01). Conclusions: These results should be considered in the current mosquitoes control programs in Tunisia. The use of pesticides and insecticides by both agricultural and public health departments in Tunisia should be more rational to reduce the development of resistance in populations. Different insecticide applications should be implemented alternately. Keywords: Resistance, Anopheles labranchiae, Deltamethrin pyrethroid, Synergism, Kdr mutation, Tunisi