ABSTRACT
Abstract:tbackground:Chemicals are used for rapid control of large area; although misuse of those insecticide leads to resistance; resurgence of pests and finally replacement of insecticide which is unaffordable in developing Country.Objectives:This study aimed to determine the susceptibility status of Culex quinquefasciatus larvae to four organophosphate insecticides; Temephos; Fenthion; Fenitrothion and Chlorpyrifos.Material et methods.Following WHO standard protocols; larval susceptibility tests were carried out in 3 localities;namely Khartoum; Omdurman and Khartoum North. Mortality rates and lethal concentration (LC 50 and LC 95) were calculated for four types of organophosphate insecticides: includes; Temephos; Fenthion; Fenitrithion and Chlorpyrifos.results: Susceptibility of Culex quinquefasciatus; prevalent in the three greater localities of Khartoum State was determined against four organophosphates (Temephos; Fenitrothion; Fenthion and Chlorpyrifos) were confirmed resistant (mortality below 80). Studies were carried out on late 3rd or early 4th instar larvae of these species using standard WHO technique. Based on concentration mortality data LC 50 and LC 95 values were calculated. LC 50 values as observed for the above four insecticides in the three greater localities Khartoum North ; Khartoum and Omdurman for Fenitrothion were 0.8097; 0.0398 and 0.0432?g per litre ; for Temephos 0.47; 3.85 and 12.82 ?g per litre and for Fenthion .15; 0.11 and 0.91 ?g per litreand finally for Chlorpyrifos 0.31; 0.39 and 13.76 ?g per litre respectively.Conclusion: The study concluded that;Cx. quinquefasciatus larvae in Khartoum State create a resistance to the tested larvicides(Fenthion;Temephos; Fenitrothion and Chlorpyrifos).recommendations:Use of non-chemical control methods in addition to using insecticide mixture is important tactics to manage insecticides resistance
Subject(s)
Culex , Insecticides , Malaria , Organophosphorus CompoundsABSTRACT
Background: During the mid-1970s, larvicides have become available that are highly effective, yet selective in action, and therefore environmentally safe to non-target organisms, as well as for human exposure(1). Objectives: The small field trial was carried out from 12th of January to 16th of February 2008 in Khartoum State to evaluate the efficacy and persistence mosquito dunk® (Bti) against mosquito larvae and to measure the effect of physic-chemical properties on mosquito dunk. Material & Methods: The efficacy and persistence of Bacillus thuringiensis subspecies israelensis (mosquito dunk®) as a biological control agent against mosquito larvae was conducted in Khartoum State. Twelve ponds were used as natural breeding habitats of mosquitoes; six of them were treated with dunk at a rate of 1 dunk per 100 square feet and six ponds left untreated (control). Results: The study revealed that more than 80% reduction in immature stages density was observed up to 5, 3 and 2 weeks for the 3rd, 2nd and 4th instars of Anopheline spp., respectively. However, the study showed that the mosquito dunk was noteffective (under 80% mortality) against 1st, instar larvae and pupae of Anopheline species as well as Culex developmental stages. Conclusion & Interpretations: The dunk was very effective in controlling 3rd and 4th instars of Anopheles spp; for 2 weeks interval. Therefore we propose a surface application regime of once every 2 weeks for mosquito dunk
Subject(s)
Bacillus thuringiensis , Mosquito Control/methods , National Health Programs , SudanABSTRACT
Abstract:background et objectives:Mosquito control is becoming increasingly difficult because of the developmentof resistance in vectors to conventional insecticides. The resistance in vectors warrants development of newer insecticides for mosquito control besides use of other counter-measures. This study aimed to determine the susceptibility of adult and larvae of Cx.quinquefasciatus mosquitoes (Diptera: Culicidae) to malathion; temephos; lambdacyhalothrin and permethrin insecticides in Khartoum locality.Material et methods:Susceptibility of Culex quinquefasciatus mosquitoes to malathion; lambdacyhalothrin and permethrin; and of the larvae to temephos in Khartoum locality was carried out; following WHO standard susceptibility tests. One to three days old female mosquitoes; which were reared from field collected immature stages; were exposed to discriminating dosages of the insecticides; for respective exposure periods. Then knockdown time and 24-hours mortality were recorded. For larvae which were exposed to a series of temephos concentrations; and LC 50 and LC 90 values were calculated.results:The study revealed that;Culex quinquefasciatus is predominant in Khartoum locality. Evidence of resistance was revealed to malathion and the two pyrethroids against Culex quinquefasciatus. The average KDT 50 values consider high and indicated resistance. But larvae stages were found to be susceptible to temephos.Interpretation et conclusion:Resistance of the field population of Cx. quinquefasciatus in Khartoum was revealed to malathion; lambdacyhalothrin and permethrin. On the other hand; the same population of Cx. quinquefasciatus is still sensitive to temephos. Therefore; the vector control unit should consider introducing rotation of insecticidesas a management strategy to increase the duration of the usage of the current insecticides. Furthermore; a rationalized use of insecticides coupled with regular monitoring of insecticide resistance is recommended to mitigate the rapid emergence of insecticide resistance