Remote Effect of Insecticide-Treated Nets and the Personal Protection against Malaria Mosquito Bites.

Experimental huts are part of the WHO process for testing and evaluation of Insecticide Treated Nets (ITN) in semi-field conditions. Experimental Hut Trials (EHTs) mostly focus on two main indicators (i.e.

Proposed use of spatial mortality assessments as part of the pesticide evaluation scheme for vector control.

Background: The WHO Pesticide Evaluation Scheme to evaluate the efficacy of insecticides does not include the testing of a lethal effect at a distance. A tool was developed to evaluate the spatial mortality of an insecticide product against adult mosquitoes at a distance under laboratory and field conditions. Operational implications are discussed.

Efficacy of an insecticide paint against malaria vectors and nuisance in West Africa--part 2: field evaluation.

Background: Widespread resistance of the main malaria vector Anopheles gambiae to pyrethroids reported in many African countries and operational drawbacks to current IRS methods suggest the convenience of exploring new products and approaches for vector control. Insecticide paint Inesfly 5A IGR™, containing two organophosphates (OPs), chlorpyrifos and diazinon, and one insect growth regulator (IGR), pyriproxyfen, was tested in Benin, West Africa, for 12 months.

Methods: Field trials were conducted in six experimental huts that were randomly allocated to one or two layers of insecticide at 1 Kg/6 m2 or control.

Efficacy of an insecticide paint against insecticide-susceptible and resistant mosquitoes - part 1: laboratory evaluation.

Background: The main malaria vector Anopheles gambiae and the urban pest nuisance Culex quinquefasciatus are increasingly resistant to pyrethroids in many African countries. There is a need for new products and strategies. Insecticide paint Inesfly 5A IGR™, containing two organophosphates (OPs), chlorpyrifos and diazinon, and insect growth regulator (IGR), pyriproxyfen, was tested under laboratory conditions for 12 months following WHOPES Phase I procedures.

New protective battle-dress impregnated against mosquito vector bites.

Background: Mixing repellent and organophosphate (OP) insecticides to better control pyrethroid resistant mosquito vectors is a promising strategy developed for bed net impregnation. Here, we investigated the opportunity to adapt this strategy to personal protection in the form of impregnated clothes.

Methods: We compared standard permethrin impregnated uniforms with uniforms manually impregnated with the repellent KBR3023 alone and in combination with an organophosphate, Pirimiphos-Methyl (PM).

Field efficacy of pyrethroid treated plastic sheeting (durable lining) in combination with long lasting insecticidal nets against malaria vectors.

Background: Insecticide treated plastic sheeting (ITPS), sometimes known as durable lining, has potential as a long-lasting insecticidal surface for malaria vector control when used as lining for interior walls and ceilings inside the home. Against a backdrop of increasing long lasting net (LN) coverage, we examined the effect of combining permethrin-treated plastic sheeting (ITPS) with LNs in Burkina Faso.

Methods: A verandah trap experimental hut trial of ITPS with or without Olyset LN was conducted in the Vallée du Kou near Bobo-Dioulasso, where the two molecular forms of Anopheles gambiae s.

Field efficacy of a new mosaic long-lasting mosquito net (PermaNet 3.0) against pyrethroid-resistant malaria vectors: a multi centre study in Western and Central Africa.

Background: Due to the spread of pyrethroid-resistance in malaria vectors in Africa, new strategies and tools are urgently needed to better control malaria transmission. The aim of this study was to evaluate the performances of a new mosaic long-lasting insecticidal net (LLIN), i.e.

Synergy between repellents and organophosphates on bed nets: efficacy and behavioural response of natural free-flying An. gambiae mosquitoes.

Background: Chemicals are used on bed nets in order to prevent infected bites and to kill aggressive malaria vectors. Because pyrethroid resistance has become widespread in the main malaria vectors, research for alternative active ingredients becomes urgent. Mixing a repellent and a non-pyrethroid insecticide seemed to be a promising tool as mixtures in the laboratory showed the same features as pyrethroids.

Managing insecticide resistance in malaria vectors by combining carbamate-treated plastic wall sheeting and pyrethroid-treated bed nets.

Background: Pyrethroid resistance is now widespread in Anopheles gambiae, the major vector for malaria in sub-Saharan Africa. This resistance may compromise malaria vector control strategies that are currently in use in endemic areas. In this context, a new tool for management of resistant mosquitoes based on the combination of a pyrethroid-treated bed net and carbamate-treated plastic sheeting was developed.

Evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent deet.

Background: N,N-Diethyl-3-methylbenzamide (deet) remains the gold standard for insect repellents. About 200 million people use it every year and over 8 billion doses have been applied over the past 50 years. Despite the widespread and increased interest in the use of deet in public health programmes, controversies remain concerning both the identification of its target sites at the olfactory system and its mechanism of toxicity in insects, mammals and humans.

Mixture for controlling insecticide-resistant malaria vectors.

The spread of resistance to pyrethroids in the major Afrotropical malaria vectors Anopheles gambiae s.s. necessitates the development of new strategies to control resistant mosquito populations.

Dynamics of multiple insecticide resistance in the malaria vector Anopheles gambiae in a rice growing area in South-Western Burkina Faso.

Background: Insecticide resistance of the main malaria vector, Anopheles gambiae, has been reported in south-western Burkina Faso, West Africa. Cross-resistance to DDT and pyrethroids was conferred by alterations at site of action in the sodium channel, the Leu-Phe kdr mutation; resistance to organophosphates and carbamates resulted from a single point mutation in the oxyanion hole of the acetylcholinesterase enzyme designed as ace-1R.

Methods: An entomological survey was carried out during the rainy season of 2005 at Vallée du Kou, a rice growing area in south-western Burkina Faso.

Identification and geographic distribution of the ACE-1R mutation in the malaria vector Anopheles gambiae in south-western Burkina Faso, West Africa.

Resistance of Anopheles gambiae to organophosphate and carbamate insecticides was first reported in Côte d'Ivoire, West Africa. Subsequent studies revealed that it resulted from a single point mutation in the oxyanion hole of the acetycholinesterase enzyme (ace-1(R) mutation). We investigated the distribution and prevalence of the ace-1(R) mutation in An.

Synergy between repellents and non-pyrethroid insecticides strongly extends the efficacy of treated nets against Anopheles gambiae.

Background: To manage the kdr pyrethroid-resistance in Anopheline malaria vectors, new compounds or new strategies are urgently needed. Recently, mixing repellents (DEET) and a non-pyrethroid insecticide (propoxur) was shown to be as effective as deltamethrin, a standard pyrethroid, under laboratory conditions, because of a strong synergy between the two compounds. In the present study, the interactions between two repellents (DEET and KBR 3023) and a non-pyrethroid insecticide (pyrimiphos methyl or PM) on netting were investigated.

Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon.

Background: Recent field studies indicated that insecticide-treated bednets (ITNs) maintain their efficacy despite a high frequency of the knock-down resistance (kdr) gene in Anopheles gambiae populations. It was essential to evaluate ITNs efficacy in areas with metabolic-based resistance.

Methods: Bifenthrin was used in this experiment because it is considered a promising candidate for bednets impregnation.

Synergism between insecticides permethrin and propoxur occurs through activation of presynaptic muscarinic negative feedback of acetylcholine release in the insect central nervous system.

Although synergism between pesticides has been widely documented, the physiological mechanisms by which an insecticide synergizes another remains unclear. Toxicological and electrophysiological studies were carried out on two susceptible pest species (the mosquito Culex quinquefasciatus and the cockroach Periplaneta americana) to understand better the physiological process involved in pyrethroid and carbamate interactions. Larval bioassays were conducted with the susceptible reference strain SLAB of C.

Spinosad: a new larvicide against insecticide-resistant mosquito larvae.

Among the characteristics of spinosad that are worth noting is its environmentally favorable toxicity profile. It is a compound of biological origin, whose insecticide action is highly effective against a great number of insects. Laboratory larval bioassays of spinosad on Aedes aegypti, Culex quinquefasciatus, and Anopheles gambiae (specimens that were either susceptible or resistant to pyrethroids, carbamates, and organophosphates) showed that this product had a lethal action (mortality after 24 h of exposure) regardless of the original status, susceptible or resistant, of the mosquito larvae.

Assessment of laboratory and field assays of sunlight-induced killing of mosquito larvae by photosensitizers.

The effectiveness of light-induced killing of mosquito larvae in the presence of photosensitizers was studied with larvae of Aedes aegypti (L.), Anopheles stephensi (Liston), and Culex quinquefasciatus Say grown in the laboratory and of Cx. quinquefasciatus grown under field conditions.

Combination of a non-pyrethroid insecticide and a repellent: a new approach for controlling knockdown-resistant mosquitoes.

Although pyrethroid-treated materials are a promising tool for the prevention and the control of dengue in the tropics, the development of pyrethroid resistance in the main mosquito vector (Aedes aegypti) may negate their use for personal and/or community protection. In that context, the efficacy of a mixture of a repellent (N,N-diethyl toluamide [DEET]) and a non-pyrethroid insecticide (propoxur) was investigated under laboratory conditions against both pyrethroid-susceptible and pyrethroid-resistant mosquitoes with the knockdown resistance (kdr) mutation. The results showed that a combination of propoxur and DEET induced a knockdown effect and mortality as high as deltamethrin (a standard pyrethroid) against the susceptible strain, and significantly higher efficacy against the pyrethroid-resistant strain.

Experimental hut evaluation of bednets treated with an organophosphate (chlorpyrifos-methyl) or a pyrethroid (lambdacyhalothrin) alone and in combination against insecticide-resistant Anopheles gambiae and Culex quinquefasciatus mosquitoes.

Background: Pyrethroid resistant mosquitoes are becoming increasingly common in parts of Africa. It is important to identify alternative insecticides which, if necessary, could be used to replace or supplement the pyrethroids for use on treated nets. Certain compounds of an earlier generation of insecticides, the organophosphates may have potential as net treatments.

Topical applications of pyrethroid and organophosphate mixtures revealed positive interactions against pyrethroid-resistant Anopheles gambiae.

The efficacy of a binary mixture of bifenthrin (pyrethroid) and chlorpyrifos-methyl (organophosphate) has been tested against susceptible and pyrethroid-resistant strains of Anopheles gambiae Giles, the major malaria vector in sub-Saharan Africa. Dose-mortality regression lines were determined for each insecticide alone and in mixtures by topical applications on adult female mosquitoes. A combination index (CI) was used to quantify the interactions occurring between the pyrethroid and organophosphate insecticides.

Dinotefuran: a potential neonicotinoid insecticide against resistant mosquitoes.

Because pyrethroid, organophosphate, and carbamate resistance is more and more developed in mosquitoes of medical importance, there is an urgent need for alternative insecticides for vector control. Dinotefuran, a new neonicotinoid insecticide commercialized by Mitsui Chemicals (Tokyo, Japan), could be a useful candidate in public health because it shows low mammalian toxicity and great insecticidal activity against a broad range of pests. In this study, the intrinsic toxicity of dinotefuran was evaluated by larval bioassay and topical application against different mosquito strains of Anopheles gambiae Giles, Culex quinquefasciatus Say, and Aedes aegypti L.

Dosage-dependent effects of permethrin-treated nets on the behaviour of Anopheles gambiae and the selection of pyrethroid resistance.

Background: The evolution and spread of pyrethroid resistance in Anopheles gambiae s.s, the major malaria vector in sub-Saharan Africa, is of great concern owing to the importance of pyrethroid-treated nets in the WHO global strategy for malaria control. The impact of kdr (the main pyrethroid-resistance mechanism) on the behaviour of An.

Efficacy of insecticide mixtures against larvae of Culex quinquefasciatus (Say) (Diptera: Culicidae) resistant to pyrethroids and carbamates.

The efficacy of insecticide mixtures of permethrin (pyrethroid) and propoxur (carbamate) was tested by larval bioassays on two strains of Culex quinquefasciatus (Say), one resistant to pyrethroids and the other resistant to carbamates. The method consisted in combining one insecticide at the highest concentration causing no mortality (LC0) with increasing concentrations of the second one. The concentration-mortality regression lines were determined for permethrin and propoxur alone and in combination, and synergism ratios (SR) were calculated in order to determine the magnitude of an increase or decrease in efficacy with use of the mixtures.

Evidence for selection of insecticide resistance due to insensitive acetylcholinesterase by carbamate-treated nets in Anopheles gambiae s.s. (Diptera: Culicidae) from Côte d'Ivoire.

Pyrethroid-treated nets are an efficient tool for reducing malaria transmission and morbidity. The recent evolution of pyrethroid resistance in several Anopheles species represents a major threat for the future success of roll back malaria in Africa. The possible use of nonpyrethroid insecticides, such as carbamates, on nets is a promising alternative solution because these insecticides are effective against susceptible and pyrethroid-resistant populations of Anopheles and Culex mosquitoes.