Elevated activity of an Epsilon class glutathione transferase confers DDT resistance in the dengue vector, Aedes aegypti.

Glutathione transferases (GSTs) play a central role in the detoxification of xenobiotics such as insecticides and elevated GST expression is an important mechanism of insecticide resistance. In the mosquito, Anopheles gambiae, increased expression of an Epsilon class GST, GSTE2, confers resistance to DDT. We have identified eight GST genes in the dengue vector, Aedes aegypti.

Field evaluation of a recombinant glutathione S-transferase-based pyrethroid quantification assay.

A recombinant glutathione S-transferase (GST)-based pyrethroid quantification assay was field-tested in Ifakara, Tanzania. Initial laboratory tests suggested that all reagents used in the assay should be sufficiently stable for field use, provided that domestic refrigeration facilities were available. Insecticide-impregnated bednets were collected from a region where a social marketing programme was in progress.

The Anopheles gambiae detoxification chip: a highly specific microarray to study metabolic-based insecticide resistance in malaria vectors.

Metabolic pathways play an important role in insecticide resistance, but the full spectra of the genes involved in resistance has not been established. We constructed a microarray containing unique fragments from 230 Anopheles gambiae genes putatively involved in insecticide metabolism [cytochrome P450s (P450s), GSTs, and carboxylesterases and redox genes, partners of the P450 oxidative metabolic complex, and various controls]. We used this detox chip to monitor the expression of the detoxifying genes in insecticide resistant and susceptible An.

Insect glutathione transferases and insecticide resistance.

Glutathione transferases (GSTs) are a diverse family of enzymes found ubiquitously in aerobic organisms. They play a central role in the detoxification of both endogenous and xenobiotic compounds and are also involved in intracellular transport, biosynthesis of hormones and protection against oxidative stress. Interest in insect GSTs has primarily focused on their role in insecticide resistance.

Characterization of the promoters of Epsilon glutathione transferases in the mosquito Anopheles gambiae and their response to oxidative stress.

Epsilon class GSTs (glutathione transferases) are expressed at higher levels in Anopheles gambiae mosquitoes that are resistant to DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane] than in insecticide-susceptible individuals. At least one of the eight Epsilon GSTs in this species, GSTe2, efficiently metabolizes DDT to DDE [1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane]. In the present study, we investigated the factors regulating expression of this class of GSTs.

The spread of the Leu-Phe kdr mutation through Anopheles gambiae complex in Burkina Faso: genetic introgression and de novo phenomena.

During extensive sampling in Burkina Faso and other African countries, the Leu-Phe mutation producing the kdr pyrethroid resistance phenotype was reported in both Anopheles gambiae ss and A. arabiensis. This mutation was widely distributed at high frequency in the molecular S form of A.

Genetic mapping of genes conferring permethrin resistance in the malaria vector, Anopheles gambiae.

Resistance to permethrin in an East African population of the major malaria vector, Anopheles gambiae is multifactorial. A mutated sodium channel allele and enhanced insecticide metabolism contribute to the resistance phenotype. We used microsatellite markers to scan the genome for quantitative trait loci (QTL) associated with permethrin resistance.

The molecular basis of insecticide resistance in mosquitoes.

Insecticide resistance is an inherited characteristic involving changes in one or more insect gene. The molecular basis of these changes are only now being fully determined, aided by the availability of the Drosophila melanogaster and Anopheles gambiae genome sequences. This paper reviews what is currently known about insecticide resistance conferred by metabolic or target site changes in mosquitoes.

Field issues related to effectiveness of insecticide-treated nets in Tanzania.

Insecticide-treated nets (ITNs) impregnated with pyrethroid insecticides have become one of the most promising interventions to prevent malaria in highly endemic areas. Despite the large body of experience documenting their health impact and the best way to distribute them, some key practical issues remain unresolved. For example, the duration of effective life of a net under field conditions is unknown.

Structure of an insect delta-class glutathione S-transferase from a DDT-resistant strain of the malaria vector Anopheles gambiae.

Glutathione S-transferases (GSTs) are a major family of detoxification enzymes which possess a wide range of substrate specificities. Most organisms possess many GSTs belonging to multiple classes. Interest in GSTs in insects is focused on their role in insecticide resistance; many resistant insects have elevated levels of GST activity.

An adult-specific CYP6 P450 gene is overexpressed in a pyrethroid-resistant strain of the malaria vector, Anopheles gambiae.

Many malaria control programmes are based on insecticide application as adulticides, often in the form of pyrethroid-impregnated bed nets. However, the efficacy of this control measure can be reduced by genetic changes in vector insecticide susceptibility. Pyrethroid resistance has been detected in the major African malaria vector, Anopheles gambiae, and has been attributed to a combination of target site insensitivity and increased oxidative metabolism of the insecticide, catalysed by cytochrome P450s.

The Anopheles gambiae glutathione transferase supergene family: annotation, phylogeny and expression profiles.

Background: Twenty-eight genes putatively encoding cytosolic glutathione transferases have been identified in the Anopheles gambiae genome. We manually annotated these genes and then confirmed the annotation by sequencing of A. gambiae cDNAs.

Malaria parasite and vector genomes: partners in crime.

The publication of the genome sequences of the malaria parasite Plasmodium falciparum and the insect vector Anopheles gambiae paves the way for scientists to study these organisms by using technologies developed to observe global changes in transcription and translation, as well as computational tools. Researchers are now able to investigate complex changes involved in development, growth and reaction to external factors. Given the medical importance of these organisms, much of this work is targeted on drug or insecticide discovery (including mechanisms of resistance to existing treatments), but the genome information also provides the opportunity to develop novel therapies.

Molecular evidence for a kdr-like pyrethroid resistance mechanism in the malaria vector mosquito Anopheles stephensi.

The mosquito Anopheles stephensi Liston (Diptera: Culicidae) is the urban vector of malaria in several countries of the Middle East and Indian subcontinent. Extensive use of residual insecticide spraying for malaria vector control has selected An. stephensi resistance to DDT, dieldrin, malathion and other organophosphates throughout much of its range and to pyrethroids in the Middle East.

Malaria: past problems and future prospects. After more than a decade of neglect, malaria is finally black on the agenda for both biomedical research and public health politics.

After more than a decade of neglect, malaria is finally back on the agenda for both biomedical research and public health politics

Knowledge and beliefs about malaria transmission and practices for vector control in southern Mexico.

Objective: To investigate the knowledge and beliefs about malaria transmission and practices for vector control in eight villages on the coastal plain of Chiapas, Mexico.

Material And Methods: A cross-sectional survey was conducted during May and June 1995 in Chiapas, Mexico. A questionnaire to investigate family structure, knowledge on malaria transmission, preventive measures and attitudes towards seeking treatment was applied to both family heads of a sample of households.

Heterologous expression of four glutathione transferase genes genetically linked to a major insecticide-resistance locus from the malaria vector Anopheles gambiae.

A cluster of eight genes encoding glutathione transferases (GSTs) are located on division 33B of polytene chromosome arm 3R of the African malaria mosquito, Anopheles gambiae. This region of the genome contains a major 1,1,1-trichloro-2,2-bis-( p -chlorophenyl)ethane (DDT)-resistance locus, rtd1. These GSTs belong to the insect-specific Epsilon class and share between 22.

First report of the kdr mutation in Anopheles gambiae M form from Burkina Faso, west Africa.

The kdr mutation, conferring resistance to pyrethroid insecticides, has been reported in several West-African populations of Anopheles gambiae S form and in the M form populations from tropical forest of Benin. We report the finding of a single M specimen collected in the rice-field area of Vallée du Kou (Burkina Faso) showing the mutation at the heterozygous state. The monitoring of kdr mutation in An.

KDR mutation, a genetic marker to assess events of introgression between the molecular M and S forms of Anopheles gambiae (Diptera: Culicidae) in the tropical savannah area of West Africa.

A sodium channel 'kdr'-type mutation was identified in the M form of Anopheles gambiae from Burkina Faso in the tropical savannah area belt. The molecular M form of An. gambiae is found at high frequencies in the flooded rice cultivation area of Kou Valley, where the insecticide selection pressure is limited.

Pyrethroid and DDT cross-resistance in Aedes aegypti is correlated with novel mutations in the voltage-gated sodium channel gene.

Samples of the dengue vector mosquito Aedes aegypti (L.) (Diptera: Culicidae) were collected from 13 localities between 1995 and 1998. Two laboratory strains, Bora (French Polynesia) and AEAE, were both susceptible to DDT and permethrin; all other strains, except Larentuka (Indonesia) and Bouaké (Ivory Coast), contained individual fourth-instar larvae resistant to permethrin.

The role of agricultural use of insecticides in resistance to pyrethroids in Anopheles gambiae s.l. in Burkina Faso.

Agricultural use of insecticides is involved in the selection of resistance to these compounds in field populations of mosquitoes in Burkina Faso. Anopheles gambiae s.l.