Graham John Small

IVCC

Background The recent reduction in malaria burden in Côte d’Ivoire is largely attributable to the use of long-lasting insecticidal nets (LLINs). However, this progress is threatened by insecticide resistance and behavioral changes in Anopheles gambiae sensu lato (s.l.) populations and residual malaria transmission, and complementary tools are requi...

Background Restricting the placement of active ingredients (AIs) to specific panels on insecticide-treated nets (ITNs) has the potential to reduce the amount of AI required to treat a net. If the restricted placement of the AIs can exploit mosquito behaviour, particularly where they interact with the bed net interface, and not impact the net's effe...

Introduction Malaria transmission is known to be perennial and heterogeneous in Benin. Studies assessing local malaria prevalence, transmission levels and vector characteristics are critical for designing, monitoring and evaluating new vector control interventions in community trials. We conducted a study in the Zakpota sub-district of central Beni...

VECTRON™ T500 is a wettable powder IRS formulation of broflanilide, a newly discovered insecticide. We performed a two-arm non-inferiority community randomised evaluation of VECTRON™ T500, compared to Fludora® Fusion against pyrethroid-resistant Anopheles gambiae s.l. in an area of high coverage with pyrethroid-only nets in the Za-Kpota District of...

Background The recent reduction in malaria burden in Côte d’Ivoire is largely attributable to use of long-lasting insecticidal nets (LLINs). However, this progress is threatened by insecticide resistance and behavioral changes in Anopheles gambiae sensu lato (s.l.) populations and residual malaria transmission, and complementary tools are required....

Background: VECTRONTM T500 is a wettable powder IRS formulation of broflanilide, a newly discovered insecticide. We performed a two-arm non-inferiority community randomised evaluation of VECTRONTM T500, compared to Fludora® Fusion against pyrethroid-resistant Anopheles gambiae s.l. in an area of high coverage with pyrethroid-only nets in the Za-Kpo...

Insecticides are widely used to control the insects that spread human infectious diseases, in particular falciparum malaria. This widespread use has driven insecticide resistance (IR) to high levels that may threaten the effectiveness of future control programmes. There is interest in identifying deployment methods that alleviate the pressures driv...

Background: Broflanilide is a new insecticide being developed for malaria vector control. As new insecticide chemistries become available, strategies to preserve the susceptibility of local malaria vectors and extend their useful life need to be considered before large scale deployment. This requires the development of appropriate testing procedur...

Background Due to the rapid expansion of pyrethroid-resistance in malaria vectors in Africa, Global Plan for Insecticide Resistance Management (GPIRM) has recommended the development of long-lasting insecticidal nets (LLINs), containing insecticide mixtures of active ingredients with different modes of action to mitigate resistance and improve LLIN...

Management of insecticide resistance in vector control requires development and evaluation of active ingredients (AIs) with new modes of action. VECTRON™ T500 is a wettable powder formulation used for Indoor Residual Spraying (IRS) containing 50% of broflanilide as an AI. This study evaluated the efficacy of VECTRON™ T500 sprayed on blocks of diffe...

Novel insecticides are urgently needed to control insecticide-resistant populations of Anopheles malaria vectors. Broflanilide acts as a non-competitive antagonist of the gamma-aminobutyric acid receptor and has shown prolonged effectiveness as an indoor residual spraying product (VECTRON T500) in experimental hut trials against pyrethroid-resistan...

Background Broflanilide is a newly discovered insecticide with a novel mode of action targeting insect γ-aminobutyric acid receptors. The efficacy of VECTRON™ T500, a wettable powder formulation of broflanilide, was assessed for IRS against wild pyrethroid-resistant malaria vectors in experimental huts in Benin. Methods VECTRON™ T500 was evaluated...

VECTRON T500 shows potential to provide substantial and prolonged control of malaria transmitted by pyrethroid-resistant mosquito vectors when applied for IRS. Its addition to the current list of WHO-approved IRS insecticides will provide a suitable option to facilitate rotation of IRS products with different modes of action

Background: Broflanilide is a new insecticide being developed for malaria vector control. As new insecticide chemistries become available, strategies to preserve the susceptibility of local malaria vectors and extend their useful life need to be considered before large scale deployment. This requires the development of appropriate testing procedure...

Background: Optimising insecticide use and managing insecticide resistance are important to sustain gains against malaria using long-lasting insecticidal nets (LLINs). Restricting insecticides to where mosquitoes are most likely to make multiple contacts could reduce the quantity of insecticide needed to treat the nets. Previous studies have shown...

Novel insecticides are urgently needed to control insecticide resistant populations of Anopheles malaria vectors. Broflanilide acts as a non-competitive antagonist of the gamma-aminobutyric acid (GABA) receptor and has shown prolonged effectiveness as an indoor residual spraying (IRS) product (VECTRON™ T500) in experimental hut trials against pyret...

Background: Malaria cases in some areas could be attributed to vector resistant to the insecticide. World Health Organization recommended insecticides for vector control are limited in number. It is essential to find rotational partners for existing Indoor Residual Spraying (IRS) products. VECTRON ™ T500 is a novel insecticide with broflanilide as...

Background: Optimising insecticide use and managing insecticide resistance are important to sustain gains against malaria using long-lasting insecticidal nets (LLINs). Restricting insecticides to where mosquitoes are most likely to make multiple contacts could reduce insecticide needed to treat nets. Previous studies have shown that nets partially...

Durability monitoring of insecticide-treated nets (ITNs) containing a pyrethroid in combination with a second active ingredient (AI) must be adapted so that the insecticidal bioefficacy of each AI can be monitored independently. An effective way to do this is to measure rapid knock down of a pyrethroid-susceptible strain of mosquitoes to assess the...

Abstract Background: Malaria cases in some areas could be attributed to vector resistant to the insecticide. World Health Organization recommended insecticides for vector control are limited in number. It is essential to find rotational partners for existing Indoor Residual Spraying (IRS) products. VECTRON™ T500 is a novel insecticide with broflan...

Durability monitoring of insecticide-treated nets (ITNs) containing a pyrethroid in combination with a second active ingredient (AI) must be adapted so that the insecticidal bioefficacy of each AI can be monitored independently. An effective way to do this is to measure rapid knock down of a pyrethroid-susceptible strain of mosquitoes to assess the...

Background Indoor residual spraying (IRS) is a major method of malaria vector control across sub-Saharan Africa. Effective control is being undermined by the rapid spread of insecticide resistance. There is major investment in development of new insecticides for IRS that possess novel modes of action, long residual activity, low mammalian toxicity...

Mosquito vector control products are a key component of malaria control programmes in sub-Saharan Africa. With increasing insecticide resistance in malaria-endemic countries, new vector control products are urgently needed, and these must be developed, tested and registered before they can be deployed. Vital to the testing of these products are the...

Background Insecticidal mosquito vector control products are vital components of malaria control programmes. Test facilities are key in assessing the effectiveness of vector control products against local mosquito populations, in environments where they will be used. Data from these test facilities must be of a high quality to be accepted by regula...

Background Although malaria and Anopheles mosquito vectors are highly prevalent in Côte d’Ivoire, limited data are available to help understand the malaria vector density and transmission dynamics in areas bordering the country. To address this gap, the Anopheles mosquito species diversity, the members of the Anopheles gambiae complex and the trans...

Background: Strengthening capacity for public health research is essential to the generation of high-quality, reliable scientific data. This study focuses on a research capacity strengthening project supporting seven test facilities in Africa conducting studies on mosquito vector control products towards Good Laboratory Practice (GLP) certification...

Novel chemistry for vector control is urgently needed to counter insecticide resistance in mosquitoes. Here a new meta-diamide insecticide, broflanilide (TENEBENAL TM), was evaluated in East African experimental huts in Moshi, northern Tanzania. Two consecutive experimental hut trials with broflanilide 50WP were conducted; the first evaluating the...

Background: Strengthening capacity for public health research is essential to the generation of high-quality, reliable scientific data. This study focuses on a research capacity strengthening project supporting seven test facilities in Africa conducting studies on mosquito vector control products towards Good Laboratory Practice (GLP) certification...

Background Although malaria and Anopheles mosquito vectors are highly prevalent in Côte d'Ivoire, data are still lacking on disease transmission dynamics in cross-border areas. To address this lack of information, we assessed the Anopheles mosquito vector species diversity, the An. gambiae complex members and the transmission of malaria in four cro...

Background: With increasing insecticide resistance in malaria-endemic countries there is an urgent need for safe and effective novel vector control products. To improve the capacity of facilities that test insecticides in sub-Saharan Africa, a programme is supporting seven facilities towards Good Laboratory Practice (GLP) certification, the globall...

Background: With insecticide resistance in malaria vectors spreading in geographical range and intensity, there is a need for compounds with novel modes of action to maintain the successes achieved to date by long-lasting insecticidal nets and indoor residual sprays, used as part of an insecticide resistance management strategy. Screening existing...

Background: With insecticide resistance in malaria vectors spreading in geographical range and intensity, there is a need for compounds with novel modes of action to maintain the successes achieved to date by long-lasting insecticidal nets and indoor residual sprays, used as part of an insecticide resistance management strategy. Screening existing...

The effects of sulfuryl fluoride (SF) fumigation and heat treatment on the populations of stored product insect pests in 2 flour mills (A and B) in England, UK, were studied. SF fumigation was conducted in 7 areas of mill A at an accumulated rate of 271-755 g h m-3. In mill B, heat treatment was conducted in 6 areas for between 25 and 36 h. The hea...

The insect populations of 6 flour mills in Europe (4 in the UK and 2 in Italy) were monitored at 3-14 days before and up to 4 months after fumigation using insect traps. Fumigation was very effective in controlling populations of Tribolium sp. and maintained it at a low level up to 3 months or more after application, even with high initial levels o...

Soil fumigants are used extensively in the protection of crops against parasitic nematodes and other soil borne pests. The active ingredient in Telone II soil fumigant is 1,3-Dichloropropene (1,3-D) which has a wide range of uses in Europe as a pre-plant nematocide. During the use of soil fumigants such as 1,3-D a range of non-target soil dwelling...

The impact of sulfuryl fluoride and methyl bromide fumigations upon populations of flour beetles (Tribolium spp.) and of Mediterranean flour moth (Ephestia kuehniella), was evaluated in UK flour mills. Two mills were selected for fumigation with sulfuryl fluoride and two mills for fumigation with methyl bromide. Traps baited with aggregation pherom...

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. was resistant to permethrin and DDT in cotton-growing and urban areas, but susceptible in areas with limited insecticide selection pressure (rice fields and control areas). Neverth...

A novel glutathione S-transferase (GST)-based pyrethroid resistance mechanism was recently identified in Nilaparvata lugens [Vontas, Small and Hemingway (2001) Biochem. J. 357, 65-72]. To determine the nature of GSTs involved in conferring this resistance, the GSTs from resistant and susceptible strains of N. lugens were partially purified by anion...

Anopheles funestus Giles has been implicated as a major malaria vector in sub-Saharan Africa where pyrethroid insecticides are widely used in agriculture and public health. Samples of this species from northern Kwazulu/Natal in South Africa and the Beluluane region of southern Mozambique showed evidence of resistance to pyrethroid insecticides. Ins...

Selection of a laboratory colony of the brown planthopper Nilaparvata lugens with the pyrethroids permethrin and lambda-cyhalothrin increased its resistance to both insecticides. Biochemical analysis and synergistic studies with metabolic inhibitors indicated that elevated glutathione S-transferases (GSTs) with a predominant peroxidase activity con...

Recombinant glutathione S-transferase (agGST1-6) from the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) was expressed in Escherichia coli using a pET3a vector system. The expressed enzyme was biochemically active with reduced glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). Activity of agGST1-6 with GSH and CDNB was...

Glutathione S-transferases (GSTs) belong to a family of detoxification enzymes that conjugate glutathione to various xenobiotics, thus facilitating their expulsion from the cell. GST activity is elevated in many insecticide-resistant insects, including the DDT-resistant malaria vector Anopheles gambiae. Crystals of the recombinant form of a GST fro...

Widespread resistance to organophosphorus insecticides (OPs) in Nilaparvata lugens is associated with elevation of carboxylesterase activity. A cDNA encoding a carboxylesterase, Nl-EST1, has been isolated from an OP-resistant Sri Lankan strain of N. lugens. The full-length cDNA codes for a 547-amino acid protein with high homology to other esterase...

Organophosphorus and carbamate insecticide resistance in Nilaparvata lugens is based on amplification of a carboxylesterase gene, Nl-EST1. An identical gene occurs in susceptible insects. Quantitative real-time PCR was used to demonstrate that Nl-EST1 is amplified 3-7-fold in the genome of resistant compared to susceptible planthoppers. Expression...

Glutathione S-transferase (GST) activity assays in insects are usually performed by spectrophotometric kinetic measurements of conjugated product formation with substrates such as reduced glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB). This requires a spectrophotometer that can measure absorbance in the UV range and microcentrifugation to...

The major insecticide resistance mechanism in the brown planthopper Nilaparvata lugens involves overproduction of esterases. Esterases purified from a resistant strain appeared as a ladder of bands on isoelectric focussing (IEF) gels from pI 4.7 to 5.0. Two-dimensional electrophoresis showed that isozymes ranged in size from 66 to 68 kDa with those...

Elevated esterase Estbeta1 was purified from larvae of newly isolated strains of the mosquito Culex quinquefasciatus from Colombia (COL) and Trinidad (TRI) with resistance to organophosphate (OP) insecticides. Insecticide interactions were compared with those of elevated Estbeta1(2) from the OP-resistant Habana strain and the non-elevated Estbeta1(...

Esterase amplification is the major organophosphorus (OP) insecticide resistance mechanism in Culex mosquitoes. The amplified Estalpha2(1)¿Estbeta2(1) esterases are found in > 90% of resistant populations worldwide, whereas amplified DNAs (amplicons) containing Estbeta1s are much rarer. Individuals with the Estbeta1 amplicons appear to be at a sele...

Esterases from insecticide resistant and susceptible Blattella germanica (L.) were examined biochemically. Two strains were utilized: Johnson Wax (JWax; susceptible), and Munsyana (MA; chlorpyrifos LD50 and LD95 resistance ratio 5.2 and 10.0). On native polyacrylamide gel electrophoresis (PAGE), MA had four visible esterase electromorphs (El, E2, E...

A combination of insecticidal, biochemical, and electrophoretic assays were conducted on adult male and 1st instars of a field-collected strain of German cockroach, Blattella germanica (L.) (Muncie'86), to characterize its insecticide resistance. In topical applications to adult males, 11 technical grade insecticides were tested over 3 yr. These in...

The organophosphate resistance-associated elevated esterases Estα2, Estβ1 and Estβ2 were purified to homogeneity from larvae of the Cuban Habana strain. The bimolecular rate constants (kas) of Habana Estβ1 with a range of organophosphates were not significantly different to those of PelRR Estβ21 , and were higher with some organop...

Pyrethroid-impregnated bednets are being used nationwide in The Gambia. The future success of this malaria control programme depends partly on the vectors remaining susceptible to those insecticides used for treating the nets. The present study was carried out on the south bank of the river Gambia, during the first large scale trial of nets in this...

Thirty strains of Blattella germanica (L.) reported to be pyrethroid resistant were collected from three continents. Greater than 2-fold resistance to the pyrethroids cyfluthrin, fenvalerate, cypermethrin, and lambda cyhalothrin appeared in 15 of these strains. Twelve of these strains were also resistant to chlorpyrifos and propoxur. All the field...

The resistance status of 14 strains of Blattella germanica (L.) from four countries was determined for chlorpyrifos and propoxur compared with a standard reference susceptible strain. Thirteen strains were resistant to chlorpyrifos; 12 strains were resistant to propoxur. Resistance ratios for chlorpyrifos ranged from 8- to 462-fold at LC90; for pro...

Multi-resistant strains of Blattella germanica are now common, and strategies for their continued control using conventional insecticides need to be devised rationally if long-term suppression of these nuisance insects is to be achieved. Newer insecticides such as growth regulators may have a role in such strategies, but these cannot be used wholly...

In Turkey, the mosquito Anopheles sacharovi has been under field selection pressure sequentially with DDT, dieldrin, malathion and pirimiphos-methyl over a period of 30 years for the purpose of malaria control. In 1984, the field population of An.sacharovi in the malarious Çukurova plain of Adana Province contained an altered acetylcholinesterase-b...

Use of malathion for mosquito control in Cuba for 7 years up to 1986 has selected for elevated non-specific esterase and altered acetylcholinesterase (AChE) resistance mechanisms in populations of the pest mosquito Culex quinquefasciatus Say. These mechanisms are still present in relatively high frequencies in the Havana area, despite the replaceme...

A description of the eggs of Toxorhynchites moctezuma is presented, accompanied with photographs using both light and electron microscopy. Field observations on the oviposition behavior of this species are also described. In addition, the eggs of five Toxorhynchites species are compared and three photographed.