Combining indoor residual spraying with chlorfenapyr and long-lasting insecticidal bed nets for improved control of pyrethroid-resistant Anopheles gambiae: an experimental hut trial in Benin.

BACKGROUND: Neither indoor residual spraying (IRS) nor long-lasting insecticidal nets (LLINs) are able to fully interrupt transmission in holoendemic Africa as single interventions. The combining of IRS and LLINs presents an opportunity for improved control and management of pyrethroid resistance through the simultaneous presentation of unrelated insecticides. METHOD: Chlorfenapyr IRS and a pyrethroid-impregnated polyester LLIN (WHO approved) were tested separately and together in experimental huts in southern Benin against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus. The bed nets were deliberately holed with either six or 80 holes to examine the effect of increasing wear and tear on protectiveness. Anopheles gambiae were genotyped for the kdr gene to assess the combination's potential to prevent the selection of pyrethroid resistance. RESULTS: The frequency of kdr was 84%. The overall mortality rates of An. gambiae were 37% and 49% with the six-hole and 80-hole LLINs, respectively, and reached 57% with chlorfenapyr IRS. Overall mortality rates were significantly higher with the combination treatments (82-83%) than with the LLIN or IRS individual treatments. Blood feeding (mosquito biting) rates were lowest with the 6-hole LLIN (12%), intermediate with the 80-hole LLIN (32%) and highest with untreated nets (56% with the 6-hole and 54% with the 80-hole nets). Blood feeding (biting) rates and repellency of mosquitoes with the combination of LLIN and chlorfenapyr IRS showed significant improvement compared to the IRS treatment but did not differ from the LLIN treatments indicating that the LLINs were the primary agents of personal protection. The combination killed significantly higher proportions of Cx. quinquefasciatus (51%, 41%) than the LLIN (15%, 13%) or IRS (32%) treatments. CONCLUSION: The chlorfenapyr IRS component was largely responsible for controlling pyrethroid-resistant mosquitoes and the LLIN component was largely responsible for blood feeding inhibition and personal protection. Together, the combination shows potential to provide additional levels of transmission control and personal protection against pyrethroid-resistant mosquitoes, thereby justifying the additional resources required. Chlorfenapyr has potential to manage pyrethroid resistance in the context of an expanding LLIN/IRS strategy

Comportement de principaux bioagresseurs et maladies du cotonnier sur les variétés éprouvées de cotonnier (Gossypium hirsutum) sous différentes doses d’engrais à Angaradébou au Bénin

Au Bénin, la filière coton participe activement à l’économie    nationale.Quatre nouvelles variétés issues du Centre de Recherches  Agricoles Coton et Fibres ont été testées au Nord Bénin dans l'optique d'identifier la variété la mieux adaptée. Ces variétés ont été comparées à la variété H 279-1en vulgarisation. L’objectif est  d’évaluer les   comportements des variétés vis-à-vis des bioagresseurs et des maladies dans la zone. Le dispositif expérimental est un split plot à six répétitions, composé d’un facteur principal représenté par trois doses d’engrais  chimique à savoir D1 (témoin) = 150 kg de NPKSB + 50 kg d’Urée à  l’hectare, D2=200 kg de NPKSB + 50 kg d’Urée à l’hectare et D3= 250 kg de NPKSB + 50 kg d’Urée à l’hectare. Le facteur secondaire est composé de cinq variétés : H 279-1, I875-3, E956-2, H769-5 et H782-3. Il a été révélé que la pression parasitaire a été la même au niveau de toutes les variétés et ne dépend pas des doses d’engrais  appliquées. Les variétés E956-2 et H782-3 sont moins sensibles à la bactériose que les variétés H 279-1,  I875-3 et H 769-5 avec des valeurs respectivement de 0,37;0,29; 0,67; 0,68 et 0,59 plants attaqués sur 10 observés.Mots clés: Comportement, variétés, engrais chimique, pression parasitaire, ravageurs, bactériose

Diversité et évaluation participative des cultivars du manioc (Manihot esculenta Crantz) au Centre Bénin

Le manioc est une plante alimentaire qui contribue fortement à la sécurité alimentaire au Bénin. Pour évaluer sa diversité variétale, les performances  agronomiques, technologiques et culinaires de ses cultivars dans la région centrale du Bénin, 41 villages ont été prospectés. Sous réserve de  synonymie, 107  cultivars de manioc ont été recensés dont 59 élites. L’indice de diversité de Shannon est de 3,78 et traduit une importante diversité variétale. Le nombre de  cultivars recensés varie de 3 à 26 par village (10 en moyenne). Dans les villages où une perte de diversité variétale est notée, son taux a varié de 6,25 à 80% avec  un taux moyen de 42,22% par village. Les cultivars à produire sont choisis sur la base de 21 critères dont les plus importants sont la forte productivité (16,37% de reponses), la qualité et le rendement en gari (15,52% de reponses) et la précocité (13,27% de reponses). Les contraintes de production (9 au total) perçues par les producteurs peuvent etre levées par l’utilisation des  cultivars performants. L’évaluation participative a révélé l’existence de très peu de cultivars performants par  rapport aux paramètres biotiques et abiotiques. La mise en place d’un programme d’amélioration et de création variétale est fortement recommandée pour la relance de la production du manioc au Bénin.Mots clés : Bénin, critère de préférence, cultivar élite, diversité variétale, évaluation participative, manioc

Repellent effect and insecticidal activities of Bridelia ferruginea, Blighia sapida, and Khaya senegalensis leaves powders and extracts against Dinoderus porcellus in infested dried yam chips

Open Access Article; Published online: 21 June 2017Dinoderus porcellus is considered as the most important pest of stored yam chips and compounds extracted from plants can be used for its control. The present study aimed to test the insecticidal and repellent activities of powders and extracts of leaves of Bridelia ferruginea, Blighia sapida, and Khaya senegalensis against D. porcellus. The efficacy of plant powders was compared with the synthetic pesticide Antouka (Permethrin 3 g/kg + pirimiphos 16 g/kg). The results of the experiment revealed that all plant powders were effective as repellents. Antouka was more effective as insecticidal than the plant powders and minimal weight loss was observed with B. sapida at 2%. Among treatments, propanol extract of K. senegalensis at 5% was found to elicit the highest repellent effect on D. porcellus. The LC50 results revealed that the acetone extract of K. senegalensis is the most toxic (0.29 μL/insect) to the pest, while the propanol extract of B. ferruginea at 5% exhibited strong fumigant toxicity against D. porcellus, with 88.89% of pest mortality at 160 μL/L air. The findings from the current work proved that plant powders and extracts of the three plants are sources of botanical insecticides which may be used in the integrated management of D. porcellus

Loss of protection with insecticide-treated nets against pyrethroid-resistant Culex quinquefasciatus mosquitoes once nets become holed: an experimental hut study

ABSTRACT: BACKGROUND: An important advantage of pyrethroid-treated nets over untreated nets is that once nets become worn or holed a pyrethroid treatment will normally restore protection. The capacity of pyrethroids to kill or irritate any mosquito that comes into contact with the net and prevent penetration of holes or feeding through the sides are the main reasons why treated nets continue to provide protection despite their condition deteriorating over time. Pyrethroid resistance is a growing problem among Anopheline and Culicine mosquitoes in many parts of Africa. When mosquitoes become resistant the capacity of treated nets to provide protection might be diminished, particularly when holed. An experimental hut trial against pyrethroid-resistant Culex quinquefasciatus was therefore undertaken in southern Benin using a series of intact and holed nets, both untreated and treated, to assess any loss of protection as nets deteriorate with use and time. RESULTS: There was loss of protection when untreated nets became holed; the proportion of mosquitoes blood feeding increased from 36.2% when nets were intact to between 59.7% and 68.5% when nets were holed to differing extents. The proportion of mosquitoes blood feeding when treated nets were intact was 29.4% which increased to 43.6-57.4% when nets were holed. The greater the number of holes the greater the loss of protection regardless of whether nets were untreated or treated. Mosquito mortality in huts with untreated nets was 12.9-13.6%; treatment induced mortality was less than 12%. The exiting rate of mosquitoes into the verandas was higher in huts with intact nets. CONCLUSION: As nets deteriorate with use and become increasingly holed the capacity of pyrethroid treatments to restore protection is greatly diminished against resistant Culex quinquefasciatus mosquitoes

Efficacy of Pyrethroid-Pyriproxyfen and Pyrethroid-Chlorfenapyr Long-Lasting Insecticidal Nets (LLINs) for the Control of Non-Anopheles Mosquitoes: Secondary Analysis from a Cluster Randomised Controlled Trial (cRCT)

The efficacy of a vector control tool in reducing mosquito biting is crucial for its acceptability. The present study compared the vector density of Culex spp. And Mansonia spp. across clusters, which received two dual-active ingredient (a.i.) long-lasting insecticidal nets (LLINs) and a standard pyrethroid-only LLIN, and assessed the seasonality of these mosquito genera. A total of 85,723 Culex spp. and 144,025 Mansonia spp. were caught over the study period. The density of Culex and Mansonia was reduced in all three arms over the study period. There was no evidence of a significant reduction in the indoor or outdoor density of Culex spp. in either dual-a.i. LLIN arm as compared to the standard pyrethroid-only net arm. A similar trend was observed with Mansonia spp. A high density of Culex spp. was found both in rainy and dry seasons, while for Mansonia spp., this was mainly observed during the rainy season. These results suggest that the novel insecticides in the dual-a.i. LLINs did not have an additional impact on these species and that pyrethroids might still be effective on them. Further work is required to determine whether these species of mosquitoes have resistance to the insecticides tested in this trial

Chlorfenapyr: a pyrrole insecticide for the control of pyrethroid or DDT resistant Anopheles gambiae (Diptera: Culicidae) mosquitoes.

Owing to the development and spread of pyrethroid resistance in Anopheles gambiae in Africa there is an urgent need to develop alternative insecticides to supplement the pyrethroids. Chlorfenapyr is a pyrrole insecticide first commercialized for the control of agricultural pests and termites. Performance against An. gambiae bearing kdr (pyrethroid and DDT resistance) or Ace-1(R) insensitive acetylcholinesterase (organophosphate and carbamate resistance) mechanisms was studied using a variety of adult bioassay tests including a simulated-experimental hut system (tunnel tests) that allows uninhibited mosquito behaviour/insecticide interactions. Strains resistant to pyrethroids and organophosphates showed no cross resistance to chlorfenapyr. In cone bioassays on treated netting the mortality of adult mosquitoes showed an unexpected curvilinear response, with highest mortality occurring at intermediate dosages. Adults expressed irritability to chlorfenapyr at higher dosages, which might explain the dosage-mortality trend. Toxic activity of chlorfenapyr was slow compared to conventional neurotoxic insecticides and additional mortality occurred between 24h and 72 h. In tunnel tests, the dosage-mortality trend showed a more typical sigmoid response and most mortality occurred during the first 24h. Mosquito penetration through the holed, treated netting showed only limited inhibition and blood-feeding was not inhibited. Mortality rates in the kdr strain exposed to chlorfenapyr treated netting in tunnel tests were much higher than with permethrin treated netting over the same 100-500 mg/m(2) dosage range. Chlorfenapyr has potential for malaria control in treated-net or residual spraying applications in areas where mosquitoes are pyrethroid resistant. For treated-net applications chlorfenapyr might be combined with pyrethroid as a mixture to provide personal protection as well as to give control of resistant mosquitoes

Is K-O Tab 1-2-3((R)) long lasting on non-polyester mosquito nets?

Many societies use locally sourced mosquito nets made from a variety of materials. For protecting against malaria these require regular re-treatment with insecticide. K-O Tab 1-2-3 is a 'dip-it-yourself' long-lasting formulation with time-limited interim recommendation from WHO for treatment of washed white and coloured polyester nets for up to 15 washes. To determine wash-resistance on different fabrics, nets made of polyester, polyethylene, cotton or nylon were treated with K-O Tab 1-2-3 and washed up to 20 times using standard WHO washing procedures. Efficacy was assessed using cone and cylinder bioassays and tunnel tests, and deltamethrin content using high-pressure liquid chromatography. Polyethylene and cotton nets treated with K-O Tab 1-2-3 and washed 20 times achieved the WHO threshold of >80% mortality in tunnel tests. Polyethylene matched the performance of polyester in all bioassays in contrast to cotton and nylon which produced low mortality and knock-down in cone and cylinder bioassays. After 20 washes 16.5% of the loading dose of deltamethrin remained on the polyester nets compared with 28.7% on polyethylene, 38.9% on cotton and 2.2% on nylon. Cotton nets retained a high concentration of insecticide but the relatively poor performance in terms of knock-down and mortality suggest most insecticide is bound within the cotton fibres rather than on the surface. K-O Tab 1-2-3 renders insecticide wash fast on polyethylene nets, less so on cotton and nylon. Nets made from polyethylene can be treated in the home to render the insecticide long lasting

Evaluation of indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-susceptible Anopheles arabiensis and pyrethroid-resistant Culex quinquefasciatus mosquitoes.

Chlorfenapyr is a pyrrole insecticide with a unique non-neurological mode of action. Laboratory bioassays of chlorfenapyr comparing the mortality of pyrethroid-susceptible and -resistant Anopheles gambiae s.s. and Culex quinquefasciatus mosquitoes indicated that operational cross-resistance is unlikely to occur (resistance ratio ranged between 0 and 2.1). Three trials of chlorfenapyr indoor residual spraying were undertaken in experimental huts in an area of rice irrigation in northern Tanzania that supports breeding of A. arabiensis. Daily mosquito collections were undertaken to assess product performance primarily in terms of mortality. In the second trial, 250mg/m(2) and 500mg/m(2) chlorfenapyr were tested for residual efficacy over 6 months. Both dosages killed 54% of C. quinquefasciatus, whilst for A. arabiensis 250mg/m(2) killed 48% compared with 41% for 500mg/m(2); mortality was as high at the end of the trial as at the beginning. In the third trial, 250mg/m(2) chlorfenapyr was compared with the pyrethroid alpha-cypermethrin dosed at 30mg/m(2). Chlorfenapyr performance was equivalent to the pyrethroid against A. arabiensis, with both insecticides killing 50% of mosquitoes. Chlorfenapyr killed a significantly higher proportion of pyrethroid-resistant C. quinquefasciatus (56%) compared with alpha-cypermethrin (17%). Chlorfenapyr has the potential to be an important addition to the limited arsenal of public health insecticides for indoor residual control of A. arabiensis and pyrethroid-resistant species of mosquito