Analysis of the Genetic Variation of the Fruitless Gene within the Anopheles gambiae (Diptera: Culicidae) Complex Populations in Africa.

Targeting genes involved in sexual determinism, for vector or pest control purposes, requires a better understanding of their polymorphism in natural populations in order to ensure a rapid spread of the construct. By using genomic data from An. gambiae s.l., we analyzed the genetic variation and the conservation score of the fru gene in 18 natural populations across Africa. A total of 34,339 SNPs were identified, including 3.11% non-synonymous segregating sites. Overall, the nucleotide diversity was low, and the Tajima's D neutrality test was negative, indicating an excess of low frequency SNPs in the fru gene. The allelic frequencies of the non-synonymous SNPs were low (freq < 0.26), except for two SNPs identified at high frequencies (freq > 0.8) in the zinc-finger A and B protein domains. The conservation score was variable throughout the fru gene, with maximum values in the exonic regions compared to the intronic regions. These results showed a low genetic variation overall in the exonic regions, especially the male sex-specific exon and the BTB-exon 1 of the fru gene. These findings will facilitate the development of an effective gene drive construct targeting the fru gene that can rapidly spread without encountering resistance in wild populations.

Essential oils of plants and their combinations as an alternative adulticides against Anopheles gambiae (Diptera: Culicidae) populations.

The persistence of malaria and the increasing of resistance of Anopheles gambiae species to chemicals remain major public health concerns in sub-Saharan Africa. Faced to these concerns, the search for alternative vector control strategies as use of essential oils (EOs) need to be implemented. Here, the five EOs from Cymbopogon citratus, Cymbopogon nardus, Eucalyptus camaldulensis, Lippia multiflora, Ocimum americanum obtained by hydro distillation were tested according to World Health Organization procedures on An. gambiae "Kisumu" and field strains collected in "Vallée du Kou". Also, the binary combinations of C. nardus (Cn) and O. americanum (Oa) were examined. As results, among the EOs tested, L. multiflora was the most efficient on both An. gambiae strains regarding KDT50 (50% of mosquitoes knock down time) and KDT95 and rate of morality values. Our current study showed that C8 (Cn 80%: Oa 20%) and C9 (Cn 90%: Oa 10%), were the most toxic to An. gambiae strain "Vallée de Kou" (VK) with the mortality rates reaching 80.7 and 100% at 1% concentration, respectively. These two binary combinations shown a synergistic effect on the susceptible population. However, only C9 gave a synergistic effect on VK population. The bioactivity of the two EOs, C. nardus and O. americanum, was improved by the combinations at certain proportions. The resistance ratios of all EOs and of the combinations were low (< 5). The combinations of C. nardus and O. americanum EOs at 90: 10 ratio and to a lesser extent L. multiflora EO, could be used as alternative bio-insecticides against malaria vectors resistant to pyrethroids in vector control programmes.

Alternatives to Pyrethroid Resistance: Combinations of Cymbopogon nardus and Ocimum americanum Essential Oils Improve the Bioefficiency Control Against the Adults' Populations of Aedes aegypti (Diptera: Culicidae).

Dengue vector control strategies are mostly based on chemicals use against Aedes aegypti populations. The current study aimed at investigating the insecticidal effects of essential oils (EOs) obtained from five plant species, Cymbopogon citrates (D. C.) Stapf. (Poaceae), Cymbopogon nardus (Linn.) Rendle (Poaceae), Eucalyptus camaldulensis Linn. (Myrtaceae), Lippia multiflora Moldenke (Verbenaceae), and Ocimum americanum Linn. Lamiaceae, and combinations of Cymbopogon nardus and Ocimum americanum on Ae. aegypti populations from Bobo-Dioulasso. For this purpose, adults of the susceptible and field strains of Ae. aegypti were tested in WHO tubes with EO alone and binary combinations of O. americanum (OA) and C. nardus (CN; scored from C1 to C9). The extraction of the essential oils was done by hydrodistillation, and their components were determined by GC/MS. Among the 5 EOs tested, L. multiflora essential oil was the most efficient, with KDT50 values below 60 min on all Ae. aegypti strains tested, and also with a rate of mortality up to 100 and 85% for Bora Bora and Bobo-Dioulasso strains, respectively. This efficacy may be due to its major compounds which are with major compounds as ß-caryophyllene, p-cymene, thymol acetate, and 1.8 cineol. Interestingly, on all strains, C8 combination showed a synergistic effect, while C2 showed an additive effect. These combinations exhibit a rate of mortality varying from 80 to 100%. Their toxicity would be due to the major compounds and the putative combined effects of some major and minor compounds. More importanly, L. multiflora EO and combinations of C. nardus and O. americanum EO, may be used as alternatives against pyrethroid resistant of Ae. aegypti.

Spatial-temporal pattern of malaria in Burkina Faso from 2013 to 2020.

Despite the implementation of different strategies to fight against malaria in Burkina Faso since 2005, it remains today the leading cause of hospitalization and death. Adapting interventions to the spatial and temporal distribution of malaria could help to reduce this burden. This study aims to determine the structure and stability of malaria hotspots in Burkina Faso, with the objective of adapting interventions at small geographical scales. Data on malaria cases from 2013 to 2020 were acquired at municipalities level. Municipality-wise malaria endemicity levels were mapped through geographical information system (GIS) tools. Spatial statistical analysis using Kulldoff sweeps were carried out to identify malaria hotspots. Then we mapped the monthly malaria risk. Malaria is endemic in all the municipalities of Burkina Faso. However, two stable main spatial clusters (South-Western and Eastern part of the country) are emerging with seasonal reinforcement. Interventions targeting the identified clusters could significantly reduce the incidence of malaria in Burkina Faso. This also prompts for further studies to identify the local determinants of this high transmission for the future success of malaria control.

Mark-release-recapture experiment in Burkina Faso demonstrates reduced fitness and dispersal of genetically-modified sterile malaria mosquitoes.

Every year, malaria kills approximately 405,000 people in Sub-Saharan Africa, most of them children under the age of five years. In many countries, progress in malaria control has been threatened by the rapid spread of resistance to antimalarial drugs and insecticides. Novel genetic mosquito control approaches could play an important role in future integrated malaria control strategies. In July 2019, the Target Malaria consortium proceeded with the first release of hemizygous genetically-modified (GM) sterile and non-transgenic sibling males of the malaria mosquito Anopheles coluzzii in Burkina Faso. This study aimed to determine the potential fitness cost associated to the transgene and gather important information related to the dynamic of transgene-carrying mosquitoes, crucial for next development steps. Bayesian estimations confirmed that GM males had lower survival and were less mobile than their wild type (WT) siblings. The estimated male population size in Bana village, at the time of the release was 28,000 - 37,000. These results provide unique information about the fitness and behaviour of released GM males that will inform future releases of more effective strains of the A. gambiae complex.

Preparing an Insectary in Burkina Faso to Support Research in Genetic Technologies for Malaria Control.

The Institut de Recherche en Sciences de la Santé (IRSS) of Burkina Faso, West Africa, was the first African institution to import transgenic mosquitoes for research purposes. A shift from the culture of mosquito research to regulated biotechnology research and considerable management capacity is needed to set up and run the first insectary for transgenic insects in a country that applied and adapted the existing biosafety framework, first developed for genetically modified (GM) crops, to this new area of research. The additional demands arise from the separate regulatory framework for biotechnology, referencing the Cartagena Protocol on Biosafety, and the novelty of the research strain, making public understanding and acceptance early in the research pathway important. The IRSS team carried out extensive preparations following recommendations for containment of GM arthropods and invested efforts in local community engagement and training with scientific colleagues throughout the region. Record keeping beyond routine practice was established to maintain evidence related to regulatory requirements and risk assumptions. The National Biosafety Agency of Burkina Faso, Agence Nationale de Biosécurité (ANB), granted the permits for import of the self-limiting transgenic mosquito strain, which took place in November 2016, and for conducting studies in the IRSS facility in Bobo-Dioulasso. Compliance with permit terms and conditions of the permits and study protocols continued until the conclusion of studies, when the transgenic colonies were terminated. All this required close coordination between management and the insectary teams, as well as others. This article outlines the experiences of the IRSS to support others undertaking such studies. The IRSS is contributing to the ongoing development of genetic technologies for malaria control, as a partner of Target Malaria. The ultimate objective of the innovation is to reduce malaria transmission by using GM mosquitoes of the same species released to reduce the disease-vectoring native populations of Anopheles gambiae s.l.

Insecticide resistance profiles in malaria vector populations from Sud-Kivu in the Democratic Republic of the Congo.

BACKGROUND: Insecticide resistance has become a widespread problem causing a decline in the effectiveness of vector control tools in sub-Saharan Africa. In this situation, ongoing monitoring of vector susceptibility to insecticides is encouraged by the WHO to guide national malaria control programmes. Our study was conducted from April to November 2018 in Tchonka (Sud-Kivu, Democratic Republic of the Congo) and reported primary data on the resistance status of Anopheles funestus and Anopheles gambiae. METHODS: Insecticide susceptibility bioassays were performed on wild populations of A. funestus and A. gambiae using WHO insecticide-impregnated papers at discriminating concentration. In addition, PCR was performed to identify mosquito species and to detect kdr and ace-1R mutations involved in insecticide resistance. RESULTS: Bioassay results show resistance to all tested insecticides except pirimiphos-methyl, propoxur, fenitrothion and malathion with a mortality rate ranging from 95.48 to 99.86%. The addition of piperonyl butoxide (PBO) increased the susceptibility of vectors to deltamethrin and alpha-cypermethrin by exhibiting a mortality ranging from 91.50 to 95.86%. The kdr mutation was detected at high frequencies (approximately 0.98) within A. gambiae while ace-1R was not detected. CONCLUSIONS: This study provides useful data on the insecticide resistance profiles of malaria vector populations to better manage vector control. Our results highlight that, despite the high level of resistance, organophosphorus compounds and pyrethroids + PBO remain effective against the vectors.

Malaria vectors diversity, insecticide resistance and transmission during the rainy season in peri-urban villages of south-western Burkina Faso.

BACKGROUND: This study reports an updated description on malaria vector diversity, behaviour, insecticide resistance and malaria transmission in the Diébougou and Dano peri-urban areas, Burkina Faso. METHODS: Mosquitoes were caught monthly using CDC light traps and pyrethrum spray catches. Mosquitoes were identified using morphological taxonomic keys. PCR techniques were used to identify the species of the Anopheles gambiae complex and insecticide resistance mechanisms in a subset of Anopheles vectors. The Plasmodium sporozoite infection status and origins of blood meals of female mosquitoes were determined by ELISA methods. Larvae were collected, breed in the insectary and tested for phenotypic resistance against four insecticides using WHO bioassays. RESULTS: This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management. CONCLUSIONS: This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management.

Short Persistence and Vector Susceptibility to Ficam 80WP (bendiocarb active ingredient) During Pilot Application of Indoor Residual Spraying in Burkina Faso, West Africa.

Indoor residual spraying (IRS) was applied in addition to the use of long-lasting insecticidal nets in the South West in Burkina Faso, where Anopheles gambiae s.l. the major malaria vector was resistant to pyrethroids. This study was designed to evaluate the efficacy and residual life of bendiocarb (active ingredient) used for spraying on different wall surfaces (mud and cement). Cone bioassays were done monthly with the susceptible An. gambiae 'Kisumu' strain and the local wild populations to determine the duration for which insecticide was effective in killing mosquitoes. Cone bioassay data showed low efficacy and short persistence of bendiocarb applied on mud and cement walls, lasting 2 mo with the susceptible insectary strain and less than 1 mo with An. gambiae wild populations. In addition, WHO tube assays confirmed resistance of An. gambiae wild populations to 0.1% bendiocarb with mortality rates less than 80% in both study sites (sprayed and unsprayed sites). The pilot study of IRS with bendiocarb showed that the residual efficacy of bendiocarb was very short, and resistance to bendiocarb was confirmed in wild populations of An. gambiae s.l. Therefore, Ficam 80 WP was not suitable for IRS in this area due to the short residual duration related mainly to vectors resistance to bendiocarb. While waiting for innovative malaria control tool, alternative insecticide (organophosphate or neonicotinoid classes) or combinations of insecticides have to be used for insecticide resistance management in Burkina Faso.

Monitoring Insecticide Susceptibility in Aedes Aegypti Populations from the Two Biggest Cities, Ouagadougou and Bobo-Dioulasso, in Burkina Faso: Implication of Metabolic Resistance.

In West Africa, Aedes aegypti remains the major vector of dengue virus. Since 2013, dengue fever has been reemerging in Burkina Faso with annual outbreaks, thus becoming a major public health problem. Its control relies on vector control, which is unfortunately facing the problem of insecticide resistance. At the time of this study, although data on phenotypic resistance were available, information related to the metabolic resistance in Aedes populations from Burkina Faso remained very scarce. Here, we assessed the phenotypic and the metabolic resistance of Ae. aegypti populations sampled from the two main urban areas (Ouagadougou and Bobo-Dioulasso) of Burkina Faso. Insecticide susceptibility bioassays to chlorpyriphos-methyl 0.4%, bendiocarb 0.1% and deltamethrin 0.05% were performed on natural populations of Ae. aegypti using the WHO protocol. The activity of enzymes involved in the rapid detoxification of insecticides, especially non-specific esterases, oxidases (cytochrome P450) and glutathione-S-transferases, was measured on individual mosquitos. The mortality rates for deltamethrin 0.05% were low and ranged from 20.72% to 89.62% in the Bobo-Dioulasso and Ouagadougou sites, respectively. When bendiocarb 0.1% was tested, the mortality rates ranged from 7.73% to 71.23%. Interestingly, in the two urban areas, mosquitoes were found to be fully susceptible to chlorpyriphos-methyl 0.4%. Elevated activity of non-specific esterases and glutathione-S-transferases was reported, suggesting multiple resistance mechanisms involved in Ae. aegypti populations from Bobo-Dioulasso and Ouagadougou (including cytochrome P450). This update to the insecticide resistance status within Ae. aegypti populations in the two biggest cities is important to better plan dengue vectors control in the country and provides valuable information for improving vector control strategies in Burkina Faso, West Africa.

Experimental hut evaluation of DawaPlus 3.0 LN and DawaPlus 4.0 LN treated with deltamethrin and PBO against free-flying populations of Anopheles gambiae s.l. in Vallée du Kou, Burkina Faso.

BACKGROUND: In view of widespread pyrethroid resistance in malaria vectors in Africa, two long-lasting insecticidal nets (LLINs) incorporated with a synergist, piperonyl butoxide (PBO), DawaPlus 3.0 (deltamethrin + PBO in the roof panel; deltamethrin alone in the side panels) and DawaPlus 4.0 (deltamethrin + PBO in all panels), were evaluated in an experimental hut trial in a rice growing irrigated area in Burkina Faso. Efficacy of nets was tested against free-flying malaria vector, Anopheles gambiae s.l., with high pyrethroid resistance involving L1014F kdr and CYP6P3P450 resistance mechanisms. METHODOLOGY: The efficacy of unwashed and 20-times washed DawaPlus 3.0 (polyethylene roof panel with 120 mg/m2 deltamethrin and 440 mg/m2 PBO; polyester side panels with deltamethrin 100 mg/m2) and DawaPlus 4.0 (same composition as roof of DawaPlus 3.0) was evaluated against DawaPlus 2.0 (80 mg/m2 deltamethrin; positive control). Volunteer sleepers and treatments were rotated in huts using a Latin square design on 63 consecutive nights during August-October 2016. Mortality, human blood-feeding inhibition, deterrence and exit rates of An. gambiae s.l. were monitored. PRINCIPAL FINDINGS: Significantly higher rates of mortality and blood-feeding inhibition were observed with unwashed DawaPlus 4.0 (36%; 47.5%) than unwashed DawaPlus 3.0 (11.8%; 33.3%), DawaPlus 2.0 (4.3%; 6.4%) or untreated net (P < 0.05). Washing reduced personal protective efficacy yet PBO-LLINs were more protective and both met the WHO criteria. CONCLUSIONS: The PBO-containing DawaPlus 4.0 significantly protected against An. gambiae s.l. in the study area. Unwashed DawaPlus 3.0 gave low to moderate protection against the positive control. PBO inhibits oxidase action; hence in areas with active malaria transmission having oxidase mechanisms, PBO nets could confer additional personal protection.

Effect of Bacillus thuringiensis var. israelensis Sugar Patches on Insecticide Resistant Anopheles gambiae s.l. Adults.

BACKGROUND: Large distribution of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) contributed to a significant decrease in malarial mortality. Unfortunately, large insecticide resistance in malaria vectors occurred and is a threat to the future use of these control approaches. The purpose of this study was to explore a new approach for vector control. Patches containing Bacillus thuringiensis var. israelensis (Bti) solubilized Cry toxins mixed with sugar were developed and tested in the laboratory with pyrethroid-resistant Anopheles gambiae s.l. using tunnel tests. METHODS: Mosquitoes were released at 6:00 p.m. into a large tunnel separated by a bed net, perforated with nine holes, from a smaller chamber with a guinea pig. Nine Bti sugar patches (BSPs) were attached to the bed net between the nine holes. Fourteen hours later (8:00 a.m.), mosquitoes were collected from the tunnel and the guinea pig chamber. Live females were kept in cups and were fed a sugar solution (5%) for 72 h and delayed mortality was followed. The results were reported as passing, blood fed and mortality rates. RESULTS: Mosquito populations that are resistant to the insecticides in the bed net, exhibited high mortality (60%) in the presence of the BSPs. Untreated bed nets with patches in the tunnel test killed 66-95% of the mosquitoes that landed and untreated bed nets were superior to treated bed nets. CONCLUSION: BSPs efficiently kill resistant mosquitoes that land on treated and untreated bed nets and thus could ultimately reduce the number of vector-borne malarial mosquitoes.

Surveys of Arboviruses Vectors in Four Cities Stretching Along a Railway Transect of Burkina Faso: Risk Transmission and Insecticide Susceptibility Status of Potential Vectors.

Background: A severe outbreak of dengue occurred in Burkina Faso in 2016, with the most cases reported in Ouagadougou, that highlights the necessity to implement vector surveillance system. This study aims to estimate the risk of arboviruses transmission and the insecticide susceptibility status of potential vectors in four sites in Burkina Faso. Methods: From June to September 2016, house-to-house cross sectional entomological surveys were performed in four cities stretching along a southwest-to-northeast railway transect. The household surveys analyzed the presence of Aedes spp. larvae in containers holding water and the World Health Organization (WHO) larval abundance indices were estimated. WHO tube assays was used to evaluate the insecticide susceptibility within Aedes populations from these localities. Results: A total of 31,378 mosquitoes' larvae were collected from 1,330 containers holding water. Aedes spp. was the most abundant (95.19%) followed by Culex spp. (4.75%). Aedes aegypti a key vector of arboviruses (ARBOV) in West Africa was the major Aedes species found (98.60%). The relative larval indices, house index, container and Breteau indexes were high, up to 70, 35, and 10, respectively. Aedes aegypti tended to breed mainly in discarded tires and terracotta jars. Except in Banfora the western city, Ae. aegypti populations were resistant to deltamethrin 0.05% in the other localities with low mortality rate under 20% in Ouagadougou whereas they were fully susceptible to malathion 5% whatever the site. Intermediate resistance was observed in the four sites with mortality rates varying between 78 and 94% with bendiocarb 0.1%. Conclusions: This study provided basic information on entomological indices that can help to monitor the risks of ARBOV epidemics in the main cities along the railway in Burkina Faso. In these cities, all larval indices exceeded the risk level of ARBOV outbreak. Aedes aegypti the main species collected was resistant to deltamethrin 0.05% and bendiocarb 0.1% whereas they were fully susceptible to malathion 5%. The monitoring of insecticide resistance is also important to be integrated to the vector surveillance system in Burkina Faso.

Insecticide resistance mechanisms in Anopheles gambiae complex populations from Burkina Faso, West Africa.

Vector control constitutes a fundamental approach in reducing vector density and the efficient option to break malaria transmission in Africa. Malaria vectors developed resistance to almost all classes of insecticides recommended by WHO for vector control in most places of African countries and may compromise the vector control strategies. This study updated the resistance status of Anopheles gambiae complex populations to insecticides recommended for vector control in the western part of Burkina Faso. Insecticide susceptibility bioassays were performed on seven natural populations of An. gambiae complex from western Burkina Faso in the 2016 rainy season using the WHO protocol. Biochemical assays were carried out according to the WHO protocol on the same populations to estimate detoxifying enzymes activities including non-specific esterases (NSEs), oxidases (cytochrome P450) and Glutathione-S-Transferases (GSTs). Polymerase Chain Reactions (PCRs) were performed for the identification of the An. gambiae complex species as well as the detection of kdr-west and ace-1 mutations. Susceptibility bioassays showed that An. gambiae complex was multi-resistant to pyrethroids, DDT and carbamates in almost all areas. The mortality rates ranged from 10 to 38%, 2.67 to 59.57% and 64.38 to 98.02% for Deltamethrin, DDT and Bendiocarb respectively. A full susceptibility (100%) to an organophosphate, the Chlorpyrifos-methyl, was observed at the different sites. Three (3) species of the An. gambiae complex were identified: An. gambiae s.s, An. coluzzii and An. arabiensis. The frequencies of the kdr-w mutation were highly widespread (0.66 to 0.98) among the three species of the complex. The ace-1 mutation was detected at low frequencies (0 to 0.12) in An. gambiae s.s and An. coluzzii. A high level of GSTs and NSEs were observed within the different populations of the An. gambiae complex. Several mechanisms of insecticide resistance were found simultaneously in the same populations of An. gambiae complex conferring high multi-resistance to DDT, Carbamate and Pyrethroids. The full susceptibility of An. gambiae complex to organophosphates is a useful data for the national malaria control program in selecting the most appropriate products to both maintain the effectiveness of vector control strategies and best manage insecticide resistance as well as developing new alternative strategies for the control of major malaria vectors in Burkina Faso.

Targeted application of an organophosphate-based paint applied on windows and doors against Anopheles coluzzii resistant to pyrethroids under real life conditions in Vallée du Kou, Burkina Faso (West Africa).

BACKGROUND: A novel strategy applying an organophosphate-based insecticide paint on doors and windows in combination with long-lasting insecticide-treated nets (LLINs) was tested for the control of pyrethroid-resistant malaria vectors in a village setting in Vallée du Kou, a rice-growing area west of Burkina Faso. METHODS: Insecticide Paint Inesfly 5A IGR™, comprised of two organophosphates and an insect growth regulator, was applied to doors and windows and tested in combination with pyrethroid-treated LLINs. The killing effect was monitored for 5 months by early morning collections of anophelines and other culicids. The residual efficacy was evaluated monthly by WHO bioassays using Anopheles gambiae 'Kisumu' and local populations of Anopheles coluzzii resistant to pyrethroids. The spatial mortality efficacy (SME) at distances of 1 m was also assessed against pyrethroid-susceptible and -resistant malaria vectors. The frequency of L1014F kdr and Ace-1 R G119S mutations was, respectively, reported throughout the study. The Insecticide Paint Inesfly 5A IGR had been tested in past studies yielding a long-term mortality rate of 80% over 12 months against An. coluzzii, the local pyrethroid-resistant malaria vector. The purpose of the present study is to test if treating smaller, targeted surfaces (e.g. doors and windows) was also efficient in killing malaria vectors. RESULTS: Treating windows and doors alone yielded a killing efficacy of 100% for 1 month against An. coluzzii resistant to pyrethroids, but efficacy reduced quickly afterwards. Likewise, WHO cone bioassays yielded mortalities of 80-100% for 2 months but declined to 90 and 40% 2 and 3 months after treatment, respectively. Mosquitoes exposed to insecticide paint-treated surfaces at distances of 1 m, yielded mortality rates of about 90-80% against local pyrethroids-resistant An. coluzzii during the first 2 months, but decreased to 30% afterwards. Anopheles coluzzii was reported to be exclusively the local malaria vector and resistant to pyrethroids with high L1014 kdr frequency. CONCLUSION: The combination of insecticide paint on doors and windows with LLINs yielded high mortality rates in the short term against wild pyrethroid-resistant malaria vector populations. A high SME was observed against laboratory strains of pyrethroid-resistant malaria vectors placed for 30 min at 1 m from the treated/control walls. The application of the insecticide paint on doors and windows led to high but short-lasting mortality rates. The strategy may be an option in a context where low cost, rapid responses need to be implemented in areas where malaria vectors are resistant to pyrethroids.

Studies of Transgenic Mosquitoes in Disease-Endemic Countries: Preparation of Containment Facilities.

Novel approaches to area-wide control of vector species offer promise as additional tools in the fight against vectored diseases. Evaluation of transgenic insect strains aimed at field population control in disease-endemic countries may involve international partnerships and should be done in a stepwise approach, starting with studies in containment facilities. The preparations of both new-build and renovated facilities are described, including working with local and national regulations regarding land use, construction, and biosafety requirements, as well as international guidance to fill any gaps in regulation. The examples given are for containment categorization at Arthropod Containment Level 2 for initial facility design, classification of wastes, and precautions during shipping. Specific lessons were derived from preparations to evaluate transgenic (non-gene drive) mosquitoes in West and East African countries. Documented procedures and the use of a non-transgenic training strain for trial shipments and culturing were used to develop competence and confidence among the African facility staff, and along the chain of custody for transport. This practical description is offered to support other research consortia or institutions preparing containment facilities and operating procedures in conditions where research on transgenic insects is at an early stage.

Evaluation of efficacy of Interceptor® G2, a long-lasting insecticide net coated with a mixture of chlorfenapyr and alpha-cypermethrin, against pyrethroid resistant Anopheles gambiae s.l. in Burkina Faso.

BACKGROUND: Malaria vectors have acquired widespread resistance throughout sub-Saharan Africa to many of the currently used insecticides. Hence, there is an urgent need to develop alternative strategies including the development of new insecticides for effective management of insecticide resistance. To maintain progress against malaria, it is necessary to identify other residual insecticides for mosquito nets. In the present WHOPES phase II analogue study, the utility of chlorfenapyr, a pyrrole class insecticide mixed with alpha-cypermethrin on a long-lasting mosquito bed net was evaluated against Anopheles gambiae s.l. METHODS: Bed nets treated with chlorfenapyr and alpha-cypermethrin and mixture of both compounds were tested for their efficacy on mosquitoes. Washed (20 times) and unwashed of each type of treated nets and were tested according to WHOPES guidelines. Efficacy of nets were expressed in terms of blood-feeding inhibition rate, deterrence, induced exophily and mortality rate. The evaluation was conducted in experimental huts of Vallée du Kou seven (VK7) in Burkina Faso (West Africa) following WHOPES phase II guidelines. In addition, a WHOPES phase I evaluation was also performed. RESULTS: Mixture treated nets killed significantly (P < 0.05) more mosquitoes than solo alpha-cypermethrin nets, unwashed and washed. Proportionally, this equated to mortalities of 78 and 76% (for mixture nets) compared to only 17 and 10% (for solo alpha-cypermethrin) to An. gambiae, respectively. In contrast mixture net proportions were not significantly (P > 0.05) different from nets treated with chlorfenapyr 200 mg/m2 unwashed (86%). The washed and unwashed nets treated with the mixtures resulted in personal protection against An. gambiae s.l. biting 34 and 44%. In contrast the personal protection observed for washed and unwashed alpha-cypermethrin treated nets generated (14 and 24%), and chlorfenapyr solo treated net was rather low (22%). CONCLUSION: Among all nets trialled, the combination of chlorfenapyr and alpha-cypermethrin on bed nets provided better mortality in phase II after 20 washes. Results suggest that this combination could be a potential insecticide resistance management tool for preventing malaria transmission in areas compromised by the spread of pyrethroid resistance.

Parasitological Indices of Malaria Transmission in Children under Fifteen Years in Two Ecoepidemiological Zones in Southwestern Burkina Faso.

Twenty years after the latest publications performed on the parasitological indices of malaria transmission in northwest of the second city of Burkina Faso, it was important to update the epidemiological profile of malaria in children under the age of 15 years. The objective of this study was to determine and compare the parasitological parameters of malaria transmission by season, area, and age in the two zones (rice and savanna) in the northwest of Bobo-Dioulasso, Burkina Faso. Overall, the results showed that there was no significant difference in the parasitological indices of malaria transmission within children under fifteen years between the rice site and the savannah site and whatever the season (P > 0.05). The profound environmental modifications that occurred in the rice zone would have led to changes in vector behavior and consequently to changes in the epidemiological profile of malaria, contrary to the results obtained since the last publications. An entomological study correlated with this study is therefore necessary for effective decision-making for the malaria control in both areas. Future research must now focus on the impact that these profound environmental modifications of rice area are having on malaria control in Burkina Faso.

Evidence that agricultural use of pesticides selects pyrethroid resistance within Anopheles gambiae s.l. populations from cotton growing areas in Burkina Faso, West Africa.

Many studies have shown the role of agriculture in the selection and spread of resistance of Anopheles gambiae s.l. to insecticides. However, no study has directly demonstrated the presence of insecticides in breeding sources as a source of selection for this resistance. It is in this context that we investigated the presence of pesticide residues in breeding habitats and their formal involvement in vector resistance to insecticides in areas of West Africa with intensive farming. This study was carried out from June to November 2013 in Dano, southwest Burkina Faso in areas of conventional (CC) and biological cotton (BC) growing. Water and sediment samples collected from breeding sites located near BC and CC fields were submitted for chromatographic analysis to research and titrate the residual insecticide content found there. Larvae were also collected in these breeding sites and used in toxicity tests to compare their mortality to those of the susceptible strain, Anopheles gambiae Kisumu. All tested mosquitoes (living and dead) were analyzed by PCR for species identification and characterization of resistance genes. The toxicity analysis of water from breeding sites showed significantly lower mortality rates in breeding site water from biological cotton (WBC) growing sites compared to that from conventional cotton (WCC) sites respective to both An. gambiae Kisumu (WBC: 80.75% vs WCC: 92.75%) and a wild-type strain (49.75% vs 66.5%). The allele frequencies L1014F, L1014S kdr, and G116S ace -1R mutations conferring resistance, respectively, to pyrethroids and carbamates / organophosphates were 0.95, 0.4 and 0.12. Deltamethrin and lambda-cyhalothrin were identified in the water samples taken in October/November from mosquitoes breeding in the CC growing area. The concentrations obtained were respectively 0.0147ug/L and 1.49 ug/L to deltamethrin and lambdacyhalothrin. Our results provided evidence by direct analysis (biological and chromatographic tests) of the role of agriculture as a source of selection pressure on vectors to insecticides used in growing areas.