Comparative Repellency of Selected Plants to Adult Anopheles gambiea complex (Gilles) in the Laboratory

Aims: The study evaluated the repellency effects of some tropical plants and shrubs found in semi- rural communities of Badagry Area of Lagos state; which are acclaimed to have the potentials of repelling mosquitoes from human dwellings. The repellency effects of Moringa oleifera, Morinda lucida, Magnifera indica and Phyllanthus muellerianus to adult Anopheles gambiea was evaluated in the Laboratory. Study Design: The study was carried out at Central Research Laboratory of Lagos State University, Ojo, Lagos, Nigeria and Central Research Laboratory of University of Lagos, Akoka, Lagos, Nigeria. Powdered of dried test plants were prepared and admix with coconut husk as inert, different concentrations were rubbed on the forearm of volunteers and repellency to blood starved female Anopheles mosquitoes was observed. Methodology: Test plants were collected from Badagry area of Lagos State, they were identified at University of Lagos Herbarium and given numbers. They were dried between 10 and 14 days at temperature of 25-27oC and powdered. Different concentrations of the powder mixed with powdered coconut husk was used to treat volunteers forearms and they were exposed to 0-2 two day old adult unfed mosquitoes in an aluminum glass cage fitted with net as arm entrance and repellency was observed for a period of 180 minutes, with landing counts taken every 30 minutes. The test plants were also subjected to qualitative and quantitative phytochemical analysis at University of Lagos Central Research Laboratory. Results: Results showed that all test plants were able to repel Anopheles mosquitoes in the study, repellency was shown in descending order Moringa oleifera with 88%, Magnifera indica 83%, Phyllantus muellerianuss 80% and Morinda lucida 72%. There was no statistical significance in percentage repellency at 95% CL. The result of phytochemical screening of the test plants showed that only M .indica indicated presence of saponing (36.99%). While M.oleifera has highest phenol content (45.6%3), Alkaloid (38.68%), steroid (24.89%) and Tannin (33.19%). Flavonoid and reducing sugar quantity was highest in M. indica (39.39%) and (55.18%) respectively. Conclusion: The plants were able to show repellency to Anopheles gambiae a nuisance malaria vector of serious medical importance. These plants are available in all tropical areas of Africa, they can therefore be used to prevent nuisance and painful mosquito bites which could be a sustainable way to prevent mosquito vectored diseases

High vectorial transmission of malaria in urban and rural settings in the northern, western and eastern regions of Côte d’Ivoire

Background & objectives: Malaria remains a public health problem in Côte d’Ivoire. To cope with this issue, the Ministry of Health established strategies through Long-Lasting Insecticidal Nets (LLINs) and artemisinin-based medicines. To better understand the influence of periodic mass distribution of LLINs on malaria transmission, this entomological survey was conducted in three regions of Côte d’Ivoire. Methods: Mosquitoes were sampled by Human Landing Catches (HLC) in urban and rural settings of Korhogo, Man and Abengourou. Mosquitoes were identified morphologically and by molecular methods. Plasmodium falciparum infection was assessed by ELISA, and the Entomological Inoculation Rates (EIR) were calculated for each species and setting. Results: Only An. gambiae s.l. was identified in Korhogo and in Abengourou while An. gambiae s.l. and An. funestus s.l. was reported in Man. An. coluzzii was the most abundant species of the An. gambiae siblings collected in Abengourou, and in Man while An. gambiae was most abundant in Korhogo. In urban settings, malaria vectors showed high aggressiveness (>11 bites per person per night) and the annual EIR was high (83.22-438.44 infectious bites per person per year). In rural settings, malaria vectors showed also high aggressiveness (19-52 b/p/n). The annual EIR is very high (>94 ib/p/yr). However, the weakest EIR was recorded in the northern region with 94.90 ib/p/yr. Interpretation & conclusion: This work indicates that malaria transmission remains high and heterogeneous across Côte d’Ivoire, despite repeated mass distribution of LLINs. Also, in Man, malaria transmission is more intense with the involvement of two main vectors. Furthermore, in the village of Korhogo, the EIR remained relatively low.

Anopheles gambiae Larval Development and Toxicity抯 Reduction of Conventional Agriculture Insecticides in the Laboratory Conditions

Background: Vector control of Malaria is mainly made by using impregnated bed nets and insecticides pulverizations indoor or/and outdoor. Besides, appearance and development of resistance抯 phenomenon among mosquito populations to insecticides, constitute a significant obstacle this fighting. Aims: To highlighting a neutralization phenomenon of three insecticides (methyl-parathion, dimethoate and cypermethrin) during development of the Anopheles gambiae s.s. larvae. Methodology: Two setups followed one after the other were designed. In setup 1, four concentrations (with four replicates each) were freshly prepared and independently received a first batch of 100 first instars An. gambiae s.s. After emergence of adults from this first batch, the same test media were simply filtered and received a second batch of first instars larvae to make setup 2. Three endpoints were measured in this study: the duration of larval phase, the larval mortality, and the size of adults. Results: The development duration and mortality of larvae decreased significantly at setup 2 with cypermethrin and methyl-parathion. Thus, the duration of larval stage decreased from 10.18 days at setup 1 to 7.84 days at setup 2 for 0.010 礸/l (highest concentration) with cypermethrin and from 10.20 days at setup 1 to 8.27 days at setup 2 for 0.144 礸/l (highest concentration) with methyl-parathion. The larval mortality dropped from 79.32 % at setup 1 to 12.00 % at setup 2 for the highest concentration of cypermethrin and from 76.42 % at setup 1 to 12.50 % at setup 2 for the highest concentration of methyl-parathion. While adults size significantly increased in setup 2. For males, wing抯 length increased from 3.28 mm at setup 1 to 3.49 mm at setup 2 for the highest concentration of cypermethrin, from 3.31 mm at setup 1 to 3.49 mm at setup 2 for the highest concentration of methyl-parathion. In female, wing抯 length increased from 3.52 mm at setup 1 to 3.68 mm at setup 2 for the highest concentration of cypermethrin, from 3.49 mm at setup 1 to 3.68 mm at setup 2 for the highest concentration of methyl-parathion. Conclusion: This work shows that mosquito larvae, especially An. gambiae are able to modify breeding medium to improve its fitness during their development.

Potential of the Ethanol Extract of Aerial Parts of Diplazium esculentum (Retz) SW. AS Larvicide against Anopheles gambiae Giles and Culex quinquefasciatus Say

Plant products have been tested as insecticides against mosquitoes as they are promising candidates to replace conventional insecticides. This study was carried out to evaluate the larvicidalpotential of ethanol extract of the aerial parts of Diplazium esculentumagainst Anopheles gambiaeand Culex quinquefasciatus. Ethanol extract of the aerial parts of D. esculentumwas screened for its phytochemical constituents and used for larvicidal assay. A stock solution of the extract (5g in Original Research Article Umohata et al.; IJTDH, 41(3): 40-47, 2020; Article no.IJTDH.5566841100ml of water) was prepared. From the stock solution, 0.45, 0.60, 0.75, 0.90 and 1.05%w/v concentrations of the extract were obtained for the study. Each concentration of the extract had 3 replicates. The control was also replicated. Twenty (20) third instar larvae each of Anopheles gambiae andCulex quinquefasciatuswere separately exposed to each extract concentration for a duration of 48 hours. Larval nutrient was added to each experimental set up. Observations were made after 24 and 48 hours exposure period.Phytochemical screening revealed the presence of some plant metabolites. Mortality of larvae exposed to the extract increased with increased concentration and exposure time. This study revealed a differential susceptibility of larvae of the two mosquito species to the extract as evident by the 24h LC50values obtained which were 0.355 and 2.468%w/v for An. gambiaeand Cx.quinquefasciatus respectively. Exposure of An. gambiaelarvae to the extract resulted in 100% mortality even with the least concentration of 0.45%w/v after 48 hours exposure period while the highest concentration of extract (1.05%w/v) resulted in 53.33% mortality of Cx.quinquefasciatuslarvae, after an exposure period of 48 hours. Results obtained from this study suggest that the aerial parts of D. esculentumif further explored would be useful in the control of An. gambiae andCx.quinquefasciatus.

Genome-wide analysis of various paralogs of aminopeptidase N (APN) gene in Anopheles gambiae (Diptera: Culicidae)

Malaria continues to be a life threatening infectious disease throughout the tropical region of the world.aminopeptidase N1 (APN1) is one of the best choices for developing new Malaria Transmission-blockingvaccines. In this study an attempt has been made to overview genome-wide identification of APN genes inAnopheles gambiae. A total of eighteen A. gambiae APN sequences were found that contain conserved HEXXHand GAMEN signature sequences, indicate that large numbers of APN isomers present in mosquitoes. MultipleAPN paralogs exist as a gene cluster may propose that huge synthesis of APNs is required for rapid digestion ofpeptides over a brief period. Gene structure study shows high sequence variations among them. Protein–proteininteractions show that APN1 is highly connected protein, supporting their role as hub with other five types ofAPNs involved in glutathione metabolism, act as hub protein and disruption of one of these proteins may affectthe whole pathway

Anopheles gambiae no Brasil: antecedentes para um " alastramento silencioso ", 1930-1932 / Anopheles gambiae in Brazil: the background to a " silent spread, " 1930-1932

Resumo O artigo analisa a chegada e identificação do mosquito africano Anopheles gambiae no Brasil em 1930 e as primeiras reações de cientistas e autoridades de saúde pública contra as epidemias de malária causadas por essa espécie. Apesar de ter sido reconhecido como perigoso vetor da malária, sua presença em território nacional foi negligenciada a partir de 1932, após ações emergenciais na capital do Rio Grande do Norte, favorecendo um alastramento silencioso que resultou em uma grande epidemia de malária em 1938. São abordadas questões científicas e políticas que contribuíram para que o combate ao mosquito fosse colocado em segundo plano nas articulações entre a Divisão Sanitária Internacional da Fundação Rockefeller e autoridades brasileiras até 1937.

Abstract The article analyzes the arrival and identification of the African mosquito Anopheles gambiae in Brazil in 1930, and the initial reactions of scientists and public health authorities against the epidemics of malaria caused by this species. Although this mosquito was recognized as a dangerous vector of malaria, its presence in Brazil was neglected after initial emergency actions in the city of Natal in 1932; this encouraged it to spread silently, resulting in a major malaria epidemic in 1938. This article examines scientific and political issues which caused the fight against mosquitoes to be pushed into the background until 1937 in cooperative efforts between the Rockefeller Foundation's International Health Division and the Brazilian authorities.

Assessment of Level of Susceptibility of Anopheles gambiae S.L to Public Health Insecticides in a Malaria Vector Sentinel Site, Rivers State, Nigeria

Aims: To investigate the status of susceptibility of Anopheles gambiae sensu lato (Diptera: Culicidae) mosquitoes to the WHO-approved insecticides for indoor residual spraying in field collected samples in a malaria vector sentinel site in Nigeria and Ts to provide an update on the current status of resistance to the major insecticide classes in wild populations of Anopheles gambiae sensu lato Study Design: Field and laboratory –experimental design was used in this study. Place and Duration of the Study: The study was carried out at a malaria surveillance site, established by the National Malaria Elimination Programme at Oduoha-Emohua in Rivers State, between April to September, 2015. Methodology: Anopheles larvae were collected from stagnant pools around the malaria surveillance site. The mosquitoes were reared to adulthood in the insectary and identified using morphological keys. Two- to three-day old adult female mosquitoes were exposed to standard diagnostic doses of Deltamethrin, Lambdacyhalothrin, Alphacympermethrin, Permethrin, Bendiocarb, Propoxur, DDT and Premiphos-Methyl using standard WHO protocols, insecticide susceptibility test kits and treated papers. Knockdown every 10 min and mortality 24 h post exposure was noted. All Anopheles mosquitoes tested belonged to the Anopheles gambiae-complex. Results: Mortality results indicated that the vectors were susceptible to Bendiocarb and Alphacympermethrin with mortality rates of 100% and 98% respectively. There was complete resistance to Deltamethrin, Lambdacyhalothrin, Permethrin, Propoxur, DDT and Premiphos-Methyl with mortality ranges of 25%-65%. Conclusion: The present study shows the effectiveness of Bendiocarb and Alphacympermethrin in malaria control with indoor residual spraying. It also provides baseline information for monitoring the status of insecticide resistance in Rivers State.

Efficacy of Tithonia diversifolia and Momordica charantia Leaves Extracts against Malaria Vector, Anopheles gambiae Gile (Diptera: Culicidae)

The gastrointestinal tracts were cut open and the contents of the various sections were put into separate Petri dishes containing normal saline. The skin and the bladder were observed directly under a dissecting microscope for the presence of cysts and monogeneans. The parasites were fixed and preserved in 70% alcohol following standard procedure. Parasites recovered from the gastrointestinal tracts of the anurans include Cosmocerca ornata, Deising, 1861,Cosmocerca cummutata, Diesing, 1851 Paracosmocerca mucronata, Kung and Wu, 1945, Ampliceacum africanum, Taylor, 1924, Gendria liberrei Bain and Philipon, 1969 and Chenospirura asturiHsu, 1957Others were Procamallus brevis Kung, 1948 and Camallanus dimitrovi Durette-Desset and Batcharov, 1974. Some of the parasites are zoonotic while a few others are established parasites of African fishes and water Birds raising probable public health concerns from the findings. Further works aimed at unravelling the biodiversity of hosts and parasites in thelush ecosystem of Ondo state, as well as identification of organisms involved in the life cycle are noted. Methodology: Larvae and pupae of Anopheles gambiaewere reared inthe laboratory at ambient temperature of 28±2°Cand relative humidity of 75±5%. The leave extracts of T. diversifolia and M. charantia were extracted with methanol and were prepared at concentrations, 0.1%, 0.2%, 0.3%, 0.4% and 0.5%. The larvae and pupae of A. gambiae were exposed to these concentrations of the plant extract for 24 hours. Mortality of the larvae and pupae was monitored and recorded. Probit analysis was used to determine the LC50. Results: Date of this research revealed that at all levels of concentrations, mortality of both the larvae and pupae of this insect increased with increase in the concentrations regardless the type of plant extract used. The leave extract of T. diversifoliahavinga lower value of LC50(larvae: 0.20%; Pupae: 0.27%) was more potent than extract from M. charantiahaving a higher value of LC50(larvae: 0.31%; Pupae: 0.44%) after 24 hours Post Treatment of larvae and pupae of A. gambiae. T. diversifoliahad significanteffect on the larvae of A. gambiaewith percentage mortality ranges from 23.33-100% within 24hrs of exposure when compared with M. charantiathat had 16.67-100% of mortality larvae of A. gambiae.Conclusion: The obtained results from this research revealed that extracts from the two plants exhibited great insecticidal properties against larvae and pupae of A. gambiae. Therefore, more exploration on the use of these plants for the development of insecticides at commercial level should be done

Larvicidal Activity of Crude Extracts of Vernonia cinerea Less (Asteraceae) against the Larvae of Anopheles gambiae in Bobo Dioulasso, Burkina Faso

Aims: This study aims to evaluate the larvicidal activity of lyophilized methanolic extracts, hydro-methanolic extracts and aqueous extracts of Vernonia cinerea Less against the 3rd and 4th instars larvae of Anopheles gambiae. Place and Duration of Study: Pharmacognosy Laboratory, Department of Biomedical Sciences, Centre MURAZ /Research Institute for Health; Ministry of Health, Bobo-Dioulasso, between February 2017 and January 2018. Institut de Recherche en Sciences de la Santé/Direction Régionale de l’Ouest (IRSS) Bobo-Dioulasso, between March 2017 and January 2018. Methodology: The whole plant material was collected in Banfora, located at West of Burkina Faso. The 80% methanolic, 50/50% hydro-methanolic and aqueous extracts were obtained by using the classical natural product extraction method of the laboratory. Extracts were lyophilized and a series of concentrations of the extracts ranging from 0.001 – 100 mg/L were prepared. The larvicidal activity of lyophilized extracts has been tested against the 3rd and 4thAnopheles gambiae larvae. The larval mortality was evaluated after 24 hours and 48 hours of exposure. The percent of means of mortality was calculated. Lethal Concentration LC50 and LC90 values were determined. Results: In the laboratory, the results of methanolic extract at 100 mg/L achieved (100%) mortality against Anopheles gambiae after 24 hours of exposure.The same extract at 10 mg/L generated (95.85±1.26%) of mortality outside the laboratory. The 80% methanolic extract showed Lethal Concentration LC50 of 11.07 mg/L and Lethal Concentration LC90 of 81.38 mg/L (after 24 hours). The 50/50% hydro-methanolic extracts achieved Lethal Concentration LC50 of 22.27 mg/L against 3417.78 mg/L respectively inside and outside of the laboratory. Conclusion: The methanolic extract is the most effective in killing on the larvae compared to the other extracts tested. Vernonia cinerea Less possesses larvicidal activity against Anopheles gambiae larvae. It may be a possible source of mosquito vector control. This study provided promising finding for using crude extracts of Vernonia cinerea Less in controlling larvae of malaria vectors.

Larvicidal efficacy of monoterpenes against the larvae of Anopheles gambiae

Objective: To evaluate the larvicidal efficacy of eight volatile components of essential oils against 3rd instar larvae of Anopheles gambiae s.s. Methods: Larvicidal effects of each compound were evaluated in both laboratory and semi-field trials. Stock solution was prepared and serial dilutions were made in six concentrations for each compound. A total of 20 larvae were exposed to larvicides for each replicate and monitored at intervals of 12, 24, 48 and 72 h. Larvae monitoring was done on basis of dead and live larvae in all intervals. Results: All assayed compounds were larvicides and presented varying degrees of larval toxicity, with LC

Bioprospection for Repellent Effect of Natural Volatiles from Ocimum suave Willd Growing in Dar es Salaam, Tanzania against Anopheles Mosquitoes.

Essential oil was extracted from Ocimum suave Willd leaves by water distillation and tested for repellency effectiveness against Anopheles gambiae adult mosquitoes. The percentage yield of the essential oil was 0.2%. Six concentrations of O. suave essential oil were applied on human skin of four volunteers, and the repellency effectiveness which was analyzed by PoloPlus (LeOra software version 1.0, 2002-2014), revealed promising RC50, RC75, RC90 and RC99 with their confidence limits as 0.1161 mg/cm2 (0.02067 - 0.1767 mg/cm2), 0.2823 mg/cm2 (0.22328 - 0.3654 mg/cm2), 0.4319 mg/cm2 (0.35226 - 0.58862 mg/cm2) and 0.98934 mg/cm2 (0.54731 - 0.99972 mg/cm2), respectively. O. suave essential oil exhibited high Anopheles mosquitos’ repellency effectiveness which merits further scientific attention for the development of natural repellents for the control of malaria and other mosquito borne diseases. These findings provides a scientific evidence and base for formulation for further mosquito repellency semi-field and field trials for the development of cheaper and affordable new mosquito repellent product(s) to meet human healthcare needs in the prevention and control of malaria and other mosquito transmitted infections.

Biocidal activities of Solvent Extracts of Azadirachta indica against Some Endemic Tropical Vector-borne Diseases.

The biocidal efficacy of Chloroform (CEX), n-Hexane (HEX), Acetone (AEX) and Ethanol (EEX) extracts, of the bark and root of Azadirachta indica (Neem), were investigated against Anopheles gambiae and Bulinus globosus in a two-phased rapid and final screening test. Results of the phytochemical screening, indicated phytochemical constituents like; Flavonoids, Tannins, phenols, saponin, phytates, glycosides and triterpenes. All extracts were active (≥500ppm), during the rapid screening phase; hence final screening phase was also carried out. Results of the final screening shows that, the snail (B. globosus), were more susceptible to all solvent extracts compared to the mosquito larvae (An. gambiae). The ethanol extract of the bark against the snail (EEXbS) induced the highest mortality with LC50 value of 0.35ppm compared to the least, chloroform extract of the root against the larvae (CEXrL, LC50=46.0 ppm). The positive control induced mortality to both snails and larvae at 1ppm, while there was no mortality induced by the negative control. The results confirm solvent extracts of neem bark and root as potential biocidal agent against disease vectors.

Molecular docking of Anopheles gambiae and Aedes aegypti glutathione S-transferases epsilon 2 (GSTE2) against usnic acid: an evidence of glutathione conjugation

The aim of this study was to develop a theoretical model using Anopheles gambiae GSTE2 structure as template for Aedes aegypti GSTE2 by homology modeling Docking simulations were performed for both the enzymes against usnic acid in neutral and anionic forms. Ramachandran plot revealed that 93.9% of the GSTE2 model residues were located on most favored regions. Model evaluation was made by the ANOLEA and GROMOS analysis. Docking results indicated that the enzymes were able to form glutathione-conjugate with usnic acid in both the forms (anionic and neutral).

Ovipositional Behavior of <i>Anopheles gambiae</i> Mosquitoes

Mosquito eggs laid within two hours are necessary for transgenic (injection) studies, because mosquito eggs become hard after that period. Thus, in order to have eggs available within this two-hour window, it is important for transgenic studies to understand the ovipositional behavior of <i>Anopheles gambiae s.s.</i>. In the present study, the ovipositional behavior of <i>An. gambiae s.s.</i> (Kisumu) was investigated in several different conditions: age of mosquitoes, time post blood meal to access oviposition substrate, and light conditions. Two groups of mosquitoes, 3–5 day old and 9–11 day old mosquitoes were blood-fed. For those mosquito groups, an oviposition dish was set either at 48 hours or 72 hours after the blood meal either in a light condition or in an artificial dark condition. The number of laid eggs was compared among different conditions. The 3–5 day old mosquitoes apparently produced a higher number of eggs than 9–11 day old ones, while there was no significant difference between the 2 groups. The number of laid eggs per one surviving blood-fed mosquito in the dark condition was significantly higher than that in the light condition (<i>p</i> = 0.03). Providing an oviposition dish at 72 hours after blood meal resulted in a significantly higher number of laid eggs per one surviving blood-fed mosquito compared to providing an oviposition dish at 48 hours after blood meal (<i>p</i> = 0.03). In conclusion, the optimal condition to have readily available egg supply in the present study for transgenic analysis was as follows: 3–5 days old mosquitoes with an oviposition dish placed at 72 hours after the blood meal in a dark environment.

Ovipositional Behavior of <i>Anopheles gambiae</i> Mosquitoes

Mosquito eggs laid within two hours are necessary for transgenic (injection) studies, because mosquito eggs become hard after that period. Thus, in order to have eggs available within this two-hour window, it is important to understand the ovipositional behavior of <i>Anopheles gambiae s.s.</i>. In the present study, the ovipositional behavior of <i>An. gambiae s.s.</i> (Kisumu) was investigated in several different conditions: age of mosquitoes, time post blood meal to access oviposition substrate, and light conditions. Two groups of mosquitoes, 3–5 days old and 9–11 days old were blood-fed. For those mosquito groups, an oviposition dish was set either at 48 hours or 72 hours after the blood meal either in a light condition or in an artificial dark condition. The number of laid eggs was compared among the different conditions. The 3–5 day-old mosquitoes apparently produced a higher number of eggs than 9–11 day-old mosquitoes, while there was no significant difference between the two groups. The number of laid eggs per one surviving blood-fed mosquito in the dark condition was significantly higher than that in the light condition (<i>p</i> = 0.03). Providing an oviposition dish at 72 hours after blood meal resulted in a significantly higher number of laid eggs per one surviving blood-fed mosquito than at 48 hours after blood meal (<i>p</i> = 0.03). In conclusion, the optimal condition to have readily available egg supply for transgenic analysis was as follows: 3–5 day-old mosquitoes with an oviposition dish placed at 72 hours after the blood meal in a dark environment.

Larvicidal and Brine Shrimp Activities of Vitex Schiliebenii Extracts and Isolated Phytoecdysteroids on Anopheles gambiae Giles S S Larvae.

Acetone, methanol and aqueous extracts of the leaves, stem bark and root bark of Vitex schiliebenii belonging to the family Verbenaceae were evaluated for their larvicidal activity against late 3rd/early 4th Anopheles gambiae Giles s.s. larvae (Diptera: Culicidae). The extracts of the acetone leaves and stem bark were active with LC50 values of 14.6 and 17.4 ppm respectively at 24 hrs. These extracts exhibited low toxicity to brine shrimps with LC50 values of 180.9 and 154.4 ppm respectively. The constituents in these extracts were isolated and evaluated and the phytoecdysteroids 20-hydroxyecdysone (1) and stigmasterol (2) were identified as the active principles in the acetone stem bark while γ-sitosterol (3) was the active principle of the acetone leaf extract. The methanol leaf extract, the stem bark aqueous extract and the acetone root bark also showed potency against the mosquito species.

Larvicidal activity of Kotschya uguenensis plant powders and methanol extracts against Anopheles gambiae s.s. larvae in the laboratory and in simulated ponds.

Polar constituents of Kotschya uguenensis Verdc. (Fabaceae) do not exhibit acute toxicity but cause growth disruption of Anopheles gambiae s.s. Gile (Diptera: Culicidae) larvae with eventual death. Time-course larvicidal effects of powders of root and stem barks and their crude methanol extracts in form of emulsions were compared in the laboratory and in artificial semi-field ponds. Kotschya uguenensis powders of root and stem barks and emulsions of their crude methanol extracts were assayed against An. gambiae s.s according to protocols of WHO 1996 & 2005. All formulations were equally effective under laboratory conditions giving 100% larval mortality within three days at a dose of 50 μg/ml of the extracts or concentrations of powders corresponding to the same level of extractable material. Under semi-field conditions, suspensions of the powder materials appeared to perform better than emulsions of methanol extracts. Time taken to give 80% mortality (LT80) of larvae and pupa at 0.1% w/v was 6.06 days for powders of root bark and 5.60 days for powders of stem bark. The LT80 for the root bark extract at 200 μg/ml was 8.28 days while that for the stem bark methanol extract was 12.47 days. No residual effects of the test materials on the larvae or pupae were evident in semi-field ponds 14 days after the reintroduction of the test materials. Our results suggest that, for the control of anophelines in the field, a weekly application of appropriate amounts of powders of K. uguenensis may be effective.

Experimental hut evaluation of Fendona 6SC®-treated bednets and Interceptor® long-lasting nets against Anopheles gambiae s.l. in Burkina Faso.

Background & objectives: Malaria prevention relies heavily on insecticide-treated bednets. Even though the benefits of bednets have been proven that in most of the studies carried out in Africa, their efficacy remains dependent on local conditions. In this study, under field conditions, we evaluated the efficacy of two LLINs (PermaNet® vs Interceptor®) and two bednet treatment kits (K-O TAB® vs Fendona 6SC®) against Anopheles gambiae s.l. Methods: Bednets were evaluated using experimental huts in the village of Pissy located in the Saponé health district of Burkina Faso. Treatments and sleepers were randomly rotated between huts. Results are expressed in terms of induced exophily, mortality after 24 h and blood-feeding inhibition. Results: A total of 1392 An. gambiae s.l. mosquitoes were collected during 120 nights in the experimental huts. The overall mortality rates were 85.4% (CL: 79.7–91.4) and 77.5% (CL: 56.9–97.3) for PermaNet® and Interceptor®, respectively. For the conventionally treated bednets, the mortality was 78.2% (CL: 63.13–96.7) with the Fendona 6SC®-treated nets and 75.5% (CL: 61.2–93) with the K-O TAB®-treated nets. The proportion of blood-fed mosquitoes was significantly higher in the untreated bednet arm than in the treated one, as well as for long-lasting nets than for conventionally treated nets. The entry rate did not vary significantly according to the bednet type, but the treated bednets increased the level of exophily by at least 43%. Conclusion: In the field, the Fendona 6SC® kit and the Interceptor bednets showed comparable efficacy to the already used K-O TAB® kit and PermaNet® bednets. These results could help National Malaria Program managers to formulate appropriate policy for effective vector control.

Evaluation of Field Performance of Insecticide-Treated Mosquito Nets in North-Western Burkina Faso.

Aims: The aim of the study was to evaluate the field performance of insecticide-treated mosquito nets (ITNs) in north-western Burkina Faso. Study design: Cross-sectional survey. Place and Duration: The study took place between September and November 2008 (end of rainy season) in rural north-western Burkina Faso. Methodology: Standard WHO bioassays were performed on field-collected ITNs from three areas of different insecticide pressure: semi-urban Nouna town, three villages with cotton agriculture, and three villages without cotton agriculture. Data on age and washing frequency of ITNs was collected, and deltamethrin content was determind by HPLC. Results: The mean age of field-collected ITNs was 2.1 years. The mosquito mortality rate (Anopheles gambiae sl.) after 24 hours was 4% for the negative controls, 90% for the positive controls, and 73% for field-used ITNs. Differences in mosquito mortality between sub-areas disappeared after controlling for confounding variables. Conclusion: This study demonstrates that under real life conditions, deltamethrin still shows some level of effectiveness despite ongoing insecticide pressure. However, deltamethrin resistance has been observed in other parts of the country and thus close surveillance of ITN efficacy is needed. More frequent replacement of ITNs is also recommended.

Species composition of the Anopheles gambiae complex across eco-vegetational zones in Bayelsa State, Niger Delta region, Nigeria.

Background & objectives: Correct vector identification is an important task in the planning and implementation of malaria vector control programmes. This study was designed to provide baseline information on the species composition and distribution of members of the Anopheles gambiae complex in three eco-vegetational zones in Bayelsa state, Nigeria. Methods: Adult mosquitoes were collected by pyrethrum spray catch (PSC) in randomly selected houses during September 2009–August 2010. Anopheles mosquitoes were identified using standard morphological keys. Mosquitoes identified as An. gambiae s.l. were used for species specific PCR-assays. Results: Out of 203 Anopheles gambiae s.l. successfully amplified, 180 (88.7%) were Anopheles gambiae s.s., 14 (6.9%) were An. melas and 9 (4.4%) were An. arabiensis. The variation in the sibling species composition of An. gambiae s.l. was not significant (p >0.05). Anopheles gambiae s.s. was predominant in all the collections with three sibling species occurring in all the eco-vegetational zones. Interpretation & conclusion: The observation of An. melas in the fresh water swamp forest of Yenagoa is of importance in malaria epidemiology. These findings are of importance in the planning and implementation of malaria vector control strategy in the three eco-vegetational zones of Bayelsa state.