8 research outputs found
Update on resistance status of Anopheles gambiae s.s. to conventional insecticides at a previous WHOPES field site, "Yaokoffikro", 6 years after the political crisis in Côte d'Ivoire.
No full textBACKGROUND: At Yaokoffikro field site near Bouaké, in central Côte d'Ivoire, a group of experimental huts built in 1996 served over many years for the evaluation of insecticides against highly resistant mosquitoes. Breeding sites of mosquitoes and selection pressure in the area were maintained by local farming practices until a war broke out in September 2002. Six years after the crisis, we conducted bioassays and biochemical analysis to update the resistance status of Anopheles gambiae s.s. populations and detect other potential mechanisms of resistance that might have evolved. METHODS: An. gambiae s.s. larvae from Yaokoffikro were collected in breeding sites and reared to adults. Resistance status of this population to insecticides was assessed using WHO bioassay test kits for adult mosquitoes with seven insecticides: two pyrethroids, a pseudo-pyrethroid, an organochloride, two carbamates and an organophosphate.Molecular and biochemical assays were carried out to identify the L1014F kdr and ace-1R alleles in individual mosquitoes and to detect potential increase in mixed function oxidases (MFO), non-specific esterases (NSE) and glutathione S-transferases (GST) activity. RESULTS: High pyrethroids, DDT and carbamate resistance was confirmed in An. gambiae s.s. populations from Yaokoffikro. Mortality rates were less than 70% with pyrethroids and etofenprox, 12% with DDT, and less than 22% with the carbamates. Tolerance to fenitrothion was observed, with 95% mortality after 24 h.PCR analysis of samples from the site showed high allelic frequency of the L1014F kdr (0.94) and the ace-1R (0.50) as before the crisis. In addition, increased activity of NSE, GST and to a lesser extent MFO was found relative to the reference strain Kisumu. This was the first report detecting enhanced activity of these enzymes in An. gambiae s.s from Yaokoffikro, which could have serious implications in detoxification of insecticides. Their specific roles in resistance should be investigated using additional tools. CONCLUSION: The insecticide resistance profile at Yaokoffikro appears multifactorial. The site presents a unique opportunity to evaluate its impact on the protective efficacy of insecticidal products as well as new tools to manage these complex mechanisms. It calls for innovative research on the behaviour of the local vector, its biology and genetics that drive resistance
Impact of the involvement of hospitals in Benin in the actions of the world program “Save Lives: Clean Your Hands» edition 2014
No full textKnowledge of health care workers and ability of healthcare facilities in preventing of Ebola virus diseases/lassa fever in Benin
No full textAn Electrochromic Device Combining Polypyrrole And Wo3 - I. Liquid Electrolyte
No full textIn this work we assembled an electrochromic device using as active materials an organic conductive polymer and a transition metal oxide. We studied the materials used to assemble the device separately, and in complete devices. These materials were: polypyrrole doped with dodecylsulfate and tungsten oxide. The substrates used were glass slides coated with tin doped indium oxide, and the electrolyte was a propylene carbonate solution of lithium perchlorate. We adjusted the charge balance and the chromatic contrast of the devices by controlling the thickness of the polypyrrole films. To illustrate the results obtained, we describe two devices with different polypyrrole film thicknesses. The chromatic contrast in the visible and near-infrared wavelength range is 40% and the electrical and optical properties of the devices remain unchanged after 104 double potential chronoamperometric steps. Copyright © 1996 Elsevier Science Ltd.411828052816Osaka, T., Ogano, S., Naoi, K., (1989) J. Electrochem. Soc., 136, p. 306Somasini, N.L.D., MacDiarmid, A.G., (1988) J. Appl. Electrochem., 18, p. 92Goto, F., Okabayashi, K., Yoshida, T., Morimoto, H., (1987) J. Power Sources, 20, p. 243Noufi, R., Nozik, A.J., White, J., Warren, L.F., (1982) J. Electrochem. Soc., 129, p. 226Josowiaz, M., Janata, J., (1986) J. Anal. Chem., 58, p. 514Bull, R.A., Fan, F.R., Bard, A.J., (1984) J. Electrochem. Soc., 131, p. 687Heinze, J., (1991) Synth. Met., 41, p. 2805Zoppi, R.A., De Paoli, M.-A., (1993) Quim. Nova, 16, p. 560Scrosati, B., Laminated electrochromic displays and windows (1993) Applications of Electroactive Polymers, p. 267. , (Edited by B. Scrosati), Chapman and Hall, LondonGustafson, J.C., Inganas, O., (1994) Synth. Met., 62, p. 17Mastragostino, M., Marinangeli, A.M., Corradini, A., Giacobbe, C., (1989) Synth. Met., 28, pp. C501Kobayashi, T., Yoneyama, H., Tamura, H., (1984) J. Electroanal. Chem., 161, p. 419Garnier, F., Tourillon, G., Gazard, M., Dubois, J.E., (1983) J. Electroanal. Chem., 148, p. 299De Paoli, M.-A., Panero, S., Paserini, S., Scrosati, B., (1990) Adv. Mater., 2, p. 480Peres, R.C.D., Pernaut, J.M., De Paoli, M.-A., (1989) Synth. Met., 28, pp. C59Peres, R.C.D., De Paoli, M.-A., Torresi, R., (1992) Synth. Met., 48, p. 259Matencio, T., De Paoli, M.-A., Peres, R.C.D., Torresi, R.M., Cordoba De Torresi, S.I., (1995) Synth. Met., 72, p. 59Duek, E.A.R., De Paoli, M.-A., (1994) Adv. Mat., 4, p. 287Duek, E.A.R., De Paoli, M.-A., Mastragostino, M., (1993) Adv. Mater., 5, p. 650Tassi, E.L., De Paoli, M.-A., (1994) Electrochim. Acta, 39, p. 2481Rocco, A.M., De Paoli, M.-A., (1993) J. Braz. Chem. Soc., 4, p. 97De Paoli, M.-A., Rocco, A.M., Lourenço, A., submittedReichman, B., Bard, A.J., (1979) Electrochem. Kinetics, 126, p. 583Peres, R.C.D., De Paoli, M.-A., Torresi, R., (1992) Synth. Met., 48, p. 259Bange, K., Gambke, T., (1990) Adv. Mater., 2, p. 1
Field and Laboratory Evaluation of Bioefficacy of\ud an Insect Growth Regulator (Dimilin) as a Larvicide\ud Against Mosquito and Housefly Larvae
No full textThe inhibitory function of Dimilin (Diflubenzuron), mostly a chitin synthesis regulator, on the ecdysis of mosquitoes (Anopheles gambiae s.l., Culex quinquefasciatus) and housefly was evaluated in the field and in laboratory. Three formulations of Diflubenzuron were evaluated in this study: Dimilin, Wettable powder (25%), Dimilin granules (2%), and Dimilin tablets (2%). The laboratory and field evaluation used different rates of concentrations of these formulations. Generally, at higher dosages larvae developments, eggs hatchability and pupation were impossible. The development of mosquitoes was significantly higher in control while highly depressed in different dosages of treatment in both laboratory and field experiments. In houseflies, the adult population decreased sharply after treatment of their breeding sites while pupae mortality was noticed to be high in laboratory-treated samples. Dimilin could be opted as one of the choice of the larval control chemicals to be incorporated in the integrated vector control programmes in urban and rural area
Electrochemistry, Polymers And Opto-electronic Devices: A Combination With A Future
No full textElectrochemistry came into life with the invention of the pile, by Volta in 1800. He combined different metal discs with a piece of tissue, swollen with an aqueous salt solution. The so-called Pila di Volta used a polymer for the first time in an electrochemical device and can be seen as a powerful idea to create new devices. Recently, polymers became an alternative to make thin and flexible devices. Thus, we find transparent plastic electrodes based on poly(ethylene terephtalate) coated with a transition metal oxide. There are also polymer electrolytes based on complexes of inorganic salts and poly(ethylene oxide) derivatives, with reasonable ionic conductivity in the absence of solvents. Finally, the electroactive polymers are efficient substitutes for the inorganic semiconductors because they can be synthetically tailored to produce the desired electronic answer. 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Insecticide resistance in the West African malaria vector Anopheles gambiae and investigation of alternative tools for its delay
No full textThere is a current policy to eliminate malaria in the African continent. Pyrethroid-incorporated Long Lasting Insecticidal Nets (LLINs) and/or Indoor Residual Spraying (IRS) are the chemical weapons being deployed to achieve that goal. Rather worryingly, resistance to pyrethroids is well documented in the major vectors of malaria in Africa, and could decimate the contribution that vector control can make to any successful elimination agenda over the next decade. DDT (Dichlorodiphenyltrichloroethane) for IRS is cost effective but undesirable because of its environmental impact. There is a need to identify pyrethroid resistance mechanisms in the areas being scaled up, evaluate their direct impact on the efficacy of these tools and identify novel tools that might have potential as alternatives to pyrethroids and DDT for net or indoor residual treatments. This thesis reports that pyrethroid, organophosphate (Ops) & carbamate resistance is present in the Mopti (M) and Savanah (S) molecular forms of the major vector of malaria, Anopheles gambiae, in two West African countries, Benin and Ivory Coast where LLINs are currently being deployed,. Mechanisms for pyrethroids include elevated oxidase activities and the knock down resistance (kdr) gene at high frequency (>80%) whereas an insensitive acetylcholinesterase conferred Ops and carbamate resistance. Experimental hut tests in Southern Benin showed that the efficacy of Insecticide Treated Net (ITN) and IRS with the pyrethroid lambdacyalothrin was seriously compromised by pyrethroid resistance in the M form of An. gambiae, as opposed to the North where there is no record of pyrethroid resistance. This type of pyrethroid resistance, now spreading through West African populations of the M molecular form of An. gambiae, appears to have major operational significance in other areas such as Bioko, Niger and Burkina Faso. The alternative candidate insecticides, indoxacarb (an oxadiazine), chlorfenapy (a pyrrole) and chlorpyrifos methyl (an organophosphate) were evaluated, in the laboratory and/or in the field. In the laboratory, indoxacarb and chlorfenapyr on netting were more toxic than permethrin over the same dosage range (100-500mg/m2). Toxic activity was rather slow and bloodfeeding of mosquitoes was uninhibited in the presence of either insecticide. The experimental hut tests conducted in Southern Benin indicated that chlorfenapyr has high potential for IRS, killing 82.9% of pyrethroid resistant An. gambiae and 69% of Culex quinquefasciatus. Likewise, IRS with chlorpyrifos methyl CS (Capsule Suspension) was very efficacious at the same site in Benin. It killed 95.5% of pyrethroid resistant An. gambiae that entered a hut and showed activity on walls that lasted for more than 9 months without significant decay. If applied at high coverage, chlorpyrifos methyl CS should show higher, more-sustained levels of malaria transmission control than that achievable with DDT or pyrethroids. The feasibility of applying synthetic insect repellents on bednets (RTNs) to control insecticide resistant mosquitoes was explored in the second country, Ivory Coast. The results of tests done in experimental huts showed that formulations of volatile DEET (N,N-diethyl-3-methylbenzamide) and ethyl butylacetylaminopropionate (IR3535) on nets reduced bloodfeeding and the entry rate of mosquitoes into huts. An unexpected result was the 69-76% mortality of An. gambiae and 51-61% mortality of Cx. quinquefasciatus in huts containing RTNs. The DEET-based product provided better efficacy but was short-lived. Further treatment of netting with a formulation of DEET in which the repellent is gradually released from a capsule that binds the repellent strongly, showed that the formulation repels, inhibits blood-feeding and kills mosquitoes for a period of at least 6 months under laboratory conditions. Application of repellents to nets warrants further investigation as well as their development as alternatives to pyrethroids. Because it will not be possible to go for malaria elimination with the current tools, based on pyrethroids only, the results obtained with chlorfenapyr, indoxacarb and chlorpyrifos methyl should encourage further studies aiming at supplementing pyrethroids for vector control in areas where malaria mosquitoes are resistant to pyrethroids. <br/
Average Household Size and the Eradication of Malaria
No full textEfforts to eradicate malaria during the 20th century succeeded in some parts of the world but failed in others. Malaria also disappeared spontaneously in several countries for reasons that remain an enigma. The connection between malaria and poverty has long been noted. Here we focus on a specific aspect: household size, which has hitherto received little attention. We find strong evidence that when average household size drops below four persons, the probability of malaria eradication jumps dramatically and its incidence in the population drops significantly. This effect is independent of all commonly-studied explanatory variables and was globally valid across all climate zones irrespective of counter measures, vector species, or Plasmodium species. We propose an explanation based on the dispersal mechanism of the parasite. Malaria is transmitted at night by mosquito bite. The mosquito typically spreads the Plasmodium only locally over short distances to new human victims. To survive, the Plasmodium depends on infected humans making social contacts over longer distances. When household size decreases sufficiently, these contacts cross a threshold value that changes the balance between extinctions and replacements and the Plasmodium disappears on its own. We test this interpretation by contrasting our malaria model with dengue fever, which is also poverty-related and mosquito-borne but transmitted differently, namely through daytime exposure. Household size is uncorrelated with dengue incidence, whereas an indicator of outdoor work that is insignificant in the malaria model is highly significant for dengue. We conclude that poverty-induced malaria infection risks are likely to persist, but a focus on reducing effective household size can be a feasible and promising means of its eradication.Malaria;dengue fever, household size, DDT
