RESUMO
BACKGROUND: From 2008 to 2013, a prevention intervention against malaria based on indoor residual spraying (IRS) was implemented in Benin. From 2008 to 2012, Ficam M(®), a bendiocarb-containing product was used for house spraying, in association with pirimiphos methyl EC (Actellic EC) in 2013. This operation aimed to strengthen the effectiveness of treated nets so as to expedite the achievement of Millennium Development Goals (MDGs): the reduction of morbidity and mortality due to malaria by 75 % from 2000 to 2015. METHODS: Monitoring and evaluation (M&E) was implemented in order to evaluate the impact of IRS intervention on malaria transmission. Anopheles gambiae s.l. populations were sampled by human landing catch. In addition, window exit traps and pyrethrum spray catches were performed to assess exophagic behaviour of Anopheles vectors the main malaria vector in the treated areas. The residual activity of insecticide in the treated walls was also assessed using WHO bioassay test. RESULTS: The purpose of this project was to draw attention to new challenges and future prospects for the success of IRS in Benin. The main strength of the intervention was a large-scale operation in which more than 80 % of the houses were treated due to the strong adhesion of population. In addition, a significant reduction of the EIR in areas under IRS were observed. However, there were many challenges including the high cost of IRS implementation and the identification of suitable areas to implement IRS. This was because of the low and short residual effect of the insecticides recommended for IRS and the management strategy for vector resistance to insecticides. This indicated that challenges are accompanied by suggested solutions. For the cost of IRS to be accessible to states, then local organizations need to be created in partnership with the National Malaria Control Programme (NMCP) in order to ensure relevant planning and implementation of IRS. CONCLUSION: As an anticipatory measure against vector resistance, this paper proposes various methods, such as periodic IRS based on a combination of two or three insecticides of different classes used in rotation every two or three years.
Assuntos
Anopheles , Insetos Vetores , Resistência a Inseticidas , Inseticidas , Malária/prevenção & controle , Controle de Mosquitos , Animais , Anopheles/fisiologia , Benin , Habitação , Insetos Vetores/fisiologia , Controle de Mosquitos/economia , Compostos Organotiofosforados , Fenilcarbamatos , Dinâmica PopulacionalRESUMO
BACKGROUND: The impact of indoor residual spraying (IRS) and long-lasting insecticide nets (LLINs), key components of the national malaria control strategy of Mali, is threatened by vector insecticide resistance. The objective of this study was to assess the level of insecticide resistance in Anopheles gambiae sensu lato populations from Mali against four classes of insecticide recommended for IRS: organochlorines (OCs), pyrethroids (PYs), carbamates (CAs) and organophosphates (OPs). Characterization of resistance was done in 13 sites across southern Mali and assessed presence and distribution of physiological mechanisms that included target-site modifications: knockdown resistance (kdr) and altered acetycholinesterase (AChE), and/or metabolic mechanisms: elevated esterases, glutathione S-transferases (GSTs), and monooxygenases. METHODS: The World Health Organization (WHO) tube test was used to determine phenotypic resistance of An. gambiae s.l. to: dichlorodiphenyltrichloroethane (DDT) (OC), deltamethrin (PY), lambda-cyhalothrin (PY), bendiocarb (CA), and fenitrothion (OP). Identification of sibling species and presence of the ace-1 (R) and Leu-Phe kdr, resistance-associated mutations, were determined using polymerase chain reaction (PCR) technology. Biochemical assays were conducted to detect increased activity of GSTs, oxidases and esterases. RESULTS: Populations tested showed high levels of resistance to DDT in all 13 sites, as well as increased resistance to deltamethrin and lambda-cyhalothrin in 12 out of 13 sites. Resistance to fenitrothion and bendiocarb was detected in 1 and 4 out of 13 sites, respectively. Anopheles coluzzii, An. gambiae sensu stricto and Anopheles arabiensis were identified with high allelic frequencies of kdr in all sites where each of the species were found (13, 12 and 10 sites, respectively). Relatively low allelic frequencies of ace-1 (R) were detected in four sites where this assessment was conducted. Evidence of elevated insecticide metabolism, based on oxidase, GSTs and esterase detoxification, was also documented. CONCLUSION: Multiple insecticide-resistance mechanisms have evolved in An. coluzzii, An. gambiae s.s. and An. arabiensis in Mali. These include at least two target site modifications: kdr, and ace-1 (R) , as well as elevated metabolic detoxification systems (monooxygenases and esterases). The selection pressure for resistance could have risen from the use of these insecticides in agriculture, as well as in public health. Resistance management strategies, based on routine resistance monitoring to inform insecticide-based malaria vector control in Mali, are recommended.
Assuntos
Anopheles/efeitos dos fármacos , Insetos Vetores/efeitos dos fármacos , Resistência a Inseticidas , Inseticidas/farmacologia , Animais , Anopheles/enzimologia , Anopheles/genética , Bioensaio , Carbamatos/farmacologia , DDT/farmacologia , Feminino , Genótipo , Hidrocarbonetos Clorados/farmacologia , Insetos Vetores/enzimologia , Insetos Vetores/genética , Resistência a Inseticidas/genética , Resistência a Inseticidas/fisiologia , Mali , Mutação , Organofosfatos/farmacologia , Vigilância em Saúde Pública , Piretrinas/farmacologiaRESUMO
BACKGROUND: To validate assumptions about the length of the distribution-replacement cycle for long-lasting insecticidal nets (LLINs) in Rwanda, the Malaria and other Parasitic Diseases Division, Rwanda Ministry of Health, used World Health Organization methods to independently confirm the three-year LLIN serviceable life span recommendation of WHO. METHODS: Approximately 3,000 coded LLINs, distributed as part of a national campaign, were monitored in six sites, by means of six-monthly visits to selected houses. Two indicators, survivorship/attrition, a measure of the number of nets remaining, and fabric integrity, the proportion of remaining nets in either 'good', 'serviceable' or 'needs replacement' condition, based on holes in the net material, were tracked. To validate the assumption that the intervention would remain effective for three years, LLIN coverage, calculated using either survivorship, or integrity, by removing nets in the 'needs replacement' category from the survivorship total, was compared with the predicted proportion of nets remaining, derived from a net loss model, that assumes an LLIN serviceable life of three years. RESULTS: After two years, there was close agreement between estimated LLIN survivorship at all sites, 75% (range 64-84%), and the predicted proportion of nets remaining, 75%. However, when integrity was considered, observed survivorship at all sites, declined to 42% (range 10-54%). CONCLUSIONS: More than half, 58%, of the LLINs fell into the 'needs replacement' category after two years. While these nets were counted for survivorship, they were judged to be of little-to-no benefit to a user. Therefore, when integrity was taken into account, survivorship was significantly lower than predicted, suggesting that net serviceable life was actually closer to two, rather than three years, and, by extension, that the impact of the intervention during year three of the LLIN distribution-replacement cycle could be well below that seen in years one and two.
Assuntos
Transmissão de Doença Infecciosa/prevenção & controle , Mosquiteiros Tratados com Inseticida/estatística & dados numéricos , Malária/prevenção & controle , Humanos , Mosquiteiros Tratados com Inseticida/provisão & distribuição , Ruanda/epidemiologia , Fatores de TempoRESUMO
BACKGROUND: LLIN distribution, every three years, is a key intervention of Benin's malaria control strategy. However, data from the field indicate that LLIN lifespan appears to vary based on both intrinsic (to the LLIN) and extrinsic factors. METHODS: We monitored two indicators of LLIN durability, survivorship and integrity, to validate the three-year-serviceable-life assumption. Interviews with net owners were used to identify factors associated with loss of integrity. RESULTS: Observed survivorship, after 18 months, was significantly less (p<0.0001) than predicted, based on the assumption that nets last three years. Instead, it was closer to predicted survivorship based on a two-year LLIN serviceable life assumption (p=0.03). Furthermore, the integrity of nearly one third of 'surviving' nets was so degraded that they were in need of replacement. Five factors: washing frequency, proximity to water for washing, location of kitchen, type of cooking fuel, and low net maintenance were associated with loss of fabric integrity. CONCLUSION: A two-year serviceable life for the current LLIN intervention in Benin would be a more realistic program assumption.
Assuntos
Mosquiteiros Tratados com Inseticida , Inseticidas/administração & dosagem , Malária/prevenção & controle , Controle de Mosquitos/métodos , Animais , Benin , Culicidae , Falha de Equipamento , Humanos , Fatores de TempoRESUMO
We present a method for designing optical fibers that support field-flattened, ring-like higher order modes, and show that the effective and group indices of its modes can be tuned by adjusting the widths of the guide's field-flattened layers or the average index of certain groups of layers. The approach provides a path to fibers that have simultaneously large mode areas and large separations between the propagation constants of their modes.
Assuntos
Desenho Assistido por Computador , Tecnologia de Fibra Óptica/instrumentação , Modelos Teóricos , Espalhamento de Radiação , Simulação por Computador , Desenho de Equipamento , Análise de Falha de EquipamentoRESUMO
We present a detailed theoretical investigation of cladding-pumped Raman fiber amplification in an unexplored parameter space of high conversion efficiency (> 60%) and high brightness enhancement (> 1000). Fibers with large clad-to-core diameter ratios can provide a promising means for Raman-based brightness enhancement of diode pump sources. Unfortunately, the diameter ratio cannot be extended indefinitely since the intensity generated in the core can greatly exceed that in the cladding long before the pump is fully depleted. If left uncontrolled, this leads to the generation of parasitic second-order Stokes wavelengths in the core, limiting the conversion efficiency and as we will show, clamping the achievable brightness enhancement. Using a coupled-wave formalism, we present the upper limit on brightness enhancement as a function of diameter ratio for conventionally guided fibers. We further present strategies for overcoming this limit based upon depressed well core designs. We consider two configurations: 1) pulsed cladding-pumped Raman fiber amplifier (CPRFA) and 2) cw cladding-pumped Raman fiber laser (CPRFL).
RESUMO
We analyze the scalability of diffraction-limited fiber lasers considering thermal, non-linear, damage and pump coupling limits as well as fiber mode field diameter (MFD) restrictions. We derive new general relationships based upon practical considerations. Our analysis shows that if the fiber's MFD could be increased arbitrarily, 36 kW of power could be obtained with diffraction-limited quality from a fiber laser or amplifier. This power limit is determined by thermal and non-linear limits that combine to prevent further power scaling, irrespective of increases in mode size. However, limits to the scaling of the MFD may restrict fiber lasers to lower output powers.
Assuntos
Amplificadores Eletrônicos , Desenho Assistido por Computador , Tecnologia de Fibra Óptica/instrumentação , Lasers , Modelos Teóricos , Refratometria/instrumentação , Transferência de Energia , Desenho de Equipamento , Análise de Falha de EquipamentoRESUMO
An important component of malaria control programs is the ability to assess the effectiveness of the insecticide in insecticide-treated nets (ITNs) during normal usage. The standard technique to measure insecticidal activity is the World Health Organization (WHO) cone test, which in many circumstances, may be difficult to implement. We have evaluated an alternative technique, the colorimetric field test (CFT) on a group of 24-month-old Permanet® 2.0 (Vestergaard-Frandsen, Denmark) nets collected in Colombia. The CFT, which measures surface levels (SL) of deltamethrin is compared with standard high-performance liquid chromatography (HPLC) and the WHO cone test. Effective concentrations of deltamethrin for 80% mortality (EC80) were determined from the CFT and HPLC results. Distribution of insecticide SL after 24 months of use reveal that sampling of the midsection best represents the condition of the entire net. We conclude that the CFT is a practical alternative to the WHO cone test for assessing ITN efficacy.
Assuntos
Bioensaio , Mosquiteiros Tratados com Inseticida , Inseticidas , Controle de Mosquitos/métodos , Nitrilas , Piretrinas , Animais , Anopheles , Análise Custo-Benefício , Humanos , Malária/prevenção & controle , Controle de Mosquitos/economia , Mosquitos Vetores , Organização Mundial da SaúdeRESUMO
BACKGROUND: The National Malaria Control Program (NMCP) has been using pirimiphos methyl for the first time for indoor residual spraying (IRS) in Benin. The first round was a success with a significant decrease of entomological indicators of malaria transmission in the treated districts. We present the results of the entomological impact on malaria transmission. Entomologic parameters in the control area were compared with those in intervention sites. METHODS: Mosquito collections were carried out in three districts in the Atacora-Dongo region of which two were treated with pirimiphos methyl (Actellic 50EC) (Tanguiéta and Kouandé) and the untreated (Copargo) served as control. Anopheles gambiae s.l. populations were sampled monthly by human landing catch. In addition, window exit traps and pyrethrum spray catches were performed to assess exophagic behavior of Anopheles vectors. In the three districts, mosquito collections were organized to follow the impact of pirimiphos methyl IRS on malaria transmission and possible changes in the behavior of mosquitoes. The residual activity of pirimiphos methyl in the treated walls was also assessed using WHO bioassay test. RESULTS: A significant reduction (94.25%) in human biting rate was recorded in treated districts where an inhabitant received less than 1 bite of An. gambiae per night. During this same time, the entomological inoculation rate (EIR) dramatically declined in the treated area (99.24% reduction). We also noted a significant reduction in longevity of the vectors and an increase in exophily induced by pirimiphos methyl on An. gambiae. However, no significant impact was found on the blood feeding rate. Otherwise, the low residual activity of Actellic 50 EC, which is three months, is a disadvantage. CONCLUSION: Pirimiphos methyl was found to be effective for IRS in Benin. However, because of the low persistence of Actellic 50EC used in this study on the treated walls, the recourse to another more residual formulation of pirimiphos methyl is required.
Assuntos
Anopheles/efeitos dos fármacos , Inseticidas/farmacologia , Malária/transmissão , Controle de Mosquitos/métodos , Compostos Organotiofosforados/farmacologia , Animais , Benin/epidemiologia , Bioensaio , Habitação , Humanos , Insetos Vetores , Inseticidas/administração & dosagem , Malária/epidemiologia , Malária/prevenção & controle , Compostos Organotiofosforados/administração & dosagemRESUMO
We demonstrate a cladding-pumped Raman fiber amplifier (CPRFA) whose brightness-enhancement factor depends on the cladding-to-core diameter ratio. The pump and the signal are coupled independently into different input arms of a pump-signal combiner, and the output is spliced to the Raman amplifier fiber. The CPRFA generates 20 microJ, 7 ns pulses at 1100 nm at a 2.2 kHz repetition rate with 300 microJ (25.1 kW peak power) of input pump energy. The amplified signal's peak power is 2.77 kW, and the brightness-enhancement factor is 192--the highest peak power and brightness enhancement achieved in a CPRFA at any wavelength, to our knowledge.
RESUMO
OBJECTIVES: To assess the burden of malaria in San Esteban, Department of Olancho, Honduras, and provide recommendations for control. METHODS: Malaria causes appreciable morbidity in San Esteban. In 2006, health workers reported an increase in malaria cases and requested recommendations for control. In 2005, 385 cases (Plasmodium vivax, 316; P. falciparum, 69) were detected from 4 007 blood smears in the San Esteban laboratory (slide positivity rate = 9.6%). During May-July 2006, we assessed the burden of malaria and made recommendations. We reviewed epidemiologic data from slide-confirmed malaria cases in 2005 and 2006 and conducted a knowledge, attitudes, and practices survey in households to assess malaria diagnostic, treatment, and prevention practices. RESULTS: During May-July 2006, 143 laboratory-confirmed malaria cases were detected (P. vivax, 134; P. falciparum, 9) in San Esteban, compared with 104 (P. vivax, 79; P. falciparum, 25) in May-July 2005. From January 2005 to July 2006, 538 cases were detected in San Esteban, with increased frequency in May-October and the highest incidence in children 0-14 years old. We administered 112 surveys in 19 communities. Seventy percent of respondents reported a history of malaria in a household member, with the highest frequency reported in mothers (45%) and children under 14 years old (37%). Most households did not have mosquito protection such as bed nets, screens, or indoor residual insecticide. CONCLUSIONS: Malaria is ongoing in San Esteban, with increased incidence in children. We recommend increased availability and promotion of insecticide-treated bed nets, improved timing and coverage of indoor residual spraying, and improved community malaria practices through education sessions.
Assuntos
Malária Falciparum/epidemiologia , Malária Falciparum/prevenção & controle , Malária Vivax/epidemiologia , Malária Vivax/prevenção & controle , Adolescente , Adulto , Criança , Pré-Escolar , Efeitos Psicossociais da Doença , Feminino , Honduras/epidemiologia , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
For what we believe to be the first time, an optical resonance transition rubidium laser (5(2)P(1/2)-->5(2)S(1/2)) has been demonstrated with a hydrocarbon-free buffer gas. Prior demonstrations of alkali resonance transition lasers have used ethane as either the buffer gas or a buffer gas component to promote rapid fine-structure mixing. However, our experience suggests that the alkali vapor reacts with the ethane producing carbon as one of the reaction products. This degrades long term laser reliability. Our recent experimental results with a "clean" helium-only buffer gas system demonstrate all the advantages of the original alkali laser system, but without the reliability issues associated with the use of ethane.
RESUMO
We report what we believe to be the first demonstration of a multimode-diode-pumped gas laser: Rb vapor operating on the 795 nm D1 resonance transition. Peak output of approximately 1 W was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.
RESUMO
Population inversion of the 2P 1/2 and 2S 1/2 levels and continuous-wave, three-level laser oscillation at 795 nm on the D1 transition of the rubidium atom has been demonstrated. Using a titanium sapphire laser as a pump source, we obtained a slope power efficiency of 54% relative to absorbed pump power, consistent with homogeneous broadening of the rubidium pump and laser transitions. The end-pumped rubidium laser performance was well described by use of literature spectroscopic and kinetic data in a model that takes into account ground-level depletion and a pump spectral bandwidth that is substantially larger than the collisionally broadened pump transition spectral width.
RESUMO
OBJECTIVES: To assess the burden of malaria in San Esteban, Department of Olancho, Honduras, and provide recommendations for control. METHODS: Malaria causes appreciable morbidity in San Esteban. In 2006, health workers reported an increase in malaria cases and requested recommendations for control. In 2005, 385 cases (Plasmodium vivax, 316; P. falciparum, 69) were detected from 4 007 blood smears in the San Esteban laboratory (slide positivity rate = 9.6 percent). During May-July 2006, we assessed the burden of malaria and made recommendations. We reviewed epidemiologic data from slide-confirmed malaria cases in 2005 and 2006 and conducted a knowledge, attitudes, and practices survey in households to assess malaria diagnostic, treatment, and prevention practices. RESULTS: During May-July 2006, 143 laboratory-confirmed malaria cases were detected (P. vivax, 134; P. falciparum, 9) in San Esteban, compared with 104 (P. vivax, 79; P. falciparum, 25) in May-July 2005. From January 2005 to July 2006, 538 cases were detected in San Esteban, with increased frequency in May-October and the highest incidence in children 0-14 years old. We administered 112 surveys in 19 communities. Seventy percent of respondents reported a history of malaria in a household member, with the highest frequency reported in mothers (45 percent) and children under 14 years old (37 percent). Most households did not have mosquito protection such as bed nets, screens, or indoor residual insecticide. CONCLUSIONS: Malaria is ongoing in San Esteban, with increased incidence in children. We recommend increased availability and promotion of insecticide-treated bed nets, improved timing and coverage of indoor residual spraying, and improved community malaria practices through education sessions.
OBJETIVOS: Evaluar la carga de malaria en San Esteban, departamento de Olancho, Honduras, y ofrecer recomendaciones para su control. MÉTODOS: La malaria es causa de una considerable morbilidad en San Esteban. En 2006, los trabajadores sanitarios informaron un aumento de casos de malaria y solicitaron recomendaciones para su control. En 2005, en el laboratorio de San Esteban se detectaron 385 casos (316 por Plasmodium vivax y 69 por P. falciparum) en 4 007 frotis sanguíneos (tasa de positividad: 9,6 por ciento). Entre mayo y julio de 2006 se evaluó la carga de malaria y se hicieron las recomendaciones. Se revisaron los datos epidemiológicos de los casos confirmados de 2005 y 2006 y se aplicó una encuesta sobre conocimientos, actitudes y hábitos en los hogares para evaluar las prácticas relacionadas con el diagnóstico, el tratamiento y la prevención de la malaria. RESULTADOS: Entre mayo y julio de 2006 en San Esteban se detectaron 143 casos de malaria confirmados por el laboratorio (134 por P. vivax y 9 por P. falciparum), en comparación con 104 (79 por P. vivax y 25 por P. falciparum) entre mayo y julio de 2005. Entre enero de 2005 y julio de 2006 se detectaron 538 casos en San Esteban, con un aumento en la frecuencia entre mayo y octubre y la mayor incidencia en niños de 0 a 14 años. Se aplicaron 112 encuestas en 19 comunidades. De los que respondieron, 70 por ciento había tenido algún miembro del hogar con malaria, con una mayor frecuencia en las madres (45 por ciento) y los menores de 14 años (37 por ciento). La mayoría de los hogares carecían de protección contra los mosquitos, como mosquiteros para las camas y ventanas o fumigación de interiores. CONCLUSIONES: La malaria se mantiene en aumento en San Esteban, con una mayor incidencia en los niños. Se recomienda incrementar la disponibilidad y la promoción de mosquiteros tratados con insecticidas, mejorar la periodicidad y la cobertura de la fumigación de interiores y mejorar los hábitos...