RESUMO
BACKGROUND: The Magude Project assessed the feasibility of eliminating malaria in Magude district, a low transmission setting in southern Mozambique, using a package of interventions, including long-lasting insecticidal nets (LLINs). As the efficacy of LLINs depends in part on their physical integrity, this metric was quantified for Olyset® Nets post mass-distribution, in addition to net use, care and handling practices and other risk factors associated with net physical integrity. METHODS: Nets were collected during a cross-sectional net evaluation, nine months after the Magude project commenced, which was 2 years after the nets were distributed by the National Malaria Control Programme (NMCP). The physical integrity of the nets was assessed by counting and sizing the holes at different positions on each net. A structured questionnaire was administered to assess how the selected net was used and treated (care, wash and repair). Net bio-efficacy was assessed following the standard World Health Organization (WHO) cone bioassay procedures. RESULTS: Out of the 170 Olyset® Nets included in the analysis, 63.5% had been used the night before. The main reason for not using a net was the notion that there were no mosquitoes present. The average number of people using each net was 1.79. Two thirds of the nets had only been washed once or twice since distribution. Most nets (80.9%) were holed and 18% were torn, but none of the risk factors were significantly associated with net integrity, except for presence of mice in the household. Less than half of the participants noticed holes in holed nets, and of those only 38.6% attempted to repair those. None of the six nets that were tested for bio-efficacy passed the WHO threshold of 80% mosquito mortality. CONCLUSION: Overall the majority of Olyset® Nets were in serviceable condition two years post-distribution, but their insecticidal effect may have been lost. This study-together with previous evidence on suboptimal access to and use of LLINs in Magude district-highlights that LLINs as an intervention could have been optimized during the Magude project to achieve maximum intervention impact.
Assuntos
Culicidae , Mosquiteiros Tratados com Inseticida , Inseticidas , Malária , Humanos , Animais , Camundongos , Estudos Transversais , Moçambique , Controle de Mosquitos/métodos , Malária/prevenção & controleRESUMO
BACKGROUND: Different anopheline species (even within a species group/complex) can differ in their feeding and resting behaviours, which impact both malaria transmission patterns as well as the efficacy of vector control interventions. While morphological identification of sampled specimens is an important first step towards understanding species diversity and abundance, misidentification can result in the implementation of less effective vector control measures, and consequently smaller reductions in the number of local malaria cases. Focusing on southern Mozambique, a malaria pre-elimination area where malaria remains persistent, the aims of this preliminary study were to use molecular identification (CO1 and ITS2 barcoding) to (1) validate the results from the morphological identification (with a particular focus on Anopheles pharoensis and Anopheles squamosus), and (2) have a closer look at the Anopheles coustani group (which includes Anopheles tenebrosus and Anopheles ziemanni). METHODS: Female anopheline mosquitoes (n = 81) were identified morphologically and subsequently sequenced at the ribosomal DNA internal transcribed spacer region 2 (ITS2) and/or cytochrome oxidase subunit 1 (CO1) loci towards species determination. RESULTS: Out of the 62 specimens that were identified morphologically to species, 4 (6.5%) were misidentified. Regarding the An. coustani group, morphological identification showed that several members are present in southern Mozambique, including An. coustani sensu lato (s.l.), An. ziemanni and An. tenebrosus. However, based on both ITS2 and CO1 sequences, the exact species remains unknown for the latter two members until voucher sequences are available for comparison. CONCLUSION: The reason(s) for morphological misidentification of anopheline mosquitoes need to be mitigated. This is usually related to both the capacity (i.e. training) of the microscopist to identify anopheline species, and the information provided in the dichotomous identification key. As the An. coustani complex contributes to (residual) malaria transmission in sub-Saharan Africa, it may play a role in the observed persistent malaria in southern Mozambique. A better baseline characterizing of the local anophelines species diversity and behaviours will allow us to improve entomological surveillance strategies, better understand the impact of vector control on each local vector species, and identify new approaches to target those vector species.
Assuntos
Anopheles , Malária , Animais , Feminino , Anopheles/genética , Moçambique , Mosquitos Vetores , Malária/epidemiologia , DNA Ribossômico , Complexo IV da Cadeia de Transporte de Elétrons/genéticaRESUMO
BACKGROUND: Insecticide resistance in malaria vectors can be spatially highly heterogeneous, yet population structure analyses frequently find relatively high levels of gene flow among mosquito populations. Few studies have contemporaneously assessed phenotypic, genotypic and population structure analysis on mosquito populations and none at fine geographical scales. In this study, genetic diversity, population structure, and insecticide resistance profiles of Anopheles funestus and Anopheles arabiensis were examined across mosquito populations from and within neighbouring villages. METHODS: Mosquitoes were collected from 11 towns in southern Mozambique, as well as from different neighbourhoods within the town of Palmeira, during the peak malaria transmission season in 2016. CDC bottle bioassay and PCR assays were performed with Anopheles mosquitoes at each site to determine phenotypic and molecular insecticide resistance profiles, respectively. Microsatellite analysis was conducted on a subsample of mosquitoes to estimate genetic diversity and population structure. RESULTS: Phenotypic insecticide resistance to deltamethrin was observed in An. funestus sensu stricto (s.s.) throughout the area, though a high level of mortality variation was seen. However, 98% of An. funestus s.s. were CYP6P9a homozygous resistant. An. arabiensis was phenotypically susceptible to deltamethrin and 99% were kdr homozygous susceptible. Both Anopheles species exhibited high allelic richness and heterozygosity. Significant deviations from Hardy-Weinberg equilibrium were observed, and high linkage disequilibrium was seen for An. funestus s.s., supporting population subdivision. However, the FST values were low for both anophelines (- 0.00457 to 0.04213), Nm values were high (9.4-71.8 migrants per generation), AMOVA results showed almost 100% genetic variation among and within individuals, and Structure analysis showed no clustering of An. funestus s.s. and An. arabiensis populations. These results suggest high gene flow among mosquito populations. CONCLUSION: Despite a relatively high level of phenotypic variation in the An. funestus population, molecular analysis shows the population is admixed. These data indicate that CYP6P9a resistance markers do not capture all phenotypic variation in the area, but also that resistance genes of high impact are likely to easily spread in the area. Conversely, other strategies, such as transgenic mosquito release programmes will likely not face challenges in this locality.
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Anopheles , Inseticidas , Malária , Piretrinas , Humanos , Animais , Inseticidas/farmacologia , Anopheles/genética , Moçambique , Mosquitos Vetores/genética , Piretrinas/farmacologia , Resistência a Inseticidas/genética , Malária/epidemiologiaRESUMO
BACKGROUND: To eliminate malaria in southern Mozambique, the National Malaria Control Programme and its partners are scaling up indoor residual spraying (IRS) activities in two provinces, Gaza and Inhambane. An entomological surveillance planning tool (ESPT) was used to answer the programmatic question of whether IRS would be effective in target geographies, given limited information on local vector bionomics. METHODS: Entomological intelligence was collected in six sentinel sites at the end of the rainy season (April-May 2018) and the beginning of the dry season (June-July 2018). The primary objective was to provide an 'entomological snapshot' by collecting question-based, timely and high-quality data within one single week in each location. Host-seeking behaviour (both indoors and outdoors) was monitored by human-baited tent traps. Indoor resting behaviour was quantified by pyrethrum spray catches and window exit traps. RESULTS: Five different species or species groups were identified: Anopheles funestus sensu lato (s.l.) (66.0%), Anopheles gambiae s.l. (14.0%), Anopheles pharoensis (1.4%), Anopheles tenebrosus (14.1%) and Anopheles ziemanni (4.5%). Anopheles funestus sensu stricto (s.s.) was the major vector among its sibling species, and 1.9% were positive for Plasmodium falciparum infections. Anopheles arabiensis was the most abundant vector species within the An. gambiae complex, but none tested positive for P. falciparum infections. Some An. tenebrosus were positive for P. falciparum (1.3%). When evaluating behaviours that impact IRS efficacy, i.e. endophily, the known primary vector An. funestus s.s., was found to rest indoors-demonstrating at least part of its population will be impacted by the intervention if insecticides are selected to which this vector is susceptible. However, other vector species, including An. gambiae s.l., An. tenebrosus, An. pharoensis and An. ziemanni, showed exophilic and exophagic behaviours in several of the districts surveilled. CONCLUSION: The targeted approach to entomological surveillance was successful in collecting question-based entomological intelligence to inform decision-making about the use of IRS in specific districts. Endophilic An. funestus s.s. was documented as being the most prevalent and primary malaria vector suggesting that IRS can reduce malaria transmission, but the presence of other vector species both indoors and outdoors suggests that alternative vector control interventions that target these gaps in protection may increase the impact of vector control in southern Mozambique.
Assuntos
Anopheles , Malária Falciparum , Malária , Animais , Humanos , Inteligência , Malária Falciparum/epidemiologia , Mosquitos Vetores , MoçambiqueRESUMO
BACKGROUND: Long-lasting insecticidal nets (LLINs) are the primary malaria prevention and control intervention in many parts of sub-Saharan Africa. While LLINs are expected to last at least 3 years under normal use conditions, they can lose effectiveness because they fall out of use, are discarded, repurposed, physically damaged, or lose insecticidal activity. The contributions of these different interrelated factors to durability of nets and their protection against malaria have been unclear. METHODS: Starting in 2009, LLIN durability studies were conducted in seven countries in Africa over 5 years. WHO-recommended measures of attrition, LLIN use, insecticidal activity, and physical integrity were recorded for eight different net brands. These data were combined with analyses of experimental hut data on feeding inhibition and killing effects of LLINs on both susceptible and pyrethroid resistant malaria vectors to estimate the protection against malaria transmission-in terms of vectorial capacity (VC)-provided by each net cohort over time. Impact on VC was then compared in hypothetical scenarios where one durability outcome measure was set at the best possible level while keeping the others at the observed levels. RESULTS: There was more variability in decay of protection over time by country than by net brand for three measures of durability (ratios of variance components 4.6, 4.4, and 1.8 times for LLIN survival, use, and integrity, respectively). In some countries, LLIN attrition was slow, but use declined rapidly. Non-use of LLINs generally had more effect on LLIN impact on VC than did attrition, hole formation, or insecticide loss. CONCLUSIONS: There is much more variation in LLIN durability among countries than among net brands. Low levels of use may have a larger impact on effectiveness than does variation in attrition or LLIN degradation. The estimated entomological effects of chemical decay are relatively small, with physical decay probably more important as a driver of attrition and non-use than as a direct cause of loss of effect. Efforts to maximize LLIN impact in operational settings should focus on increasing LLIN usage, including through improvements in LLIN physical integrity. Further research is needed to understand household decisions related to LLIN use, including the influence of net durability and the presence of other nets in the household.
Assuntos
Mosquiteiros Tratados com Inseticida/estatística & dados numéricos , Inseticidas , Malária/prevenção & controle , Controle de Mosquitos/estatística & dados numéricos , Mosquitos Vetores , Angola , Benin , Gâmbia , Quênia , Malária/transmissão , Malaui , Modelos Teóricos , Moçambique , SenegalRESUMO
BACKGROUND: Insecticide resistance poses a serious threat to insecticide-based interventions in Africa. There is a fear that resistance escalation could jeopardize malaria control efforts. Monitoring of cases of aggravation of resistance intensity and its impact on the efficacy of control tools is crucial to predict consequences of resistance. METHODS: The resistance levels of an Anopheles funestus population from Palmeira, southern Mozambique, were characterized and their impact on the efficacy of various insecticide-treated nets established. RESULTS: A dramatic loss of efficacy of all long-lasting insecticidal nets (LLINs), including piperonyl butoxide (PBO)-based nets (Olyset Plus), was observed. This An. funestus population consistently (2016, 2017, and 2018) exhibited a high degree of pyrethroid resistance. Molecular analyses revealed that this resistance escalation was associated with a massive overexpression of the duplicated cytochrome P450 genes CYP6P9a and CYP6P9b, and also the fixation of the resistance CYP6P9a_R allele in this population in 2016 (100%) in contrast to 2002 (5%). However, the low recovery of susceptibility after PBO synergist assay suggests that other resistance mechanisms could be involved. CONCLUSIONS: The loss of efficacy of pyrethroid-based LLINs with and without PBO is a concern for the effectiveness of insecticide-based interventions, and action should be taken to prevent the spread of such super-resistance.
Assuntos
Anopheles/efeitos dos fármacos , Resistência a Inseticidas/efeitos dos fármacos , Inseticidas/farmacologia , Malária/tratamento farmacológico , Mosquitos Vetores/efeitos dos fármacos , Butóxido de Piperonila/farmacologia , Piretrinas/farmacologia , África , Alelos , Animais , Sistema Enzimático do Citocromo P-450/metabolismo , Feminino , Humanos , Mosquiteiros Tratados com Inseticida/parasitologia , Malária/parasitologia , Controle de Mosquitos/métodos , MoçambiqueRESUMO
BACKGROUND: Pyrethroid resistance in the major malaria vector Anopheles funestus is rapidly expanding across Southern Africa. It remains unknown whether this resistance has a unique origin with the same molecular basis or is multifactorial. Knowledge of the origin, mechanisms and evolution of resistance are crucial to designing successful resistance management strategies. RESULTS: Here, we established the resistance profile of a Zambian An. funestus population at the northern range of the resistance front. Similar to other Southern African populations, Zambian An. funestus mosquitoes are resistant to pyrethroids and carbamate, but in contrast to populations in Mozambique and Malawi, these insects are also DDT resistant. Genome-wide microarray-based transcriptional profiling and qRT-PCR revealed that the cytochrome P450 gene CYP6M7 is responsible for extending pyrethroid resistance northwards. Indeed, CYP6M7 is more over-expressed in Zambia [fold-change (FC) 37.7; 13.2 for qRT-PCR] than CYP6P9a (FC15.6; 8.9 for qRT-PCR) and CYP6P9b (FC11.9; 6.5 for qRT-PCR), whereas CYP6P9a and CYP6P9b are more highly over-expressed in Malawi and Mozambique. Transgenic expression of CYP6M7 in Drosophila melanogaster coupled with in vitro assays using recombinant enzymes and assessments of kinetic properties demonstrated that CYP6M7 is as efficient as CYP6P9a and CYP6P9b in conferring pyrethroid resistance. Polymorphism patterns demonstrate that these genes are under contrasting selection forces: the exceptionally diverse CYP6M7 likely evolves neutrally, whereas CYP6P9a and CYP6P9b are directionally selected. The higher variability of CYP6P9a and CYP6P9b observed in Zambia supports their lesser role in resistance in this country. CONCLUSION: Pyrethroid resistance in Southern Africa probably has multiple origins under different evolutionary forces, which may necessitate the design of different resistance management strategies.
Assuntos
Anopheles/genética , Sistema Enzimático do Citocromo P-450/genética , Malária/parasitologia , Polimorfismo Genético , África , Animais , Animais Geneticamente Modificados/genética , Animais Geneticamente Modificados/metabolismo , Anopheles/efeitos dos fármacos , Anopheles/metabolismo , Sistema Enzimático do Citocromo P-450/química , Sistema Enzimático do Citocromo P-450/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Resistência a Medicamentos/efeitos dos fármacos , Resistência a Medicamentos/genética , Feminino , Perfilação da Expressão Gênica , Variação Genética , Genoma , Haplótipos , Inseticidas/toxicidade , Cinética , Piretrinas/toxicidade , Reação em Cadeia da Polimerase em Tempo Real , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genéticaRESUMO
BACKGROUND: The Aedes albopictus mosquito is of medical concern due to its ability to transmit viral diseases, such as dengue and chikungunya. Aedes albopictus originated in Asia and is now present on all continents, with the exception of Antarctica. In Mozambique, Ae. albopictus was first reported in 2015 within the capital city of Maputo, and by 2019, it had become established in the surrounding area. It was suspected that the mosquito population originated in Madagascar or islands of the Western Indian Ocean (IWIO). The aim of this study was to determine its origin. Given the risk of spreading insecticide resistance, we also examined relevant mutations in the voltage-sensitive sodium channel (VSSC). METHODS: Eggs of Ae. albopictus were collected in Matola-Rio, a municipality adjacent to Maputo, and reared to adults in the laboratory. Cytochrome c oxidase subunit I (COI) sequences and microsatellite loci were analyzed to estimate origins. The presence of knockdown resistance (kdr) mutations within domain II and III of the VSSC were examined using Sanger sequencing. RESULTS: The COI network analysis denied the hypothesis that the Ae. albopictus population originated in Madagascar or IWIO; rather both the COI network and microsatellites analyses showed that the population was genetically similar to those in continental Southeast Asia and Hangzhou, China. Sanger sequencing determined the presence of the F1534C knockdown mutation, which is widely distributed among Asian populations, with a high allele frequency (46%). CONCLUSIONS: These results do not support the hypothesis that the Mozambique Ae. albopictus population originated in Madagascar or IWIO. Instead, they suggest that the origin is continental Southeast Asia or a coastal town in China.
Assuntos
Aedes , Resistência a Inseticidas , Mosquitos Vetores , Animais , Moçambique , Resistência a Inseticidas/genética , Aedes/genética , Aedes/efeitos dos fármacos , Mosquitos Vetores/genética , Mosquitos Vetores/efeitos dos fármacos , Mutação , Complexo IV da Cadeia de Transporte de Elétrons/genética , Inseticidas/farmacologia , Madagáscar , Repetições de Microssatélites/genética , Feminino , Canais de Sódio Disparados por Voltagem/genéticaRESUMO
BACKGROUND: Understanding the survival strategies of malaria vectors at the edges of their distribution, where they are under stress from environmental conditions, may lead to the development of novel control techniques and may help predict the effects of climate change on these mosquitoes. METHODS: The population dynamics of an isolated population of Anopheles funestus from the peninsula of Linga Linga in southern Mozambique was studied over a period of 104 weeks from March 2009 to May 2011 by 917 light-trap and 390 exit collections, mostly in an area close to a seasonal pond. RESULTS: Over the sampling period, 3,684 An. funestus females were caught. Densities decreased with increasing distance from the pond. In 2009 and 2010, a single annual peak in An. funestus density coincident with the single annual peak in rainfall was observed, but a clear population peak was absent during the first 21 weeks of 2011. In between population peaks, An. funestus remained present at low densities. In light trap collections, the proportion of gravid mosquitoes was significantly higher during the 'low season' (the period between peaks) than during the peak season (RR = 4.3, p<0.001). In contrast, in exit collections, the proportion of gravid mosquitoes was significantly lower during low season than during the peak season (RR = 0.64, p<0.01). Also, in light traps, the proportion of part-fed females was higher during the low season than during the peak season (RR = 4.5, p<0.001), whereas this was inversed for engorged females (RR = 0.46, p<0.05).Thirteen out of 289 (4.5%) An. funestus tested positive in the sporozoite ELISA. The proportion of sporozoite positive females was higher during the low season (6.25%, six out of 96) than during the peaks (3.63%, seven out of 193), but this difference was not significant. CONCLUSIONS: It is suggested that a proportion of the mosquito population may become gonotrophically discordant during the long dry season resulting in enhanced mosquito survival and sustained malaria transmission.
Assuntos
Anopheles/fisiologia , Vetores de Doenças , Animais , Anopheles/crescimento & desenvolvimento , Anopheles/parasitologia , Antígenos de Protozoários/análise , Clima , Ensaio de Imunoadsorção Enzimática , Feminino , Estudos Longitudinais , Moçambique , Dinâmica Populacional , Reprodução , Estações do AnoRESUMO
The Magude Project assessed the feasibly of eliminating malaria in a low transmission setting in southern Mozambique using a package of interventions. This study measured the ownership, access and use of long-lasting insecticide treated nets (LLINs) and inequalities in these indicators across household wealth, size and population subgroups, to understand the protection that LLINs provided during the project. Data were obtained from various household surveys. At least 31% of the nets distributed during the 2014 and 2017 campaigns were lost during the first year post-distribution. Most nets (77.1%) present in the district were Olyset Nets. LLIN access never exceeded 76.3% and use varied seasonally between 40% and 76.4%. LLIN access limited LLIN use during the project, especially during the high transmission season. LLIN ownership, access and use were lower in harder-to-reach localities, in poorer and larger households. Children and women below 30 had poorer access to LLINs than the overall population. Net use was lowest among school-aged children and young adults, especially among young males, and highest in children under 5, pregnant women, in older adults and in households that received indoor residual spraying (IRS). This study revealed that LLIN mass-distribution campaigns alone are not sufficient to achieve the high level of net protection needed during elimination programs and that reviewing the LLIN allocation scheme, top-up distributions and/or community engagement campaigns is needed, also to reduce inequalities in populations' access to LLINs.
Assuntos
Mosquiteiros Tratados com Inseticida , Propriedade , Criança , Masculino , Adulto Jovem , Humanos , Feminino , Gravidez , Idoso , Moçambique , Controle de Mosquitos , Estudos Transversais , Receptores Proteína Tirosina QuinasesRESUMO
Indoor residual spraying of insecticides (IRS) is a key malaria vector control strategy. Whilst human attitude towards IRS is monitored before or shortly after implementation, human activities leading to the modification of insecticide-treated walls post-IRS are not. This could inadvertently reduce the protective effects of IRS. We monitored the extent of modifications to the sprayed indoor wall surfaces by household owners for six months post-IRS campaigns in two districts targeted for malaria elimination in southern Mozambique. In parallel, we assessed building of any additional rooms onto compounds, and mosquito net use. We quantified the contribution of wall modifications, added rooms, prolonged spray campaigns, and product residual efficacies on actual IRS coverage and relative mosquito bite reduction, using a mechanistic approach. Household owners continually modified insecticide-treated walls and added rooms onto compounds. Household surveys in southern Mozambique showed frequent modification of indoor walls (0-17.2% of households modified rooms monthly) and/or added rooms (0-16.2% of households added rooms monthly). Actual IRS coverage reduced from an assumed 97% to just 39% in Matutuine, but only from 96% to 91% in Boane, translating to 43% and 5.8% estimated increases in relative daily mosquito bites per person. Integrating post-IRS knowledge, attitude, and practice (KAP) surveys into programmatic evaluations to capture these modification and construction trends can help improve IRS program efficiency and product assessment.
RESUMO
The "Magude project" aimed but failed to interrupt local malaria transmission in Magude district, southern Mozambique, by using a comprehensive package of interventions, including indoor residual spraying (IRS), pyrethroid-only long-lasting insecticide treated nets (LLINs) and mass-drug administration (MDA). Here we present detailed information on the vector species that sustained malaria transmission, their association with malaria incidence and behaviors, and their amenability to the implemented control interventions. Mosquitoes were collected monthly between May 2015 and October 2017 in six sentinel sites in Magude district, using CDC light traps both indoors and outdoors. Anopheles arabiensis was the main vector during the project, while An. funestus s.s., An. merus, An. parensis and An. squamosus likely played a secondary role. The latter two species have never previously been found positive for Plasmodium falciparum in southern Mozambique. The intervention package successfully reduced vector sporozoite rates in all species throughout the project. IRS was effective in controlling An. funestus s.s. and An. parensis, which virtually disappeared after its first implementation, but less effective at controlling An. arabiensis. Despite suboptimal use, LLINs likely provided significant protection against An. arabiensis and An. merus that sought their host largely indoors when people where in bed. Adding IRS on top of LLINs and MDA likely added value to the control of malaria vectors during the Magude project. Future malaria elimination attempts in the area could benefit from i) increasing the use of LLINs, ii) using longer-lasting IRS products to counteract the increase in vector densities observed towards the end of the high transmission season, and iii) a higher coverage with MDA to reduce the likelihood of human infection. However, additional interventions targeting vectors that survive IRS and LLINs by biting outdoors or indoors before people go to bed, will be likely needed to achieve local malaria elimination.
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Anopheles , Mosquiteiros Tratados com Inseticida , Inseticidas , Malária , Piretrinas , Animais , Humanos , Inseticidas/farmacologia , Malária/epidemiologia , Malária/prevenção & controle , Controle de Mosquitos , Mosquitos VetoresRESUMO
Characterizing persistent malaria transmission that occurs after the combined deployment of indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) is critical to guide malaria control and elimination efforts. This requires a detailed understanding of both human and vector behaviors at the same temporal and spatial scale. Cross-sectional human behavior evaluations and mosquito collections were performed in parallel in Magude district, Mozambique. Net use and the exact time when participant moved into each of five environments (outdoor, indoor before bed, indoor in bed, indoor after getting up, and outdoor after getting up) were recorded for individuals from three different age groups and both sexes during a dry and a rainy season. Malaria mosquitoes were collected with CDC light traps in combination with collection bottle rotators. The percentage of residual exposure to host-seeking vectors that occurred in each environment was calculated for five local malaria vectors with different biting behaviors, and the actual (at observed levels of LLIN use) and potential (i.e. if all residents had used an LLIN) personal protection conferred by LLINs was estimated. Anopheles arabiensis was responsible for more than 74% of residents' residual exposure to host-seeking vectors during the Magude project. The other four vector species (An. funestus s.s., An. parensis, An. squamosus and An. merus) were responsible for less than 10% each. The personal protection conferred by LLINs prevented only 39.2% of the exposure to host-seeking vectors that survived the implementation of both IRS and LLINs, and it differed significantly across seasons, vector species and age groups. At the observed levels of bednet use, 12.5% of all residual exposure to host-seeking vectors occurred outdoor during the evening, 21.9% indoor before going to bed, almost two thirds (64%) while people were in bed, 1.4% indoors after getting up and 0.2% outdoor after leaving the house. Almost a third of the residual exposure to host-seeking vectors (32.4%) occurred during the low transmission season. The residual bites of An. funestus s.s. and An. parensis outdoors and indoor before bedtime, of An. arabiensis indoors when people are in bed, and of An. squamosus both indoors and outdoors, are likely to have sustained malaria transmission throughout the Magude project. By increasing LLIN use, an additional 24.1% of exposure to the remaining hosts-seeking vectors could have been prevented. Since An. arabiensis, the most abundant vector, feeds primarily while people are in bed, increasing net use and net feeding inhibition (through e.g. community awareness activities and the selection of more effective LLINs) could significantly reduce the exposure to remaining host-seeking mosquitoes. Nonetheless, supplementary interventions aiming to reduce human-vector contact outdoors and/or indoors before people go to bed (e.g. through larval source management, window and eave screening, eave tubes, and spatial repellents) will be needed to reduce residual exposure to the outdoor and early biting An. funestus s.s. and An. parensis.
Assuntos
Anopheles , Inseticidas , Malária , Animais , Anopheles/fisiologia , Estudos Transversais , Progressão da Doença , Feminino , Humanos , Malária/prevenção & controle , Masculino , Mosquitos Vetores , Receptores Proteína Tirosina QuinasesRESUMO
Indoor residual spraying (IRS) has been and remains an important malaria control intervention in southern Mozambique, South Africa and Eswatini. A better understanding of the effectiveness of IRS campaigns is critical to guide future elimination efforts. We analyze the three IRS campaigns conducted during a malaria elimination demonstration project in southern Mozambique, the "Magude project", and propose a new method to calculate the efficacy of IRS campaigns adjusting for IRS coverage, pace of house spraying and IRS residual efficacy on different wall types. Anopheles funestus sensu lato (s.l.) and An. gambiae s.l. were susceptible to pirimiphos-methyl and DDT. Anopheles funestus s.l. was resistant to pyrethroids, with 24h post-exposure mortality being lower for An. funestus sensu stricto (s.s.) than for An. parensis (collected indoors). The percentage of structures sprayed was above 90% and percentage of people covered above 86% in all three IRS campaigns. The percentage of households sprayed was above 83% in 2015 and 2016, but not assessed in 2017. Mosquito mortality 24h post-exposure stayed above 80% for 196 days after the 2016 IRS campaign and 222 days after the 2017 campaign and was 1.5 months longer on mud walls than on cement walls. This was extended by up to two months when 120h post-exposure mortality was considered. The district-level realized IRS efficacy was 113 days after the 2016 campaign. While the coverage of IRS campaigns in Magude were high, IRS protection did not remain optimal for the entire high malaria transmissions season. The use of a longer-lasting IRS product could have further supported the interruption of malaria transmission in the district. To better estimate the protection afforded by IRS campaigns, National Malaria Control Programs and partners are encouraged to adjust the calculation of IRS efficacy for IRS coverage, pace of house spraying during the campaign and IRS efficacy on different wall types combined with wall type distribution in the sprayed area.
Assuntos
Anopheles , Inseticidas , Malária , Piretrinas , Animais , DDT , Humanos , Malária/prevenção & controle , Controle de Mosquitos/métodos , Mosquitos Vetores , Organização Mundial da SaúdeRESUMO
BACKGROUND: Malaria vector control by indoor residual spraying was reinitiated in 2006 with DDT in Zambézia province, Mozambique. In 2007, these efforts were strengthened by the President's Malaria Initiative. This manuscript reports on the monitoring and evaluation of this programme as carried out by the Malaria Decision Support Project. METHODS: Mosquitoes were captured daily through a series of 114 window exit traps located at 19 sentinel sites, identified to species and analysed for sporozoites. Anopheles mosquitoes were collected resting indoors and tested for insecticide resistance following the standard WHO protocol. Annual cross sectional household parasite surveys were carried out to monitor the impact of the control programme on prevalence of Plasmodium falciparum in children aged 1 to 15 years. RESULTS: A total of 3,769 and 2,853 Anopheles gambiae s.l. and Anopheles funestus, respectively, were captured from window exit traps throughout the period. In 2010 resistance to the pyrethroids lambda-cyhalothrin and permethrin and the carbamate, bendiocarb was detected in An. funestus. In 2006, the sporozoite rate in An. gambiae s.s. was 4% and this reduced to 1% over 4 rounds of spraying. The sporozoite rate for An. funestus was also reduced from 2% to 0 by 2008. Of the 437 Anopheles arabiensis identified, none were infectious. Overall prevalence of P. falciparum in the sentinel sites fell from 60% to 32% between October 2006 and October 2008. CONCLUSION: Both An. gambiae s.s. and An. funestus were controlled effectively with the DDT-based IRS programme in Zambézia, reducing disease transmission and burden. However, the discovery of pyrethroid resistance in the province and Mozambique's policy change away from DDT to pyrethroids for IRS threatens the gains made here.
Assuntos
Anopheles/efeitos dos fármacos , Resistência a Inseticidas , Inseticidas/farmacologia , Malária Falciparum/epidemiologia , Malária Falciparum/prevenção & controle , Controle de Mosquitos/métodos , Piretrinas/farmacologia , Adolescente , Animais , Criança , Pré-Escolar , Estudos Transversais , DDT/farmacologia , Feminino , Humanos , Lactente , Malária Falciparum/diagnóstico , Masculino , Moçambique , Plasmodium falciparum/isolamento & purificação , PrevalênciaRESUMO
Indoor residual spraying (IRS) is one of the main malaria vector control strategies in Mozambique alongside the distribution of insecticide treated nets. As part of the national insecticide resistance management strategy, Mozambique introduced SumiShield™ 50WG, a third generation IRS product, in 2018. Its residual efficacy was assessed in southern Mozambique during the 2018-2019 malaria season. Using a susceptible Anopheles arabiensis strain, residual efficacy was assessed on two different wall surfaces, cement and mud-plastered walls, using standard WHO (World Health Organization) cone bioassay tests at three different heights. Female mosquitoes of two age groups (2-5 and 13-26 day old) were exposed for 30 minutes, after which mortality was observed 24h, 48h, 72h, and 96h and 120h post-exposure to assess (delayed) mortality. Lethal times (LT) 90, LT50 and LT10 were estimated using Bayesian models. Mortality 24h post exposure was consistently below 80%, the current WHO threshold value for effective IRS, in both young and old mosquitoes, regardless of wall surface type. Considering delayed mortality, residual efficacies (mosquito mortality equal or greater than 80%) ranged from 1.5 to ≥12.5 months, with the duration depending on mortality time post exposure, wall type and mosquito age. Looking at mortality 72h after exposure, residual efficacy was between 6.5 and 9.5 months, depending on wall type and mosquito age. The LT50 and LT10 (i.e. 90% of the mosquitoes survive exposure to the insecticides) values were consistently higher for older mosquitoes (except for LT10 values for 48h and 72h post-exposure mortality) and ranged from 0.9 to 5.8 months and 0.2 to 7.8 months for LT50 and LT10, respectively. The present study highlights the need for assessing mosquito mortality beyond the currently recommended 24h post exposure. Failure to do so may lead to underestimation of the residual efficacy of IRS products, as delayed mortality will lead to a further reduction in mosquito vector populations and potentially negatively impact disease transmission. Monitoring residual efficacy on relevant wall surfaces, including old mosquitoes that are ultimately responsible for malaria transmission, and assessing delayed mortalities are critical to provide accurate and actionable data to guide vector control programmes.
Assuntos
Anopheles , Guanidinas/administração & dosagem , Inseticidas/administração & dosagem , Controle de Mosquitos/métodos , Neonicotinoides/administração & dosagem , Tiazóis/administração & dosagem , Aerossóis , Fatores Etários , Animais , Feminino , Habitação , MoçambiqueRESUMO
BACKGROUND: Malaria is by far the greatest cause of morbidity and mortality in Angola, being responsible for 50% of all outpatient attendance and around 22% of all hospital deaths, yet by 2003 only 2% of under-5s used insecticide-treated nets. Entomological studies are an essential foundation for rational malaria control using insecticide-treated nets and indoor residual spraying, but there have been no published studies of malaria vectors in Angola over the 27 years of the civil war, to its end in 2002. This paper describes studies arising from a WHO-sponsored visit in support of the National Malaria Control Programme. METHODS: During April 2001, mosquitoes were sampled by indoor pyrethrum spray collection from four sites in the semi-arid coastal provinces of Luanda and Benguela and two sites in Huambo province, in the humid tropical highlands. Collections took place towards the end of the rainy season and were used to determine the Anopheles species present, their sporozoite rates and the frequency of a kdr allele conferring resistance to pyrethroid insecticides. RESULTS: A PCR test for the Anopheles gambiae complex showed a preponderance of An. gambiae, with indoor resting densities ranging from 0.9 to 23.5 per house. Of 403 An. gambiae identified to molecular form, 93.5% were M-form and 6.5% S-form. M and S were sympatric at 4 sites but no M/S hybrids were detected. The highest proportion of S-form (20%) was in samples from Huambo, in the humid highlands. Anopheles funestus was found at one site near Luanda. The sporozoite rate of mosquitoes, determined by an ELISA test, was 1.9% for An. gambiae (n = 580) and 0.7% for An. funestus (n = 140). Of 218 An. gambiae (195 M-form and 23 S-form) genotyped for the West African kdr-resistance allele, all were homozygous susceptible. CONCLUSION: An. gambiae M-form is the most important and widespread malaria vector in the areas studied but more extensive studies of malaria vectors are required to support the malaria control programme in Angola. These should include standard insecticide resistance biossays and molecular assays that can detect both metabolic resistance and target site insensitivity.
Assuntos
Anopheles/parasitologia , Insetos Vetores/parasitologia , Resistência a Inseticidas/genética , Plasmodium falciparum/isolamento & purificação , Angola , Animais , Anopheles/classificação , Anopheles/efeitos dos fármacos , Anopheles/genética , Demografia , Ensaio de Imunoadsorção Enzimática/métodos , Ensaio de Imunoadsorção Enzimática/veterinária , Genótipo , Homozigoto , Insetos Vetores/classificação , Insetos Vetores/efeitos dos fármacos , Insetos Vetores/genética , Malária/transmissão , Plasmodium falciparum/crescimento & desenvolvimento , Esporozoítos/crescimento & desenvolvimentoRESUMO
Isolated areas, such as the 2 × 7 km peninsula of Linga Linga in Mozambique, are the places where malaria might be most easily eliminated. Currently available control strategies include long-lasting insecticidal bednets impregnated with pyrethroid insecticides (LLINs), rapid diagnostic tests (RDTs) for diagnosis and artemisinin based combination therapy (ACT) for treatment and these were applied on the peninsula. In 2007, following a census of the population and mapping of 500 households, five annual all-age prevalence surveys were conducted. Information on LLIN use, house construction, and animal ownership was obtained. A spatially structured generalized additive model indicated that malaria risk was greatest towards the northern end of the peninsula and that people living in houses with grass or thatch roofs had a greater risk of malaria than those living in houses with corrugated iron roofs. Incidence peaked nine weeks after rainfall (r (2) = 0.34, p = 0.0002). From 2009 incidence was measured at a centrally based project clinic. The proportion of under nine-year-old resident attendees diagnosed with malaria decreased significantly from 48% in 2009, to 35% in 2010 and 25% in 2011. At the same time, there was a shift in the peak age of cases from 1-4 year olds to 5-9 year olds. Nevertheless, in order to further reduce malaria transmission in an area such as Linga Linga, additional vector control measures need to be considered.
Assuntos
Anopheles , Insetos Vetores , Malária/transmissão , Animais , Anopheles/classificação , Anopheles/parasitologia , Anopheles/fisiologia , Feminino , Insetos Vetores/classificação , Insetos Vetores/parasitologia , Insetos Vetores/fisiologia , Malária/parasitologia , Moçambique , Oocistos/fisiologia , Especificidade da Espécie , Esporozoítos/fisiologiaRESUMO
Focal control of malaria vectors, a potentially cost-effective alternative to conventional control, requires a spatio-temporal understanding of the mosquitoes. Trapping of African malaria vectors has generally been limited to inside houses making distribution estimates dependent on the location of dwellings. The development of tent-traps to sample outdoor biting mosquitoes has enabled more independent estimates. Here we describe both temporal and spatial variation in mosquito movements in an irrigation project village in southern Mozambique. Six hundred and ninety-three tent-trap collections (525 of which were paired with light-trap collections), 552 exit collections and 391 collections of mosquitoes resting inside houses were undertaken from March 2005 to April 2006. Fifteen species of mosquito were collected (five exclusively as larvae). Mansonia africana was the most common finding, numbers being greatest away from the village. Only Anopheles funestus, An. tenebrosus and Culex quinquefasciatus were collected in greater numbers in light-traps compared to tent-traps. Among the common mosquitoes, correlations in numbers of mosquito collected in paired tent and in light-traps were significant for all but An. tenebrosus. Inverse distance weighting was used to produce raster density maps of the most common mosquitoes. All species, with minor variations, in both hot and cool seasons, were collected in greatest numbers close to the edges of the village where water suitable for larval development was available. All exophilic anophelines species tested negative for sporozoites. It is suggested that focal control of larvae, applied by the villagers themselves, could be a suitable alternative to conventional control in this and similar villages.