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1.
Sci Adv ; 6(20): eaay5487, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32426490

RESUMO

Yearly, a quarter billion people are infected and a half a million killed by the mosquito-borne disease malaria. Lack of real-time observational tools for continuously assessing the unperturbed mosquito flight activity in situ limits progress toward improved vector control. We deployed a high-resolution entomological lidar to monitor a half-kilometer static transect adjacent to a Tanzanian village. We evaluated one-third million insect observations during five nights, four days, and one annular solar eclipse. We demonstrate in situ lidar classification of several insect families and their sexes based on their modulation signatures. We were able to compare the fine-scale spatiotemporal activity patterns of malaria vectors during ordinary days and an eclipse to disentangle phototactic activity patterns from the circadian mechanism. We observed an increased insect activity during the eclipse attributable to mosquitoes. These unprecedented findings demonstrate how lidar-based monitoring of distinct mosquito activities could advance our understanding of vector ecology.

3.
Malar J ; 19(1): 109, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-32156280

RESUMO

BACKGROUND: Residents of malaria-endemic communities spend several hours outdoors performing different activities, e.g. cooking, story-telling or eating, thereby exposing themselves to potentially-infectious mosquitoes. This compromises effectiveness of indoor interventions, notably long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacy against mosquitoes of hessian fabric mats and ribbons treated with the spatial repellent, transfluthrin, and fitted to chairs and outdoor kitchens, respectively. METHODS: Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of locally-made transfluthrin-emanating chairs and hessian ribbons were tested in outdoor environments of 28 households in dry and wet seasons, using volunteer-occupied exposure-free double net traps. CDC light traps were used to estimate host-seeking mosquito densities within open-structure outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24 h-mortality. Finally, The World Health Organization insecticide susceptibility tests were conducted on wild-caught Anopheles from the villages. RESULTS: Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Two-thirds of these spaces were sited under trees, and only one third (34.4%) were built-up. The outdoor structures were usually makeshift kitchens having roofs and partial walls. Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70-85%, while transfluthrin-treated hessian ribbons fitted to the outdoor kitchens caused 77-81% reduction in the general peri-domestic area. Almost all the field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. The An. arabiensis were susceptible to non-pyrethroids (pirimiphos methyl and bendiocarb), but resistant to pyrethroids commonly used on LLINs (deltamethrin and permethrin). CONCLUSION: Most houses had actively-used peri-domestic outdoor spaces where exposure to mosquitoes occurred. The transfluthrin-treated chairs and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant field-caught malaria vectors. These two new prototype formats for transfluthrin emanators, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.

5.
Malar J ; 18(1): 83, 2019 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-30885205

RESUMO

BACKGROUND: Mosquito biting rates and host preferences are crucial determinants of human exposure to vector-borne diseases and the impact of vector control measures. The human landing catch (HLC) is a gold standard method for measuring human exposure to bites, but presents risks to participants by requiring some exposure to mosquito vectors. Mosquito electrocuting traps (METs) represent an exposure-free alternative to HLCs for measuring human exposure to malaria vectors. However, original MET prototypes were too small for measuring whole-body biting rates on humans or large animals like cattle. Here a much larger MET capable of encompassing humans or cattle was designed, and its performance was evaluated relative to both the original small MET and HLC and for quantifying malaria vector host preferences. METHODS: Human landing catch, small human-baited METs (MET-SH), and large METs baited with either a human (MET-LH) or calves (MET-LC) were simultaneously used to capture wild malaria vectors outdoors in rural southern Tanzania. The four capture methods were compared in a Latin-square design over 20 nights. Malaria vector host preferences were estimated through comparison of the number of mosquitoes caught by large METs baited with either humans or cattle. RESULTS: The MET-LH caught more than twice as many Anopheles arabiensis than either the MET-SH or HLC. It also caught higher number of Anopheles funestus sensu lato (s.l.) compared to the MET-SH or HLC. Similar numbers of An. funestus sensu stricto (s.s.) were caught in MET-LH and MET-SH collections. Catches of An. arabiensis with human or cattle-baited large METs were similar, indicating no clear preference for either host. In contrast, An. funestus s.s. exhibited a strong, but incomplete preference for humans. CONCLUSIONS: METs are a sensitive, practical tool for assessing mosquito biting rates and host preferences, and represent a safer alternative to the HLC. Additionally these findings suggest the HLC underestimate whole-body human exposure. MET collections indicated the An. funestus s.s. population in this setting had a higher than expected attack rate on cattle, potentially making eliminating of this species more difficult with human-targetted control measures. Supplementary vector control tools targetted at livestock may be required to effectively tackle this species.


Assuntos
Anopheles/fisiologia , Entomologia/métodos , Comportamento Alimentar , Especificidade de Hospedeiro , Adulto , Animais , Bovinos , Entomologia/instrumentação , Feminino , Humanos , Masculino , População Rural , Tanzânia , Adulto Jovem
6.
Lancet Planet Health ; 3(3): e132-e143, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30904112

RESUMO

BACKGROUND: In the city of Dar es Salaam, Tanzania, rapid and spontaneous scale-up of window screening occurred through purely horizontal commercial distribution systems without any public subsidies or promotion. Scale-up of window screening coincided with a planned evaluation of programmatic, vertically managed scale-up of regular larvicide application as an intervention against malaria vectors and transmission. We aimed to establish whether scale-up of window screening was associated with suppression of mosquito populations, especially for malaria vectors that strongly prefer humans as their source of blood. METHODS: This study was a re-analysis of a previous observational series of epidemiological data plus new analyses of previously partly reported complementary entomological data, from Dar es Salaam. Between 2004 and 2008, six rounds of cluster-sampled, rolling, cross-sectional parasitological and questionnaire surveys were done in urban Dar es Salaam to assess the effect of larviciding and other determinants of malaria risk, such as use of bed nets and antimalarial drugs, socioeconomic status, age, sex, travel history, mosquito-proofed housing, and spending time outdoors. The effects of scaled-up larvicide application and window screening were estimated by fitting generalised linear mixed models that allowed for both spatial variation between survey locations and temporal autocorrelation within locations. We also conducted continuous longitudinal entomological surveys of outdoor human biting rates by mosquitoes and experimental measurements of mosquito host preferences. FINDINGS: Best-fit models of Plasmodium falciparum malaria infection prevalence among humans were largely consistent with the results of the previous analyses. Re-analysis of previously reported epidemiological data revealed that most of the empirically fitted downward time trend in P falciparum malaria prevalence over the course of the study (odds ratio [OR] 0·04; 95% CI 0·03-0·06; p<0·0001), which was not previously reported numerically or attributed to any explanatory factor, could be plausibly explained by association with an upward trend in city-wide window screening coverage (OR 0·07; 0·05-0·09; p<0·0001) and progressive rollout of larviciding (OR 0·50; 0·41-0·60; p<0·0001). Increasing coverage of complete window screening was also associated with reduced biting densities of all taxonomic groups of mosquitoes (all p<0·0001), especially the Anopheles gambiae complex (relative rate [RR] 0·23; 95% CI 0·16-0·33) and Anopheles funestus group (RR 0·08; 0·04-0·16), which were confirmed as the most efficient vectors of malaria with strong preferences for humans over cattle. Larviciding was also associated with reduced biting densities of all mosquito taxa (p<0·0001), to an extent that varied consistently with the larvicide targeting scheme and known larval ecology of each taxon. INTERPRETATION: Community-wide mosquito proofing of houses might deliver greater impacts on vector populations and malaria transmission than previously thought. The spontaneous nature of the scale-up observed here is also encouraging with regards to practicality, acceptability, and affordability in low-income settings. FUNDING: United States Agency for International Development, Bill & Melinda Gates Foundation, Wellcome Trust, and Valent BioSciences LLC.

7.
Parasit Vectors ; 11(1): 544, 2018 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-30305147

RESUMO

BACKGROUND: Across most of sub-Saharan Africa, malaria is transmitted by mosquitoes from the Anopheles gambiae complex, comprising seven morphologically indistinguishable but behaviourally-diverse sibling species with ecologically-distinct environmental niches. Anopheles gambiae and An. arabiensis are the mostly widely distributed major malaria vectors within the complex, while An. quadriannulatus is sparsely distributed. METHODS: Indoor residual spraying (IRS) with the organophosphate pirimiphos-methyl (PM) was conducted four times between 2011 and 2017 in the Luangwa Valley, south-east Zambia. Anopheles mosquitoes were repeatedly collected indoors by several experiments with various objectives conducted in this study area from 2010 onwards. Indoor mosquito collection methods included human landing catches, Centres for Disease Control and Prevention miniature light traps and back pack aspirators. Anopheles gambiae complex mosquitoes were morphologically identified to species level using taxonomic keys, and to molecular level by polymerase chain reaction. These multi-study data were collated so that time trends in the species composition of this complex could be assessed. RESULTS: The proportion of indoor An. gambiae complex accounted for by An. quadriannulatus declined from 95.1% to 69.7% following two application PM-IRS rounds with an emulsifiable concentrate formulation from 2011 to 2013, while insecticidal net utilisation remained consistently high throughout that period. This trend continued after two further rounds of PM-IRS with a longer-lasting capsule suspension formulation in 2015 and 2016/2017, following which An. quadriannulatus accounted for only 4.5% of the complex. During the same time interval there was a correspondingly steady rise in the proportional contribution of An. arabiensis to the complex, from 3.9 to 95.1%, while the contribution of nominate An. gambiae remained stable at ≤ 0.9%. CONCLUSION: It seems likely that An. arabiensis is not only more behaviourally resilient against IRS than An. gambiae, but also than An. quadriannulatus populations exhibiting indoor-feeding, human-feeding and nocturnal behaviours that are unusual for this species. Routine, programmatic entomological monitoring of dynamic vector population guilds will be critical to guide effective selection and deployment of vector control interventions, including supplementary measures to tackle persisting vectors of residual malaria transmission like An. arabiensis.


Assuntos
Anopheles/efeitos dos fármacos , Habitação , Inseticidas/farmacologia , Controle de Mosquitos/instrumentação , Mosquitos Vetores/efeitos dos fármacos , Compostos Organotiofosforados/farmacologia , Vento , Animais , Anopheles/classificação , Meio Ambiente , Comportamento Alimentar/efeitos dos fármacos , Humanos , Malária/epidemiologia , Malária/prevenção & controle , Malária/transmissão , Controle de Mosquitos/métodos , Estudos Retrospectivos , Zâmbia/epidemiologia
8.
Malar J ; 17(1): 291, 2018 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-30097031

RESUMO

BACKGROUND: Portfolio effects were first described as a basis for mitigating against financial risk by diversifying investments. Distributing investment across several different assets can stabilize returns and reduce risks by statistical averaging of individual asset dynamics that often correlate weakly or negatively with each other. The same simple probability theory is equally applicable to complex ecosystems, in which biological and environmental diversity stabilizes ecosystems against natural and human-mediated perturbations. Given the fundamental limitations to how well the full complexity of ecosystem dynamics can be understood or anticipated, the portfolio effect concept provides a simple framework for more critical data interpretation and pro-active conservation management. Applied to conservation ecology purposes, the portfolio effect concept informs management strategies emphasizing identification and maintenance of key ecological processes that generate complexity, diversity and resilience against inevitable, often unpredictable perturbations. IMPLICATIONS: Applied to the reciprocal goal of eliminating the least valued elements of global biodiversity, specifically lethal malaria parasites and their vector mosquitoes, simply understanding the portfolio effect concept informs more cautious interpretation of surveillance data and simulation model predictions. Malaria transmission mediated by guilds of multiple vectors in complex landscapes, with highly variable climatic and meteorological conditions, as well as changing patterns of land use and other human behaviours, will systematically tend to be more resilient to attack with vector control than it appears based on even the highest quality surveillance data or predictive models. CONCLUSION: Malaria vector control programmes may need to be more ambitious, interpret their short-to-medium term assessments of intervention impact more cautiously, and manage stakeholder expectations more conservatively than has often been the case thus far.


Assuntos
Anopheles/fisiologia , Malária/prevenção & controle , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , Animais , Anopheles/parasitologia , Malária/psicologia , Mosquitos Vetores/parasitologia
9.
R Soc Open Sci ; 5(5): 161055, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29892341

RESUMO

Geophysical topographic metrics of local water accumulation potential are freely available and have long been known as high-resolution predictors of where aquatic habitats for immature Anopheles mosquitoes are most abundant, resulting in elevated densities of adult malaria vectors and human infection burden. Using existing entomological and epidemiological survey data, here we illustrate how topography can also be used to map out the interfaces between wet, unoccupied valleys and dry, densely populated uplands, where malaria vector densities and infection risk are focally exacerbated. These topographically identifiable geophysical boundaries experience disproportionately high vector densities and malaria transmission risk, because this is where Anopheles mosquitoes first encounter humans when they search for blood after emerging or ovipositing in the valleys. Geophysical topographic indicators accounted for 67% of variance for vector density but for only 43% for infection prevalence, so they could enable very selective targeting of interventions against the former but not the latter (targeting ratios of 5.7 versus 1.5 to 1, respectively). So, in addition to being useful for targeting larval source management to wet valleys, geophysical topographic indicators may also be used to selectively target adult Anopheles mosquitoes with insecticidal residual sprays, fencing, vapour emanators or space sprays to barrier areas along their fringes.

11.
Am J Trop Med Hyg ; 98(5): 1216-1217, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29582735
12.
Adv Parasitol ; 99: 345-379, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29530309

RESUMO

BACKGROUND: Additional vector control tools (VCTs) are needed to supplement insecticide-treated nets (ITNs) and indoor residual spraying (IRS) to achieve malaria elimination in many settings. To identify options for expanding the malaria vector control toolbox, we conducted a systematic review of the availability and quality of the evidence for 21 malaria VCTs, excluding ITNs and IRS. METHODS: Six electronic databases and grey literature sources were searched from January 1, 1980 to September 28, 2015 to identify systematic reviews, Phase I-IV studies, and observational studies that measured the effect of malaria VCTs on epidemiological or entomological outcomes across any age groups in all malaria-endemic settings. Eligible studies were summarized qualitatively, with quality and risk of bias assessments undertaken where possible. Of 17,912 studies screened, 155 were eligible for inclusion and were included in a qualitative synthesis. RESULTS: Across the 21 VCTs, we found considerable heterogeneity in the volume and quality of evidence, with 7 VCTs currently supported by at least one Phase III community-level evaluation measuring parasitologically confirmed malaria incidence or infection prevalence (insecticide-treated clothing and blankets, insecticide-treated hammocks, insecticide-treated livestock, larval source management (LSM), mosquito-proofed housing, spatial repellents, and topical repellents). The remaining VCTs were supported by one or more Phase II (n=13) or Phase I evaluation (n=1). Overall the quality of the evidence base remains greatest for LSM and topical repellents, relative to the other VCTs evaluated, although existing evidence indicates that topical repellents are unlikely to provide effective population-level protection against malaria. CONCLUSIONS: Despite substantial gaps in the supporting evidence, several VCTs may be promising supplements to ITNs and IRS in appropriate settings. Strengthening operational capacity and research to implement underutilized VCTs, such as LSM and mosquito-proofed housing, using an adaptive, learning-by-doing approach, while expanding the evidence base for promising supplementary VCTs that are locally tailored, should be considered central to global malaria elimination efforts.


Assuntos
Erradicação de Doenças/métodos , Erradicação de Doenças/tendências , Malária/prevenção & controle , Controle de Mosquitos/métodos , Controle de Mosquitos/tendências , Animais , Humanos , Malária/transmissão
13.
Math Biosci ; 295: 36-47, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29031707

RESUMO

The efficiency of spatial repellents and long-lasting insecticide-treated nets (LLINs) is a key research topic in malaria control. Insecticidal nets reduce the mosquito-human contact rate and simultaneously decrease mosquito populations. However, LLINs demonstrate dissimilar efficiency against different species of malaria mosquitoes. Various factors have been proposed as an explanation, including differences in insecticide-induced mortality, flight characteristics, or persistence of attack. Here we present a discrete agent-based approach that enables the efficiency of LLINs, baited traps and Insecticide Residual Sprays (IRS) to be examined. The model is calibrated with hut-level experimental data to compare the efficiency of protection against two mosquito species: Anopheles gambiae and Anopheles arabiensis. We show that while such data does not allow an unambiguous identification of the details of how LLINs alter the vector behavior, the model calibrations quantify the overall impact of LLINs for the two different mosquito species. The simulations are generalized to community-scale scenarios that systematically demonstrate the lower efficiency of the LLINs in control of An. arabiensis compared to An. gambiae.


Assuntos
Comportamento de Busca por Hospedeiro/fisiologia , Mosquiteiros Tratados com Inseticida , Modelos Biológicos , Controle de Mosquitos , Mosquitos Vetores/patogenicidade , Animais , Anopheles/parasitologia , Anopheles/patogenicidade , Simulação por Computador , Humanos , Mosquiteiros Tratados com Inseticida/estatística & dados numéricos , Malária/prevenção & controle , Malária/transmissão , Cadeias de Markov , Conceitos Matemáticos , Método de Monte Carlo , Controle de Mosquitos/estatística & dados numéricos , Mosquitos Vetores/parasitologia , Especificidade da Espécie
14.
Malar J ; 16(1): 423, 2017 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-29061127

RESUMO

BACKGROUND: Bed nets reduce malaria-related illness and deaths, by forming a protective barrier around people sleeping under them. When impregnated with long-lasting insecticide formulations they also repel or kill mosquitoes attempting to feed upon sleeping humans, and can even suppress entire populations of malaria vectors that feed predominantly upon humans. Nevertheless, an epidemiological study in 2012 demonstrated higher malaria prevalence among bed net users than non-users in urban Dar es Salaam, Tanzania. METHODS: Focus group discussions were conducted with women from four selected wards of Dar es Salaam city, focusing on four major themes relating to bed net use behaviours: (1) reasons for bed net use, (2) reasons for not using bed nets, (3) stimuli or reminders for people to use a bed net (4) perceived reasons for catching malaria while using a bed net. An analytical method by framework grouping of relevant themes was used address key issues of relevance to the study objectives. Codes were reviewed and grouped into categories and themes. RESULTS: All groups said the main reason for bed net use was protection against malaria. Houses with well-screened windows, with doors that shut properly, and that use insecticidal sprays against mosquitoes, were said not to use bed nets, while frequent attacks from malaria was the main stimulus for people to use bed nets. Various reasons were mentioned as potential reasons that compromise bed net efficacy, the most common of which were: (1) bed net sharing by two or more people, especially if one occupant tends to come to bed late at night, and does not tuck in the net 71%; (2) one person shares the bed but does not use the net, moving it away from the side on which s/he sleeps 68%; (3) ineffective usage habits, called ulalavi, in which a sprawling sleeper either touches the net while sleeping up against it or leaves a limb hanging outside of it 68%. Less common reasons mentioned included: (1) Small bed nets which become un-tucked at night (31%); (2) Bed nets with holes large enough to allow mosquitoes to pass (28%); and (3) Going to bed late after already being bitten outdoors (24%). CONCLUSIONS: Behaviours associated with bed net use like; bed sharing, bed net non compliant-bedfellow, sleeping pattern like ulalavi and some physical bed net attributes compromise its effectiveness and supposedly increase of malaria infection to bed net users. While some well-screened houses looked to instigate low malaria prevalence to non-bed net users.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Mosquiteiros Tratados com Inseticida/estatística & dados numéricos , Malária/epidemiologia , Controle de Mosquitos/métodos , Feminino , Humanos , Prevalência , Tanzânia/epidemiologia
15.
Malar J ; 16(1): 410, 2017 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-29020970

RESUMO

BACKGROUND: The effectiveness of malaria prevention with long-lasting insecticidal nets and indoor residual spraying is limited by emerging insecticide resistance, evasive mosquito behaviours that include outdoor biting, sub-optimal implementation and inappropriate use. New vector control interventions are required and their potential effectiveness will be enhanced if existing household perceptions and practices are integrated into intervention design. METHODS: This qualitative descriptive study used focus groups discussions, in-depth interviews and photovoice methods to explore mosquito control perceptions and practices among residents in four study sites in Dar es Salaam, Tanzania. RESULTS: Mosquitoes were perceived as a growing problem, directly attributed to widespread environmental deterioration and lack of effective mosquito control interventions. Malaria and nuisance biting were perceived as the main problem caused by mosquitoes. Breeding sites were clearly distinguished from resting sites but residents did not differentiate between habitats producing malaria vector mosquitoes and others producing mostly nuisance mosquitoes. The most frequently mentioned protection methods in the wealthiest locations were bed nets, aerosol insecticide sprays, window screens, and fumigation, while bed nets were most frequently mentioned and described as 'part of the culture' in the least wealthy locations. Mosquito-proofed housing was consistently viewed as desirable, but considered unaffordable outside wealthiest locations. Slapping and covering up with clothing were most commonly used to prevent biting outdoors. Despite their utility outdoors, topical repellents applied to the skin were considered expensive, and viewed with suspicion due to perceived side effects. Improving the local environment was the preferred method for preventing outdoor biting. Affordability, effectiveness, availability, practicality, as well as social influences, such as government recommendations, socialization and internalization (familiarization and habit) were described as key factors influencing uptake. CONCLUSIONS: Outdoor transmission is widely accepted as an obstacle to malaria elimination. Larval source management, targeting both malaria vectors and nuisance-biting mosquitoes, is the preferred method for mosquito control among the residents of Dar es Salaam and should be prioritized for development alongside new methods for outdoor personal protection. Even if made available, effective and affordable, these additional interventions may require time and user experience to achieve positive reputations and trustworthiness.


Assuntos
Participação da Comunidade , Conhecimentos, Atitudes e Prática em Saúde , Controle de Mosquitos/estatística & dados numéricos , Percepção , Adulto , Feminino , Humanos , Malária/prevenção & controle , Masculino , Pessoa de Meia-Idade , Controle de Mosquitos/métodos , Mosquitos Vetores , Tanzânia , Adulto Jovem
16.
BMJ Glob Health ; 2(2): e000198, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28589015

RESUMO

Protecting individuals and households against mosquito bites with long-lasting insecticidal nets (LLINs) or indoor residual spraying (IRS) can suppress entire populations of unusually efficient malaria vector species that predominantly feed indoors on humans. Mosquitoes which usually feed on animals are less reliant on human blood, so they are far less vulnerable to population suppression effects of such human-targeted insecticidal measures. Fortunately, the dozens of mosquito species which primarily feed on animals are also relatively inefficient vectors of malaria, so personal protection against mosquito bites may be sufficient to eliminate transmission. However, a handful of mosquito species are particularly problematic vectors of residual malaria transmission, because they feed readily on both humans and animals. These unusual vectors feed often enough on humans to be potent malaria vectors, but also often enough on animals to evade population control with LLINs, IRS or any other insecticidal personal protection measure targeted only to humans. Anopheles arabiensis and A. coluzzii in Africa, A. darlingi in South America and A. farauti in Oceania, as well as A. culicifacies species E, A. fluviatilis species S, A. lesteri and A. minimus in Asia, all feed readily on either humans or animals and collectively mediate residual malaria transmission across most of the tropics. Eliminating malaria transmission by vectors exhibiting such dual host preferences will require aggressive mosquito population abatement, rather than just personal protection of humans. Population suppression of even these particularly troublesome vectors is achievable with a variety of existing vector control technologies that remain underdeveloped or underexploited.

17.
BMJ Glob Health ; 2(2): e000211, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28589022

RESUMO

Vector control using long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) accounts for most of the malaria burden reductions achieved recently in low and middle-income countries (LMICs). LLINs and IRS are highly effective, but are insufficient to eliminate malaria transmission in many settings because of operational constraints, growing resistance to available insecticides and mosquitoes that behaviourally avoid contact with these interventions. However, a number of substantive opportunities now exist for rapidly developing and implementing more diverse, effective and sustainable malaria vector control strategies for LMICs. For example, mosquito control in high-income countries is predominantly achieved with a combination of mosquito-proofed housing and environmental management, supplemented with large-scale insecticide applications to larval habitats and outdoor spaces that kill off vector populations en masse, but all these interventions remain underused in LMICs. Programmatic development and evaluation of decentralised, locally managed systems for delivering these proactive mosquito population abatement practices in LMICs could therefore enable broader scale-up. Furthermore, a diverse range of emerging or repurposed technologies are becoming available for targeting mosquitoes when they enter houses, feed outdoors, attack livestock, feed on sugar or aggregate into mating swarms. Global policy must now be realigned to mobilise the political and financial support necessary to exploit these opportunities over the decade ahead, so that national malaria control and elimination programmes can access a much broader, more effective set of vector control interventions.

18.
BMJ Glob Health ; 2(2): e000212, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28589023

RESUMO

Residual malaria transmission can persist despite high coverage with effective long-lasting insecticidal nets (LLINs) and/or indoor residual spraying (IRS), because many vector mosquitoes evade them by feeding on animals, feeding outdoors, resting outdoors or rapidly exiting from houses after entering them. However, many of these behaviours that render vectors resilient to control with IRS and LLINs also make them vulnerable to some emerging new alternative interventions. Furthermore, vector control measures targeting preferred behaviours of mosquitoes often force them to express previously rare alternative behaviours, which can then be targeted with these complementary new interventions. For example, deployment of LLINs against vectors that historically fed predominantly indoors on humans typically results in persisting transmission by residual populations that survive by feeding outdoors on humans and animals, where they may then be targeted with vapour-phase insecticides and veterinary insecticides, respectively. So while the ability of mosquitoes to express alternative behaviours limits the impact of LLINs and IRS, it also creates measurable and unprecedented opportunities for deploying complementary additional approaches that would otherwise be ineffective. Now that more diverse vector control methods are finally becoming available, well-established entomological field techniques for surveying adult mosquito behaviours should be fully exploited by national malaria control programmes, to rationally and adaptively map out new opportunities for their effective deployment.

19.
Geospat Health ; 12(1): 494, 2017 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-28555474

RESUMO

This study investigated whether passively collected routine health facility data can be used for mapping spatial heterogeneities in malaria transmission at the level of local government housing cluster administrative units in Dar es Salaam, Tanzania. From June 2012 to January 2013, residential locations of patients tested for malaria at a public health facility were traced based on their local leaders' names and geo-referencing the point locations of these leaders' houses. Geographic information systems (GIS) were used to visualise the spatial distribution of malaria infection rates. Spatial scan statistics was deployed to detect spatial clustering of high infection rates. Among 2407 patients tested for malaria, 46.6% (1121) could be traced to their 411 different residential housing clusters. One small spatially aggregated cluster of neighbourhoods with high prevalence was identified. While the home residence housing cluster leader was unambiguously identified for 73.8% (240/325) of malaria-positive patients, only 42.3% (881/2082) of those with negative test results were successfully traced. It was concluded that recording simple points of reference during routine health facility visits can be used for mapping malaria infection burden on very fine geographic scales, potentially offering a feasible approach to rational geographic targeting of malaria control interventions. However, in order to tap the full potential of this approach, it would be necessary to optimise patient tracing success and eliminate biases by blinding personnel to test results.


Assuntos
Instalações de Saúde/estatística & dados numéricos , Malária/epidemiologia , Malária/transmissão , Sistemas de Informação Geográfica , Humanos , Prevalência , Tanzânia/epidemiologia
20.
Emerg Infect Dis ; 23(5): 782-789, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28418299

RESUMO

We assessed window screens and eave baffles (WSEBs), which enable mosquitoes to enter but not exit houses, as an alternative to indoor residual spraying (IRS) for malaria vector control. WSEBs treated with water, the pyrethroid lambda-cyhalothrin, or the organophosphate pirimiphos-methyl, with and without a binding agent for increasing insecticide persistence on netting, were compared with IRS in experimental huts. Compared with IRS containing the same insecticide, WSEBs killed similar proportions of Anopheles funestus mosquitoes that were resistant to pyrethroids, carbamates and organochlorines and greater proportions of pyrethroid-resistant, early exiting An. arabiensis mosquitoes. WSEBs with pirimiphos-methyl killed greater proportions of both vectors than lambda-cyhalothrin or lambda-cyhalothrin plus pirimiphos-methyl and were equally efficacious when combined with binding agent. WSEBs required far less insecticide than IRS, and binding agents might enhance durability. WSEBs might enable affordable deployment of insecticide combinations to mitigate against physiologic insecticide resistance and improve control of behaviorally resistant, early exiting vectors.


Assuntos
Mosquiteiros Tratados com Inseticida , Malária/prevenção & controle , Controle de Mosquitos , Mosquitos Vetores , Animais , Humanos , Malária/epidemiologia , Malária/transmissão , Mortalidade , Controle de Mosquitos/métodos , Mosquitos Vetores/parasitologia
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