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Omar S. Akbari - One of the best experts on this subject based on the ideXlab platform.
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methods for the generation of heritable germline mutations in the Disease Vector culex quinquefasciatus using clustered regularly interspaced short palindrome repeats associated protein 9
Insect Molecular Biology, 2020Co-Authors: Nannan Liu, Omar S. Akbari, Robyn Raban, Xuegui WangAbstract:Culex quinquefasciatus is a Vector of many Diseases that adversely impact human and animal health; however, compared to other mosquito Vectors limited genome engineering technologies have been characterized for this Vector. Clustered regularly interspaced short palindrome repeats-associated protein 9 (CRISPR-Cas9) based technologies are a powerful tool for genome engineering and functional genetics and consequently have transformed genetic studies in many organisms. Our objective was to improve upon the limited technologies available for genome editing in C. quinquefasciatus to create a reproducible and straightforward method for CRISPR-Cas9-targeted mutagenesis in this Vector. Here we describe methods to achieve high embryo survival and mutagenesis rates and we provide details on the injection supplies and procedures, embryo handling and guide RNA (gRNA) target designs. Through these efforts, we achieved embryo survival rates and germline mutagenesis rates that greatly exceed previously reported rates in this Vector. This work is also the first to characterize the white gene marker in this species, which is a valuable phenotypic marker for future transgenesis or mutagenesis of this Vector. Overall, these tools provide the framework for future functional genetic studies in this important Disease Vector and may support the development of future gene drive and genetic technologies that can be used to control this Vector.
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The Developmental Transcriptome of Ae. albopictus, a Major Worldwide Human Disease Vector
2019Co-Authors: Stephanie Gamez, Igor Antoshechkin, Stelia C. Mendez-sanchez, Omar S. AkbariAbstract:Abstract Aedes albopictus mosquitoes are important Vectors for a number of human pathogens including the Zika, dengue, and chikungunya viruses. Capable of displacing Aedes aegypti populations, it adapts to cooler environments which increases its geographical range and transmission potential. There are limited control strategies for Aedes albopictus mosquitoes which is likely attributed to the lack of comprehensive biological studies on this emerging Vector. To fill this void, here using RNAseq we characterized Aedes albopictus mRNA expression profiles at 47 distinct time points throughout development providing the first high-resolution comprehensive view of the developmental transcriptome of this worldwide human Disease Vector. This enabled us to identify several patterns of shared gene expression among tissues as well as sex-specific expression patterns. Moreover, to illuminate the similarities and differences between Aedes aegypti, a related human Disease Vector, we performed a comparative analysis using the two developmental transcriptomes. We identify life stages were the two species exhibited significant differential expression among orthologs. These findings provide insights into the similarities and differences between Aedes albopictus and Aedes aegypti mosquito biology. In summary, the results generated from this study should form the basis for future investigations on the biology of Aedes albopictus mosquitoes and provide a goldmine resource for the development of transgene-based Vector control strategies.
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methods for the generation of heritable germline mutations in the Disease Vector culex quinquefasciatus using crispr cas9
bioRxiv, 2019Co-Authors: Nannan Liu, Robyn Raban, Xuegui Wang, Omar S. AkbariAbstract:Abstract Culex quinquefasciatus is Vector of many Diseases that adversely impact human and animal health; however, compared to other mosquito Vectors limited genome engineering technologies have been characterized for this Vector. CRISPR-Cas9 based technologies are a powerful tool for genome engineering and functional genomics and consequently have transformed genomics studies in many organisms. Our objective was to improve upon the limited technologies available for genome editing in Cx. quinquefasciatus to create a reproducible and straightforward method for CRISPR-Cas9-targeted mutagenesis in this Vector. Here we describe methods to both improve embryo survival rates as well as mutagenesis rates by optimizing injection supplies and equipment, embryo injection procedures, embryo handling and gRNA target design. Through these efforts, we achieved embryo survival rates and germline mutagenesis rates that greatly exceed any previously reported rates in this Vector. This work was also the first characterize the white gene marker, which is a valuable phenotypic marker for future transgenesis or mutagenesis of this Vector. In the end, these tools provide the framework for future functional genomic studies in this important Disease Vector and may support the development of future gene drive and genetic technologies that can be used to control this Vector.
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visual olfactory integration in the human Disease Vector mosquito aedes aegypti
bioRxiv, 2019Co-Authors: Clément Vinauger, Omar S. Akbari, Floris Van Breugel, Lauren T Locke, Kennedy K S Tobin, Michael H Dickinson, Adrienne L Fairhall, Jeffrey A. RiffellAbstract:Summary Mosquitoes rely on the integration of multiple sensory cues, including olfactory, visual, and thermal stimuli, to detect, identify and locate their hosts [1–4]. Although we increasingly know more about the role of chemosensory behaviours in mediating mosquito-host interactions [1], the role of visual cues remains comparatively less studied [3], and how the combination of olfactory and visual information is integrated in the mosquito brain remains unknown. In the present study, we used a tethered-flight LED arena, which allowed for quantitative control over the stimuli, to show that CO2 exposure affects target-tracking responses, but not responses to large-field visual stimuli. In addition, we show that CO2 modulates behavioural responses to visual objects in a time-dependent manner. To gain insight into the neural basis of this olfactory and visual coupling, we conducted two-photon microscopy experiments in a new GCaMP6s-expressing mosquito line. Imaging revealed that the majority of ROIs in the lobula region of the optic lobe exhibited strong responses to small-field stimuli, but showed little response to a large-field stimulus. Approximately 20% of the neurons we imaged were modulated when an attractive odour preceded the visual stimulus; these same neurons also elicited a small response when the odour was presented alone. By contrast, imaging in the antennal lobe revealed no modulation when visual stimuli were presented before or after the olfactory stimulus. Together, our results are the first to reveal the dynamics of olfactory modulation in visually evoked behaviours of mosquitoes, and suggest that coupling between these sensory systems is asymmetrical and time-dependent.
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Germline Cas9 expression yields highly efficient genome engineering in a major worldwide Disease Vector, Aedes aegypti
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Ming Li, Ting Yang, Christian S. Bowman, Bradley J. White, Omar S. AkbariAbstract:The development of CRISPR/Cas9 technologies has dramatically increased the accessibility and efficiency of genome editing in many organisms. In general, in vivo germline expression of Cas9 results in substantially higher activity than embryonic injection. However, no transgenic lines expressing Cas9 have been developed for the major mosquito Disease Vector Aedes aegypti. Here, we describe the generation of multiple stable, transgenic Ae. aegypti strains expressing Cas9 in the germline, resulting in dramatic improvements in both the consistency and efficiency of genome modifications using CRISPR. Using these strains, we disrupted numerous genes important for normal morphological development, and even generated triple mutants from a single injection. We have also managed to increase the rates of homology-directed repair by more than an order of magnitude. Given the exceptional mutagenic efficiency and specificity of the Cas9 strains we engineered, they can be used for high-throughput reverse genetic screens to help functionally annotate the Ae. aegypti genome. Additionally, these strains represent a step toward the development of novel population control technologies targeting Ae. aegypti that rely on Cas9-based gene drives.
Clément Vinauger - One of the best experts on this subject based on the ideXlab platform.
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visual olfactory integration in the human Disease Vector mosquito aedes aegypti
bioRxiv, 2019Co-Authors: Clément Vinauger, Omar S. Akbari, Floris Van Breugel, Lauren T Locke, Kennedy K S Tobin, Michael H Dickinson, Adrienne L Fairhall, Jeffrey A. RiffellAbstract:Summary Mosquitoes rely on the integration of multiple sensory cues, including olfactory, visual, and thermal stimuli, to detect, identify and locate their hosts [1–4]. Although we increasingly know more about the role of chemosensory behaviours in mediating mosquito-host interactions [1], the role of visual cues remains comparatively less studied [3], and how the combination of olfactory and visual information is integrated in the mosquito brain remains unknown. In the present study, we used a tethered-flight LED arena, which allowed for quantitative control over the stimuli, to show that CO2 exposure affects target-tracking responses, but not responses to large-field visual stimuli. In addition, we show that CO2 modulates behavioural responses to visual objects in a time-dependent manner. To gain insight into the neural basis of this olfactory and visual coupling, we conducted two-photon microscopy experiments in a new GCaMP6s-expressing mosquito line. Imaging revealed that the majority of ROIs in the lobula region of the optic lobe exhibited strong responses to small-field stimuli, but showed little response to a large-field stimulus. Approximately 20% of the neurons we imaged were modulated when an attractive odour preceded the visual stimulus; these same neurons also elicited a small response when the odour was presented alone. By contrast, imaging in the antennal lobe revealed no modulation when visual stimuli were presented before or after the olfactory stimulus. Together, our results are the first to reveal the dynamics of olfactory modulation in visually evoked behaviours of mosquitoes, and suggest that coupling between these sensory systems is asymmetrical and time-dependent.
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Learning and Memory in Disease Vector Insects.
Trends in parasitology, 2016Co-Authors: Clément Vinauger, Chloé Lahondère, Anna Cohuet, Claudio R. Lazzari, Jeffrey A. RiffellAbstract:Learning and memory plays an important role in host preference and parasite transmission by Disease Vector insects. Historically there has been a dearth of standardized protocols that permit testing their learning abilities, thus limiting discussion on the potential epidemiological consequences of learning and memory to a largely speculative extent. However, with increasing evidence that individual experience and associative learning can affect processes such as oviposition site selection and host preference, it is timely to review the recently acquired knowledge, identify research gaps and discuss the implication of learning in Disease Vector insects in perspective with control strategies.
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Circadian modulation of learning ability in a Disease Vector insect, Rhodnius prolixus
Journal of Experimental Biology, 2015Co-Authors: Clément Vinauger, Claudio R. LazzariAbstract:Despite the drastic consequences it may have on the transmission of parasites, the ability of Disease Vectors to learn and retain information has just begun to be characterised. The kissing bug Rhodnius prolixus, a Vector of Chagas Disease, is an excellent model, particularly because conditioning the proboscis extension response (PER) constitutes a valuable paradigm to study their cognitive abilities under carefully controlled conditions. Another characteristic of these bugs is the temporal organisation of their different activities in a bimodal endogenous daily rhythm. This offers the opportunity to address the implication of the circadian system in learning and memory. Using aversive conditioning of the PER, we tested whether the ability of kissing bugs to learn and remember information varies during the day. We found that bugs perform well during the night, but not during the day: their ability to acquire information - but not their ability to retrieve it - is modulated by time. When the bugs were kept under constant conditions in order to analyse the origin of this rhythm, the rhythm continued to free run, showing its endogenous and truly circadian nature. These results are the first to evince the effect of the circadian system on the learning abilities of Disease Vectors and one of the few in insects in general.
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olfactory learning and memory in the Disease Vector mosquito aedes aegypti
The Journal of Experimental Biology, 2014Co-Authors: Clément Vinauger, Eleanor K Lutz, Jeffrey A. RiffellAbstract:Olfactory learning in blood-feeding insects, such as mosquitoes, could play an important role in host preference and Disease transmission. However, standardised protocols allowing testing of their learning abilities are currently lacking, and how different olfactory stimuli are learned by these insects remains unknown. Using a Pavlovian conditioning paradigm, we trained individuals and groups of Aedes aegypti mosquitoes to associate an odorant conditioned stimulus (CS) with a blood-reinforced thermal stimulus (unconditioned stimulus; US). Results showed, first, that mosquitoes could learn the association between L-lactic acid and the US, and retained the association for at least 24 h. Second, the success of olfactory conditioning was dependent upon the CS – some odorants that elicited indifferent responses in naive mosquitoes, such as L-lactic acid and 1-octen-3-ol, were readily learned, whereas others went from aversive to attractive after training ( Z -3-hexen-1-ol) or were untrainable (β-myrcene and benzyl alcohol). Third, we examined whether mosquitoes9 ability to learn could interfere with the action of the insect repellent DEET. Results demonstrated that pre-exposure and the presence of DEET in the CS reduced the aversive effects of DEET. Last, the nature of the formed memories was explored. Experiments using cold-shock treatments within the first 6 h post-training (for testing anaesthesia-resistant memory) and a protein synthesis inhibitor (cycloheximide; to disrupt the formation of long-term memory) both affected mosquitoes9 performances. Together, these results show that learning is a crucial component in odour responses in A. aegypti , and provide the first evidence for the functional role of different memory traces in these responses.
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Learned host preference in a Chagas Disease Vector, Rhodnius prolixus.
Acta tropica, 2011Co-Authors: Clément Vinauger, Marcos H. Pereira, Claudio R. LazzariAbstract:It has been largely assumed that the individual experience of Disease Vector insects may affect host choice and, as a consequence, have an important influence on parasite transmission. In particular, it is speculated that Vector insects should be able to learn and remember the most and/or less defensive hosts, shifting their preference accordingly. Nevertheless, despite the invested efforts in testing the capacity to learn and remember information of blood-sucking insects, only little conclusive information has been obtained hitherto. Recently, the ability of Rhodnius prolixus to associate a behaviourally neutral odour to the perspective of either obtaining a blood-meal or being punished has been demonstrated, the same odour becoming attractant or repellent for the bugs, respectively, according to the individual previous experience. The present work represents a step forward in the study of the cognitive abilities of Chagas Disease Vectors and their influence on host choice. We tested whether or not bugs bias their choice for a host based on the association of its odour with a negative experience. Our results show that whereas naive bugs presented no preference when confronted to the odour of two different hosts, bugs previously exposed to the contingency of the odour of one host and a mechanical perturbation mimicking defensive behaviour, biased their preference towards the other host. This constitutes the first evidence of olfactory conditioning to host odours in triatomine bugs, Vectors of Chagas Disease and one of the few available up to date on haematophagous insects. The epidemiological significance of this finding is discussed.
Jeffrey A. Riffell - One of the best experts on this subject based on the ideXlab platform.
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visual olfactory integration in the human Disease Vector mosquito aedes aegypti
bioRxiv, 2019Co-Authors: Clément Vinauger, Omar S. Akbari, Floris Van Breugel, Lauren T Locke, Kennedy K S Tobin, Michael H Dickinson, Adrienne L Fairhall, Jeffrey A. RiffellAbstract:Summary Mosquitoes rely on the integration of multiple sensory cues, including olfactory, visual, and thermal stimuli, to detect, identify and locate their hosts [1–4]. Although we increasingly know more about the role of chemosensory behaviours in mediating mosquito-host interactions [1], the role of visual cues remains comparatively less studied [3], and how the combination of olfactory and visual information is integrated in the mosquito brain remains unknown. In the present study, we used a tethered-flight LED arena, which allowed for quantitative control over the stimuli, to show that CO2 exposure affects target-tracking responses, but not responses to large-field visual stimuli. In addition, we show that CO2 modulates behavioural responses to visual objects in a time-dependent manner. To gain insight into the neural basis of this olfactory and visual coupling, we conducted two-photon microscopy experiments in a new GCaMP6s-expressing mosquito line. Imaging revealed that the majority of ROIs in the lobula region of the optic lobe exhibited strong responses to small-field stimuli, but showed little response to a large-field stimulus. Approximately 20% of the neurons we imaged were modulated when an attractive odour preceded the visual stimulus; these same neurons also elicited a small response when the odour was presented alone. By contrast, imaging in the antennal lobe revealed no modulation when visual stimuli were presented before or after the olfactory stimulus. Together, our results are the first to reveal the dynamics of olfactory modulation in visually evoked behaviours of mosquitoes, and suggest that coupling between these sensory systems is asymmetrical and time-dependent.
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Learning and Memory in Disease Vector Insects.
Trends in parasitology, 2016Co-Authors: Clément Vinauger, Chloé Lahondère, Anna Cohuet, Claudio R. Lazzari, Jeffrey A. RiffellAbstract:Learning and memory plays an important role in host preference and parasite transmission by Disease Vector insects. Historically there has been a dearth of standardized protocols that permit testing their learning abilities, thus limiting discussion on the potential epidemiological consequences of learning and memory to a largely speculative extent. However, with increasing evidence that individual experience and associative learning can affect processes such as oviposition site selection and host preference, it is timely to review the recently acquired knowledge, identify research gaps and discuss the implication of learning in Disease Vector insects in perspective with control strategies.
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olfactory learning and memory in the Disease Vector mosquito aedes aegypti
The Journal of Experimental Biology, 2014Co-Authors: Clément Vinauger, Eleanor K Lutz, Jeffrey A. RiffellAbstract:Olfactory learning in blood-feeding insects, such as mosquitoes, could play an important role in host preference and Disease transmission. However, standardised protocols allowing testing of their learning abilities are currently lacking, and how different olfactory stimuli are learned by these insects remains unknown. Using a Pavlovian conditioning paradigm, we trained individuals and groups of Aedes aegypti mosquitoes to associate an odorant conditioned stimulus (CS) with a blood-reinforced thermal stimulus (unconditioned stimulus; US). Results showed, first, that mosquitoes could learn the association between L-lactic acid and the US, and retained the association for at least 24 h. Second, the success of olfactory conditioning was dependent upon the CS – some odorants that elicited indifferent responses in naive mosquitoes, such as L-lactic acid and 1-octen-3-ol, were readily learned, whereas others went from aversive to attractive after training ( Z -3-hexen-1-ol) or were untrainable (β-myrcene and benzyl alcohol). Third, we examined whether mosquitoes9 ability to learn could interfere with the action of the insect repellent DEET. Results demonstrated that pre-exposure and the presence of DEET in the CS reduced the aversive effects of DEET. Last, the nature of the formed memories was explored. Experiments using cold-shock treatments within the first 6 h post-training (for testing anaesthesia-resistant memory) and a protein synthesis inhibitor (cycloheximide; to disrupt the formation of long-term memory) both affected mosquitoes9 performances. Together, these results show that learning is a crucial component in odour responses in A. aegypti , and provide the first evidence for the functional role of different memory traces in these responses.
Michael J. Levy - One of the best experts on this subject based on the ideXlab platform.
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A real-time search strategy for finding urban Disease Vector infestations
Epidemiologic Methods, 2020Co-Authors: Erica Billig Rose, Jason Roy, Ricardo Castillo-neyra, Michelle E. Ross, Carlos Condori-pino, Jennifer K. Peterson, Cesar Naquira-velarde, Michael J. LevyAbstract:AbstractObjectivesContaining domestic Vector infestation requires the ability to swiftly locate and treat infested homes. In urban settings where Vectors are heterogeneously distributed throughout a dense housing matrix, the task of locating infestations can be challenging. Here, we present a novel stochastic compartmental model developed to help locate infested homes in urban areas. We designed the model using infestation data for the Chagas Disease Vector species Triatoma infestans in Arequipa, Peru.MethodsOur approach incorporates Disease Vector counts at each observed house, and the Vector’s complex spatial dispersal dynamics. We used a Bayesian method to augment the observed data, estimate the insect population growth and dispersal parameters, and determine posterior infestation probabilities of households. We investigated the properties of the model through simulation studies, followed by field testing in Arequipa.ResultsSimulation studies showed the model to be accurate in its estimates of two parameters of interest: the growth rate of a domestic triatomine bug colony and the probability of a triatomine bug successfully invading a new home after dispersing from an infested home. When testing the model in the field, data collection using model estimates was hindered by low household participation rates, which severely limited the algorithm and in turn, the model’s predictive power.ConclusionsWhile future optimization efforts must improve the model’s capabilities when household participation is low, our approach is nonetheless an important step toward integrating data with predictive modeling to carry out evidence-based Vector surveillance in cities.
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A real-time search strategy for finding urban Disease Vector infestations
2020Co-Authors: Erica Billig Rose, Jason Roy, Ricardo Castillo-neyra, Michelle E. Ross, Carlos Condori-pino, Jennifer K. Peterson, Cesar Naquira-velarde, Michael J. LevyAbstract:Containing domestic Vector infestation requires the ability to swiftly locate and treat infested homes. In urban settings where Vectors are heterogeneously distributed throughout a dense housing matrix, the task of locating infestations can be challenging. Here, we present a novel stochastic compartmental model developed to help locate infested homes in urban areas. We designed the model using infestation data for the Chagas Disease Vector species Triatoma infestans in Arequipa, Peru. Our approach incorporates Disease Vector counts at each observed house, and the Vector9s complex spatial dispersal dynamics. We used a Bayesian method to augment the observed data, estimate the insect population growth and dispersal parameters, and determine posterior infestation probabilities of households. We investigated the properties of the model through simulation studies, followed by field testing in Arequipa. Simulation studies showed the model to be accurate in its estimates of two parameters of interest: the growth rate of a domestic triatomine bug colony and the probability of a triatomine bug successfully invading a new home after dispersing from an infested home. When testing the model in the field, data collection using model estimates was hindered by low household participation rates, which severely limited the algorithm and in turn, the model9s predictive power. While future optimization efforts must improve the model9s capabilities when household participation is low, our approach is nonetheless an important step toward integrating data with predictive modeling to carry out evidence-based Vector surveillance in cities.
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geographical and environmental factors driving the increase in the lyme Disease Vector ixodes scapularis
Ecosphere, 2012Co-Authors: Camilo E Khatchikian, Michael J. Levy, Melissa A Prusinski, Melissa Stone, Bryon P Backenson, Ingnang Wang, Dustin BrissonAbstract:The population densities of many organisms have changed dramatically in recent history. Increases in the population density of medically relevant organisms are of particular importance to public health as they are often correlated with the emergence of infectious Diseases in human populations. Our aim is to delineate increases in density of a common Disease Vector in North America, the blacklegged tick, and to identify the environmental factors correlated with these population dynamics. Empirical data that capture the growth of a population are often necessary to identify environmental factors associated with these dynamics. We analyzed temporally- and spatially-structured field collected data in a geographical information systems framework to describe the population growth of blacklegged ticks (Ixodes scapularis) and to identify environmental and climatic factors correlated with these dynamics. The density of the ticks increased throughout the study's temporal and spatial ranges. Tick density increases were positively correlated with mild temperatures, low precipitation, low forest cover, and high urbanization. Importantly, models that accounted for these environmental factors accurately forecast future tick densities across the region. Tick density increased annually along the south-to-north gradient. These trends parallel the increases in human incidences of Diseases commonly Vectored by I. scapularis. For example, I. scapularis densities are correlated with human Lyme Disease incidence, albeit in a non-linear manner that disappears at low tick densities, potentially indicating that a threshold tick density is needed to support epidemiologically-relevant levels of the Lyme Disease bacterium. Our results demonstrate a connection between the biogeography of this species and public health.
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Rational spatio-temporal strategies for controlling a Chagas Disease Vector in urban environments
Journal of the Royal Society Interface, 2010Co-Authors: Michael J. Levy, Fernando S. Malaga Chavez, Juan G. Cornejo Del Carpio, Daril A. Vilhena, F. Ellis Mckenzie, Joshua B. PlotkinAbstract:The rational design of interventions is critical to controlling communicable Diseases, especially in urban environments. In the case of the Chagas Disease Vector Triatoma infestans, successful control is stymied by the return of the insect after the effectiveness of the insecticide wanes. Here, we adapt a genetic algorithm, originally developed for the travelling salesman problem, to improve the spatio-temporal design of insecticide campaigns against T. infestans, in a complex urban environment. We find a strategy that reduces the expected instances of Vector return 34-fold compared with the current strategy of sequential insecticide application to spatially contiguous communities. The relative success of alternative control strategies depends upon the duration of the effectiveness of the insecticide, and it shows chaotic fluctuations in response to unforeseen delays in a control campaign. We use simplified models to analyse the outcomes of qualitatively different spatio-temporal strategies. Our results provide a detailed procedure to improve control efforts for an urban Chagas Disease Vector, as well as general guidelines for improving the design of interventions against other Disease agents in complex environments.
Ricardo E Gurtler - One of the best experts on this subject based on the ideXlab platform.
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Chagas Disease Vector control and Taylor's law
PLoS neglected tropical diseases, 2017Co-Authors: Joel E. Cohen, Maria C Cecere, Lucía I. Rodríguez-planes, María Sol Gaspe, Marta Victoria Cardinal, Ricardo E GurtlerAbstract:Background Large spatial and temporal fluctuations in the population density of living organisms have profound consequences for biodiversity conservation, food production, pest control and Disease control, especially Vector-borne Disease control. Chagas Disease Vector control based on insecticide spraying could benefit from improved concepts and methods to deal with spatial variations in Vector population density. Methodology/Principal findings We show that Taylor's law (TL) of fluctuation scaling describes accurately the mean and variance over space of relative abundance, by habitat, of four insect Vectors of Chagas Disease (Triatoma infestans, Triatoma guasayana, Triatoma garciabesi and Triatoma sordida) in 33,908 searches of people's dwellings and associated habitats in 79 field surveys in four districts in the Argentine Chaco region, before and after insecticide spraying. As TL predicts, the logarithm of the sample variance of bug relative abundance closely approximates a linear function of the logarithm of the sample mean of abundance in different habitats. Slopes of TL indicate spatial aggregation or variation in habitat suitability. Predictions of new mathematical models of the effect of Vector control measures on TL agree overall with field data before and after community-wide spraying of insecticide. Conclusions/Significance A spatial Taylor's law identifies key habitats with high average infestation and spatially highly variable infestation, providing a new instrument for the control and elimination of the Vectors of a major human Disease.
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intensified surveillance and insecticide based control of the chagas Disease Vector triatoma infestans in the argentinean chaco
PLOS Neglected Tropical Diseases, 2013Co-Authors: Juan M Gurevitz, Uriel Kitron, María Sol Gaspe, Gustavo Fabian Enriquez, Yael M Provecho, Ricardo E GurtlerAbstract:Background The elimination of Triatoma infestans, the main Chagas Disease Vector in the Gran Chaco region, remains elusive. We implemented an intensified control strategy based on full-coverage pyrethroid spraying, followed by frequent Vector surveillance and immediate selective insecticide treatment of detected foci in a well-defined rural area in northeastern Argentina with moderate pyrethroid resistance. We assessed long-term impacts, and identified factors and procedures affecting spray effectiveness. Methods and Findings After initial control interventions, timed-manual searches were performed by skilled personnel in 4,053 sites of 353–411 houses inspected every 4–7 months over a 35-month period. Residual insecticide spraying was less effective than expected throughout the three-year period, mainly because of the occurrence of moderate pyrethroid resistance and the limited effectiveness of selective treatment of infested sites only. After initial interventions, peridomestic infestation prevalence always exceeded domestic infestation, and timed-manual searches consistently outperformed householders' bug detection, except in domiciles. Most of the infestations occurred in houses infested at baseline, and were restricted to four main ecotopes. Houses with an early persistent infestation were spatially aggregated up to a distance of 2.5 km. An Akaike-based multi-model inference approach showed that new site-level infestations increased substantially with the local availability of appropriate refugia for triatomine bugs, and with proximity to the nearest site found infested at one or two preceding surveys. Conclusions and Significance Current Vector control procedures have limited effectiveness in the Gran Chaco. Selective insecticide sprays must include all sites within the infested house compound. The suppression of T. infestans in rural areas with moderate pyrethroid resistance requires increased efforts and appropriate management actions. In addition to careful, systematic insecticide applications, housing improvement and development policies that improve material conditions of rural villagers and reduce habitat suitability for bugs will contribute substantially to sustainable Vector and Disease control in the Gran Chaco.
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reinfestation sources for chagas Disease Vector triatoma infestans argentina
Emerging Infectious Diseases, 2006Co-Authors: Maria C Cecere, Gonzalo M Vazquezprokopec, Ricardo E Gurtler, Uriel KitronAbstract:Reinfestation by Triatoma infestans after insecticide spraying has caused elimination efforts in the dry Chaco region to fail repeatedly. The sources and spatial extent that need to be considered to understand the reinfestation pattern and to plan a comprehensive control program were studied in 2 adjacent rural communities in northwestern Argentina from 1993 to 1997. The effects of external, residual, and primary sources on the reinfestation pattern were evaluated by using geographic information systems, satellite imagery, spatial statistics, and 5-year retrospective data for 1,881 sites. The reinfestation process depended on primary internal sources and on surrounding infested communities. In the dry Chaco, successfully reducing the risk for reinfestation in a community depends on treating all communities and isolated sites within 1,500 m of the target community. In addition, during the surveillance phase, spraying all sites within 500 m of new foci will delay reinfestation.