Current vector control challenges in the fight against malaria
TL;DR: Key ecological obstacles that limit the effectiveness of vector control include the variation in mosquito behavior, development of insecticide resistance, presence of behavioral avoidance, high vector biodiversity, competitive and food web interactions, lack of insights on mosquito dispersal and mating behavior, and the impact of environmental changes on mosquito ecological traits.
About: This article is published in Acta Tropica.The article was published on 2017-10-01. It has received 227 citations till now. The article focuses on the topics: Indoor residual spraying & Mosquito control.
Citations
More filters
TL;DR: The synthesis of multifunctional Ul-ZnO Nps using widely available seaweed products can be promoted as a potential eco-friendly option to chemical methods currently used for nanosynthesis of antimicrobials and insecticides.
Abstract: The bioactivity of semiconductor nanocomplexes has been poorly studied in the field of pesticide science. In this research, the synthesis of zinc nanoparticles was accomplished through new effortless green chemistry process, using the Ulva lactuca seaweed extract as a reducing and capping agent. The production of U. lactuca-fabricated ZnO nanoparticles (Ul-ZnO Nps) was characterized by powder X-ray diffraction (XRD), UV-visible, Fourier transform infrared (FTIR) spectroscopy, selected area electron diffraction (SAED) analysis and transmission electron microscopy (TEM). The U. lactuca-fabricated ZnO NPs were tested for their photodegradative action against organic dyes, as well as for antibiofilm and larvicidal activities. The UV visible absorbance spectrum of Ul-ZnO NPs exhibited the absorbance band at 325nm and TEM highlighted average crystallite sizes of nanoparticles of 10-50nm. Methylene blue (MB) dye was efficiently corrupted under sunlight in presence of Ul-ZnO NPs. Excellent bactericidal activity was shown by the Ul-ZnO Nps on Gram positive (Bacillus licheniformis and Bacillus pumilis) and Gram negative (Escherichia coliand Proteus vulgaris) bacteria. High antibiofilm potential was noted under both dark and sunlight conditions. The impact of a single treatment with Ul-ZnO NPs on biofilm architecture was also analyzed by confocal laser scanning microscopy (CLSM) on both Gram positive and Gram negative bacteria. Moreover, Ul-ZnO NPs led to 100% mortality of Aedes aegypti fourth instar larvae at the concentration of 50μg/ml within 24h. The effects of ZnO nanoparticle-based treatment on mosquito larval morphology and histology were monitored. Overall, based on our results, we believe that the synthesis of multifunctional Ul-ZnO Nps using widely available seaweed products can be promoted as a potential eco-friendly option to chemical methods currently used for nanosynthesis of antimicrobials and insecticides.
276 citations
Journal Article•
TL;DR: Vector control with microbial larvicides enhanced the malaria control achieved with ITNs alone, and anti-larval measures are a promising complement to ITN distribution in the economically important highland areas and similar transmission settings in Africa.
Abstract: Introduction A marked increase in malaria has recently been noted in the African highlands, largely due to the rise of drug-resistant strains of Plasmodium falciparum parasites. (1-4) The ecological features of the western highlands of Kenya support stable parasite transmission, and increasing population pressure has led to the clearance of natural swamps, massive deforestation and crop cultivation in the valley bottoms. (5,6) Because of these agricultural changes, many water bodies are now exposed to the sun and provide ideal conditions for vector proliferation and increased malaria transmission. (7) Malaria control in these highlands is based on insecticide-treated nets (ITNs), indoor-residual spraying (IRS) with insecticides and prompt and effective treatment of clinical malaria. (8) Many believe integrated vector management (IVM), targeting both larval and adult mosquitoes, is the future for malaria control. (9-11) While ITNs are currently the priority strategy, there is growing interest in attacking the aquatic stages of malaria vectors with microbial larvicides, in conjunction with environmental management. (5,6,12-21) Presently, microbial larvicides are being used in an operational context only in Dar es Salaam, in the United Republic of Tanzania. (22,23) However, in the future larvicide application will be expanded to many of the 15 countries included in the President's Malaria Initiative and this interest is likely to spread to other African countries. While IVM is often advocated,(10,11) there is little evidence from the recent scientific literature on the effectiveness of this approach. We have demonstrated that microbial larvicides reduced malaria vector mosquito larvae and adult females by > 90% in a rural town in western Kenya. (19) However, the effectiveness of this approach for reducing the incidence of malaria among vulnerable children remains unproven. ITNs are a firm favourite in the armamentarium against malaria and their protective efficacy is well known, (24,25) with reductions of 40-70% in human mosquito biting rates. (23,26) In this study we used a "pre-test/post-test control group" design to investigate the contributions of both mosquito larval control with microbials and ITNs to reducing the burden of malaria in the Kakamega and Vihiga highlands of western Kenya, an area moderately endemic for the disease. (27) Methods Study area Six highland valley communities (at an altitude of 1453-1632 m) were recruited in two densely populated districts in Kenya (28) (Table 1). These hilly areas were characterized by step-sided valleys with flat bottoms and plateaus, where most homes were built. Small streams ran along the valley bottoms and papyrus swamps were common. Valleys were approximately 2-4 [km.sup.2] in area and at least 1 km apart. Baseline entomological and clinical data were collected for 17 months (February 2004 to June 2005), after which microbial larvicide was applied to all aquatic habitats in three of the six study sites at weekly intervals for a further 19 months (July 2005 to January 2007). At the same time, larviciding was initiated by project staff in half the sites (Table 1) and ITNs were gradually introduced in all study communities by the National Malaria Control Programme through government health facilities and nongovernmental organizations (NGOs). After baseline monitoring, three valleys were selected for Group 1, the larval control intervention (LCI), and another three for Group 2, the non-LCI group. Since the study valleys varied considerably in their entomological and epidemiological characteristics, the sites were grouped so that at baseline both groups were similar in the total number of aquatic habitats, the proportion of available habitats colonized by Anopheles larvae, the density and seasonality of adult mosquito household infestation, and malaria prevalence (Table 1). Group 2 was chosen as the control because one of the sites in the group bordered a malaria study site of the Kenya Medical Research Institute and we were afraid that treatment in our site would interfere with malaria transmission in the neighbouring site. …
198 citations
TL;DR: Insect nanotoxicology research trends are critically discussed, outlining major challenges to predict the ecotoxicological consequences arising from the real-world use of nanoparticles as pesticides.
Abstract: The employment of nanoparticles obtained through various synthesis routes as novel pesticides recently attracted high research attention. An impressive number of studies have been conducted to test their toxic potential against a wide number of arthropod pests and vectors, with major emphasis on mosquitoes and ticks. However, precise information on the mechanisms of action of nanoparticles against insects and mites are limited, with the noteworthy exception of silica, alumina, silver, and graphene oxide nanoparticles on insects, while no information is available for mites. Here, I summarize current knowledge about the mechanisms of action of nanoparticles against insects. Both silver and graphene oxide nanoparticles have a significant impact on insect antioxidant and detoxifying enzymes, leading to oxidative stress and cell death. Ag nanoparticles also reduced acetylcholinesterase activity, while polystyrene nanoparticles inhibited CYP450 isoenzymes. Au nanoparticles can act as trypsin inhibitors and disrupt development and reproduction. Metal nanoparticles can bind to S and P in proteins and nucleic acids, respectively, leading to a decrease in membrane permeability, therefore to organelle and enzyme denaturation, followed by cell death. Besides, Ag nanoparticles up- and downregulate key insect genes, reducing protein synthesis and gonadotrophin release, leading to developmental damages and reproductive failure. The toxicity of SiO2 and Al2O3 nanoparticles is due to their binding to the insect cuticle, followed by physico-sorption of waxes and lipids, leading to insect dehydration. In the final section, insect nanotoxicology research trends are critically discussed, outlining major challenges to predict the ecotoxicological consequences arising from the real-world use of nanoparticles as pesticides.
178 citations
Cites background from "Current vector control challenges i..."
...The large-scale employment of reliable control strategies to be used against arthropod pests and vectors is a key challenge for current entomology and parasitology (Benelli and Mehlhorn 2016; Benelli and Beier 2017; Benelli and Duggan 2018)....
[...]
TL;DR: In this article, the authors used an inexpensive method for the synthesis of silver nanoparticles (AgNPs) using Garcinia mangostana bark, which was further characterized using scanning electron microscope for morphology and the elemental composition was detected via energy dispersive X-ray analysis.
Abstract: In this present investigation, we used an inexpensive method for the synthesis of silver nanoparticles (AgNPs) using Garcinia mangostana bark. The phyto-assisted AgNPs further characterized using scanning electron microscope for morphology and the elemental composition was detected via energy dispersive X-ray analysis. The domain size was characterized with the help of X-ray diffraction and UV–Vis spectrophotometric analysis for surface plasmon resonance. The possible functional groups were identified with the help of Fourier transform infrared spectroscopy. Antibacterial properties of nanoparticles were evaluated against Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Bacillus cereus and Klebsiella pneumoniae, using agar well diffusion method. Ultimately, the mosquitocidal activity of silver nanoparticles was assessed in the laboratory against fourth instar larvae of Aedes aegypti with LC50 of 5.93 mg L−1 which shows the potential larvicidal effect. To find out the mode of action for larvicidal activity, Agarose gel electrophoresis was carried out. We hypothesize that the toxicity of AgNPs against dengue vectors may be attributed to the small size of these AgNPs, which allows passage through the insect cuticle and into individual cells where they interfere with molting and other physiological processes.
147 citations
TL;DR: This review covers the huge amount of literature available on plant extracts tested as mosquito larvicides, particularly aqueous and alcoholic ones, due to their easy formulation in water without using surfactants, and concludes that 29 of them have outstanding larvicidal activity against major vectors belonging to the genera Anopheles, Aedes and Culex.
144 citations
References
More filters
TL;DR: There are multiple channels by which malaria impedes development, including effects on fertility, population growth, saving and investment, worker productivity, absenteeism, premature mortality and medical costs.
Abstract: Where malaria prospers most, human societies have prospered least. The global distribution of per-capita gross domestic product shows a striking correlation between malaria and poverty, and malaria-endemic countries also have lower rates of economic growth. There are multiple channels by which malaria impedes development, including effects on fertility, population growth, saving and investment, worker productivity, absenteeism, premature mortality and medical costs.
2,320 citations
University of Oxford1, Swiss Tropical and Public Health Institute2, University of Basel3, University of California, San Francisco4, Tulane University5, Imperial College London6, World Health Organization7, University of Bath8, Institute for Health Metrics and Evaluation9, Wellcome Trust Centre for Human Genetics10, National Institutes of Health11
TL;DR: It is found that Plasmodium falciparum infection prevalence in endemic Africa halved and the incidence of clinical disease fell by 40% between 2000 and 2015, and interventions have averted 663 (542–753 credible interval) million clinical cases since 2000.
Abstract: Since the year 2000, a concerted campaign against malaria has led to unprecedented levels of intervention coverage across sub-Saharan Africa. Understanding the effect of this control effort is vital to inform future control planning. However, the effect of malaria interventions across the varied epidemiological settings of Africa remains poorly understood owing to the absence of reliable surveillance data and the simplistic approaches underlying current disease estimates. Here we link a large database of malaria field surveys with detailed reconstructions of changing intervention coverage to directly evaluate trends from 2000 to 2015, and quantify the attributable effect of malaria disease control efforts. We found that Plasmodium falciparum infection prevalence in endemic Africa halved and the incidence of clinical disease fell by 40% between 2000 and 2015. We estimate that interventions have averted 663 (542-753 credible interval) million clinical cases since 2000. Insecticide-treated nets, the most widespread intervention, were by far the largest contributor (68% of cases averted). Although still below target levels, current malaria interventions have substantially reduced malaria disease incidence across the continent. Increasing access to these interventions, and maintaining their effectiveness in the face of insecticide and drug resistance, should form a cornerstone of post-2015 control strategies.
2,135 citations
TL;DR: ITNs are highly effective in reducing childhood mortality and morbidity from malaria, but universal deployment will require major financial, technical, and operational inputs.
Abstract: Background
Malaria is an important cause of illness and death in many parts of the world, especially in sub-Saharan Africa. There has been a renewed emphasis on preventive measures at community and individual levels. Insecticide-treated nets (ITNs) are the most prominent malaria preventive measure for large-scale deployment in highly endemic areas.
Objectives
To assess the impact of insecticide-treated bed nets or curtains on mortality, malarial illness (life-threatening and mild), malaria parasitaemia, anaemia, and spleen rates.
Search methods
I searched the Cochrane Infectious Diseases Group trials register (January 2003), CENTRAL (The Cochrane Library, Issue 1, 2003), MEDLINE (1966 to October 2003), EMBASE (1974 to November 2002), LILACS (1982 to January 2003), and reference lists of reviews, books, and trials. I handsearched journals, contacted researchers, funding agencies, and net and insecticide manufacturers.
Selection criteria
Individual and cluster randomized controlled trials of insecticide-treated bed nets or curtains compared to nets without insecticide or no nets. Trials including only pregnant women were excluded.
Data collection and analysis
The reviewer and two independent assessors reviewed trials for inclusion. The reviewer assessed the risk of bias in the trials, and extracted and analysed data.
Main results
Fourteen cluster randomized and eight individually randomized controlled trials met the inclusion criteria. Five trials measured child mortality: ITNs provided 17% protective efficacy (PE) compared to no nets (relative rate 0.83, 95% confidence interval (CI) 0.76 to 0.90), and 23% PE compared to untreated nets (relative rate 0.77, 95% CI 0.63 to 0.95). About 5.5 lives (95% CI 3.39 to 7.67) can be saved each year for every 1000 children protected with ITNs. In areas with stable malaria, ITNs reduced the incidence of uncomplicated malarial episodes in areas of stable malaria by 50% compared to no nets, and 39% compared to untreated nets; and in areas of unstable malaria: by 62% for compared to no nets and 43% compared to untreated nets for Plasmodium falciparum episodes, and by 52% compared to no nets and 11% compared to untreated nets for P. vivax episodes. When compared to no nets and in areas of stable malaria, ITNs also had an impact on severe malaria (45% PE, 95% CI 20 to 63), parasite prevalence (13% PE), high parasitaemia (29% PE), splenomegaly (30% PE), and their use improved the average haemoglobin level in children by 1.7% packed cell volume.
Authors' conclusions
ITNs are highly effective in reducing childhood mortality and morbidity from malaria. Widespread access to ITNs is currently being advocated by Roll Back Malaria, but universal deployment will require major financial, technical, and operational inputs.
1,708 citations
TL;DR: It is speculated about the mechanisms that could cause malaria to have such a large impact on the economy, such as foreign investment and economic networks within the country, and a second independent measure of malaria has a slightly higher correlation with economic growth in the 1980-1996 period.
Abstract: Malaria and poverty are intimately connected. Controlling for factors such as tropical location, colonial history, and geographical isolation, countries with intensive malaria had income levels in 1995 of only 33% that of countries without malaria, whether or not the countries were in Africa. The high levels of malaria in poor countries are not mainly a consequence of poverty. Malaria is geographically specific. The ecological conditions that support the more efficient malaria mosquito vectors primarily determine the distribution and intensity of the disease. Intensive efforts to eliminate malaria in the most severely affected tropical countries have been largely ineffective. Countries that have eliminated malaria in the past half century have all been either subtropical or islands. These countries' economic growth in the 5 years after eliminating malaria has usually been substantially higher than growth in the neighboring countries. Cross-country regressions for the 1965-1990 period confirm the relationship between malaria and economic growth. Taking into account initial poverty, economic policy, tropical location, and life expectancy, among other factors, countries with intensive malaria grew 1.3% less per person per year, and a 10% reduction in malaria was associated with 0.3% higher growth. Controlling for many other tropical diseases does not change the correlation of malaria with economic growth, and these diseases are not themselves significantly negatively correlated with economic growth. A second independent measure of malaria has a slightly higher correlation with economic growth in the 1980-1996 period. We speculate about the mechanisms that could cause malaria to have such a large impact on the economy, such as foreign investment and economic networks within the country.
1,576 citations
TL;DR: State-of-the-art information on resistance in insect vectors of disease is reviewed and new strategies to develop novel strategies with which to truly manage resistance are proposed.
Abstract: ▪ Abstract Insecticide resistance is an increasing problem in many insect vectors of disease Our knowledge of the basic mechanisms underlying resistance to commonly used insecticides is well established Molecular techniques have recently allowed us to start and dissect most of these mechanisms at the DNA level The next major challenge will be to use this molecular understanding of resistance to develop novel strategies with which we can truly manage resistance State-of-the-art information on resistance in insect vectors of disease is reviewed in this context
1,405 citations