scholarly journals Anopheles gambiae s. l. larval control: An important method for malaria control

2021 ◽  
Vol 6 (3) ◽  
pp. 027-034
Author(s):  
Nazaire Aïzoun
Keyword(s):  
Anopheles Gambiae ◽  
Malaria Control ◽  
Malaria Elimination ◽  
Rainy Season ◽  
Enzyme Inhibitor ◽  
Integrated Control ◽  
Detoxification Enzymes ◽  
Malaria Vectors ◽  
Important Method ◽  
Susceptibility Tests

The current study aimed to investigate on the control tools against larvae and adults of Anopheles gambiae s. l. and then explore the detoxification enzymes mechanisms conferring permethrin tolerance in Anopheles gambiae s. l. larvae in Benin. Larvae and pupae were collected from March to July and August to November 2018 during the rainy season in Bopa district in Mono department in south-western Benin, West Africa. Larval bioassays were performed on these collected Anopheles gambiae s. l. larvae using permethrin as larvicide and synergist piperonyl butoxide (PBO) as enzyme inhibitor or synergist. WHO susceptibility tests were also conducted on adult unfed female mosquitoes aged 3-5 days old with impregnated papers of permethrin (0.75%). The results showed that malaria elimination in Benin needs integrated control. Both larvae or pupae and adults malaria vectors must be controlled.

Insecticide susceptibility status in individual species of the Anopheles gambiae complex (Diptera: Culicidae) in an area of The Gambia where pyrethroid impregnated bednets are used extensively for malaria control

1995 ◽  
Vol 85 (2) ◽  
pp. 229-234 ◽  
Author(s):  
J. Hemingway ◽  
S.W. Lindsay ◽  
G.J. Small ◽  
M. Jawara ◽  
F.H. Collins
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Malaria Control ◽  
The Gambia ◽  
Malaria Vectors ◽  
Cross Resistance ◽  
Individual Species ◽  
Sentinel Site ◽  
Malaria Control Programme ◽  
Biochemical Assays

AbstractPyrethroid-impregnated bednets are being used nationwide in The Gambia. The future success of this malaria control programme depends partly on the vectors remaining susceptible to those insecticides used for treating the nets. The present study was carried out on the south bank of the river Gambia, during the first large scale trial of nets in this country. Thus this area represents a sentinel site for detecting insecticide resistance in local vectors. This study gives an example of how a system of early detection for resistance problems can be set up in a relatively complex situation where multiple vectors and non-vectors are present. Samples of the Anopheles gambiae complex were caught indoors using light traps in twelve villages used in the bednet study. In all villages A. gambiae sensu stricto Giles was the predominant member of the complex as determined using the rDNA-PCR diagnostic assay. Limited bioassays with DDT and permethrin, and biochemical assays for a range of insecticide resistance mechanisms suggest that the A. gambiae complex remains completely susceptible to all major classes of commonly used insecticides including pyrethroids. Biochemical assays suggest that a low frequency of DDT resistance may occur in A. melas Theobald. This is based on elevated glutathione S-transferase levels coupled with increased levels of DDT metabolism and does not involve cross-resistance to pyrethroids. Therefore we do not envisage a decline in the efficacy of treated nets against malaria vectors in the study area in the immediate future, although monitoring should be continued whilst wide-scale use of impregnated bednets is operational.

scholarly journals Pollutants and insecticides drive local adaptation in African malaria mosquitoes

2016 ◽  
Author(s):  
Colince Kamdem ◽  
Caroline Fouet ◽  
Stephanie Gamez ◽  
Bradley J. White
Keyword(s):  
Anopheles Gambiae ◽  
Local Adaptation ◽  
Mosquito Species ◽  
Sensu Stricto ◽  
Detoxification Enzymes ◽  
Malaria Vectors ◽  
Breeding Sites ◽  
Reduced Representation ◽  
Malaria Epidemiology ◽  
Rural And Urban

ABSTRACTThe Anopheles gambiae complex contains a number of highly anthropophilic mosquito species that have acquired exceptional ability to thrive in complex human habitats. Thus, examining the evolutionary history of this Afrotropical mosquito may yield vital information on the selective processes that occurred during the adaptation to human-dominated environments. We performed reduced representation sequencing on 941 mosquitoes of the Anopheles gambiae complex collected across four ecogeographic zones in Cameroon. We find evidence for genetic and geographic subdivision within An. coluzzii and An. gambiae sensu stricto – the two most significant malaria vectors in the region. Importantly, in both species, rural and urban populations are genetically differentiated. Genome scans reveal pervasive signatures of selection centered on genes involved in xenobiotic resistance. Notably, a selective sweep containing detoxification enzymes is prominent in urban mosquitoes that exploit polluted breeding sites. Overall, our study suggests that recent anthropogenic environmental modifications and widespread use of insecticides are driving population differentiation and local adaptation in vectors with potentially significant consequences for malaria epidemiology.

scholarly journals Patterns of human exposure to malaria vectors in Zanzibar and implications for malaria elimination efforts

2019 ◽  
Author(s):  
April Monroe ◽  
Dickson Msaky ◽  
Samson Kiware ◽  
Brian Tarimo ◽  
Sarah Moore ◽  
...  
Keyword(s):  
Malaria Elimination ◽  
Rainy Season ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
Weighted Estimates ◽  
Behavior Change Interventions ◽  
Increased Risk ◽  
Itn Use ◽  
Indoor And Outdoor

Abstract Background: Zanzibar provides a good case study for malaria elimination. The islands have experienced a dramatic reduction in malaria burden since the introduction of effective vector control interventions and case management. Malaria prevalence has now been maintained below 1% for the past decade and the islands can feasibly aim for elimination. Methods: To better understand factors that may contribute to remaining low-level malaria transmission in Zanzibar, layered human behavioral and entomological research was conducted between December 2016 and December 2017 in 135 randomly selected households across six administrative wards selected based on high annual parasite incidence and receipt of indoor residual spraying (IRS). The study included: 1) household surveys, 2) structured household observations of nighttime activity and sleeping patterns, and 3) paired indoor and outdoor mosquito collections. Entomological and human behavioral data were integrated to provide weighted estimates of exposure to vector bites, accounting for proportions of people indoors or outdoors, and protected by insecticide-treated nets (ITNs) each hour of the night. Results: The percentage of study participants outdoors and away from home peaked in the early evening with a higher percentage of males observed away throughout the night compared to females. Overall, 92% of female Anopheles mosquitoes were caught in the rainy season compared to 8% in the dry season and 72% were caught outdoors compared to 28% indoors. Observed levels of ITN use were estimated to prevent an average of 42% of exposure to vector bites of all exposure that would otherwise occur. For ITN users, use of an ITN while asleep prevented an estimated two-thirds (66%) of exposure to vector bites and nearly three quarters (73%) of remaining exposure was estimated to occur outdoors. Discussion/Conclusions: This study identified gaps in malaria prevention in Zanzibar with results directly applicable for improving ongoing program activities. While overall biting risk was low, the most notable finding was that current levels of ITN use are estimated to prevent less than half of exposure to malaria vector bites. Variation in ITN use across sites suggests that additional gains could be made through targeted social and behavior change interventions in sites with low levels of ITN use, with additional focus on increasing net use in the rainy season when biting risk is higher. However, even for ITN users, gaps in protection remain, with a majority of exposure to vector bites occurring outdoors before going to sleep. Supplemental interventions targeting outdoor exposure to malaria vectors, and groups that may be at increased risk of exposure to malaria vectors, should be explored. Interventions such as larval source management, which can reduce both indoor and outdoor-biting vector populations, could also be considered.

scholarly journals Characterization of resistance profile (intensity and mechanisms) of Anopheles gambiae in three communes of northern Benin, West Africa

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Casimir Dossou Kpanou ◽  
Hermann W. Sagbohan ◽  
Fortuné Dagnon ◽  
Germain G. Padonou ◽  
Razaki Ossè ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
High Intensity ◽  
Mortality Rates ◽  
Detoxification Enzymes ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Biochemical Tests ◽  
Diagnostic Dose

Abstract Background The selection and the spread of insecticide resistance in malaria vectors to the main classes of insecticides used in vector control tools are a major and ongoing challenge to malaria vector control programmes. This study aimed to determine the intensity of vector resistance to insecticides in three regions of Benin with different agro-ecological characteristics. Methods Larvae of Anopheles gambiae sensu lato (s.l.) were collected from September to November 2017 in different larval sites in three northern Benin communes: Parakou, Kandi and Malanville. Two to five-day-old, non-blood-fed, female mosquitoes were exposed to papers impregnated with deltamethrin, permethrin and bendiocarb at dosages of 1 × the diagnostic dose, 5 × and 10 × to determine the intensity of resistance in these vectors. Molecular frequencies of the kdr L1014F and ace-1R G119S insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled at each study site. Results Resistance to pyrethroids (permethrin and deltamethrin) was recorded in all three communes with mortality rates below 60% using the diagnostic dose (1x). The results obtained after exposure of An. gambiae to permethrin 10 × were 99% in Kandi, 98% in Malanville and 99% in Parakou. With deltamethrin 10x, mortality rates were 100% in Kandi, 96% in Malanville and 73% in Parakou. For the diagnostic dose of bendiocarb, suspected resistance was recorded in the communes of Malanville (97%) and Kandi (94%) while sensitivity was observed in Parakou (98%).Using the 10 × dose, mortality was 98% in Kandi, 100% in Malanville and 99% in Parakou. The frequencies of the kdr L1014F allele varied between 59 and 83% depending on the sites and species of the An. gambiae complex, while the frequency of the ace-1R G119S gene varied between 0 and 5%. Biochemical tests showed high levels of oxidase and esterase activity compared to the susceptible colony strain of An. gambiae sensu stricto (Kisumu strain). Conclusion Anopheles gambiae showed a generalized loss of susceptibility to permethrin and deltamethrin but also showed moderate to high intensity of resistance in different regions of Benin. This high intensity of resistance is a potential threat to the effectiveness of vector control.

scholarly journals Temporal Distribution and Abundance of Mosquito Vectors in Dhaka City

2021 ◽  
Vol 46 (1) ◽  
pp. 27-35
Author(s):  
MG Sharower ◽  
MA Latif ◽  
SM Uddin
Keyword(s):  
Anopheles Gambiae ◽  
Sibling Species ◽  
Rainy Season ◽  
Temporal Distribution ◽  
Malaria Vectors ◽  
Dhaka City ◽  
Mosquito Vectors ◽  
Anopheles Gambiae S.S ◽  
Culex Fatigans ◽  
Highly Correlated

Species of Anopheles, Aedes and Culex mosquitoes showed that Anopheles gambiae s.s had the highest number (43.5%) out of the three malaria vectors (viz. Anopheles gambiae, An. arabiensis and An. funestus). For Aedes and Culex species, Aedes aegypti (37.6%) and Culex fatigans (37.1%) had the highest prevalence out of their sibling species. Temperature and rainfall were highly correlated with the abundance of mosquito vectors. It was observed that the rainy season (March to October) recorded the highest number (Total 11 specie) of mosquito vectors collected with the peak (Aedes aegypty, 140) in the months of July (932) and August (976) while the lowest (333) collection was in the dry season (November to February) with lowest (333) in the month of February when there was little or no rains. Asiat. Soc. Bangladesh, Sci. 46(1): 27-35, June 2020

scholarly journals Patterns Of Insecticide Resistance Among Anopheles Gambiae Mosquitoes In Five Districts In Uganda: 2011-2015

2020 ◽  
Author(s):  
Denis Okethwangu ◽  
Damian Rutazaana ◽  
Daniel Kyabayinze ◽  
Doreen Birungi ◽  
Claire Biribawa ◽  
...  
Keyword(s):  
Mortality Rate ◽  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Mortality Rates ◽  
World Health ◽  
Malaria Vectors ◽  
Mosquito Vector ◽  
Global Public Health ◽  
Test Kit ◽  
Susceptibility Tests

Abstract Background: Malaria ranks among the leading global public health challenges. Resistance to insecticides used in vector control by malaria vectors threatens the effectiveness of this intervention. We analyzed data from routine susceptibility tests conducted in sentinel sites in five Ugandan districts to determine the status and pattern of insecticide resistance among Anopheles gambiae mosquito vectors, and to assess the trend of mortality rates of the vector. Methods: We conducted a cross-sectional study using secondary data from sentinel sites in Apac, Kanungu, Hoima, Tororo, and Wakiso Districts of Uganda. Chemicals from different classes of insecticides were subjected to susceptibility tests, which included both the World Health Organization (WHO) standard test kit and the Centers for Disease Control and Prevention (CDC) bottle bioassay tests. Resistance was defined according to the standard WHO criteria of insecticide resistance. The Fisher’s Exact Test was used to determine the difference in mortality rates across years in the study period.Results: A total of eight chemicals were used in the selected districts over the years of study. Out of the 5 districts, we found that the average mortality rate of the mosquito vector by the carbamates was over 98% in 3 districts. In Tororo and Wakiso Districts, the average was about 90%. Mortality of mosquitoes by pyrethroids used averaged less than 80% in all five districts. The organochlorines averaged less than 50% in four out of five districts. In Apac District, organochlorines averaged a mortality rate of 94%. The organophosphates averaged 100% mortality in all sentinel sites. There was no specific pattern in mortality of Anopheles gambiae by insecticides.Conclusion: There was widespread resistance to pyrethroids and organochlorines, with patchy resistance observed against carbamates. Only organophosphates showed potency in all sentinel sites. This threatens gains made in malaria control, and renews calls for continued insecticide resistance monitoring.

scholarly journals Insecticide resistance status of malaria vectors Anopheles gambiae (s.l.) of southwest Burkina Faso and residual efficacy of indoor residual spraying with microencapsulated pirimiphos-methyl insecticide

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Dieudonné Diloma Soma ◽  
Barnabas Zogo ◽  
Domonbabele François de Sales Hien ◽  
Aristide Sawdetuo Hien ◽  
Didier Alexandre Kaboré ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Burkina Faso ◽  
Anopheles Gambiae ◽  
Local Population ◽  
Residual Activity ◽  
Indoor Residual Spraying ◽  
Susceptible Strain ◽  
Malaria Vectors ◽  
Pirimiphos Methyl ◽  
Residual Efficacy

Abstract Background The rapid spread of insecticide resistance in malaria vectors and the rebound in malaria cases observed recently in some endemic areas underscore the urgent need to evaluate and deploy new effective control interventions. A randomized control trial (RCT) was conducted with the aim to investigate the benefit of deploying complementary strategies, including indoor residual spraying (IRS) with pirimiphos-methyl in addition to long-lasting insecticidal nets (LLINs) in Diébougou, southwest Burkina Faso. Methods We measured the susceptibility of the Anopheles gambiae (s.l.) population from Diébougou to conventional insecticides. We further monitored the efficacy and residual activity of pirimiphos-methyl on both cement and mud walls using a laboratory susceptible strain (Kisumu) and the local An. gambiae (s.l.) population. Results An. gambiae (s.l.) from Diébougou was resistant to DDT, pyrethroids (deltamethrin, permethrin and alphacypermethrin) and bendiocarb but showed susceptibility to organophosphates (pirimiphos-methyl and chlorpyrimiphos-methyl). A mixed-effect generalized linear model predicted that pirimiphos-methyl applied on cement or mud walls was effective for 210 days against the laboratory susceptible strain and 247 days against the local population. The residual efficacy of pirimiphos-methyl against the local population on walls made of mud was similar to that of cement (OR = 0.792, [0.55–1.12], Tukey’s test p-value = 0.19). Conclusions If data on malaria transmission and malaria cases (as measured trough the RCT) are consistent with data on residual activity of pirimiphos-methyl regardless of the type of wall, one round of IRS with pirimiphos-methyl would have the potential to control malaria in a context of multi-resistant An. gambiae (s.l.) for at least 7 months.

scholarly journals Addressing key gaps in implementation of mosquito larviciding to accelerate malaria vector control in southern Tanzania: results of a stakeholder engagement process in local district councils

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Salum A. Mapua ◽  
Marceline F. Finda ◽  
Ismail H. Nambunga ◽  
Betwel J. Msugupakulya ◽  
Kusirye Ukio ◽  
...  
Keyword(s):  
Malaria Control ◽  
Public Engagement ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Production Plant ◽  
Community Members ◽  
Key Informants ◽  
Larval Source Management ◽  
Source Management

Abstract Background Larval source management was historically one of the most effective malaria control methods but is now widely deprioritized in Africa, where insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are preferred. However, in Tanzania, following initial successes in urban Dar-es-Salaam starting early-2000s, the government now encourages larviciding in both rural and urban councils nationwide to complement other efforts; and a biolarvicide production-plant has been established outside the commercial capital. This study investigated key obstacles and opportunities relevant to effective rollout of larviciding for malaria control, with a focus on the meso-endemic region of Morogoro, southern Tanzania. Methods Key-informants were interviewed to assess awareness and perceptions regarding larviciding among designated health officials (malaria focal persons, vector surveillance officers and ward health officers) in nine administrative councils (n = 27). Interviewer-administered questionnaires were used to assess awareness and perceptions of community members in selected areas regarding larviciding (n = 490). Thematic content analysis was done and descriptive statistics used to summarize the findings. Results A majority of malaria control officials had participated in larviciding at least once over the previous three years. A majority of community members had neutral perceptions towards positive aspects of larviciding, but overall support for larviciding was high, although several challenges were expressed, notably: (i) insufficient knowledge for identifying relevant aquatic habitats of malaria vectors and applying larvicides, (ii) inadequate monitoring of programme effectiveness, (iii) limited financing, and (iv) lack of personal protective equipment. Although the key-informants reported sensitizing local communities, most community members were still unaware of larviciding and its potential. Conclusions The larviciding programme was widely supported by both communities and malaria control officials, but there were gaps in technical knowledge, implementation and public engagement. To improve overall impact, it is important to: (i) intensify training efforts, particularly for identifying habitats of important vectors, (ii) adopt standard technical principles for applying larvicides or larval source management, (iii) improve financing for local implementation and (iv) improve public engagement to boost community awareness and participation. These lessons could also be valuable for other malaria endemic areas wishing to deploy larviciding for malaria control or elimination.

scholarly journals Anopheles gambiae Genome Conservation as a Resource for Rational Gene Drive Target Site Selection

Insects ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 97
Author(s):  
Nace Kranjc ◽  
Andrea Crisanti ◽  
Tony Nolan ◽  
Federica Bernardini
Keyword(s):  
Anopheles Gambiae ◽  
Data Storage ◽  
Genomic Variation ◽  
Malaria Vectors ◽  
Anopheles Coluzzii ◽  
Structural Constraints ◽  
Gene Drive ◽  
Genetic Traits ◽  
A Genome ◽  
Insight Into

The increase in molecular tools for the genetic engineering of insect pests and disease vectors, such as Anopheles mosquitoes that transmit malaria, has led to an unprecedented investigation of the genomic landscape of these organisms. The understanding of genome variability in wild mosquito populations is of primary importance for vector control strategies. This is particularly the case for gene drive systems, which look to introduce genetic traits into a population by targeting specific genomic regions. Gene drive targets with functional or structural constraints are highly desirable as they are less likely to tolerate mutations that prevent targeting by the gene drive and consequent failure of the technology. In this study we describe a bioinformatic pipeline that allows the analysis of whole genome data for the identification of highly conserved regions that can point at potential functional or structural constraints. The analysis was conducted across the genomes of 22 insect species separated by more than hundred million years of evolution and includes the observed genomic variation within field caught samples of Anopheles gambiae and Anopheles coluzzii, the two most dominant malaria vectors. This study offers insight into the level of conservation at a genome-wide scale as well as at per base-pair resolution. The results of this analysis are gathered in a data storage system that allows for flexible extraction and bioinformatic manipulation. Furthermore, it represents a valuable resource that could provide insight into population structure and dynamics of the species in the complex and benefit the development and implementation of genetic strategies to tackle malaria.

scholarly journals The regulatory genome of the malaria vector Anopheles gambiae: integrating chromatin accessibility and gene expression

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
José L Ruiz ◽  
Lisa C Ranford-Cartwright ◽  
Elena Gómez-Díaz
Keyword(s):  
Gene Expression ◽  
Transcriptional Regulation ◽  
Anopheles Gambiae ◽  
Mosquito Control ◽  
Regulatory Elements ◽  
Chromatin Accessibility ◽  
Malaria Vectors ◽  
Specific Gene ◽  
Mosquito Vector ◽  
Human Malaria

Abstract Anopheles gambiae mosquitoes are primary human malaria vectors, but we know very little about their mechanisms of transcriptional regulation. We profiled chromatin accessibility by the assay for transposase-accessible chromatin by sequencing (ATAC-seq) in laboratory-reared A. gambiae mosquitoes experimentally infected with the human malaria parasite Plasmodium falciparum. By integrating ATAC-seq, RNA-seq and ChIP-seq data, we showed a positive correlation between accessibility at promoters and introns, gene expression and active histone marks. By comparing expression and chromatin structure patterns in different tissues, we were able to infer cis-regulatory elements controlling tissue-specific gene expression and to predict the in vivo binding sites of relevant transcription factors. The ATAC-seq assay also allowed the precise mapping of active regulatory regions, including novel transcription start sites and enhancers that were annotated to mosquito immune-related genes. Not only is this study important for advancing our understanding of mechanisms of transcriptional regulation in the mosquito vector of human malaria, but the information we produced also has great potential for developing new mosquito-control and anti-malaria strategies.

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