scholarly journals Malaria Transmission, Vector Diversity, and Insecticide Resistance at a Peri-Urban Site in the Forest Zone of Ghana

2021 ◽  
Vol 2 ◽  
Author(s):  
Yaw Akuamoah-Boateng ◽  
Ruth C. Brenyah ◽  
Sandra A. Kwarteng ◽  
Patrick Obuam ◽  
Isaac Owusu-Frimpong ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Malaria Transmission ◽  
Urban Setting ◽  
World Health ◽  
Malaria Vectors ◽  
Urban Site ◽  
Human Landing Catch ◽  
Anopheles Coluzzii ◽  
Anopheles Gambiae S.S

IntroductionRecent surge of Anopheles resistance to major classes of World Health Organization (WHO)-approved insecticides globally necessitates the need for information about local malaria vector populations. It is believed that insecticide efficacy loss may lead to operational failure of control interventions and an increase in malaria infection transmission. We investigated the susceptibility levels of malaria vectors to all classes of WHO-approved vector control insecticides and described the dynamics of malaria transmission in a peri-urban setting.MethodsFit 3–5-day-old adults that emerged from Anopheles larvae collected from several different sites in the study area were subjected to the WHO bioassay for detecting insecticide resistance. The knockdown resistance gene (kdr) mutations within the vector populations were detected using PCR. Entomological inoculation rates were determined using the human landing catch technique and Plasmodium falciparum circumsporozoite ELISA.ResultsThe malaria vectors from the study area were resistant to all classes of insecticides tested. Out of the 284 Anopheles complex specimen assayed for the resistance study, 265 (93.30%) were identified as Anopheles gambiae s.s. The kdr gene was detected in 90% of the Anopheles gambiae s.s. assayed. In an area where Anopheles coluzzii resistance to insecticides had never been reported, the kdr gene was detected in 78% of the Anopheles coluzzii sampled. The entomological inoculation rate (EIR) for the dry season was 1.44 ib/m/n, whereas the EIR for the rainy season was 2.69 ib/m/n.ConclusionsThis study provides information on the high parasite inoculation rate and insecticide resistance of malaria vectors in a peri-urban community, which is critical in the development of an insecticide resistance management program for the community.

scholarly journals Phenotypic Insecticide Resistance in Anopheles gambiae (Diptera: Culicidae): Specific Characterization of Underlying Resistance Mechanisms Still Matters

2020 ◽  
Author(s):  
Adandé A Medjigbodo ◽  
Luc S Djogbenou ◽  
Aubin A Koumba ◽  
Laurette Djossou ◽  
Athanase Badolo ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Resistance Mechanisms ◽  
Malaria Vectors ◽  
Effective Control ◽  
Anopheles Coluzzii ◽  
Anopheles Gambiae S.S ◽  
Diagnostic Dose ◽  
Pirimiphos Methyl ◽  
Old Adult

Abstract An effective control of malaria vectors requires an extensive knowledge of mechanisms underlying the resistance-phenotypes developed by these vectors against insecticides. We investigated Anopheles gambiae mosquitoes from Benin and Togo for their intensity of insecticide resistance and we discussed the involvement of genotyped mechanisms in the resistance-phenotypes observed. Three- to five-day-old adult mosquitoes emerged from field and laboratory An. gambiae larvae were assayed using WHO tube intensity tests against various doses of deltamethrin: 1× (0.05%); 2× (0.1%); 5× (0.25%); 7.5× (0.375%) and those of pirimiphos-methyl: 0.5× (0.125%); 1× (0.25%). Members of An. gambiae complex were screened in field populations using polymerase chain reaction (PCR) assays. The presence of kdrR(1014F/1014S) and ace-1R(119S) mutations was also investigated using TaqMan and PCR-RFLP techniques, respectively. Anopheles gambiae from field were very resistant to deltamethrin, whereas KisKdr and AcerKdrKis strains displayed 100% mortality rates at 2× the diagnostic dose. In contrast, the field mosquitoes displayed a low resistance-intensity against 1× the diagnostic dose of pirimiphos-methyl, whereas AcerKis and AcerKdrKis strains showed susceptibility at 0.5× the diagnostic dose. Anopheles gambiae s.s., Anopheles coluzzii, and Anopheles arabiensis were identified. Allelic frequencies of kdrR (1014F) and ace-1R (119S) mutations in the field populations varied from 0.65 to 1 and 0 to 0.84, respectively. The field An. gambiae displayed high-resistance levels against deltamethrin and pirimiphos-methyl when compared with those of the laboratory An. gambiae-resistant strains. These results exhibit the complexity of underlying insecticide resistance mechanisms in these field malaria vectors.

High Levels of Knockdown Resistance in Anopheles coluzzii and Anopheles gambiae (Diptera: Culicidae), Major Malaria Vectors in Togo, West Africa: A 2011 Monitoring Report

2019 ◽  
Vol 56 (4) ◽  
pp. 1159-1164
Author(s):  
Koffi Mensah Ahadji-Dabla ◽  
Adjovi Djifa Amoudji ◽  
Seth Wolali Nyamador ◽  
Georges Yawo Apétogbo ◽  
Joseph Chabi ◽  
...  
Keyword(s):  
West Africa ◽  
Anopheles Gambiae ◽  
National Malaria Control Programme ◽  
Control Programme ◽  
World Health ◽  
Malaria Vectors ◽  
Malaria Control Programme ◽  
Anopheles Coluzzii ◽  
Knockdown Resistance ◽  
Anopheles Gambiae S.S

Abstract A survey of susceptibility to DDT, deltamethrin, bendiocarb, and chlorpyrifos-methyl was conducted in five localities in 2011 in Togo, West Africa, to assess the insecticide resistance status of Anopheles gambiae s.l. (Diptera: Culicidae). Female populations of An. gambaie s.l. emerged from collected larvae (F0) were exposed to insecticide-impregnated papers using World Health Organization test kits for adult mosquitoes; the susceptible reference strain Kisumu was used as a control. Resistance to DDT and deltamethrin was observed within the mosquito populations tested. Anopheles gambiae s.s. and Anopheles coluzzii represented the only species recorded in the study sites. The frequency of knockdown resistance (kdr L1014F) mutation determined using polymerase chain reaction diagnostic tests was lower in An. gambiae than in An. coluzzii in all of the localities except Kolokopé. Further investigations of An. gambiae s.l. resistance are needed in Togo to help the National Malaria Control Programme in vector control decision making and implementation of resistance management strategy.

scholarly journals Behavioral Responses of Pyrethroid-resistant Anopheles Gambiae Mosquitoes to Insecticide-treated Bed Net

2021 ◽  
Author(s):  
Maxwell G. Machani ◽  
Eric Ochomo ◽  
Fred Amimo ◽  
Andrew K. Githeko ◽  
Guiyun Yan ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Malaria Transmission ◽  
Malaria Vectors ◽  
Bed Net ◽  
Anopheles Gambiae S.S ◽  
Field Environment ◽  
Host Seeking ◽  
Seeking Behavior ◽  
Vector Behavior

Abstract Background: Long-lasting insecticidal nets are an effective tool in reducing malaria transmission. However, with increasing insecticide resistance little is known about how physiologically resistant malaria vectors behave around a human-occupied bed net, despite their importance in malaria transmission. We assessed the host-seeking behavior of the major malaria vector Anopheles gambiae s.s, when an intact human-occupied treated bed net is in place, with respect to their insecticide resistance status under semi-field conditions. Methods: Pyrethroid resistant and susceptible colonies of female Anopheles gambiae s.s aged 3-5 days that have been bred in our insectary, were color-marked with fluorescent powder and released inside a semi-field environment housing a hut which was occupied by a human host. Inside the hut, the occupant slept under an insecticide-treated bed net trap or untreated bed net trap. The window exit trap was installed to catch mosquitoes exiting the hut. A prokopack aspirator was used to collect indoor and outdoor resting mosquitoes in the morning. Clay pots were placed outside the hut to collect mosquitoes resting outdoors. Results: The proportion of resistant mosquitoes caught in the treated bed net trap was higher 43% (95% CI= [40.6-45.3]) compared to the susceptible mosquitoes 28.3% (OR=1.445; P<0.00019). The proportion of susceptible mosquitoes caught in the untreated bed net trap was higher 51.3% (95% CI= [48.8-53.6]) compared to the treated bed net trap 28.3% (95% CI= [26.3-30.5]) (OR=2.65; P<0.0001). Resistant mosquitoes were less likely to exit the house when a treated bed net was present (5.2%; 95% CI= [4.2-6.4]) compared to the susceptible mosquitoes (11.5%; 95% CI= [9.6-12.6]). The proportion of susceptible mosquitoes avoiding contact with the treated bed net and caught resting indoors in the hut (53.8%) and outdoors (64.5%) was higher compared to the resistant mosquitoes (indoors: 46.2%, outdoor: 35.4%). The susceptible females were 2.3 times more likely to stay outdoors away from the treated bed net (OR=2.25; 95% CI= [1.7-2.9]; P<0.0001).Conclusion: The results show that in the presence of a treated net, the host-seeking performance was not altered for the resistant mosquitoes, unlike the susceptible females that were observed to exit the house and remained outdoors when a treated net was used. However, further investigations of the behavior of resistant mosquitoes under natural conditions should be undertaken to confirm these observations and improve the current intervention which are threatened by insecticide resistance and altered vector behavior.

scholarly journals Evaluation of the interaction between insecticide resistance-associated genes and malaria transmission in Anopheles gambiae sensu lato in central Côte d’Ivoire

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Rosine Z. Wolie ◽  
Alphonsine A. Koffi ◽  
Ludovic P. Ahoua Alou ◽  
Eleanore D. Sternberg ◽  
Oulo N’Nan-Alla ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Malaria Transmission ◽  
Vector Competence ◽  
Quantitative Polymerase Chain Reaction ◽  
Sub Saharan Africa ◽  
Human Landing Catch ◽  
Anopheles Coluzzii ◽  
Metabolic Resistance ◽  
The Impact

Abstract Background There is evidence that the knockdown resistance gene (Kdr) L1014F and acetylcholinesterase-1 gene (Ace-1R) G119S mutations involved in pyrethroid and carbamate resistance in Anopheles gambiae influence malaria transmission in sub-Saharan Africa. This is likely due to changes in the behaviour, life history and vector competence and capacity of An. gambiae. In the present study, performed as part of a two-arm cluster randomized controlled trial evaluating the impact of household screening plus a novel insecticide delivery system (In2Care Eave Tubes), we investigated the distribution of insecticide target site mutations and their association with infection status in wild An. gambiae sensu lato (s.l.) populations. Methods Mosquitoes were captured in 40 villages around Bouaké by human landing catch from May 2017 to April 2019. Randomly selected samples of An. gambiae s.l. that were infected or not infected with Plasmodium sp. were identified to species and then genotyped for Kdr L1014F and Ace-1R G119S mutations using quantitative polymerase chain reaction assays. The frequencies of the two alleles were compared between Anopheles coluzzii and Anopheles gambiae and then between infected and uninfected groups for each species. Results The presence of An. gambiae (49%) and An. coluzzii (51%) was confirmed in Bouaké. Individuals of both species infected with Plasmodium parasites were found. Over the study period, the average frequency of the Kdr L1014F and Ace-1R G119S mutations did not vary significantly between study arms. However, the frequencies of the Kdr L1014F and Ace-1R G119S resistance alleles were significantly higher in An. gambiae than in An. coluzzii [odds ratio (95% confidence interval): 59.64 (30.81–131.63) for Kdr, and 2.79 (2.17–3.60) for Ace-1R]. For both species, there were no significant differences in Kdr L1014F or Ace-1R G119S genotypic and allelic frequency distributions between infected and uninfected specimens (P > 0.05). Conclusions Either alone or in combination, Kdr L1014F and Ace-1R G119S showed no significant association with Plasmodium infection in wild An. gambiae and An. coluzzii, demonstrating the similar competence of these species for Plasmodium transmission in Bouaké. Additional factors including behavioural and environmental ones that influence vector competence in natural populations, and those other than allele measurements (metabolic resistance factors) that contribute to resistance, should be considered when establishing the existence of a link between insecticide resistance and vector competence. Graphical Abstract

scholarly journals Rapid high throughput SYBR green assay for identifying the malaria vectors Anopheles arabiensis, Anopheles coluzzii and Anopheles gambiae s.s. Giles

PLoS ONE ◽  
2019 ◽  
Vol 14 (4) ◽  
pp. e0215669 ◽  
Author(s):  
Joseph Chabi ◽  
Arjen Van’t Hof ◽  
Louis K. N’dri ◽  
Alex Datsomor ◽  
Dora Okyere ◽  
...  
Keyword(s):  
Anopheles Gambiae ◽  
High Throughput ◽  
Anopheles Arabiensis ◽  
Sybr Green ◽  
Malaria Vectors ◽  
Anopheles Coluzzii ◽  
Anopheles Gambiae S.S ◽  
Sybr Green Assay

scholarly journals Effect of bendiocarb based (Ficam® 80% WP) Indoor Residual Spraying on feeding patterns from malaria vectors in Burkina Faso, West Africa.

2020 ◽  
Author(s):  
Sawdetuo Aristide HIEN ◽  
Dieudonné Diloma Soma ◽  
Simon Pengwende Sawadogo ◽  
Serge Bèwadéyir Poda ◽  
Moussa Namountougou ◽  
...  
Keyword(s):  
Burkina Faso ◽  
Anopheles Gambiae ◽  
Malaria Transmission ◽  
Malaria Vector ◽  
Indoor Residual Spraying ◽  
Transmission Risk ◽  
Malaria Vectors ◽  
Anopheles Coluzzii ◽  
Transmission Season ◽  
Density Methods

Abstract Background The fight against vector is essential in malaria prevention strategies in several endemic countries in Africa. In Burkina Faso, malaria transmission is seasonal in most parts of country, so a single round of spraying should provide effective protection against malaria, provided the insecticide remains effective over the entire malaria transmission season. The outcomes of indoor residual spraying towards curtailing malaria transmission are firstly to decrease the life span of vector mosquitoes and also to reduce the malaria vectors density. Methods CDC light trap and early morning collections by pyrethrum spray catches were performed monthly to determine the change in malaria vector indices in sprayed (Diebougou) and unsprayed sites (Dano). The female’s malaria vectors collected by both methods were used to determine their blood feeding, biting and sporozoites rate and malaria transmission risk estimated by entomological inoculation rate. Results Anopheles gambiae complex composed to Anopheles gambiae, Anopheles coluzzii and Anopheles arabiensis were present throughout the transmission season, but An. gambiae was the predominant species collected (P =0.0005), comprising 88% of the total collected and the most infected species. Malaria vectors densities were significantly lower in sprayed villages (n=4,303) compared with unsprayed villages (n=12,569) during post-spraying period (P = 0.0012). In addition, mean human biting rate of An. gambiae sl and An . funestus ss were significantly lower in sprayed areas compared to unsprayed areas (P<0.05). Overall, malaria vector transmission risk was significant lower in villages which received IRS (P=0.0001) whatever the malaria vectors species ( An. gambiae sl and An. funestus ss). Conclusions The results showed that in the sprayed area (Diebougou), vector densities, human biting rates and malaria transmission risks were very lower than unsprayed areas (Dano). The findings also showed a change in vector behavior especially within An. funestus which became more zoophagic following IRS. The indoor residual spraying could be recommanded as control tool in areas where malaria transmission occured a given period of year.

scholarly journals Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Polius G. Pinda ◽  
Claudia Eichenberger ◽  
Halfan S. Ngowo ◽  
Dickson S. Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Pyrethroid Resistance ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
World Health ◽  
Malaria Vectors ◽  
South Eastern

Abstract Background Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used. Methods The study used the World Health Organization (WHO) assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from three villages across two districts in south-eastern Tanzania and included four insecticide classes. Findings At baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (> 98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%. Conclusions In south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

scholarly journals Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania

2020 ◽  
Author(s):  
Polius Gerazi Pinda ◽  
Claudia Eichenberger ◽  
Halfan S Ngowo ◽  
Dickson S Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Pyrethroid Resistance ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
World Health ◽  
Malaria Vectors ◽  
South Eastern

Abstract BackgroundLong-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used.MethodsThe study used the World Health Organization (WHO) assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from three villages across two districts in south-eastern Tanzania and included four insecticide classes.FindingsAt baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (>98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%.ConclusionsIn south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

scholarly journals Insecticide Resistance Profiling of Anopheles coluzzii and Anopheles gambiae Populations in the Southern Senegal: Role of Target Sites and Metabolic Resistance Mechanisms

Genes ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1403
Author(s):  
Oumou. K. Gueye ◽  
Magellan Tchouakui ◽  
Abdoulaye K. Dia ◽  
Mouhamed B. Faye ◽  
Amblat A. Ahmed ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Resistance Mechanisms ◽  
Target Site ◽  
World Health ◽  
Anopheles Coluzzii ◽  
Partial Recovery ◽  
Metabolic Resistance ◽  
Genes Expression ◽  
Main Target

The emergence and spread of insecticide resistance among the main malaria vectors is threatening the effectiveness of vector control interventions in Senegal. The main drivers of this resistance in the Anopheles gambiae complex (e.g., An. gambiae and Anopheles coluzzii) remains poorly characterized in Senegal. Here we characterized the main target site and metabolic resistances mechanisms among the An. gambiae and An. coluzzii populations from their sympatric and allopatric or predominance area in Senegal. Larvae and pupae of An. gambiae s.l. were collected, reared to adulthood, and then used for insecticides susceptibility and synergist assays using the WHO (World Health Organisation) test kits for adult mosquitoes. The TaqMan method was used for the molecular characterization of the main target site insecticide resistance mechanisms (Vgsc-1014F, Vgsc-1014S, N1575Y and G119S). A RT-qPCR (Reverse Transcriptase-quantitative Polymerase Chaine Reaction) was performed to estimate the level of genes expression belonging to the CYP450 (Cytochrome P450) family. Plasmodium infection rate was investigated using TaqMan method. High levels of resistance to pyrethroids and DDT and full susceptibility to organophosphates and carbamates where observed in all three sites, excepted a probable resistance to bendiocarb in Kedougou. The L1014F, L1014S, and N1575Y mutations were found in both species. Pre-exposure to the PBO (Piperonyl butoxide) synergist induced a partial recovery of susceptibility to permethrin and full recovery to deltamethrin. Subsequent analysis of the level of genes expression, revealed that the CYP6Z1 and CYP6Z2 genes were over-expressed in wild-resistant mosquitoes compared to the reference susceptible strain (Kisumu), suggesting that both the metabolic resistance and target site mutation involving kdr mutations are likely implicated in this pyrethroid resistance. The presence of both target-site and metabolic resistance mechanisms in highly pyrethroid-resistant populations of An. gambiae s.l. from Senegal threatens the effectiveness and the sustainability of the pyrethroid-based tools and interventions currently deployed in the country. The Kdr-west mutation is widely widespread in An. coluzzii sympatric population. PBO or Duo nets and IRS (Indoor Residual Spraying) with organophosphates could be used as an alternative measure to sustain malaria control in the study area.

Sign in / Sign up

Export Citation Format

Share Document