Introduction: A recent study in Kenya highlighted a promising advance in malaria control by demonstrating that infecting mosquitoes with the endosymbiont Microsporidia MB blocks Plasmodium transmission. However, the i...Introduction: A recent study in Kenya highlighted a promising advance in malaria control by demonstrating that infecting mosquitoes with the endosymbiont Microsporidia MB blocks Plasmodium transmission. However, the influence of biotic and abiotic factors such as diet, relative humidity (RH) and temperature on this infection remains poorly studied. This study, aimed to gain a better understanding of this relationship. Methods: To highlight the influence of diet quantity, we defined a range of 3 quantities: 0.00375 g, 0.015 g and 0.09 g. Each quantity was tested on two groups of larvae: a group of 150 larvae infected with Microsporidia MB (MB+), and a group of 150 larvae not infected with Microsporidia MB (MB−) (control group), each divided into three replicates of 50 larvae. Each replicate was fed each morning with the assigned quantity until the pupal stage. In addition to this factor, we investigated the influence of temperature and RH. We defined three temperature-RH combinations: 21˚C-80% RH, 39˚C-50% RH, and 27˚C-75% RH. Each combination was tested on two groups of larvae: a group of 150 MB+ larvae and a group of 150 MB− larvae, each divided into three replicates of 50 larvae. Each replicate was subjected to the assigned combination until pupation. Pupae that had reached the adult stage were tested by PCR to determine their Microsporidia MB infection status for each factor studied. Results: The results showed that only the lowest quantity (0.00375 g) significantly reduced the prevalence of Microsporidia MB compared with the medium quantity (chi-2 test, χ2 = 4.9088, df = 1, p = 0.02672) and the high quantity (chi-2 test, χ2 = 4.7958, df = 1, p = 0.02853). As for temperature and RH, the combination 39˚C-50% RH led to a significant reduction in the prevalence of Microsporidia MB compared with the combination 27˚C-75% RH (chi-2 test, χ2 = 6.3736, ddl = 1, p = 0.01158) and that 21˚C-80% RH (chi-2 test, χ2 = 9.983, ddl = 1, p = 0.00158). Conclusion: This work contributes to a better understanding of some key factors linked to Microsporidia MB infection in mosquitoes. However, further research on several generations is necessary to draw more comprehensive conclusions.展开更多
Malaria incidence in urban areas has generally been low compared to rural areas but recent data indicate that urban malaria remains a public health problem. It is therefore important to understand the factors that pro...Malaria incidence in urban areas has generally been low compared to rural areas but recent data indicate that urban malaria remains a public health problem. It is therefore important to understand the factors that promote urban malaria to help formulate future vector control strategies. This study compared Anopheles gambiae s.l. (A. gambiae s.l.) species composition, distribution and insecticide resistance mechanisms between vegetable and non-vegetable growing areas in Accra Metropolis. Four sites were selected within the city of Accra which comprised of two vegetable-growing and two non-vegetable growing areas. WHO susceptibility tests were carried out on adults A. gambiae s.l. reared from larvae collected from the sites. Five insecticides were tested and the A. gambiae complex, resistance genotypes and enzyme activities of each population were characterized. All A. gambiae s.l. populations tested were resistant to all the insecticides, but relatively lower mortalities were observed in the vegetable growing areas. The mortality against 0.05% deltamethrin was 2.6% (Opeibea) and 12.5% (Korle-Bu) for the vegetable growing areas and 36.2% (Achimota) and 38.9% (Mataheko) in the non-vegetable growing areas. Anopheles gambiae s.s. (95% of Opeibea population) and Anopheles coluzzii, (98% of Korle-Bu population) were the dominant species in the vegetable growing areas. The voltage-gated sodium channel (Vgsc-1014F) frequencies of all the populations were similar but the acetylcholinesterase (ace-1) frequencies were significantly lower (p A. gambiae s.l. from Opeibea than from the other areas. The contribution of urban agriculture in the development of insecticide resistance needs to be considered in the formulation of future vector control strategies alongside other domestic usages.展开更多
Resistance to currently available insecticides in the major malaria vectors like Anopheles coluzzii is seriously reducing the effectiveness of core vector control tools. Overexpression of ATP binding cassette transpor...Resistance to currently available insecticides in the major malaria vectors like Anopheles coluzzii is seriously reducing the effectiveness of core vector control tools. Overexpression of ATP binding cassette transporters (ABC transporters) has been implicated in insecticides resistance in the major malaria vector Anopheles funestus and An. gambiae. To identify the potential role of ABC transporters in pyrethroids resistance in this work, we use verapamil-a p-glycoprotein inhibitor in a synergist bioassay with pyrethroids on one An. coluzzii populations from northern Nigeria. Genomic DNA extraction and SINE 200 PCR established that the Anopheles s. l. from Auyo, Jigawa State was An. coluzzii. Pre-exposure to verapamil followed by Permethrin results in 0.12% knockdown after 1 hour exposure and 10.7% mortality after 24 hours, which was higher than that for permethrin alone, but not statistically significant. This bioassay result reveals that ABC transporters possibly do not contribute to the resistance.展开更多
Anopheles gambiae and Anopheles coluzzii are closely related species that are predominant vectors of malaria in Africa.Recently,A.gambiae form M was renamed A.coluzzii and we now conclude on the basis of a diagnostic ...Anopheles gambiae and Anopheles coluzzii are closely related species that are predominant vectors of malaria in Africa.Recently,A.gambiae form M was renamed A.coluzzii and we now conclude on the basis of a diagnostic PCR-restriction fragment length polymorphism assay that Ag55 cells were derived from A.coluzzii.We established an Ag55 cell transcriptome,and KEGG pathway analysis showed that Ag55 cells are enriched in phagosome pathway transcripts.The Ag55 transcriptome has an abundance of specific transcripts characteristic of mosquito hemocytes.Functional E.coli bioparticle uptake experiments visualized by fluorescence microscopy and confocal microscopy and quantified by flow cytometry establish the phagocytic competence of Ag55 cells.Results from this investigation of Ag55 cell properties will guide researchers in the use and engineering of the Ag55 cell line to better enable investigations of Plasmodium,other microbes,and insecticidal toxins.展开更多
Background:The Sahel region of Chad Republic is a prime candidate for malaria pre-elimination.To facilitate preelimination efforts in this region,two populations o f A nopheles coluzzii from Central Chad Republic were...Background:The Sahel region of Chad Republic is a prime candidate for malaria pre-elimination.To facilitate preelimination efforts in this region,two populations o f A nopheles coluzzii from Central Chad Republic were characterized,their insecticide resistance profile and the possible molecular mechanisms driving the resistance in the field investigated.Methods:Bloodfed female Anopheles gom biae s.l.resting indoor,were collected at N'djamena and Massakory,Chad in 2018 and characterized for species composition,and infection rate was determined using the TaqMan assay.Susceptibility to various insecticides was assessed using WHO tube bioassays.Cone bioassays were conducted using various long-lasting insecticidal nets(LLINs).Results were analysed using Chi Square test.Knockdown resistance(kdr)and ace-1 markers were investigated by TaqMan genotyping.Results:Anopheles coluzzi was the major vector found in N’djamena(100%)and Massakory(〜94%).N〇Plasm odium was found in 147 bloodfed F0 An.coluzzii(82 from N'djamena and 65 from Massakory).High intensity pyrethroid resistance was observed with mortalities of<2%for permethrin,deltamethrin and etofenprox,and with<50%and<60%dead following exposure to 10x diagnostic doses of deltamethrin and permethrin,respectively.For both sites,<10%mortalities were observed with DDT.Synergist bioassays with piperonylbutoxide significantly recovered pyrethroid susceptibility in Massakory populations,implicating CYP450s(mortality=13.6%for permethrin,X^2=22.8,df=1,P=0.0006;mortality=13.0%for deltamethrin,x2:8.8,df=1,P<0.00031).Cone-bioassays established complete loss of efficacy of the pyrethroid-based LLINs;and a 100%recovery of susceptibility following exposure to the roof of PermaNet®3.0/containing piperonylbutoxide.Both populations were susceptible to malathion,but high bendiocarb resistance was observed in Massakory population.The absence o f a ce-1 mutation points to the role of metabolic resistance in the bendiocarb resistance.Both 1014F and 1014S mutations were found in both populations at around 60%and<20%respectively.Sequencing of intron-1 of the voltage-gated sodium channel revealed a low genetic diversity suggesting reduced polymorphism.Conclusions:Multiple resistance in An.coluzzii populations from Chad highlight challenges associated with deployment of LLINs and indoor residual spraying(IRS)in the Sahel of this country.The pyrethroid-synergists LLINs(e.g.PermaNet®3.0)and organophosphate-based IRS maybe the alternatives for malaria control in this region.展开更多
Background:The wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species.Thus,the agricultural use of insecticide targeting other pests may select for insecticide re...Background:The wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species.Thus,the agricultural use of insecticide targeting other pests may select for insecticide resistance in malaria mosquitoes.The purpose of this study is to clarify some knowledge gaps on the role of agrochemicals in the development of insecticide resistance in malaria vectors is of utmost importance for vector control.Methods:Using the CDC bottle test and the log-probit analysis,we investigated for the first time the resistance levels ofAnopheles coluzzii mosquitoes to neonicotinoids,insecticides used exclusively for crop protection in C?te d’Ivoire.The study was conducted in two agricultural regions(Tiassale and Gagnoa)and one non-agricultural region(Vitre)between June and August 2017 using clothianidin,acetamiprid and imidacloprid.Results:Mosquito populations from Tiassale and Gagnoa(agricultural settings)were determined to be resistant to acetamiprid with mortality rates being<85%at 24 h post-exposure.In Vitre(non-agricultural area)however,the mosquito population was susceptible to acetamiprid.In all three localities,mosquito populations were resistant to imidacloprid(mortality rates were 60%in Vitre,37%in Tiassale,and 13%in Gagnoa)and completely susceptible to clothianidin(100%mortality).An.coluzzii represented 100%of mosquito collected in Gagnoa,86%in Tiassale and 96%in Vitre.Conclusions:This study provides strong evidence that agricultural use of insecticides can cause insecticide resistance in malaria vector populations.Insecticide resistance driven by agrochemical usage should be considered when vector control strategies are developed.展开更多
文摘Introduction: A recent study in Kenya highlighted a promising advance in malaria control by demonstrating that infecting mosquitoes with the endosymbiont Microsporidia MB blocks Plasmodium transmission. However, the influence of biotic and abiotic factors such as diet, relative humidity (RH) and temperature on this infection remains poorly studied. This study, aimed to gain a better understanding of this relationship. Methods: To highlight the influence of diet quantity, we defined a range of 3 quantities: 0.00375 g, 0.015 g and 0.09 g. Each quantity was tested on two groups of larvae: a group of 150 larvae infected with Microsporidia MB (MB+), and a group of 150 larvae not infected with Microsporidia MB (MB−) (control group), each divided into three replicates of 50 larvae. Each replicate was fed each morning with the assigned quantity until the pupal stage. In addition to this factor, we investigated the influence of temperature and RH. We defined three temperature-RH combinations: 21˚C-80% RH, 39˚C-50% RH, and 27˚C-75% RH. Each combination was tested on two groups of larvae: a group of 150 MB+ larvae and a group of 150 MB− larvae, each divided into three replicates of 50 larvae. Each replicate was subjected to the assigned combination until pupation. Pupae that had reached the adult stage were tested by PCR to determine their Microsporidia MB infection status for each factor studied. Results: The results showed that only the lowest quantity (0.00375 g) significantly reduced the prevalence of Microsporidia MB compared with the medium quantity (chi-2 test, χ2 = 4.9088, df = 1, p = 0.02672) and the high quantity (chi-2 test, χ2 = 4.7958, df = 1, p = 0.02853). As for temperature and RH, the combination 39˚C-50% RH led to a significant reduction in the prevalence of Microsporidia MB compared with the combination 27˚C-75% RH (chi-2 test, χ2 = 6.3736, ddl = 1, p = 0.01158) and that 21˚C-80% RH (chi-2 test, χ2 = 9.983, ddl = 1, p = 0.00158). Conclusion: This work contributes to a better understanding of some key factors linked to Microsporidia MB infection in mosquitoes. However, further research on several generations is necessary to draw more comprehensive conclusions.
文摘Malaria incidence in urban areas has generally been low compared to rural areas but recent data indicate that urban malaria remains a public health problem. It is therefore important to understand the factors that promote urban malaria to help formulate future vector control strategies. This study compared Anopheles gambiae s.l. (A. gambiae s.l.) species composition, distribution and insecticide resistance mechanisms between vegetable and non-vegetable growing areas in Accra Metropolis. Four sites were selected within the city of Accra which comprised of two vegetable-growing and two non-vegetable growing areas. WHO susceptibility tests were carried out on adults A. gambiae s.l. reared from larvae collected from the sites. Five insecticides were tested and the A. gambiae complex, resistance genotypes and enzyme activities of each population were characterized. All A. gambiae s.l. populations tested were resistant to all the insecticides, but relatively lower mortalities were observed in the vegetable growing areas. The mortality against 0.05% deltamethrin was 2.6% (Opeibea) and 12.5% (Korle-Bu) for the vegetable growing areas and 36.2% (Achimota) and 38.9% (Mataheko) in the non-vegetable growing areas. Anopheles gambiae s.s. (95% of Opeibea population) and Anopheles coluzzii, (98% of Korle-Bu population) were the dominant species in the vegetable growing areas. The voltage-gated sodium channel (Vgsc-1014F) frequencies of all the populations were similar but the acetylcholinesterase (ace-1) frequencies were significantly lower (p A. gambiae s.l. from Opeibea than from the other areas. The contribution of urban agriculture in the development of insecticide resistance needs to be considered in the formulation of future vector control strategies alongside other domestic usages.
文摘Resistance to currently available insecticides in the major malaria vectors like Anopheles coluzzii is seriously reducing the effectiveness of core vector control tools. Overexpression of ATP binding cassette transporters (ABC transporters) has been implicated in insecticides resistance in the major malaria vector Anopheles funestus and An. gambiae. To identify the potential role of ABC transporters in pyrethroids resistance in this work, we use verapamil-a p-glycoprotein inhibitor in a synergist bioassay with pyrethroids on one An. coluzzii populations from northern Nigeria. Genomic DNA extraction and SINE 200 PCR established that the Anopheles s. l. from Auyo, Jigawa State was An. coluzzii. Pre-exposure to verapamil followed by Permethrin results in 0.12% knockdown after 1 hour exposure and 10.7% mortality after 24 hours, which was higher than that for permethrin alone, but not statistically significant. This bioassay result reveals that ABC transporters possibly do not contribute to the resistance.
基金The project was supported by the University of Georgia College of Agricultureand Environmental Sciences.
文摘Anopheles gambiae and Anopheles coluzzii are closely related species that are predominant vectors of malaria in Africa.Recently,A.gambiae form M was renamed A.coluzzii and we now conclude on the basis of a diagnostic PCR-restriction fragment length polymorphism assay that Ag55 cells were derived from A.coluzzii.We established an Ag55 cell transcriptome,and KEGG pathway analysis showed that Ag55 cells are enriched in phagosome pathway transcripts.The Ag55 transcriptome has an abundance of specific transcripts characteristic of mosquito hemocytes.Functional E.coli bioparticle uptake experiments visualized by fluorescence microscopy and confocal microscopy and quantified by flow cytometry establish the phagocytic competence of Ag55 cells.Results from this investigation of Ag55 cell properties will guide researchers in the use and engineering of the Ag55 cell line to better enable investigations of Plasmodium,other microbes,and insecticidal toxins.
基金A Wellcome Trust International Training Fellowship in Public Health and Tropical Medicine (WT201918/Z/16/Z)to SSI supported this work.
文摘Background:The Sahel region of Chad Republic is a prime candidate for malaria pre-elimination.To facilitate preelimination efforts in this region,two populations o f A nopheles coluzzii from Central Chad Republic were characterized,their insecticide resistance profile and the possible molecular mechanisms driving the resistance in the field investigated.Methods:Bloodfed female Anopheles gom biae s.l.resting indoor,were collected at N'djamena and Massakory,Chad in 2018 and characterized for species composition,and infection rate was determined using the TaqMan assay.Susceptibility to various insecticides was assessed using WHO tube bioassays.Cone bioassays were conducted using various long-lasting insecticidal nets(LLINs).Results were analysed using Chi Square test.Knockdown resistance(kdr)and ace-1 markers were investigated by TaqMan genotyping.Results:Anopheles coluzzi was the major vector found in N’djamena(100%)and Massakory(〜94%).N〇Plasm odium was found in 147 bloodfed F0 An.coluzzii(82 from N'djamena and 65 from Massakory).High intensity pyrethroid resistance was observed with mortalities of<2%for permethrin,deltamethrin and etofenprox,and with<50%and<60%dead following exposure to 10x diagnostic doses of deltamethrin and permethrin,respectively.For both sites,<10%mortalities were observed with DDT.Synergist bioassays with piperonylbutoxide significantly recovered pyrethroid susceptibility in Massakory populations,implicating CYP450s(mortality=13.6%for permethrin,X^2=22.8,df=1,P=0.0006;mortality=13.0%for deltamethrin,x2:8.8,df=1,P<0.00031).Cone-bioassays established complete loss of efficacy of the pyrethroid-based LLINs;and a 100%recovery of susceptibility following exposure to the roof of PermaNet®3.0/containing piperonylbutoxide.Both populations were susceptible to malathion,but high bendiocarb resistance was observed in Massakory population.The absence o f a ce-1 mutation points to the role of metabolic resistance in the bendiocarb resistance.Both 1014F and 1014S mutations were found in both populations at around 60%and<20%respectively.Sequencing of intron-1 of the voltage-gated sodium channel revealed a low genetic diversity suggesting reduced polymorphism.Conclusions:Multiple resistance in An.coluzzii populations from Chad highlight challenges associated with deployment of LLINs and indoor residual spraying(IRS)in the Sahel of this country.The pyrethroid-synergists LLINs(e.g.PermaNet®3.0)and organophosphate-based IRS maybe the alternatives for malaria control in this region.
文摘Background:The wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species.Thus,the agricultural use of insecticide targeting other pests may select for insecticide resistance in malaria mosquitoes.The purpose of this study is to clarify some knowledge gaps on the role of agrochemicals in the development of insecticide resistance in malaria vectors is of utmost importance for vector control.Methods:Using the CDC bottle test and the log-probit analysis,we investigated for the first time the resistance levels ofAnopheles coluzzii mosquitoes to neonicotinoids,insecticides used exclusively for crop protection in C?te d’Ivoire.The study was conducted in two agricultural regions(Tiassale and Gagnoa)and one non-agricultural region(Vitre)between June and August 2017 using clothianidin,acetamiprid and imidacloprid.Results:Mosquito populations from Tiassale and Gagnoa(agricultural settings)were determined to be resistant to acetamiprid with mortality rates being<85%at 24 h post-exposure.In Vitre(non-agricultural area)however,the mosquito population was susceptible to acetamiprid.In all three localities,mosquito populations were resistant to imidacloprid(mortality rates were 60%in Vitre,37%in Tiassale,and 13%in Gagnoa)and completely susceptible to clothianidin(100%mortality).An.coluzzii represented 100%of mosquito collected in Gagnoa,86%in Tiassale and 96%in Vitre.Conclusions:This study provides strong evidence that agricultural use of insecticides can cause insecticide resistance in malaria vector populations.Insecticide resistance driven by agrochemical usage should be considered when vector control strategies are developed.
