Background:Aedes borne viral diseases,notably dengue,are increasingly reported in Cameroon with Aedes aegypti being a major vector.Data on insecticide resistance of this vector and underlying mechanisms needed for out...Background:Aedes borne viral diseases,notably dengue,are increasingly reported in Cameroon with Aedes aegypti being a major vector.Data on insecticide resistance of this vector and underlying mechanisms needed for outbreak preparedness remain scarce in Cameroon.Here,we present the nationwide distribution of insecticide resistance in Ae.aegypti and investigate the potential resistance mechanisms involved.Methods::Immature stages of Ae.aegypti were collected between March and July 2017 in 13 locations across Cameroon and reared until G1/G2/G3 generation.Larval,adult bioassays,and piperonyl butoxide(PBO)synergist assays were carried out according to World Health Organization guidelines.F1534C mutation was genotyped using allele specific polymerase chain reaction in field collected adults(Go)and the polymorphism of the sodium channel gene was assessed.Theχ2 test was used to compare the mortality rate between bioassays with insecticides only and bioassays after preexposure to PBO synergist.Results:Larval bioassay revealed that all the three populations tested with temephos were susceptible.Adult bioassays showed a good level of susceptibility toward both pyrethroids tested,0.25%permethrin and 0.05%deltamethrin,with six out of 10 populations susceptible.However,two populations(Douala and Edéa)were resistant(deltamethrin[73.2–92.5%mortality],permethrin[2.6–76.3%mortality]).The resistance to 4%dichlorodiphenyltrichloroethane was observed in four out of 10 populations tested(16.8–87.1%mortality).Resistance was also reported to carbamates including 0.1%propoxur(60.8–87.1%mortality)and to 0.1%bendiocarb(82.9%mortality).All populations tested were fully susceptible to 1%fenitrothion.A partial recovery of susceptibility was observed in the pyrethroid resistant population of Douala after pre-exposed to PBO suggesting the implication of cytochrome P450 monoxygenases permethrin resistance.Genotyping and sequencing detected the F1534C kdr mutation in the two pyrethroid resistant locations of Edéa and Douala,with allelic frequency of 3.3%and 33.3%respectively.However,the high genetic diversity of the sodium channel gene supports the recent introduction of this mutation in Cameroon.Conclusions:This study revealed the contrasting resistance profiles to insecticides of Ae.aegypti populations in Cameroon suggesting that,instead of a unique nationwide control approach,a regionally adapted strategy will be needed to control this vector.The localised distribution of the F1534C kdr mutation supports this region-specific control strategy.展开更多
Background:Arboviral disease transmitted by Aedes albopictus such as dengue fever is an important threat to human health.Pyrethroid resistance raises a great challenge for mosquito control.A systematic assessment of A...Background:Arboviral disease transmitted by Aedes albopictus such as dengue fever is an important threat to human health.Pyrethroid resistance raises a great challenge for mosquito control.A systematic assessment of Ae.albopictus resistance status in China is urgently needed,and the study of correlation between pyrethroid resistance and knockdown resistance(kdr)mutations would provide information to guide the control of the Ae.albopictus vector.Methods:Five field populations of Ae.albopictus were collected from Jinan(JN),Hangzhou(HZ),Baoshan(BS),Yangpu(YP)and Haikou(HK),China in 2017.Insecticide-impregnated papers were prepared with four pyrethroid chemicals,deltamethrin,permethrin,beta-cypermethrin and lambda-cyhalothrin.The susceptibility of Ae.albopictus to pyrethroids was tested by the WHO tube assay.Kdr mutations were identified by PCR and sequencing.Moreover,the correlation analysis between kdr alleles and pyrethroid resistance was performed.Results:All five populations of Ae.albopictus showed resistance to four pyrethroid insecticides.One kdr mutant allele at codon 1532 and three at 1534 were detected with frequency of 5.33%(I1532T),44.20%(F1534S),1.83%(F1534 L)and 0.87%(F1534C),respectively.Both 1532 and 1534 mutation mosquitoes were found in the BS and YP populations.Allele I1532T was negatively correlated with deltamethrin resistance phenotype(OR<1),while F1534S mutation was positively correlated with deltamethrin and permethrin resistance(OR>1).Conclusions:The five field populations of Ae.albopictus adults were all resistant to deltamethrin,permethrin,betacypermethrin and lambda-cyhalothrin.Mutant F1534S was clearly associated with pyrethroid resistance phenotype in Ae.albopictus and this could be developed as a molecular marker to monitor the pyrethroid resistance problem in China.展开更多
Objective: To evaluate the deltamethrin pyrethroid insecticides against Anopheles labranchiae, potential malaria vector in Tunisia.Methods: Six field populations of Anopheles labranchiae mosquitoes were collected from...Objective: To evaluate the deltamethrin pyrethroid insecticides against Anopheles labranchiae, potential malaria vector in Tunisia.Methods: Six field populations of Anopheles labranchiae mosquitoes were collected from six localities in Northern and Central Tunisia between October and November 2016.Different bioassays were performed to estimate the level of resistance in each collected population. Two synergists were used to estimate the involvement of detoxification enzymes in insecticide resistance.Results: All studied strains were resistant and the RR50 ranged from 12.5 in sample #1 to72.5 in sample #6. Synergist tests using piperonyl butoxide indicated the involvement of monoxygenases enzymes in the recorded resistance. In contrast, the increase of deltamethrin mortality was not significant in presence of S,S,sributyl phosphorothioate(0.8 < SR < 1.2), suggesting no role of esterases(and/or GST) in the resistance phenotype. The correlation recorded between mortality due to DDT and the LC50 of deltamethrin insecticide indicated an insensitive sodium channel affected by Kdr mutation(Spearman rank correlation, r =-0.59, P < 0.01).Conclusions: These results should be considered in the current mosquitoes control programs in Tunisia. The use of pesticides and insecticides by both agricultural and public health departments in Tunisia should be more rational to reduce the development of resistance in populations. Different insecticide applications should be implemented alternately.展开更多
Insecticide resistance in Panonychus citri is a major obstacle to mite control in citrus orchards.Pyrethroid insecticides are continually used to control mites in China,although resistance to pyrethroids has evolved i...Insecticide resistance in Panonychus citri is a major obstacle to mite control in citrus orchards.Pyrethroid insecticides are continually used to control mites in China,although resistance to pyrethroids has evolved in some populations.Here,the resistance to the pyrethroid fenpropathrin was investigated and 7 out of 8 field-collected populations of P citri exhibited a high level of resistance,ranging from 171-fold to 15391-fold higher than the susceptible(SS)comparison strain.Three voltage-gated sodium channel(VGSC)mutations were identified in the tested populations:L1031V,F1747L,and F17511.Amplicon sequencing was used to evaluate the frequency of these mutations in the 19 field populations.L1031V and F1751I were present in all populations at frequencies of 11.6%-82.1%and 0.5%-31.8%,respectively,whereas the F1747L mutation was only present in 12 populations from Chongqing,Sichuan,Guangxi,and Yunnan provinces.Introduction of these mutations singly or in combination into transgenic flies significantly increased their resistance to fenpropathrin and these flies also exhibited reduced mortality after exposure to the pyrethroids permethrin andβ-cypermethrin.Panonychus citri VGSC homology modeling and ligand docking indicate that F1747 and F1751 form direct binding contacts with pyrethroids,which are lost with mutation,whereas L1031 mutation may diminish pyrethroid effects through an allosteric mechanism.Overall,the results provide molecular markers for monitoring pest resistance to pyrethroids and offer new insights into the basis of pyrethroid actions on sodium channels.展开更多
Background:Aedes albopictus is distributed widely in China,as a primary vector of Dengue fever and Chikungunya fever in south of China.Chemical insecticide control is one of the integrated programmes to prevent mosqui...Background:Aedes albopictus is distributed widely in China,as a primary vector of Dengue fever and Chikungunya fever in south of China.Chemical insecticide control is one of the integrated programmes to prevent mosquito-borne diseases.Long-term applications of pyrethroids have resulted in the development of resistance in Ae.albopictus populations in China.However,the susceptibility of Ae.albopictus to pyrethroids in Hainan Island was unclear.Knockdown resistance(kdr),caused by point mutations in the VGSC gene,is one of the mechanisms that confer resistance to DDT and pyrethroids.This study was to investigate the resistance level of Ae.albopictus populations in Haikou City to three pyrethroid insecticides,and elucidate the relationship between the resistant phenotype and kdr mutations.Methods:The Aedes albopictus samples were collected in Xinbu Island(XI),Longtang Town(LT),Shishan Town(ST),Baishamen Park(BP),and Flower Market(FM)from Haikou City,Hainan Island,China.The larval susceptibility to deltamethrin,permethrin and beta-cypermethrin was tested by larval bioassays,and adult susceptibility to deltamethrin and DDT was determined by adult bioassays.The degree of resistance was determined by resistance ratio value(RR50>3)for larvae and by mortality for adult.The kdr alleles at codon 1534 of the VGSC gene were genotyped.The relationship between kdr genotypes and resistant phenotypes was analyzed by Chi-square test.Results:Out of five populations,assessed by larval bioassays,XI was susceptible to deltamethrin and permethrin;LT was susceptible to permethrin and beta-cypermethrin;and ST was susceptible to permithrin.FM and BP both were resistant to all of the three pyrethroids,and FM showed the highest degree of resistance,with RR50 values from 65.17 to 436.36.A total of 493 individuals from the larval bioassays were genotyped for kdr alleles.Five alleles were detected,including two wildtype alleles,TTC(F)(67.04%)and TTT(F)(0.41%),and three mutant alleles,TGC(C)(0.30%),TCC(S)(31.54%)and TTG(L)(0.71%).There was a clear correlation between mutant alleles(or F1534S)and resistant phenotypes(P<0.01).Conclusion:Two novel kdr mutant alleles F1534S and F1534L were detected in the pyrethroid resistant populations of Ae.albopictus in Haikou Hainan,China.For the first time,the mutant F1534S was associated with pyrethroid resistance in Ae.albopictus.展开更多
基金supported by the Wellcome Trust Training Fellowship in Public Health and Tropical Medicine(204862/Z/16/Z)awarded to BKThe funders had no role in study design,data collection or analysis,decision to publish or preparation of the manuscript.
文摘Background:Aedes borne viral diseases,notably dengue,are increasingly reported in Cameroon with Aedes aegypti being a major vector.Data on insecticide resistance of this vector and underlying mechanisms needed for outbreak preparedness remain scarce in Cameroon.Here,we present the nationwide distribution of insecticide resistance in Ae.aegypti and investigate the potential resistance mechanisms involved.Methods::Immature stages of Ae.aegypti were collected between March and July 2017 in 13 locations across Cameroon and reared until G1/G2/G3 generation.Larval,adult bioassays,and piperonyl butoxide(PBO)synergist assays were carried out according to World Health Organization guidelines.F1534C mutation was genotyped using allele specific polymerase chain reaction in field collected adults(Go)and the polymorphism of the sodium channel gene was assessed.Theχ2 test was used to compare the mortality rate between bioassays with insecticides only and bioassays after preexposure to PBO synergist.Results:Larval bioassay revealed that all the three populations tested with temephos were susceptible.Adult bioassays showed a good level of susceptibility toward both pyrethroids tested,0.25%permethrin and 0.05%deltamethrin,with six out of 10 populations susceptible.However,two populations(Douala and Edéa)were resistant(deltamethrin[73.2–92.5%mortality],permethrin[2.6–76.3%mortality]).The resistance to 4%dichlorodiphenyltrichloroethane was observed in four out of 10 populations tested(16.8–87.1%mortality).Resistance was also reported to carbamates including 0.1%propoxur(60.8–87.1%mortality)and to 0.1%bendiocarb(82.9%mortality).All populations tested were fully susceptible to 1%fenitrothion.A partial recovery of susceptibility was observed in the pyrethroid resistant population of Douala after pre-exposed to PBO suggesting the implication of cytochrome P450 monoxygenases permethrin resistance.Genotyping and sequencing detected the F1534C kdr mutation in the two pyrethroid resistant locations of Edéa and Douala,with allelic frequency of 3.3%and 33.3%respectively.However,the high genetic diversity of the sodium channel gene supports the recent introduction of this mutation in Cameroon.Conclusions:This study revealed the contrasting resistance profiles to insecticides of Ae.aegypti populations in Cameroon suggesting that,instead of a unique nationwide control approach,a regionally adapted strategy will be needed to control this vector.The localised distribution of the F1534C kdr mutation supports this region-specific control strategy.
基金This work was supported by National Natural Sciences Foundation of China(No.81371848)the Infective Diseases Prevention and Cure Project of China(No.2017ZX10303404–002).
文摘Background:Arboviral disease transmitted by Aedes albopictus such as dengue fever is an important threat to human health.Pyrethroid resistance raises a great challenge for mosquito control.A systematic assessment of Ae.albopictus resistance status in China is urgently needed,and the study of correlation between pyrethroid resistance and knockdown resistance(kdr)mutations would provide information to guide the control of the Ae.albopictus vector.Methods:Five field populations of Ae.albopictus were collected from Jinan(JN),Hangzhou(HZ),Baoshan(BS),Yangpu(YP)and Haikou(HK),China in 2017.Insecticide-impregnated papers were prepared with four pyrethroid chemicals,deltamethrin,permethrin,beta-cypermethrin and lambda-cyhalothrin.The susceptibility of Ae.albopictus to pyrethroids was tested by the WHO tube assay.Kdr mutations were identified by PCR and sequencing.Moreover,the correlation analysis between kdr alleles and pyrethroid resistance was performed.Results:All five populations of Ae.albopictus showed resistance to four pyrethroid insecticides.One kdr mutant allele at codon 1532 and three at 1534 were detected with frequency of 5.33%(I1532T),44.20%(F1534S),1.83%(F1534 L)and 0.87%(F1534C),respectively.Both 1532 and 1534 mutation mosquitoes were found in the BS and YP populations.Allele I1532T was negatively correlated with deltamethrin resistance phenotype(OR<1),while F1534S mutation was positively correlated with deltamethrin and permethrin resistance(OR>1).Conclusions:The five field populations of Ae.albopictus adults were all resistant to deltamethrin,permethrin,betacypermethrin and lambda-cyhalothrin.Mutant F1534S was clearly associated with pyrethroid resistance phenotype in Ae.albopictus and this could be developed as a molecular marker to monitor the pyrethroid resistance problem in China.
文摘Objective: To evaluate the deltamethrin pyrethroid insecticides against Anopheles labranchiae, potential malaria vector in Tunisia.Methods: Six field populations of Anopheles labranchiae mosquitoes were collected from six localities in Northern and Central Tunisia between October and November 2016.Different bioassays were performed to estimate the level of resistance in each collected population. Two synergists were used to estimate the involvement of detoxification enzymes in insecticide resistance.Results: All studied strains were resistant and the RR50 ranged from 12.5 in sample #1 to72.5 in sample #6. Synergist tests using piperonyl butoxide indicated the involvement of monoxygenases enzymes in the recorded resistance. In contrast, the increase of deltamethrin mortality was not significant in presence of S,S,sributyl phosphorothioate(0.8 < SR < 1.2), suggesting no role of esterases(and/or GST) in the resistance phenotype. The correlation recorded between mortality due to DDT and the LC50 of deltamethrin insecticide indicated an insensitive sodium channel affected by Kdr mutation(Spearman rank correlation, r =-0.59, P < 0.01).Conclusions: These results should be considered in the current mosquitoes control programs in Tunisia. The use of pesticides and insecticides by both agricultural and public health departments in Tunisia should be more rational to reduce the development of resistance in populations. Different insecticide applications should be implemented alternately.
基金supported by the Science and Technology Basic Resources Investigation Program of China(2018FY101105)the National Natural Science Foundation of China(31972272,31871969)+1 种基金the Fundamental Research Funds for the Central Universities(SWU-XDPY22001)of Chinathe China Agricultural Research System of MOA and MARA.
文摘Insecticide resistance in Panonychus citri is a major obstacle to mite control in citrus orchards.Pyrethroid insecticides are continually used to control mites in China,although resistance to pyrethroids has evolved in some populations.Here,the resistance to the pyrethroid fenpropathrin was investigated and 7 out of 8 field-collected populations of P citri exhibited a high level of resistance,ranging from 171-fold to 15391-fold higher than the susceptible(SS)comparison strain.Three voltage-gated sodium channel(VGSC)mutations were identified in the tested populations:L1031V,F1747L,and F17511.Amplicon sequencing was used to evaluate the frequency of these mutations in the 19 field populations.L1031V and F1751I were present in all populations at frequencies of 11.6%-82.1%and 0.5%-31.8%,respectively,whereas the F1747L mutation was only present in 12 populations from Chongqing,Sichuan,Guangxi,and Yunnan provinces.Introduction of these mutations singly or in combination into transgenic flies significantly increased their resistance to fenpropathrin and these flies also exhibited reduced mortality after exposure to the pyrethroids permethrin andβ-cypermethrin.Panonychus citri VGSC homology modeling and ligand docking indicate that F1747 and F1751 form direct binding contacts with pyrethroids,which are lost with mutation,whereas L1031 mutation may diminish pyrethroid effects through an allosteric mechanism.Overall,the results provide molecular markers for monitoring pest resistance to pyrethroids and offer new insights into the basis of pyrethroid actions on sodium channels.
基金supported by the YM’s grant 81371848 from the National Natural Sciences Foundation of China.
文摘Background:Aedes albopictus is distributed widely in China,as a primary vector of Dengue fever and Chikungunya fever in south of China.Chemical insecticide control is one of the integrated programmes to prevent mosquito-borne diseases.Long-term applications of pyrethroids have resulted in the development of resistance in Ae.albopictus populations in China.However,the susceptibility of Ae.albopictus to pyrethroids in Hainan Island was unclear.Knockdown resistance(kdr),caused by point mutations in the VGSC gene,is one of the mechanisms that confer resistance to DDT and pyrethroids.This study was to investigate the resistance level of Ae.albopictus populations in Haikou City to three pyrethroid insecticides,and elucidate the relationship between the resistant phenotype and kdr mutations.Methods:The Aedes albopictus samples were collected in Xinbu Island(XI),Longtang Town(LT),Shishan Town(ST),Baishamen Park(BP),and Flower Market(FM)from Haikou City,Hainan Island,China.The larval susceptibility to deltamethrin,permethrin and beta-cypermethrin was tested by larval bioassays,and adult susceptibility to deltamethrin and DDT was determined by adult bioassays.The degree of resistance was determined by resistance ratio value(RR50>3)for larvae and by mortality for adult.The kdr alleles at codon 1534 of the VGSC gene were genotyped.The relationship between kdr genotypes and resistant phenotypes was analyzed by Chi-square test.Results:Out of five populations,assessed by larval bioassays,XI was susceptible to deltamethrin and permethrin;LT was susceptible to permethrin and beta-cypermethrin;and ST was susceptible to permithrin.FM and BP both were resistant to all of the three pyrethroids,and FM showed the highest degree of resistance,with RR50 values from 65.17 to 436.36.A total of 493 individuals from the larval bioassays were genotyped for kdr alleles.Five alleles were detected,including two wildtype alleles,TTC(F)(67.04%)and TTT(F)(0.41%),and three mutant alleles,TGC(C)(0.30%),TCC(S)(31.54%)and TTG(L)(0.71%).There was a clear correlation between mutant alleles(or F1534S)and resistant phenotypes(P<0.01).Conclusion:Two novel kdr mutant alleles F1534S and F1534L were detected in the pyrethroid resistant populations of Ae.albopictus in Haikou Hainan,China.For the first time,the mutant F1534S was associated with pyrethroid resistance in Ae.albopictus.
