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Controlling housefly populations relies on the use of insecticides, which inevitably leads to the development of resistance. A better and more comprehensive understanding of the spatial and temporal distribution of resistance could guide the control of houseflies. However, most studies on housefly resistance in China are scattered and poorly coordinated. We collected resistance data from houseflies in the published literature and from the vector biomonitoring system of the Chinese Center for Disease Control and Prevention. A 5- or 10-year resolution was used to study the temporal dynamics of resistance to five commonly used insecticides: deltamethrin, permethrin, beta-cypermethrin, dichlorvos, and propoxur. ArcGIS was used to visualize their spatial distributions. The correlation between year and resistance coefficient was determined using SPSS 26.0 and RStudio to explore the changes in resistance over the years. A total of 2128 data were included in this study, ranging from 1982 to 2022, based on which we found significant increases in resistance over the past forty years for the five studied insecticides. Among them, pyrethroids had the most strikingly elevated resistance level and were mainly distributed in the northern and southeastern coastal areas. Dichlorvos and propoxur had intermediate increases in resistance, and most of these increases were identified in North China and the Yangtze River. Housefly resistance to commonly used insecticides in China is increasing and spatially heterogeneous. This finding also highlights the necessity of continuous routine surveillance of housefly resistance, which could guide future housefly control operations and slow the development of resistance.
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Moscas Domésticas , Resistencia a los Insecticidas , Insecticidas , Piretrinas , Moscas Domésticas/efectos de los fármacos , Animales , China , Insecticidas/farmacología , Nitrilos , Permetrina/farmacología , PropoxurRESUMEN
BACKGROUND: Typhus group rickettsiosis (TGR), which is a neglected vector-borne infectious disease, including epidemic typhus and endemic typhus. We explored the lag effects and nonlinear association between meteorological factors and TGR incidence in Xishuangbanna Dai autonomous prefecture from 2005 to 2017, China. METHODS: A Poisson regression with a distributed lag nonlinear model (DLNM) was utilized to analyze TGR cases data and the contemporaneous meteorological data. RESULTS: A J-shaped nonlinear association between weekly mean temperature and TGR incidence was found. The cumulative exposure to weekly mean temperature indicated that the RR increased with the increment of temperature. Taking the median value as the reference, lower temperatures could decrease the risk of TGR incidence, while higher temperatures could increase the risk of TGR incidence and last for 21 weeks. We also found a reversed U-shaped nonlinear association between weekly mean precipitation and TGR incidence. Precipitation between 5 mm and 13 mm could increase the risk of TGR incidence. Taking the median value as the reference, no precipitation and lower precipitation could decrease the risk of TGR incidence, while higher precipitation could increase the risk of TGR incidence and last for 18 weeks. CONCLUSIONS: The prevention and control measures of TGR should be implemented according to climatic conditions by the local government and health departments in order to improve the efficiency.
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Clima , Tifus Epidémico Transmitido por Piojos/epidemiología , Tiempo (Meteorología) , China/epidemiología , Frío , Calor , Humanos , Incidencia , Dinámicas no Lineales , LluviaRESUMEN
Multiple surveillance traps are currently available for adult mosquito surveillance. In this study, 2 new types, the Maxttrac™ Uno and Maxttrac™ Breeze mosquito traps, were compared against the BioGents™-Sentinel trap (BGS) for overall success in collecting Aedes albopictus in a 1,027-m2 vehicle enclosure and in the field. The enclosure test results showed both traps collected significantly fewer Ae. albopictus, compared to the BGS trap. The modification of using all BG lures for each trap did not increase the number of mosquitoes collected in the 2 new traps, when compared to collection with the original lures tested in the vehicle enclosure. Field test results showed that BGS trap collected higher numbers of Ae. albopictus than the 2 new traps, regardless of switching lure or not. Overall, the BGS trap was the most effective trap and the 2 new traps could be used as additional tools for the collection of Ae. albopictus.
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Aedes , Control de Mosquitos , Feromonas , Animales , Femenino , Florida , Masculino , Control de Mosquitos/métodosRESUMEN
BACKGROUND: Culex pipiens pallens and Culex pipiens quinquefasciatus are the dominant species of Culex mosquitoes in China and important disease vectors. Long-term use of insecticides can cause mutations in the voltage-gated sodium channel (vgsc) gene of mosquitoes, but little is known about the current status and evolutionary origins of vgsc gene in different geographic populations. Therefore, this study aimed to determine the current status of vgsc genes in Cx. p. pallens and Cx. p. quinquefasciatus in China and to investigate the evolutionary inheritance of neighboring downstream introns of the vgsc gene to determine the impact of insecticides on long-term evolution. METHODS: Sampling was conducted from July to September 2021 in representative habitats of 22 provincial-level administrative divisions in China. Genomic DNA was extracted from 1308 mosquitoes, the IIS6 fragment of the vgsc gene on the nerve cell membrane was amplified using polymerase chain reaction, and the sequence was used to evaluate allele frequency and knockdown resistance (kdr) frequency. MEGA 11 was used to construct neighbor-joining (NJ) tree. PopART was used to build a TCS network. RESULTS: There were 6 alleles and 6 genotypes at the L1014 locus, which included the wild-type alleles TTA/L and CTA/L and the mutant alleles TTT/F, TTC/F, TCT/S and TCA/S. The geographic populations with a kdr frequency less than 20.00% were mainly concentrated in the regions north of 38° N, and the geographic populations with a kdr frequency greater than 80.00% were concentrated in the regions south of 30° N. kdr frequency increased with decreasing latitude. And within the same latitude, the frequency of kdr in large cities is relatively high. Mutations were correlated with the number of introns. The mutant allele TCA/S has only one intron, the mutant allele TTT/F has three introns, and the wild-type allele TTA/L has 17 introns. CONCLUSIONS: Cx. p. pallens and Cx. p. quinquefasciatus have developed resistance to insecticides in most regions of China. The neighboring downstream introns of the vgsc gene gradually decreased to one intron with the mutation of the vgsc gene. Mutations may originate from multiple mutation events rather than from a single origin, and populations lacking mutations may be genetically isolated.
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Culex , Culicidae , Insecticidas , Piretrinas , Canales de Sodio Activados por Voltaje , Animales , Insecticidas/farmacología , Intrones/genética , Mosquitos Vectores/genética , Culex/genética , Mutación , Canales de Sodio Activados por Voltaje/genética , Resistencia a los Insecticidas/genéticaRESUMEN
BACKGROUND: Flea bites could trigger a series of complex molecular responses in the host. However, our understanding of the responses at the molecular level is still relatively limited. This study quantifies the changes in gene expression in mice after flea bites by RNA sequencing (RNA-seq) from their spleens, revealing the potential biological effects of host response to flea bites. METHODS: RNA-seq was used for transcriptome analysis to screen for differentially expressed genes (DEGs) between the control mice group and the flea bite mice group. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed on DEGs. Protein-protein interaction (PPI) network analysis on DEGs related to immune processes was performed. Finally, we randomly selected several genes from the screened DEGs to validate the results from the transcriptome data by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR). RESULTS: A total of 521 DEGs were identified, including 277 upregulated and 244 downregulated. There were 258 GO terms significantly enriched by upregulated DEGs and 419 GO terms significantly enriched by downregulated DEGs. Among the upregulated DEGs, 22 GO terms were associated with immune cells (e.g., B cells and T cells) and immune regulatory processes, while among the downregulated DEGs, 58 GO terms were associated with immune cells and immune regulatory processes. Through PPI analysis, we found that CD40 molecules with significantly downregulated expression levels after flea bites may play an important role in host immune regulation. Through KEGG pathway enrichment analysis, a total of 26 significantly enriched KEGG pathways were identified. The RT-qPCR analysis results indicated that the transcriptome sequencing results were reliable. CONCLUSIONS: Through in-depth analysis of transcriptome changes in mice caused by flea bites, we revealed that flea bites could stimulate a series of biological and immunological responses in mice. These findings not only provided a deeper understanding of the impact of flea bites on the host but also provided a basis for further research on the interaction between ectoparasites and the host. We believe that digging deeper into the significance of these transcriptome changes will help reveal more about the adaptive response of the host to ectoparasites.
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Perfilación de la Expresión Génica , Transcriptoma , Xenopsylla , Animales , Ratones , Xenopsylla/genética , Mordeduras y Picaduras de Insectos/inmunología , Ontología de Genes , Mapas de Interacción de Proteínas , Bazo/inmunología , Bazo/metabolismo , Femenino , Análisis de Secuencia de ARNRESUMEN
The susceptibility of adults and larvae from four field populations of Culex pipiens pallens (Coguillett) (Diptera: Culicidae) in China to deltamethrin, beta-cypermethrin, and permethrin was investigated using the World Health Organization standard susceptibility test methods. One to 2 d old nonblood fed female mosquitoes emerged from pupae resulting from wild-caught larvae (F1 laboratory reared adults) were exposed to various doses of the pyrethroids. The larval bioassay was conducted using a range of concentrations to determine the LC50 values. Using allele-specific polymerase chain reaction, the frequency of the kdr resistance gene was determined in each population. The bioassay data indicated that deltamethrin was the most active larvicide in all four populations with resistance ratios (RR) of 1.6-3.9-fold. This was followed by beta-cypermethrin with RR of 1.1-3.3-fold, while larvae from three mosquito populations from Beijing, Jinan, and Kaifeng had developed resistance to permethrin with RR of 12.6-, 24.0-, and 18.8-fold, respectively. The overall RR of larvae for all insecticides in ascending order was Changchun < Beijing < Kaifeng < Jinan; and ranking of the adult mortality was Changchun < Jinan = Kaifeng < Beijing. For the three pyrethroids tested, the correlation coefficient among the three test methods on the four populations and one lab strain was quite weak. The R value was 0.113-0.320 when we compared kdr detection for kdr% with LC50, -0.565 to -0.793 when kdr% versus adult mortality test, and -0.750 to 0.505 for LC50 versus adult mortality. Permethrin showed the best correlation (R = -0.793) between kdr frequency and adult mortality. This indicates that levels of susceptibility changes to an insecticide should not be based on a single method of assessment.
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Culex , Insecticidas , Piretrinas , Animales , China , Culex/genética , Femenino , Resistencia a los Insecticidas/genética , Larva , Ratones , Canales de Sodio/genéticaRESUMEN
BACKGROUND: The current prevention and control strategy for Aedes albopictus heavily relies on comprehensive management, such as environmental management and chemical control. However, the wide application of pyrethroids has facilitated the development of insecticide resistance, primarily via mutations in the voltage-gated sodium channel (VGSC) gene. This study aims to develop a novel strategy for detecting mutations in the VGSC gene in Ae. albopictus using multiplex PCR-mass spectrometry (MPCR-MS) minisequencing technology. METHODS: We established a new strategy for detecting mutations in the VGSC gene in Ae. albopictus using MPCR-MS minisequencing technology. MPCR amplification and mass probe extension (MPE) were first used, followed by single nucleotide polymorphism (SNP) typing mass spectrometry, which allows the simultaneous detection of multiple mutation sites of the VGSC gene in 96 samples of Ae. albopictus. A total of 70 wild-collected Ae. albopictus were used to evaluate the performance of the method by comparing it with other methods. RESULTS: Three target sites (1016, 1532, 1534) in the VGSC gene can be detected simultaneously by double PCR amplification combined with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, achieving a detection limit of 20 fg/µl. We applied this method to 70 wild-collected Ae. albopictus, and the obtained genotypes were consistent with the routine sequencing results, suggesting the accuracy of our method. CONCLUSIONS: MPCR-MS minisequencing technology provides a sensitive and high-throughput approach to Ae. albopictus VGSC gene mutation screening. Compared with conventional sequencing, this method is economical and time-saving. It is of great value for insecticide resistance surveillance in areas with a high risk of vector-borne disease.
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Aedes , Insecticidas , Piretrinas , Canales de Sodio Activados por Voltaje , Animales , Aedes/genética , Reacción en Cadena de la Polimerasa Multiplex , Piretrinas/farmacología , Mutación , Resistencia a los Insecticidas/genética , Canales de Sodio Activados por Voltaje/genética , Insecticidas/farmacologíaRESUMEN
BACKGROUND: Strengthening the mosquito control measures undertaken by residents of an area where dengue fever is present can significantly decrease the spread of this disease. The aim of this study was to explore the effects of the source of information and knowledge of dengue fever on the mosquito control behavior of residents of areas at high risk of this disease to determine effective ways of enhancing this behavior. METHODS: A survey was conducted via face-to-face interviews or questionnaires between March and May 2021 in three regions of the province of Yunnan, China. The survey included basic information about the respondents, the source(s) of their dengue fever information, the level of their dengue fever knowledge, and the measures they had implemented to control mosquitoes. Principal component analysis was used to extract the main components of the sources of information. Correlation analysis and structural equation analysis were used to explore the impact of the sources of information and residents' dengue fever knowledge on their mosquito control behavior. RESULTS: Publicity achieved through mass media, including official WeChat accounts, magazines/newspapers, poster leaflets, television/radio and the Internet, had a direct effect on dengue fever knowledge and mosquito control behavior, and indirectly affected mosquito control behavior through dengue fever knowledge. Organized publicity campaigns, including information provided by medical staff and through community publicity, had a direct effect on dengue fever knowledge and indirectly affected mosquito control behavior through dengue fever knowledge. The residents' level of dengue fever knowledge had a significant, positive, direct effect on their mosquito control behavior. CONCLUSIONS: Mosquito control is an important measure for the prevention and control of outbreaks of dengue fever. An effective source of information can improve the level of dengue fever knowledge among residents and thus enhance their mosquito control behavior.
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Dengue , Fuentes de Información , Animales , Humanos , Control de Mosquitos , China/epidemiología , Brotes de Enfermedades , Dengue/epidemiología , Dengue/prevención & controlRESUMEN
BACKGROUND: Overseas imported dengue fever is an important factor in local outbreaks of this disease in the mainland of China. To better prevent and control such local outbreaks, the epidemiological characteristics and temporal-spatial distribution of overseas imported dengue fever cases in provincial-level administrative divisions (PLADs) where dengue fever is outbreak in the mainland of China were explored. METHODS: Using the Chinese National Notifiable Infectious Disease Reporting Information System (CNNDS), we identified overseas imported dengue fever cases in dengue fever outbreak areas in the mainland of China from 2005 to 2019 to draw the epidemic curve and population characteristic distribution of overseas imported cases in each PLAD. Based on spatial autocorrelation analysis of ArcGIS 10.5 and temporal-spatial scanning analysis of SaTScan 9.5, we analyzed the temporal-spatial distribution of overseas imported dengue fever in dengue fever outbreak areas in the mainland of China. RESULTS: A total of 11,407 imported cases, mainly from Southeast Asia, were recorded from 2005 to 2019 in these 13 PLADs. Of which 62.1% were imported into Yunnan and Guangdong Provinces. Among the imported cases, there were more males than females, mainly from the 21-50 age group. The hot spots were concentrated in parts of Yunnan, Guangdong and Fujian Provinces. We found the cluster of infected areas were expanding northward. CONCLUSIONS: Based on the analysis of overseas imported dengue cases in 13 PLADs of the mainland of China from 2005 to 2019, we obtained the epidemiological characteristics and spatial distribution of imported dengue cases. Border controls need to pay attention to key population sectors, such as 21-50 years old men and education of key populations on dengue prevention. There is a need to improve the awareness of the prevention and control of imported cases in border areas. At the same time, northern regions cannot relax their vigilance.
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Dengue , Epidemias , Adulto , China/epidemiología , Dengue/epidemiología , Brotes de Enfermedades , Femenino , Humanos , Masculino , Persona de Mediana Edad , Análisis Espacial , Adulto JovenRESUMEN
Background: Aedes albopictus, commonly known as the tiger mosquito, has attracted global attention because its bite can transmit several viruses, such as dengue virus. With the absence of an effective therapy and vaccine, mosquito control is the sole method for dengue fever control. However, Ae. albopictus has developed resistance to most insecticides, especially pyrethroids. Many scholars have conducted thorough research for the target-site of pyrethroids. The main target-site is the voltage-gated sodium channel gene (VGSC) whose mutation causes knockdown resistance (kdr). The spatial distribution of three locus kdr mutations in Ae. albopictus has not been comprehensively analyzed nationwide in China. In addition, the relationship between the frequency of kdr mutations and dengue fever has not yet been explored. Methods: A total of 2,241 Ae. albopictus samples from 49 populations from 11 provinces of mainland China were collected in 2020 and analyzed for mutations in the VGSC gene. DNAstar 7.1. Seqman and Mega-X were used to compare the sequences and read the peak map to confirm the genotypes and alleles of each mutation. ArcGIS 10.6 software was used to make interpolation and extract meteorological data of collection sites and to conduct spatial autocorrelation analysis. R 4.1.2 software was used to conduct a chi-square test for kdr mutations and dengue area and to analyze the correlation between meteorological factors and kdr mutations. Results: The overall frequencies of mutant alleles at 1016G, 1532T, and 1534S/C/L were 13.19%, 4.89%, and 46.90%, respectively. Mutations at the three loci were found at 89.80% (44/49), 44.90% (22/49), and 97.96% (48/49) of the field populations. At each of the loci V1016 and I1532, only one allele was detected, which was GGA(G) and ACC(T), respectively. Five mutant alleles were found at codon 1534: TCC/S (33.49%), TGC/C (11.96%), TTG/L (0.60%), CTC/L (0.49%), and TTA/L (0.58%). In total, 31 triple-locus genotype combinations were found, and the single locus mutation was the most common. We also found firstly triple-locus mutant individuals, whose genotypes were V/G+I/T+F/S and V/G+I/T+S/S. The 1016 and 1532 mutation rates were significantly negatively related to the annual average temperature (AAT), but the 1534 mutation rate was significantly positively related to AAT. The 1532 mutation rate was significantly positively related to the 1016 mutation rate but negatively related to the 1534 mutation rate. A relationship was observed between the 1534 codon mutation rate and dengue epidemic areas in this study. Furthermore, spatial autocorrelation analysis results showed that the mutation rates of different codons in different geographical areas had spatial aggregation and positive spatial correlation. Conclusion: This study showed that the multiple kdr mutations at codon 1016, 1532 and 1534 of Ae. albopictus were found in most areas of China. Two novel triple-locus genotype combinations, V/G+I/T+F/S and V/G+I/T+S/S, were detected in this study. In addition, the relationship between mosquito resistance and dengue fever outbreak should be further explored, especially considering the insecticide-usage history in different areas. The characteristic of spatial aggregation of VGSC gene mutation rates reminds us to notice the gene exchange and similarity of insecticide usage in the adjacent areas. The use of pyrethroids should be restricted to delay resistance development. New-type insecticides should be developed to adjust the changes in the resistance spectrum. Our study provides abundant data on the Ae. albopictus kdr gene mutation in China; these findings will be useful for the correlation analysis of molecular mechanism of insecticide resistance.
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Aedes , Dengue , Insecticidas , Piretrinas , Animales , Humanos , Insecticidas/farmacología , Aedes/genética , Mutación , Resistencia a los Insecticidas/genética , China/epidemiología , Dengue/epidemiología , Dengue/prevención & controlRESUMEN
Culex tritaeniorhynchus Gile is a major vector of Japanese encephalitis in China. The population genetics study is crucial as it helps understanding the epidemiological aspects of mosquito-brone diseases and improving vector control measures. Here, the genetic population structure of C. tritaeniorhynchus in the mainland China were estimated using the cytochrome c oxidase subunit 1 (COI) DNA barcodes region. 485 individuals of C. tritaeniorhynchus were collected from 38 sampling sites in 21 geographic populations in the mainland China. In total, 485 sequences were used to explore the population structure and genetic diversity. The results showed that the populations of C. tritaeniorhynchus had high haplotype diversity (Hd = 0.98, with 303 haplotypes), low nucleotide diversity (p = 0.02245) and high gene flow (Nm = 47.11) with two maternal lineages and four groups. An AMOVA indicated that 98.8% of the total variation originated from variation within populations. In addition, the population genetic structure exhibited by C. tritaeniorhynchus filling the vacant of the genetic structure in the mainland China. Human activities may also assist mosquito movement and migration. Gene flow among the populations of C. tritaeniorhynchus can facilitate the spread of insecticide resistance genes over geographical areas, and it will be a challenging for controlling the populations.
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OBJECTIVE: To sequence and analyze the complete genome of two new Japanese encephalitis virus (JEV) strains isolated from mosquitoes collected in Hubei province in 2008, and to understand the molecular biological characteristics of JEV in this area. METHODS: RT-PCR was used to amplify the fragments of HBZG08-09 strain and HBZG08-55 strain with 16 pairs overlapping primers after they had been recovered and identified, then the full-length genome was obtained by sequencing and splicing. Biological sequence alignment, nucleotide and amino acid sequence analysis, phylogenetic analysis and analysis of amino acid differences were performed by the software of Clustal X (1.83), MegAlign, Mega (4.0) and Genedoc (3.2). RESULTS: The genome of two new strains were both 10 965 nucleotides in length with a single open reading frame from 96 to 10 392 coding for a 3432 amino acid poly-protein, the homology of nucleotide and amino acid sequence between two isolates were 98.2% and 99.7% respectively. Further study showed that the new strains were both belonging to genotype I. Two new strains were most closely related to isolates obtained from Henan and Zhejiang province in recent years. Compared with the live attenuated vaccine strain SA-14-14-2 in China, HBZG08-09 strain had 82 amino acid divergence; HBZG08-55 had 84 amino acid divergences. But the amino acid difference occurred in sites were not the key ones affecting the toxicity or antigenic of JEV. CONCLUSION: Two new JEV isolates were both belonging to genotype I, and the key sites of amino acid were not changed.
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Culicidae/virología , Virus de la Encefalitis Japonesa (Especie)/genética , Genoma Viral , Animales , China , Virus de la Encefalitis Japonesa (Especie)/clasificación , Virus de la Encefalitis Japonesa (Especie)/aislamiento & purificación , Genotipo , Datos de Secuencia Molecular , Filogenia , ARN Viral , Alineación de SecuenciaRESUMEN
Dengue fever (DF) is one of the most rapidly spreading diseases in the world, and accurate forecasts of dengue in a timely manner might help local government implement effective control measures. To obtain the accurate forecasting of DF cases, it is crucial to model the long-term dependency in time series data, which is difficult for a typical machine learning method. This study aimed to develop a timely accurate forecasting model of dengue based on long short-term memory (LSTM) recurrent neural networks while only considering monthly dengue cases and climate factors. The performance of LSTM models was compared with the other previously published models when predicting DF cases one month into the future. Our results showed that the LSTM model reduced the average the root mean squared error (RMSE) of the predictions by 12.99% to 24.91% and reduced the average RMSE of the predictions in the outbreak period by 15.09% to 26.82% as compared with other candidate models. The LSTM model achieved superior performance in predicting dengue cases as compared with other previously published forecasting models. Moreover, transfer learning (TL) can improve the generalization ability of the model in areas with fewer dengue incidences. The findings provide a more precise forecasting dengue model and could be used for other dengue-like infectious diseases.
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Aprendizaje Profundo , Dengue/epidemiología , Predicción , Ciudades/epidemiología , Brotes de Enfermedades , Humanos , Incidencia , Redes Neurales de la ComputaciónRESUMEN
BACKGROUND: Mutation of the voltage-gated sodium channel (VGSC) gene, or knockdown resistance (kdr) gene, is an important resistance mechanism against DDT and pyrethroids for dengue vector Aedes albopictus. A phenylalanine to serine (F1534S), leucine (F1534L) and cysteine (F1534C) substitution were detected in many Ae. albopictus populations around the world, and the mutant allele frequencies have been increasing in recent years. Therefore, it is essential to establish a simple, time-saving and cost-effective procedure to monitor the alleles in large-scale studies. METHODS: Based on the mutation genotypes of the 1534 locus in the kdr gene, F/F, F/S, F/C, F/L, S/S, C/C, L/L and S/C, we designed specific forward and reverse primers and optimized the reaction conditions for establishing of the allele-specific PCR(AS-PCR) detection technique. DNA sequencing in this study was taken as the gold standard, and used to determine the accuracy of AS-PCR. RESULTS: The designed AS-PCR technique showed high specificity for distinguishing the mutations at the 1534 locus, as the accuracy for F/F, F/S, F/C, F/L, S/S, C/C and S/C were 100%, 95.35%, 100%, 100%, 100%, 100% and 100%, respectively. CONCLUSIONS: The designed AS-PCR technique effectively distinguished individual genotypes for the mutations at the 1534 locus in the kdr gene, which could facilitate the knockdown resistance surveillance in Ae. albopictus in large-scale studies.
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Aedes/genética , Dengue/transmisión , Proteínas de Insectos/genética , Resistencia a los Insecticidas , Insecticidas/farmacología , Mosquitos Vectores/genética , Reacción en Cadena de la Polimerasa/métodos , Aedes/efectos de los fármacos , Alelos , Animales , Humanos , Mosquitos Vectores/efectos de los fármacos , Mosquitos Vectores/metabolismo , MutaciónRESUMEN
Resistance evolution in target insects to Bacillus thurningiensis (Bt) cotton, Gossypium hirsutum L., is a main threat to Bt cotton technology. An increasing trend of population density of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) has been observed since 2001 in Qiuxian County (Hebei, China), where Bt cotton has been planted dominantly since 1998. This region was selected in 2006 and 2007 for estimating frequency of gene alleles conferring resistance to Bt cotton by screening the F1 progeny from single-pair cross between field-collected male and laboratory female of the Bt-resistant strain of H. armigera (F1 screen). F1 offspring from each single-pair line were screened for resistance alleles based on larval growth, development, and survival on Bt cotton leaves for 5 d. Two-year results indicated that approximately equal to 20% of field-collected males carried resistance alleles. The conservative estimate of the resistance allele frequency was 0.094 (95% CI, 0.044-0.145) for 2006 and 0.107 (95% CI, 0.055-0.159) for 2007. This is the first report of resistance allele frequency increase to such a high level in the field in China. Long-term adoption of Bt sprays, dominant planting of single-toxin-producing Bt cotton, and lack of conventional cotton refuge system might accelerate the resistance evolution in the region.
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Gossypium/parasitología , Resistencia a los Insecticidas/genética , Lepidópteros/genética , Lepidópteros/patogenicidad , Alelos , Animales , Peso Corporal , China , Cruzamientos Genéticos , Frecuencia de los Genes , Gossypium/crecimiento & desarrollo , LarvaRESUMEN
BACKGROUND: Culex tritaeniorhynchus and Culex pipiens pallens are the major vectors of the Japanese encephalitis virus and Wuchereria bancrofti, the causative agent of filariasis. The knowledge of mitochondrial genomes has been widely useful for the studies on molecular evolution, phylogenetics and population genetics. METHODS: In this study, we sequenced and annotated the mitochondrial (mt) genomes of Cx. tritaeniorhynchus and Cx. p. pallens, and performed a comparative analysis including four known mt genomes of species of the subgenus Culex (Culex). The phylogenetic relationships of Cx. tritaeniorhynchus, Cx. p. pallens and four known Culex mt genome sequences were reconstructed by maximum likelihood based on concatenated protein-coding gene sequences. RESULTS: Culex tritaeniorhynchus and Cx. p. pallens mt genomes are 14,844 bp and 15,617 bp long, both consists of 13 PCGs, 22 tRNAs, 2 rRNAs and 1 CR (not sequenced for Cx. tritaeniorhynchus). The initiation and termination codons of PCGs are ATN and TAA, respectively, except for COI starting with TCG, and COI and COII terminated with T. tRNAs have the typical clover-leaf secondary structures except for trnS ((AGN)) that is lacking the DHU stem. 16S rRNA and 12S rRNA secondary structures were drawn for the first time for mosquito mt genomes. The control region of Cx. p. pallens mt genome is 747 bp long and with four tandem repeat structures. Phylogenetic analyses demonstrated that the mt genome of Cx. tritaeniorhynchus was significantly separated from the remaining five mt genomes of Culex spp. Culex p. pipiens, Cx. p. pallens and Cx. p. quinquefasciatus formed a monophyletic clade with Cx. p. quinquefasciatus linked in the middle of the clade, and Cx. p. pallens should have the same taxonomic level as Culex p. pipiens and Cx. p. quinquefasciatus. CONCLUSIONS: The mt genomes of Cx. tritaeniorhynchus and Cx. p. pallens share the same gene composition and order with those of two other Culex species. Culex p. pallens of the Pipiens complex should have the same taxonomic level as Culex p. pipiens and Cx. p. quinquefasciatus investigated. We enriched the Culex mt genome data and provided a reference basis for further Culex mt genome sequencing and analyses.
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Culex/genética , Genoma de los Insectos , Genoma Mitocondrial , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Culex/química , Culex/clasificación , Proteínas de Insectos/química , Proteínas de Insectos/genética , Insectos Vectores/química , Insectos Vectores/clasificación , Insectos Vectores/genética , Datos de Secuencia Molecular , Filogenia , Alineación de SecuenciaRESUMEN
Selection experiments for resistance to transgenic Bt cotton expressing Cry1Ac toxin in Helicoverpa armigera (Hübner) were conducted using a leaf-feeding method with 42 selection episodes over 45 generations. The cotton bollworm developed resistance to transgenic Bt cotton after 12 generations (F12) of selection. The survival rate of F12 neonates feeding on leaves of seedling stage for 4 days and boll-opening stage for 5 days of R19 line were ca 34 and 72%, respectively, compared with ca 0 and 40% for a non-selected sister strain (NYCS), but lower than or similar to that of F12 feeding on leaves of non-Bt cotton, Sumian 12 (ca 87 or 76%). Resistance to B thuringiensis HD-1 Dipel in neonates (F12) was ca 6-fold. After 42 generations of selection, the strain developed a very high level of resistance to Cry1Ac protoxin, 210 g kg(-1) MVPII wettable powder and 200 g litre(-1) MVPII liquid formulation, the resistance ratios being 1680-, 1780- and ca 1200-fold, respectively, compared with a laboratory susceptible strain (HZS). When compared with the non-selected NYCS, the resistance ratios to the above toxins were ca 540-, 580- and 510-fold, respectively, but to Dipel only ca 16-fold. The results indicated that it is very important to develop and implement effective resistance-management strategies and to detect early resistance to Bt cotton in field populations.
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Toxinas Bacterianas/metabolismo , Gossypium/parasitología , Lepidópteros/crecimiento & desarrollo , Plantas Modificadas Genéticamente/parasitología , Precursores de Proteínas/metabolismo , Animales , Toxinas Bacterianas/genética , Toxinas Bacterianas/farmacología , Bioensayo/métodos , Gossypium/genética , Inmunidad Innata , Larva/crecimiento & desarrollo , Lepidópteros/efectos de los fármacos , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/parasitología , Plantas Modificadas Genéticamente/genética , Precursores de Proteínas/genética , Precursores de Proteínas/farmacologíaRESUMEN
Geographic variation in the susceptibility of the striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), in China to Bacillus thuringiensis (Bt) insecticidal crystal proteins Cry1Ac and Cry1Ab was studied to establish baseline information for comparing the future response of populations with increased exposure to Bt products. Rice is the major host of C. suppressalis, and Bt rice ma) be released in China in the near future. Twelve populations of the pest were collected from the major rice-growing regions of China. LC50 estimates were determined for all populations for Cry1Ac and for eight populations for Cry1Ab. The bioassay results indicated that the range of LC50 in neonate larvae to Cry1Ac and Cry1Ab was from approximately 15 to approximately 157 mg (AI)/L and approximately 2 to approximately 34 mg (AI)/L, respectively. LC50 values were lower for Cry1Ab than for Cry1Ac, and there was a significant positive correlation between the two toxins tested.
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Proteínas Bacterianas , Toxinas Bacterianas , Endotoxinas , Insecticidas , Lepidópteros , Animales , Toxinas de Bacillus thuringiensis , Proteínas Bacterianas/administración & dosificación , China , Endotoxinas/administración & dosificación , Proteínas Hemolisinas , Insecticidas/administración & dosificación , Control Biológico de VectoresRESUMEN
BACKGROUND: Carboxylesterase overproduction is a frequently observed resistance mechanism of insects to organophosphate insecticides. As a major transmitter of human diseases, mosquitoes in the Culex pipiens complex have evolved 13 carboxylesterase alleles (Ester) that confer organophosphate resistance. Six alleles, Ester(B1), Ester², Ester8, Ester9, Ester(B10), and Ester¹¹, have been observed in field populations in China, sometimes co-existing in one population. To differentiate the carboxylesterase alleles found in these field populations, PCR-RFLP was designed for use in resistance monitoring. RESULTS: Based on the DNA sequences of resistant and nonresistant carboxylesterase alleles, Ester B alleles were first amplified with PCR-specific primers and then digested with the restriction enzyme DraI. In this step, Ester² and Ester¹¹ were differentiated from the other Ester alleles. When the other Ester B alleles were digested with the restriction enzyme XbaI, Ester(B1) and the susceptible C. p. pallens Ester were screened out. Ester8 and Ester9 were differentiated from Ester(B10) and the susceptible C. p. quinquefasciatus esterase allele, respectively, by amplifying and digesting the Ester A alleles with the restriction enzyme ApaLI. The effectiveness of the custom-designed PCR-RFLP was verified in two field mosquito populations. CONCLUSIONS: A PCR-RFLP based approach was developed to differentiate carboxylesterase alleles in Culex pipiens complex mosquitoes. These processes may be useful in monitoring the evolutionary dynamics of known carboxylesterase alleles as well as in the identification of new alleles in field populations.