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Objective To explore the sensitivity of Culex pipiens pallens to common chemical insecticides in the southwestern region of Shandong Province, so as to provide a theoretical basis for the development of reasonable and effective mosquito control measures. Methods The resistance of Cx. pipiens pallens larvae to 5 chemical insecticides, such as cypermethrin, deltamethrin, DDVP, propoxur, and acetofenate were tested by using the WHO biological test method in 2018, and the co-toxicity coefficients after compounding the above-mentioned insecticides were tested by using a drug compounding method. Results The resistance indexes of Cx. pipiens pallens to cypermethrin, deltamethrin, DDVP, propoxur, and acetofenate in 3 cities were 144.43–557.54, 118.17–445.33, 6.44–19.00, 2.37–8.10, and 0.88–2.98, respectively, and expect the difference between the DDVP resistances of Cx. pipiens pallens in Jining City and Heze City was not statistically significant (P > 0.05), all the other differences were statistically significant (all P < 0.05). The synergistic coefficients of cypermethrin + DDVP, cypermethrin + propoxur, DDVP + acetofenate, and propoxur + acetofenate were 199.58 – 456.95, 190.56 – 292.37, 123.32 – 319.24, and 192.31 – 367.32, respectively. The lower synergism was observed by using the mixture of DDVP + propoxur (synergistic coefficient: 99.87–108.36) . Conclusions After decades of chemical control, Cx. pipiens pallens in the southwestern region of Shandong Province has produced different degrees of resistance to common chemical insecticides. Therefore, comprehensive control measures should be taken to control mosquito breeding and prevent the development of insecticide resistance.
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Objective To explore the characteristics of gene sequence of mtDNA-COⅠof Culex pipiens pallens from differ-ent geographical regions in Shandong Province and different resistant strains from the lab and five common mosquito species, and analyze the genetic diversity of these mosquitoes.Methods Adult mosquitoes were collected from Jinan,Jining,Qingdao cities and other places in Shandong Province.The sensitive,dichlorvos-resistant,pyrethroid-resistant and propoxur-resistant strains were reared in the lab.Five species of mosquito(Cx.pipiens pallens,Cx.tritaeniorhynchus,Anopheles sinensis,Aedes al-bopictus,and Armigeres subalbatus)were collected from Jining City and identified in the lab.mtDNA-COⅠwas specifically am-plified by PCR and sequenced.The gene sequences were compared and analyzed by the biological information systems,and the phylogenetic tree was constructed.Results The amplified mtDNA-COⅠfragments of Cx.pipiens pallens from eight different cit-ies and four different resistant strains were 528 bp in length,with 67.4% A+T contents and two mutation sites.The nucleotide se-quence homology among the different geographic strains was 99.95% and the gene sequences of the four resistant strains were the same,showing a high homogeny.The amplified mtDNA-COⅠfragments of the five species of mosquitoes were 528 bp with 408 conserved sites,120 variable sites,42 parsimony informative sites and 78 singleton sites. The A+T contents were between 65.7% and 68.0%.The nucleotide sequence homology among the different mosquito species was between 86.17% and 92.05%,and the molecular identification was consistent with the traditional morphological identification. The molecular phylogenetic study showed that the different species were clustered at their own branch at the species and genus levels,while genera Armiger-es was distantly related to the others.Conclusion mtDNA-COⅠcould not serve as the molecular marker to analyze the popula-tion genetic variation and phylogenesis of Cx.pipiens pallens from different geographical regions and different resistant strains, but it has species and genus specificities,which could be used for the identification of the mosquito species and genus.
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Objective To investigate the seasonal fluctuations of mosquitoes in Taibai Lake area of Jining City,and evaluate the application effects of two mosquito trapping tools(Gongfu Xiaoshuai mosquito lamp and WJ-C mosquito sampler),so as to provide references for the effective surveillance,prevention and control of local mosquito vectors.Methods The overnight cap-ture of mosquitoes with a man-bait net trap,Gongfu Xiaoshuai mosquito lamp,and WJ-C mosquito sampler was performed to col-lect mosquitoes.The species of adult mosquitoes and seasonal fluctuations were investigated and analyzed.Results A total of 10 914 mosquitoes belonging to 13 species,5 genera were collected with the overnight capture of mosquitoes with the man-bait net trap,and Culex tritaeniorhynchus,Cx.pipiens palllen and Mansonia uniformis were the dominant species,accounting for 77.41％of the total.The proportion of Coquillettidia ochracea increased significantly.All the adult mosquitoes appeared in June,and reached the density peak in July and August.Both of the two surveillance tools showed relatively sensitive capture perfor-mance against mosquitoes.The trapping results of WJ-C mosquito sampler were basically the same as the man-bait trapping meth-od,however,the amount of Mansonia uniformis and Coquillettidia ochracea collected by Gongfu Xiaoshuai mosquito lamp was significantly lower than that of the man-bait trapping method.Conclusions The mosquito species are varied in Taibai Lake area of Jining City.Therefore,monitoring should be strengthened.In addition,the two mosquito trapping tools are sensitive,but they have both advantages and disadvantages,thus we should better pay attention to the consistency of monitoring methods in use.
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Objective To conduct an analysis of the epidemiological changes in malaria that have occurred in Shanxian county from 2002 to 2016. Methods A retrospective study was conducted and data were collected from web-based reporting system to explore the epidemiological characteristics in Shanxian county from 2002 to 2016. All individual case information was obtained from village malaria servicers organized by the local Shandong Institute of Parasitic Diseases. Results A total of 133 cases were identified as malaria in Shanxian county during this period, including 124 indigenous cases (93.2%) and 9 imported cases (6.8%). The 124 indigenous malaria cases were infected with Plasmodium vivax (P. vivax), whereas 7 of the 9 confirmed imported cases were infected with Plasmodium falciparum (P. falciparum), 1 was infected with Plasmodium ovale (P. ovale) and 1 patient was infected with P. falciparum mixed with P. vivax. The total number of malaria cases included 86 males (64.7%) and 47 females (35.3%). Age of the patients ranged from 1 to 83 years, although most (64.7%) infections occurred in the 21-to 60-year-old age group. Remarkably, 117 of the total malaria cases (98.0%) were reported from 2006 to 2011. The epidemic season was from June to October, with the peak occurring yearly from July to September. The most common occupation of the infected patients was farmer. In total, 58.1% of the cases occurred in 3 townships, namely, Fugang, Huanggang and Caozhuang. Conclusions In Shanxian county, the local malaria incidence experienced an emerge-peak-control-eliminate status. However, due to the numbers of migrant labourers returning from Africa, imported cases were continuous and presented an increasing annual trend, which became a non-negligible and a significant impediment for malaria elimination. Therefore, the need to eliminate instances of malaria reintroduction to receptive malaria-free areas should drive strategies to align with the epidemiological changes.
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OBJECTIVE@#To conduct an analysis of the epidemiological changes in malaria that have occurred in Shanxian county from 2002 to 2016.@*METHODS@#A retrospective study was conducted and data were collected from web-based reporting system to explore the epidemiological characteristics in Shanxian county from 2002 to 2016. All individual case information was obtained from village malaria servicers organized by the local Shandong Institute of Parasitic Diseases.@*RESULTS@#A total of 133 cases were identified as malaria in Shanxian county during this period, including 124 indigenous cases (93.2%) and 9 imported cases (6.8%). The 124 indigenous malaria cases were infected with Plasmodium vivax (P. vivax), whereas 7 of the 9 confirmed imported cases were infected with Plasmodium falciparum (P. falciparum), 1 was infected with Plasmodium ovale (P. ovale) and 1 patient was infected with P. falciparum mixed with P. vivax. The total number of malaria cases included 86 males (64.7%) and 47 females (35.3%). Age of the patients ranged from 1 to 83 years, although most (64.7%) infections occurred in the 21-to 60-year-old age group. Remarkably, 117 of the total malaria cases (98.0%) were reported from 2006 to 2011. The epidemic season was from June to October, with the peak occurring yearly from July to September. The most common occupation of the infected patients was farmer. In total, 58.1% of the cases occurred in 3 townships, namely, Fugang, Huanggang and Caozhuang.@*CONCLUSIONS@#In Shanxian county, the local malaria incidence experienced an emerge-peak-control-eliminate status. However, due to the numbers of migrant labourers returning from Africa, imported cases were continuous and presented an increasing annual trend, which became a non-negligible and a significant impediment for malaria elimination. Therefore, the need to eliminate instances of malaria reintroduction to receptive malaria-free areas should drive strategies to align with the epidemiological changes.
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Objective To detect the resistance index and esterase activity of each generation of DDVP-resistant Culex mosquitoes and analyze the relationship between insecticide resistance and esterase. Methods WHO bioassay and micro-plate measurement were used for the detection. Results The resistance index increased to 12.17 after 43 generations' insecticide selection compared to 1.00 as sensitive isolate. The nonspecific esterase(NSE) activity of the mosquitoes became strengthened with the extension of the generations, and the individual frequency of those with OD values no less than 0.9 increased gradually, consistent basically to the bioassay. The AChE average inhibition rate decreased with the extended generation and increased resistance, and the individual frequency of those with inhibition rate less than 30% became strengthened with the extension of generations, showing a positive correlation. Conclusion The activity of NSE and AChE shows a correlation with DDVP resistance.