Objective To analyze larval Aedes density of 23 surveillance provinces in China from 2015 to 2017, and to provide scientific evidence for the risk assessment, early-warning, and control of Aedes-borne diseases. Methods Aedes larvae density data were collected from surveillance provinces of the dengue fever central government transfer payments project between 2015 and 2017, and were analyzed in different years and regions by SPSS 20.0 and Excel 2007 softwares. Results During the study period(2015-2017), the Breteau index(BI) in Hainan throughout the years, Zhejiang and Fujian during April to November, Guangxi during April to September, and Yunnan during June to October, were higher than 5, the Dengue virus transmission threshold, and reached dengue transmission risk level. The Mosq-ovitrap index(MOI) in Guangxi during April to October and Guangdong during March to November, were higher than 5, and showed the same trend as BI surveillance. The BI in Chongqing, Anhui, Jiangxi, Henan, Hubei, and Sichuan during most of surveillance months from May to October were higher than 5; Furthermore, BI in Henan and Hubei in most surveillance months were higher than 10, and reached dengue outbreak level. BI in Shanghai and Hunan during most surveillance months from May to September were higher than 5. BI in Hebei during June to September 2016 to 2017, and that in Shandong during July to September 2017 were higher than 5. BI during June to September 2016 and in May 2017 in Shaanxi were all greater than 5. Conclusion The dengue transmission risk varies in different provinces temporally. Overall, the category 1 provinces in southern parts of China including Guangdong, Yunnan, Guangxi, Hainan, Fujian, and Zhejiang have relatively high risk than other provinces. It is suggested that Aedes surveillance, risk assessment, early-warning, prevention and control should be strengthened in key provinces especially in south China for fostering the prevention and control of Aedes-borne diseases in the future.
Objective To investigate the resistance status of adults Musca domestica to 6 commonly used insecticides in Zhejiang province, providing scientific basis for its prevention and control. Methods We collected adult M. domestica from 12 monitoring sites in Huzhou, Jiaxing, Shaoxing, Taizhou, Yiwu, Lishui, Zhoushan, Quzhou, Wenzhou, Jinhua, Hangzhou, and Ningbo during May and October in 2017, and brought them back to the insectary. Topical application method was used to determine the resistance of M. domestica to 6 commonly used insecticides in 12 cities of Zhejiang province. Results The LD50 values of the twelve monitoring points to beta-cypermethrin, deltamethrin, permethrin, DDVP, propoxur were 0.003 0-3.281 8, 0.005 1-0.262 6, 0.003 1-0.425 3, 0.010 0-40.409 2, and 0.044 7->160.000 0 μg/♀, and the resistance ratio were 0.8-911.6, 3.6-291.8, 6.3-39.4, 1.4-892.0, and 1.9->538.2 fold. The LD50 values of the Hangzhou population to acetofenate was 1.547 8 μg/♀, the resistance ratio was 7.2 fold. Conclusion The adult M. domestica of most monitoring points have been resistant to commonly used insecticides. In practice, insecticides resistance surveillance should be highlighted, and insecticides should be used scientifically and rationally to prevent and reduce the occurrence and development of resistance.
Objective To investigate the change in population density of mosquitoes and the resistance to commonly used insecticides against larvae and adults of Culex pipiens pallens in Tangshan city, and to provide a scientific basis for mosquito control for 2016 International Horticultural Exposition. Methods The mosquito lamp method was used to determine the population density of mosquito adults for International Horticultural Exposition park and surrounding area during 2013 to 2016. The larval immersion method and the adult exposure tube method were used to determine the resistance of Cx. pipiens pallens to commonly used insecticides. The DPS software was used to calculate the median lethal concentration and its 95%CI, virulence regression equation and Chi-square values. The resistance level of different insecticides was compared with Wilcoxon H test by SPSS 17.0 software. Results The average density of mosquitoes was 4.641 per lamp hour in Tangshan city from 2013 to 2016, with the predominant species Cx. pipiens pallens. The highest average density was found in the barn among all habitats (10.556 per lamp hour). Culex pipiens pallens were the predominant species in all surveillance areas. The population density of mosquitoes showed a single-peak throughout the year, peaking in July, being 10.854 per lamp hour. Larval Cx. pipiens pallens were susceptible to DDT, cypermethrin, temephos, chlorpyrifos, tetramethrin, bendiocarb and pyriproxyfen, with the resistance ratio of 0.88, 1.94, 0.82, 0.50, 2.18, 0.53, and 0.02, respectively. All of tested larval mosquitoes were intermediately resistant to bifenthrin with the resistance ratio of 14.00 and highly resistant to ethofenprox with the resistance ratio of 57.00. Culex pipiens pallens adults showed a mortality of 25.00% when contacted deltamethrin for 1 h and mortality of 50.00% when contacted permethrin for 3 h, all tested adults were resistant to deltamethrin and permethrin. Culex pipiens pallens adults experienced 100% mortality when contacted propoxur for 2 h, which was considered susceptible. Conclusion The predominent species were Cx. pipiens pallens, density peaked in July, when comprehensive control measures should be taken. More considerations are warranted about how to choose carbamate, organophosphorus and organochlorine insecticides, prevent or slow down the occurrence of the resistance.
Objective To understand larval breeding and species composition of dengue vector mosquitoes in residential area of Gengma county during the seasonal peaks, in order to provide a scientific basis for control of mosquitoes and mosquito-borne diseases. Methods In August 2016, the Breatu index method was used to investigate the breeding and composition of Aedes larvae in all types of water containers in 6 residential areas of Gengma county. SPSS 19.0 software was utilized for data analysis by Chi-square test, Chi-square partition test and Fisher precise probability to explore the significance of species composition and positive breeding. Results In this study, a total of 361 households were surveyed, among which 62 households were confirmed positive. In total, 1 216 water containers were found, of which 106 were positive. The Breatu index(BI), house index(HI) and container index(CI) were 29.36, 17.17, and 8.72%, respectively. All of them were the highest in Mengjian township, 85.00, 60.00, and 18.48%, respectively. The BI of 4 sites reached the outbreak level for dengue fever. The main and positive water containers were buckets, which were 408 and 31 respectively. The positive rate of Aedes breeding in different types of containers was analyzed by Chi-square partition method. The highest positive rate of used tire was 32.89%(25/76) (α=0.004, P=0.002). Compared with Qingshuihe port, the composition of Aedes species in Mengding town was not statistically significant by Fisher method (P=0.123). Conclusion Aedes aegypti and Ae. albopictus, the vectors for dengue fever, were found in Gengma county, especially more predominant than that of Ae. albopictus in Mengding township and Qingshuihe port. The distribution range of Ae. aegypti showed the tendency of further expanding. The main types of Aedes breeding containers was used tires, followed by temporary containers, waste bottles, etc. These types of containers should be drained first, supplemented by adulticiding during the vector control operations.
Objective To provide scientific guidance for the prevention and control of dengue fever and Zika disease outbreak by field control of Aedes albopictus which was carried out by vegetation barrier treatment and the methods of rapid and sustainable effective control of Ae. albopictus were explored. Methods During August-October, high efficient cypermethrin microcapsule suspension (barrier treatment residual spraying) and cypermethrin emulsion were sprayed on the vegetation of Ae. albopictus. The density of Ae. albopictus was monitored by human landing counts and was observed before and after application and analyzed by Excel 2007 software. Results The density reduction rate was 96.0%, 99.0%, 85.0%, 84.0%, 47.3%, and 3.0% respectively on the first day, and in the first through the fifth weeks, respectively, in the trial of cypermethrin microcapsule suspension. The densities of the Ae. albopictus were reduced by 83.0%, 77.0%, and -25.0% respectively on the first day, and in the first and the second week, respectively, in the trail of cypermethrin emulsion. Conclusion The application of vegetation barrier treatment can persist more than 3 weeks. It has the advantages of long lasting effect, resistance to rain water wash, time and labor savings, reduction of environmental pollution,and so on. This technique has a good application prospective to mitigate outbreak of Zika virus and other infectious diseases.
Objective Given that an outbreak of dengue was occurring in neighboring city of Ningbo, to reduce the risk of local transmission caused by imported cases, to strengthen monitoring of Aedes albopictus and to provide a basis for the control of dengue vector in Ningbo city. Methods The densities of Ae. albopictus larvae in residential quarters of cities or countryside and nurseries in 11 counties, cities or regions of Ningbo were monitored by Breteau index(BI) method from 2017-09-11 to 2017-11-10, and the relationships between mosquito densities and meteorological factors were analyzed by Spearman correlation analysis and multiple linear regression analysis. Results Almost all the BI was above 5, the Dengue virus trasmission threshold, among the monitoring sites. During most of the monitoring period, the BI was above 20. The BI of later monitoring declined, but still above dangerous threshold. The BI of urban districts(17.88) was significantly lower than that of suburb(31.44); The BI of nurseries(40.25) was higher than that of residential quarters of cities(13.10) or countryside(29.46). Mosquito densities were significantly associated with average temperature(R=0.899, P=0.015), especially average minimum temperature(R=0.943, P=0.005). Conclusion The densities of Ae. albopictus larvae were generally higher above the Dengue virus trasmission threshold, and there were potential risks of dengue epidemic in Ningbo city. The surveillance system should be strengthened, and multi-layered technology of prevention and control should be reserved. Besides, average temperature, especially average minimum temperature, had a significant influence on mosquito densities.
Objective In order to understand the insecticide resistance of Musca domestica to five different commonly used insecticides in Huairou district from 2014 and 2016, and provide the basis for scientific and reasonable guidance on the selection of insecticides for its control program. Methods The drug resistance test was carried out using the membrane method, and the experimental data were analyzed by PROBIT model in SPSS(21.0) software. Results In 2014 and 2016, the wild population of M. domestica in Huairou district was susceptible to DDVP, and the resistance were 0.23 and 0.25-fold,respectively. The resistance to Deltamethrin was high, and the resistance were 157.62 and 37.15-fold, respectively; resistance to Beta-cypermethrin were very high in both years, the resistance were 181.64 and 289.06-fold, respectively. In 2016, the resistance level to Propoxur changed from low to high, and increased by 4.15 times compared to 2014; the resistance level to Chlorpyrifos was decreased by 33.58 times from low resistance to being susceptible. Conclusion The M. domestica in Huairou district showed high or extremely high resistance to pyrethroid insecticides. The resistance to DDVP and Chlorpyrifos should be further monitored and determined. Integrated control measures should be taken to control fly species.
Objective To explore the risk factors of mosquito-borne diseases and to evaluate the effect of 1% temophos granule on the mosquitoes, so as to provide information for mosquito control operations. Methods The survey used a random sampling of eight residential areas, setting up the experimental and the control group in July-September in 2017 in Qibao town, Minhang district, Shanghai. After putting 1% temophos granule(Abate) into the rain wells, we investigated the positive rate of mosquito larvae, monitored the density of adult mosquito by CO2 mosquito trap, and calculated the mosq-ovitrap index utilizing Mosq-ovitrap. The Excel 2007 software was used to establish the databas. The SPSS 21.0 software was used for statistical analysis. Counting data were expressed as percentages, and Chi square test and Rank sum test were used for correlation analysis. Statistical significant difference was decided at P<0.05. Results A total of 1 200 rainwater wells were investigated. The positive rate of mosquitoes between experimental group(74/592, 12.50%) and untreated control group(138/608, 22.70%) of rainwater wells had statistically significant differences(χ2=21.443, P=0.000). The positive rate of mosquito between experimental group(21/161, 13.04%) and control group(68/166, 40.96%) of grate type rainwater wells had statistical significance (χ2=32.163, P=0.000). Yet, the positive rate of mosquitoes between experimental group (53/431, 12.30%) and control group (70/442, 15.84%) of inspection wells had no statistical significance (χ2=2.259, P=0.133). In total, 1 696 adult mosquitoes were captured by CO2 mosquito traps. The experimental group(average density 0.58 mosquitos/hour) and control group(average density 2.36 mosquitos/hour) had statistical significance(Z=4.460, P=0.000). The test showed that the density of Culex pipiens pallens(Z=4.374, P=0.000) and the density of Aedes albopictus(Z=4.459, P=0.000) were statistically significant by rank sum test, and there was no significant difference in Cx. tritaeniorhynchus(Z=1.000, P=0.317). A total of 900 mosquito ovitraps were deployed, with 825 retrieved and 299 positives. The Mosq-ovitrap index(MOI) had statistically significant(χ2=61.285, P=0.000) between experimental and untreated control groups in Ae. albopictus, MOI in the experimental group was approximately half of the control group. Conclusion The density of larval and adult mosquitoes could be effectively reduced through dosing 1% temephos granule into rainwater wells especially grate type in residential areas. The control effect is particularly obvious to Ae. albopictus.