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Epidemiological characteristics of dengue fever and surveillance results of Aedes mosquitoes in Xishuangbanna Prefecture, Yunnan province, China, 2006-2020
FAN Jian-hua, GAO Yang, ZHU Jin, HUANG Qiang, LI Jun-ming, SU Mei-hui, ZHANG Hai-lin
Abstract228)      PDF (2509KB)(688)      
Objective To investigate the epidemiological characteristics of dengue fever and the distribution characteristics of the vector Aedes mosquitoes in Xishuangbanna Dai Autonomous Prefecture (Xishuangbanna Prefecture) of Yunnan province, China, 2006-2020. Methods The descriptive epidemiological method was used to analyze the data of cases of dengue fever. The Breteau index (BI) method was used to monitor the density of Aedes larvae. Species identification was performed for some mosquitoes collected. Excel 2010 and ArcGIS 10.2 softwares were used for database construction and plotting. SPSS 17.0 software was used to perform correlation analysis. Results A total of 8 583 confirmed cases of dengue fever were reported in Xishuangbanna Prefecture, 2006-2020, with 767 (8.94%) imported cases and 7 816 (91.06%) local cases. The mean annual incidence rate was 118.77/100 000, with the highest incidence of 327.44/100 000 in 2019. Dengue fever epidemics occurred almost every year in Jinghong city, Mengla county, and Menghai county of Xishuangbanna Prefecture, with the number of cases in the three regions accounting for 84.97% (7 293/8 583), 10.42% (894/8 583), and 4.61% (396/8 583), respectively. In Jinghong city, the annual incidence rate averaged 223.74/100 000, and reached as high as 614.02/100 000 in 2019. Cases of dengue fever were reported in 93.75% (30/32) of all townships in the prefecture, and 10 townships in Jinghong city and Mengla county had local epidemics. Imported cases were reported in each month through a year, while local cases were distributed from June to December, with a peak from August to October. The patients were aged from 5 months to 93 years, mainly between 20 and 59 years. The male-to-female ratio was 1.01:1. Most patients were commercial workers and service providers, farmers, retirees, household workers and unemployed persons. The BI was 10-50 from June to October and BI<10 in the other months, at four larval density surveillance sites of Xishuangbanna Prefecture, 2013-2020. The BI was higher in Jinghong city than in other counties in all months through the years. Ae. albopictus was found in all townships in Jinghong city, Mengla county and Menghai county, and Ae. aegypti was found in 21 townships. Among the 9 066 larvae and adult mosquitoes collected, Ae. albopictus accounted for 35.24% (3 195/9 066), Ae. aegypti accounted for 33.65% (3 051/9 066), and other mosquito species accounted for 31.11% (2 820/9 066). Conclusion There were only imported cases of dengue fever in 2006-2012 and 2020, and both imported and local epidemics occurred in 2013 and 2015-2019 in Xishuangbanna Prefecture. Imported cases from Laos and Myanmar were the main cause of local epidemics in Xishuangbanna Prefecture. The seasonal distribution of dengue fever was closely associated with the increase in mosquito density. There was no year-round transmission or cross-year transmission of dengue fever in the prefecture, and dengue fever in this area is still an imported disease. Surveillance and management of imported cases and regular mosquito control are important measures to prevent dengue epidemics in the region.
2022, 33 (2): 245-251.   doi: 10.11853/j.issn.1003.8280.2022.02.015
Effectiveness evaluation of the gridding management of dengue fever in the urban area of Jinghong, Yunnan province, China
TANG Ye-rong, JIANG Jin-yong, DU Long-fei, YANG Ming-dong, FAN Jian-hua, ZHU Jin, ZOU Jian-hong, HE Jing, YU Zhang, ZHOU Hong-ning
Abstract323)      PDF (2907KB)(1041)      
Objective To investigate the application effect of gridding management in the prevention and control of dengue fever in Jinghong, Yunnan province, China, and to provide a scientific basis for developing effective prevention and control strategies for dengue fever. Methods Based on the gridding management system of dengue fever prevention and control in Jinghong in 2019, epidemiological description and the geographic information system were used to analyze and evaluate the effectiveness of gridding management in the prevention and control of dengue fever in Jinghong in 2019. Results In 2019, 28 dengue fever grid points were divided in the urban area of Jinghong city. Imported cases occurred in June, the outbreak of dengue fever was observed in July, and the cases of dengue fever reached the peak in September (1 775 cases). For the 28 grid points in Jinghong from June to November, the monthly mean Breteau index (BI) was 11.18, 18.42, 14.62, 14.02, 5.81, and 2.09, respectively, the rate of reaching the standard of BI was 52.56%, 44.76%, 51.66%, 46.57%, 74.01%, and 91.71%, respectively, and the number of dengue cases were 8, 47, 540, 1 775, 473, and 72, respectively. Conclusion Gridding management can effectively prevent and control dengue fever by improving the rate of reaching the standard of BI in the urban area of Jinghong. It is suggested that the local government should further develop the grid management of dengue fever.
2020, 31 (3): 254-258.    doi: 10.11853/j.issn.1003.8280.2020.03.002
Identification of Japanese encephalitis viral infections in mosquitoes in Jinghong city, Yunnan province, China
PAN Hong, GAO Yang, FENG Yun, HAN Xi, ZHANG Jing, ZHU Jin, LI Wei-ping, LI Hong-bin, FAN Jian-hua, ZHANG Hai-lin
Abstract361)      PDF (829KB)(1232)      
Objective To investigate the natural infection with Dengue virus(DENV) and Japanese encephalitis virus (JEV) in mosquitoes in Jinghong city, Xishuangbanna prefecture, Yunnan province, China, and provide the scientific basis for its prevention and control. Methods Mosquito samples were collected from urban area of Jinghong in August and September 2015. Mosquito samples were tested for the nucleic acid of DENV and JEV by RT-PCR assay, and positive specimens were sequenced for C/PrM gene for homology and phylogenetic analyses. Results A total of 2 009 mosquitoes were collected in urban area of Jinghong. Aedes albopictus, Ae. aegypti, Culex(species not identified) and Ae. vexans were 896, 477, 634, and 2 of the total, respectively. The JEV RNA were detected from one pool of Culex mosquitoes and one pool of Ae. albopictus mosquitoes. The sequences of C/PrM genes of the 2 JEV strains were obtained. Homology and phylogenetic analyses showed that the 2 JEV strains are consistent with the genotypeⅠ(G-Ⅰ) and its clade of the same G-Ⅰ strains of JEV from GenBank, and the JEV strains from Jinghong were closely related to the JEV G-Ⅰ strains from Honghe prefecture of Yunnan in 2009, Dehong prefecture of Yunnan in 2010 and Gansu province, China in 2008. Mosquito samples tested negative for DENV in the study. Conclusion Existence of JEV G-Ⅰ in Jinghong city of Xishuangbanna prefecture was firstly confirmed from mosquitoes in 2015. It should be strengthened to monitor and control Japanese encephalitis epidemics in this area.
2018, 29 (4): 331-335.    doi: 10.11853/j.issn.1003.8280.2018.04.002
Study on the effect of diflubenzuron on pyrethroid-resistant dengue vector Aedes mosquitoes
KAI Wen-long, SHI Can-nan, ZHAO Chun-chun, LIU Qi-yong, SONG Xiu-ping, REN Dong-sheng, LI Hong-bin, FAN Jian-hua, ZHOU Hong-ning, MENG Feng-xia
Abstract249)      PDF (1437KB)(766)      
Objective To determine the effect of diflubenzuron on dengue vector Aedes mosquitoes and provide evidence for mosquito resistance management and vector control. Methods WHO recommended method for insect growth regulators was utilized; the resistant Aedes strains were collected from Jinghong city the dengue fever epidemic area, the data were analyzed with SPSS 24.0 to create a log-probit model to determine the IE 50 of the susceptible strains and resistant strains, calculate the resistance ratio, observe the the stage-and concentration-dependent mortality, and analyze the characteristics of diflubenzuron against Aedes mosquitoes. Results The IE 50s of the resistant strains of Ae. aegypti and Ae. albopictus were 0.002 53(95% CI:0.002 16-0.002 89) μg/ml and 0.002 33(95% CI:0.001 98-0.003 12) μg/ml, the resistant ratios were 1.77-and 1.71-fold, indicating that no cross resistance between diflubenzuron and pyrethroid. The mortality peak of Ae. albopictus and Ae. aegypti was 4-6 d post-exposure, indicating that the effect of diflubenzuron was slow as compared with commonly used conventional insecticides. Under the different concentrations, the effect was different. The low concentration mainly resulted mortality at adult stage, whilethe high concentration mostly impacted on pupal and/or larval stages. Conclusion The resistant strains of Ae. albopictus and Ae. aegypti were susceptible to diflubenzuron. The recommended dose was 0.006 μg/ml,but the lethal effect of diflubenzuron was slow. It can be used as a selective insecticide for resistance management and vector control.
2018, 29 (2): 126-129.    doi: 10.11853/j.issn.1003.8280.2018.02.003
Resistance and mortality pattern of dengue vectors exposed to pyriproxyfen in Jinghong city, Yunnan province
SHI Can-nan, KAI Wen-long, LIU Qi-yong, FAN Jian-hua, ZHOU Hong-ning, LI Hong-bin, MENG Feng-xia
Abstract332)      PDF (2565KB)(966)      

Objective To test the resistance to pyriproxyfen in dengue vectors Aedes aegypti and Ae. albopictus and observe the mortality pattern of mosquitoes at various concentrations in Jinghong city, Yunnan province, so as to provide evidence for dengue vectors control and resistance management. Methods Aedes larvae were collected from Dengue epidemic areas in Jinghong from October to November, 2015. WHO recommended methods for insect growth regulators was carried out on the 3rd instar larvae collected. The resistance ratio (RR) was calculated by comparing half inhibition of emergence concentration (IE50) of the tested wild population with the susceptible reference strain. Additionally, the mortality pattern of dengue vectors exposed to pyriproxyfen was analyzed by observing daily stage-specific mortality at various concentrations. Results The IE50s of Ae. aegypti and Ae. albopictus in Jinghong city were 0.024 47 (0.022 09-0.027 07) and 0.135 20 (0.117 10-0.156 60) μg/L. There was 13.44-fold resistance in Ae. albopictus and 0.85-fold resistance in Ae. aegypti to pyriproxyfen compared with the susceptible strains respectively. Aedes albopictus was also 5.53-fold more tolerant to pyriproxyfen than Ae. aegypti in Jinghong city. For the dead individuals, most of them died at 4-6 d after exposure to pyriproxyfen, and the peak of death for susceptible Ae. aegypti and Ae. albopictus were at 4-5 d and 4 d respectively. A wider range of death peak was observed for Jinghong population of Ae. aegypti and Ae. albopictus, which was at 4-6 d. At low concentrations, most of the dead were deformed adults and mosquitoes not completely separated from the pupae. For the susceptible reference strain, dead pupae began to occur steadily when the mortality was over 60%, and the proportion increased as the concentration went up. However, the mortality of pupae was fluctuating in Jinghong population. Conclusion In Jinghong city, Ae. aegypti larvae was susceptible to pyriproxyfen. Considering this species is preferentially found in urban areas, pyriproxyfen is recommended to use in urban areas. Although Ae. albopictus larvae have developed moderate resistance to pyriproxyfen, this larvicide still can be used in alternatery with other insecticides to delay the resistance development. It proves that pyriproxyfen is highly efficient for mosquito control and resistance management in Jinghong city. Periodic resistance monitoring must be conducted to learn the variations of resistance level timely.

2017, 28 (2): 108-112.    doi: 10.11853/j.issn.1003.8280.2017.02.003
Investigation of mosquitoes and arboviruses in Xishuangbanna,Yunnan province, China in 2011
TANG Cheng-jun, FU Shi-hong, ZHANG Hai-lin, FAN Jian-hua, YANG Wei-hong, ZHANG Yu-zhen, LV Zhi, LI Yuan-yuan, LI Hong-bin, ZHU Jin, WANG Yu, TAO Jia-ling, LI Li-hua, BAI Wei-rong, ZHA Bing, WANG Pi-yu, LIANG Guo-dong
Abstract598)      PDF (1473KB)(851)      

Objective To investigate the distribution profiles of mosquitoes and arboviruses in Xishuangbanna,Yunnan province, China, and to provide evidence for prevention and control of arbovirus diseases. Methods Mosquito samples were collected in Xishuangbanna and then used for virus isolation by cell culture. RT-PCR was used to identify arbovirus. Serum and cerebrospinal fluid samples were collected from fever patients, and the common encephalitis virus IgM antibodies were detected by ELISA. Results A total of 13 337 mosquitoes, belonging to 29 species and 5 genera, were collected. The main mosquitoes were Culex tritaeniorhynchus (79.98%, 10 667/13 337), followed by Anopheles sinensis (7.95%, 1060/13 337) and An. peditaeniatus (7.38%, 984/13 337). Several specific primers for Japanese encephalitis virus (JEV), Banna virus, alphavirus, and circovirus were used for PCR detection in 214 batches of mosquitoes, and no virus was isolated from the mosquitoes. Also, no virus was found in isolation using several types of cells. A total of 52 serum samples and 54 cerebrospinal fluid samples were collected from patients in acute stage by kits for encephalitis viruses and then subject to ELISA. There were 16 cases with JEV IgM, 4 cases with Herpes simplex virus IgM, 13 cases with mumps virus IgM, 3 cases with ECHO virus IgM, and 1 case with dengue virus IgM. Conclusion No JEV, BAV, and circovirus were detected from mosquitoes collected in Xishuangbanna,Yunnan province, China in 2011. However, serological results indicated that local fever patients were infected with several viruses such as JEV.

2012, 23 (5): 410-412,416.
Comparison of esterase isozymes in three species of backflies (Diptera:Simuliidae)
GAO Bo, ZHANG Jian-Qing, CAI Heng-Zhong, WANG Guang-Hui, FAN Jian-Hua, HUANG Jian-Qun, HUANG En-Jiong, WANG Yu-Ping, ZHANG Shu-Keng, WANG Gong-Dong
Abstract994)      PDF (343KB)(913)      

【Abstract】 Objective To explore the value of isozyme zymograms in the classification of blackflies and accumulate basic biochemical data for the study of phylogenesis. Methods EST isozymes of three blackfly species were studied by discontinuous PAGE techniques. Results Ten isozyme bands could be identified according to the electrophoresis zymograms. The differences of zymograms were significant between three blackfly species and each species had its own special zymogram. The main band among intraspecific individuals or between the larvae and pupae was alike, however, other enzyme bands were different. Conclusion EST isozyme zymograms could be used as one of the classification characteristics of blackflies.

2009, 20 (2): 138-139.