| Background:Dengue fever is an acute infectious disease caused by the dengue virus, including dengue fever (DF), dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), and the main transmission medias are Aedes aegypti and Aedes albopictus. The disease occurs mainly in tropical and subtropical regions. It has become one of the vector-borne diseases which is the most widely distributed, the largest number of incidence and the most serious harm in the world. In recent years, dengue cases are rapidly increasing, and this deadly infectious disease has been a threat to the health and safety of over1/3of the population. The World Health Organization(WHO) estimates that there were about100million cases of dengue fever and500,000cases of dengue hemorrhagic fever, and25,000people were killed in the world each year.Guangdong, Hainan, Guangxi, Fujian, and Taiwan have happened dengue epidemic. Guangdong Province is subtropical, and the natural environment is suitable for breeding of insect-borne. Guangdong has been the country hardest hit by dengue fever, accounting for about90%of the number of dengue cases of the country over the years. The dengue media in Guangdong Province is Aedes albopictus. The Aedes albopictus mainly distributed in the Asian tropical, subtropical and some temperate areas. The distribution in China is also broader, north of Liaoning, Shenyang, Dalian, Dandong, northwest to Shanxi Baoji, south of Hainan, and it is the most common mosquito species.Because of the lack of safe and effective vaccines in the prevention of dengue, Aedes monitoring is an important means of warning dengue fever occurrence effectively and controlling dengue fever epidemic. The larvae monitoring is the most traditional and common method of the dengue vector density monitoring. But the larvae monitoring has a heavy workload, the household survey is more and more difficult, and the natural water in containers that can be monitored is fewer and fewer, it is difficult to accurately reflect the mosquito density of a region, so these traditional dengue fever warning indicators are no longer applicable in the current environment. At present, there is not yet a warning system of dengue fever epidemic in China, one of the main reasons is not scientific enough of the mosquito-borne monitoring.Due to the lack of reliable scientific monitoring standards and corresponding warning threshold, the new mosquito monitoring methods are not widely applied. According to the ecological characteristics of Aedes albopictus, our laboratory designed and developed the Aedes mosquito traps, and the effect was verified in the laboratory and in the field. The Aedes traps (patent pending number:200820051015.0) can trap Aedes adult mosquitoes and lure Aedes spawning, reflect the Aedes albopictus density more sensitively, warn the dengue incidence and prevalence early, as well as facilitate the monitoring of Aedes albopictus adult mosquitoes infected.Objectives:1. To monitor the Aedes albopictus density with Aedes traps developed by our laboratory and the traditional larvae monitoring method, and provide the basis data for follow-up studies.2. To analyze and evaluate the seasonal fluctuation of Aedes albopictus density, dengue virus carrying case, and the resistance.3. To analyze and evaluate the relationship between Aedes trap effect indicators and traditional larvae monitoring indicators with the method of linear and nonlinear.Methods: 1. Aedes trap monitoring method:the monitoring scenes were a university of Baiyun district in Guangzhou and a village in Conghua. According to the ecological characteristics of Aedes albopictus, lay Aedes traps, observe4d continuously, observe and record the mosquito trapping and recycle save. According to the data obtained, calculate Aedes trap effect indicators.2. Traditional larvae monitoring:the numbers of houses, larvae breeding houses, water containers and larvae breeding containers were investigated synchronously in the residential areas to calculate House Index, Breteau Index, Container Index. Make records in the monitoring process.3. Dengue virus detection:dengue fever virus carried by Aedes albopictus was detected by RT-PCR, dengue virus type2cell suspension as a positive control, laboratory strains of mosquitoes as a negative control.4. Larvae dipping method:using the WHO biological test method, the resistance was determinated respectively to wild population and laboratory susceptible strain of Aedes albopictus. Resistance index formula:resistance index=LC50of wild population/LC50of laboratory susceptible strain.5. Statistical methods:MOI, MI,OI of different seasons in urban and rural areas used χ2test. The relationship between Aedes trap indicators and traditional indicators used Spearman correlation analysis and curve estimation analysis. The relationship between climatic factors and traditional indicators, Aedes trap indicators used Spearman correlation analysis and multivariate linear regression analysis. P<0.05was considered statistically significant.Results:1. Aedes trap monitoring of urban and rural areas:372Aedes traps were laid in urban for four seasons,349were recovered, and the recovery rate was83.82%.850Aedes traps were laid in rural for four seasons,834were recovered, and the recovery rate was98.12%. In urban and rural ovitrap positive containers were69and159, oviposition positive containers were66and113, and ovitrap and oviposition positive containers were79and165. 2. Seasonal fluctuations of Aedes albopictus density in urban and rural:The seasonal fluctuations of Aedes albopictus density were consistent in Guangzhou urban and rural. The densities reached a peak in summer [urban, rural, MOI=40.54,38.14; MI=35.14,37.63; OI=36.49,29.90], and the lowest in winter, but MOI, MI were both greater than zero in winter.3. Dengue virus detection:dengue virus were not detected in291and567Aedes albopictus vivo captured from urban and rural. Dengue virus type2cell suspension as a positive control, the result was positive. Laboratory strains of mosquitoes as a negative control, the result was negative.4. Resistance of Aedes albopictus:Anti-dichlorvos indexes were low resistance in spring and autumn(greater than two), and the sensitivity in summer(less than two) in urban. Indexes in spring and autumn were higher than in summer, but all showed a sensitivity in rural(less than two).5. Traditional larvae monitoring of a village in Conghua:355water containers were monitored from the summer of2011to the autumn of2012, including120positive containers.635houses were monitored, including8positive houses. Breteau Index requires less than20in the usual period, less than5in the outbreak period. Breteau Indexes of2011summer, autumn, winter and2012autumn (Old Village) were less than20, only2011winter was less than5,2012Spring, Summer and autumn (New Village) were more than20,2012summer (New Village) was up to87.179.6. Relationship between Aedes trap indicators and traditional indicators:The relationship between Aedes trap indicators (MOI, MI, MDI, MEI, OI, EDI, OEI) and traditional indicators (Breteau Index, Container Index) used Spearman correlation analysis. There were no correlations between Aedes traps indicators and traditional indicators, further curve estimation analysis.7. Curve estimation of Aedes traps indicators and traditional indicators: traditional indicators (Breteau Index, Container Index) as the dependent variable, Aedes traps indicators (MOI, MI, MDI, MEI, OI, EDI, OEI) as the independent variable, curve estimation was analyzed. Finally, Container Index and MOI, Container Index and MI, Container Index and MEI had curve correlations. Power model and S model were statistically significant (P<0.05), S model had the highest R2, select S model, and establish regression equations.8. Relationship between climatic factors and traditional indicators:the relationship between climatic factors (temperature, humidity, light, wind speed) and traditional indicators (Breteau Index, Container Index) used Spearman correlation analysis. In climatic factors only temperature and Breteau Index, Container Index had correlations. Temperature and Breteau Index (r=0.714, P=0.047), temperature and Container Index (r=0.850, P=0.007).9. Relationship between climatic factors and Aedes trap indicators:the relationship between climatic factors (temperature, humidity, light, wind speed) and Aedes trap indicators (MOI, MI, MDI, MEI, OI, EDI, OEI) used Spearman correlation analysis. There were no correlations between climatic factors and Aedes trap indicators (P>0.05).Conclusions:1. Aedes albopictus can be monitored throughout the year in Guangzhou urban and rural, the peak is summer, and winter can also be monitored, with the consistent results of previous studies. The Aedes trap monitoring method as a new type of mosquito-borne density monitoring method can be an alternative to traditional monitoring methods, extended to the monitoring of mosquito-borne density.2. Dengue virus were not detected in Aedes albopictus vivo in urban and rural with the conventional PCR method.3. For anti-dichlorvos situation of the wild Aedes albopictus population, only spring and autumn of urban showed low resistance (resistance indexes were less than3), the rest showed a sensitivity. Dichlorvos has a good effect on killing mosquito larvae, but the kill time should be choosed reasonably.4. The mosquito-borne density was monitored with methods of the Aedes trap and traditional larvae monitoring. Aedes traps indicators (MOI, MI, MEI) and traditional indicator (Container Index) had curve correlation and established regression equations. Regression equations quantitatively reflect the relationship between Aedes trap indicators and traditional indicators, provide a new method for the dengue fever warning, and provide the scientific basis for the popularization and application of Aedes trap monitoring.5. Spearman correlation analysis found that temperature is an important factor to affect the mosquito-borne density. The quantitative relationship between temperature and the mosquito-borne density should be studied in order to make a reasonable estimation and prediction of the seasonal variation of the mosquito-borne density. |
