| Dengue fever is an acute infectious disease transmitted by Aedes mosquitoes, which distributes primarily in tropical and subtropical countries and regions. In the world, it's approximately one hundred million cases to be infected annually, and the disease has threatened human being health greatly. In our country, dengue fever mostly distributes in Guangdong, Fujian, Hainan and Taiwan provinces, while the disease also emerges in other provinces such as Zhejiang. With global climate getting warmer gradually, this disease tends to diffuse from the south to the north. Meanwhile, trend of globalization and destroy of natural ecosystem make the prevention and control of this epidemic more complicated. As Aedes mosquito is easily affected by many environmental factors, it's difficult to use traditional measures to surveil and control the disease, so that the research and application of the new surveillance measures is urgent for the epidemiology staffs.Disease surveillance refers to collecting the information of the dynamic distribution and the influential factors consistently and systematically, and reporting the information after analysis in order to take preventive measures and evaluate the effects. Disease surveillance includes 4 basic steps, collecting, analyzing, reporting and using the information. Make full use of the information to predict the epidemics is the main purpose of disease surveillance. At present, the main surveillance methods of our country are larval survey, and the indices are house index, container index and Breteau index. The vector biology and control surveillance scheme includes mosq-ovitrap as a surveillance method, while its application is not extensive. The management of data information is an important link of the epidemic surveillance process. Before 2004, the epidemic disease information is mainly reported through paper reporting cards. After receiving the hospital's letters or phone calls, the district disease prevention control center will type into the computer by mode of reporting to the next higher level of authority. From 2004, ministry of health regulates that all the legal epidemics and other important epidemic diseases must be reported directly through computer network data system "China disease prevention control information system". The insect-borne surveillance information of dengue fever is managed by individual surveillance unit. There is no effective means to pre-warning the dengue fever in the world. Some researches think that the danger increases when the house index, container index and Breteau index are high. So most countries refer to these indexes as the warning index. In our country, the Breteau index must be lower than 20 at ordinary times. When dengue fever breaks out, the index should be controlled under 5.The main problem is that with the development of the society, the traditional surveillance methods do not fit the current society environment, while the new effective method is not yet found out. The current surveillance method in our country is larval survey. The method is used to supervise the yellow fever vector Egyptian Aedes mosquito. Shortcoming of this method is too much work and interfering factors. This method supervises the number of Aedes mosquito larvae and chrysalides, and estimates the mosquito density of the environment. With the development of modern society, the buildings in the city are mostly storied buildings. Courtyards and containers are less and less. Supervising the courtyards and containers is not enough to reflect the mosquito density. The new mosa-ovitrap designed by Lin Lifen has become one of the regular surveillance methods in our country. This device is not good at trapping the larvae. Thus, improving the traditional surveillance method is the prerequisite of preventing and predicting the dengue fever. Proper mosquito attractant is one of the solving methods.Whether "reporting of grade by grade" or "reporting direct through the computer network" mode can just fulfill the ordinary attribute information management work, while cannot fulfill the work from geography concept. Lack of geography space information of the disease will lead to hardly reflecting geography space distribution characters and space relations, thus hardly controlling the epidemic rules of the disease. It's urgent to design a convenient disease surveillance information management system. In recent years, GIS technology developed rapidly, and has become a necessary facility to deal with and analyze the space information. Establishing an information management system based on GIS is an important instrument of surveillance, pre-warning and rapid-reacting to the epidemics. It can handle the development and change of epidemic in time, transfer the information exactly, so that the relevant agency can adopt emergency measures in time, reducing the unnecessary loss.During the course of urbanization, traditional dengue fever early-warning indexes do not suit modern society environment. Singapore has controlled the house index under 2 and the Brazil Breteau index under 5 Since 1979, while the dengue fever still exists. As the dengue fever is an acute infectious disease transmitted by Aedes mosquitoes, the density of the Aedes mosquito and some factors influencing the density will affect the prevalence of the dengue fever. We must establish a early forecasting and warning system based on dengue fever data, climate factors, environment factors, and so on. Among these factors, climate factors are important to dengue fever, and it can affect the transmission of insect-borne infectious disease. Thus, supervising changes of the climate factors and analyzing the function of these factors will help to formulate more effective strategy to control infectious diseases. Dengue fever is an insect-borne infectious disease and transmitted by Aedes mostly. Mosquito density is affected by some climate factors such as temperature, rainfall and humidity. Research on the relation between dengue fever and climate factors will help to establish a climate-based early-warning system.At present, main problems include that surveillance cannot reflect the mosquito density exactly, people cannot analyze the disease combining with local environment factors such as vegetation and climate, and cannot do the research on the space relation of the surveillance data. So it's hard to catch the dynamic change rules. In order to provide an easy-handling platform for data management, demonstration and space analysis, we have developed a series of research on dengue fever surveillance methods. In the meantime, we research the attractant for Aedes albopictus and the relation between dengue fever and climate factors. These researches offer theory base for the improvement of dengue fever surveillance system.1. Objective(1) Using geographic information system platform software to develop an information management system for dengue fever.(2) Screening potential mosquito attractant, and enhancing the surveillance effect of Aedes albopictus.(3) Analyzing the influence of climate factor, providing scientific proof for establishing dengue fever early warning mode.2. Methods2.1 Study of dengue fever information management systemWe use SuperMap Objects5.2 platform software to develop this system, with Visual Basic6.0 software as integration environment. As developing this system, the integration of dengue fever space data base is finished through SuperMap Objects core component and some software engineering technique such as active data object, data access object and data environment. After that, using dynamic link library to implement data transmission and data display between GIS component function and data base program, then constituted unified seamless interface.2.2 Influence of different attractants to Aedes albopictus surveillance effectiveness2.2.1 Preparation of attractants(1) Experiments of container colorControl group: In the bottom of Mosq-ovitraps, put a sheet of 10cm filter paper and infunde 20ml overnight tap water, then head up and mark. Black bottle group: Mosq-ovitraps are wrapped up by a plastic bag in black at its upper 2/3 part.(2) Experiments of infusionsPanicum maximum infusion group: 3g fresh Panicum maximum leaves, shorn to broken bits and soak to a beaker which filled 300ml overnight tap water, then the beaker is put to water bath of 60 degree and warmed up for two hours, after that, the liquid is filtered by gauze, which is Panicum maximum infusion. Tyre leachate group: used automobile tyre is shorn to broken bits and soaked to a beaker which filled 300ml overnight tap water, then the beaker is put to water bath of 60 degree and warmed up for two hours, after that, the liquid is filtered by gauze, that is tyre infusion. Control group was same to (1).(3) Experiments of chemical attractantsL-lactic acid group: L-lactic acid is diluted to 0.5mg/ml, 1mg/ml, 2mg/ml, 5mg/ml, 10mg/ml and 20mg/ml through overnight tap water. Control group was same to (1).(4) Experiments of yeast generated CO2 Experiment one: Add the mixture that consist of 50ml overnight tap water, 25%cane sugar solution and 0.25g yeast powder to each Mosq-ovitrap in experiment group, then stick a wrap of 3cm width filter paper in the upper part of Mosq-ovitrap. Comparison group was same to (1).Experiment two: This test had five groups, they were A group, B group, C group, D group and E group, and A group adds overnight tap water, yeast powder and cane sugar to each Mosq-ovitrap, B group adds overnight tap water and cane sugar, C group adds overnight tap water and yeast powder, D group adds overnight tap water, E group is control group which is same to (1).Experiment three: This test has six groups. A group adds 50ml 5% cane sugar solution and 0.25g yeast powder to each Mosq-ovitrap, B group adds 50ml 15% cane sugar solution and 0.25g yeast powder, C group adds 50ml 25% cane sugar solution and 0.25g yeast powder, D group adds 50ml 35% cane sugar solution and 0.25g yeast powder, E group adds 50ml 45% cane sugar solution and 0.25g yeast powder, and F group is control group which is same to (1).2.2.2 Installation and retrieval Mosq-ovitraps(1) Indoor experimentsAfter being fed mouse blood for 2 days, 50 adult female mosquitoes are placed into a large mosquito net(l.2×1.8×1.5m3) for testing. Mosq-ovitraps with different attractants are installed at four corners of the mosquito net for 5days. Then count the number of the trapped adult mosquitoes and collect the eggs laid in a white porcelain bowl and estimated with a 10x magnifier. The experiment is done for 2 times.(2) Outdoor experimentsMosq-ovitraps with different attractants are set at intervals of 20cm, and two close spots are at intervals of about 20m. Count the number of adult mosquitoes and eggs every afternoon for 7 days. Count and record mosquitoes captured and the egg positively trapped every day.2.3 The influence of climate factor to dengue feverWe collect mosquito monitoring data, dengue fever incidence and climate data for several years in Guangzhou, then use SPSS 13.0 statistic software to establish data base and do statistic analysis. The relation between mosquitoes density and climate factors is studied through statistic means of Spearson rank correlation and multiple linear regression. The relation between dengue fever and Aedes albopictus density, climate factors is analyzed by principal component logistic analysis.Use Matlab software to establish a model of BP neural network to forecast the density of Aedes albopictus. Training sample is data from 1996 to 2000, and predictive sample is data in 2001.3. Results3.1 Development of dengue fever monitoring information management system basing on GISAccording to the feature of public health, we simplify user operation and function of this system, make it more easy to apply. Main functions are as follows:(1) Document management: open workspace, close workspace, save workspace, save another workspace, print, exit, and so on.(2) Establishing data base: the system can establish new database, as well as change old database.(3) Drawing and operation to map.(4) Inquest: through map to inquire about attribute, through attribute to inquire about map.(5) Manufacture of special subject map: According to special attribute data to form subject map.(6) Space analysis: buffer area analysis. (7) Some statistic analysis to attribute data such as maximum value, minimum value, total sum and standard deviation, and so on.(8) The system can output different format results.3.2 Influence of different attractants to Aedes albopictus density monitoring effectiveness(1) Experiments of container colorIn the experiments, we find that making containers black could not strengthen their ability to catch more Aedes albopictus. Adversely, it raises the number of escaped mosquitoes. The escaping rates of mosquitoes in indoor and outdoor experiments are 50% and 66.7% respectively, while the number in Comparison group was 0.(2) Experiments of infusionThere is no significant difference in mosquito-trap positive index, mosquito-trap density index, oviposition index and oviposition density index between Panicum maximum infusion, tyre infusion and control group(P>0.05).(3) Experiments of chemical attractantsIn lactic acid experiments, with lactic acid concentration heightening, the number of Mosq-ovitraps-caught mosquitoes and eggs shows a trend of increasing to decreasing. At the concentration of 1mg/ml, the ability of lactic acid in attracting mosquito is most powerful. But in both indoor and outdoor experiments, there is no significantt difference in mosquito-trap positive index, mosquito-trap density index, oviposition index and oviposition density index between different concentration of lactic acid and control group(P>0.05).(4) Yeast generated CO2 experimentsExperiment one:By prolonging installation time, mosquito-trap positive index and mosquito-trap density index in two groups show a trend of increasing by degrees, but variation amplitude in experiment is above control group. In the period of 7 days, mosquito-trap positive index in experiment group varies from 40.74% to 74.07%, mosquito-trap density index varies from 1.64 to 3.10; mosquito-trap positive index in control group varies from 18.52% to 40.74%, mosquito-trap density index varies from 1.20 to 1.36. After mosq-ovitraps are installed for 2-7 days, there is significant difference in mosquito-trap positive index and mosquito-trap density index between experiment group and control group(P<0.05).Experiment two:By prolonging the installation time, mosquito-trap positive index and mosquito-trap density index in all groups show a trend of increasing by degrees. From high to low, mosquito-trap positive indexes are 89.66%(CO2 group), 44.83%(cane sugar group), 40.00%(yeast group), 33.33%(tap water group), 26.67%(control group); and mosquito-trap density indexes are 6.19(CO2 group), 2.08(cane sugar group), 1.58(yeast group), 1.40(tap water group), 1.75(control group). There is significant difference in mosquito-trap positive indexes among all groups each day, and mosquito-trap density index has statistical significance in all groups for 4-7 days (P<0.05).Experiment three:By prolonging the installation time, mosquito-trap positive index and mosquito-trap density index in all groups show a trend of increasing by degrees. From high to low, mosquito-trap positive indexes are 96.55%(5% sugar group), 93.33%(15% sugar group), 93.10% (25 sugar group), 90.00%(control group), 88.89%(35% sugar group), 82.76%(45% sugar group); and mosquito-trap density indexes are 5.21(45% sugar group), 5.04(5% sugar group), 4.64(15% sugar group), 4.08(35% sugar group), 3.70(25% sugar group), 2.52(control group). There is significant difference in mosquito-trap positive index among all groups for 1-5 day, and mosquito-trap density index has no statistical significance in all groups for each day (P>0.05).3.3 The influence of climate factor to dengue fever(1) Correlation analysisThere is positive correlation relation between the number of captured mosquito and homeochronous evaporation capacity, relative humidity, absolute humidity, sunshine, precipitation (P<0.05), but there is negative correlation relation with pressure(P<0.05).(2) Regression analysisWe use stepwise regression to screen main climate factors of affecting mosquito density, and the result shows that only absolute humidity could enter regression equation. Correlation coefficient of the regression model is 0.835, and coefficient ofdetermination is 0.697. The final equation is: Y =362.230 + 0.835X.We regarded Aedes albopictus density as dependent variable and regarded climate factors as independent variable to run stepwise regression analysis. The result shows that sunshine(x1), wind speed(x2), absolute humidity(x3) and temperature(x4) could enter regression equation. Correlation coefficient of the regression model is0.850, and coefficient of determination is 0.723. The final equation is: (?) =1.959 + 0.609X1 -0.186X2-0.256X3 + 0. 349X4.(3) Principal component logistic regression analysis.We choose fore-four principal constituent to take the place of independent variable, and their characteristic roots are 3.652,2.490,1.150,0.905 respectively, accumulation contribution rate is 88.626%. After principal component logistic regression analysis, we make principal component independent variable convert to incipient independent variable, and got the regression equation: (?)=exp(-3.3926-0.0005X1+0.0241X2-0.00004X3-0.0001X4+0.0253X5+0.0341X6+0.0165X7-0.0012X8+0.0202X9) / 1+exp(-3.3926-0.0005X1+0.0241X2-0.00004X3-0.0001X4+0.0253X5+0.0341X6+0.0165X7-0.0012X8+0.0202X9)(X1-X9: pressure, evaporation capacity, relative humidity, absolute humidity, sunshine, temperature, wind speed, precipitation, number of captured Aedes albopictus )(4) Using ANN method to establish a forecasting model for Aedes albopictus densityFor 25 times learning and training, network error decreases from 0.305539 to 2.93751×10-14, and predictive coincidence rate is 80%.4. ConclusionDengue fever information management system may be a operation platform that apply for data management, data display and data space analysis and so on. Meanwhile, it also apply for the related analysis of other infectious disease. So, it can become a general GIS platform system for public health research.Comparing with the control group, Panicum maximum infusion, tyre infusion could not attract Aedes albopictus entering and oviposition in mosq-ovitrap. To a certain extent, L-lactic acid could raise the ability of trap in captured Aedes albopictus, but there is no significant difference between experiment and control group, so its ability in attracting Aedes albopictus need to be confirmed in the further study. Yeast generated CO2 had strong attractive to Aedes albopictus.There is positive correlation relation between the number of captured Aedes albopictus and homeochronous evaporation capacity, relative humidity, absolute humidity, sunshine, precipitation (P<0.05), but there is negative correlation relation with pressure(P<0.05). Sunshine, wind speed, absolute humidity and temperature could significantly influence the density of Aedes albopictus in environment (P<0.05). Dengue fever has close relation with some climate factors such as temperature, sunshine, evaporation capacity and density of Aedes albopictus. The ANN forecasting model displays a good ability in forecasting Aedes albopictus density. So, we should study it further and establish dengue fever early warning model based the ANN method.
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