Studies On Development And Application Of An Aedes-trap

BackgroundDengue fever is a set of acute infectious diseases caused by Dengue virus mediumed by aedes aegypti and aedes albopictus,with a history of over 200 years. Prevailing at tropic and sub-tropic zones,dengue fever is deemed as one of the most vector borne infectious diseases,considering the widest distributing and the most infections all over the world.In China,Guangdong,Hainan,Guangxi,Fujian and Taiwan provinces are mainly epidemic areas of Dengue fever,additionally Guangzhou city is usually the epicentre of the outbreak recently.Annual statistical data suggest that,Guangdong province accounted for almost 90%of dengue fever cases in China,especially its capital,Guangzhou city accounted for almost 70%of reported cases.Aedes albopictus is the main vector of Dengue fever in Guangdong province.Strengthening the surveillance of aedes(especially aedes albopictus) is still the crucial way for preliminary alert of dengue fever epidemic.A long period of time, indoor inhabiting rate was applied for adult aedes density surveillance of aedes aegypti,while mosquito net for that of aedes albopictus,whose dangers is infection through biting by mosquitoes.Therefore,larva surveillance has become the key way for aedes albopictus abroad.To combine GIS monitoring system with oviposition trap are the frequently-used methods.Oviposition trap is able to entice mosquitoes to oviposit,whereas not able to ensnare adult mosquito,resulting in that dengue virus detection could only apply after the hatching of eggs,which is not effective for preliminary alarm and adult mosquitoes density estimated.The ways of house index, breteau index and container index have some disadvantages,such as great workloads and excessive interfering factors,so they are not fit for surveying the semi-home aedes albopictus.There has only one apparatus at present invented by Lin Li-feng and his collaborators,it not only ensnare adult mosquitoes but also allure adult ones oviposit, but some investigations showed that the mosq-ovitrap has much less attraction to aedes than their natural environment of ovipositing.ObjectiveTo improve the capabilities of ensnaring aedes albopictus and reflect their real density in vector survelliance in natural environment,to alarm the occurrence of Dengue fever,we carried out studies as followed.1.A new kind ofaedes trap with high efficiency was designed to ensnare adult ones and allure those adult spawn according to the physiologic habits of aedes.2.To achieve an Injury-free method of trapping aedes and make for monitoring adult Aedes albopictus which infected dengue virus.Methods1.The outline of Aedes- trap designThe outline for this design was established on the bases of physiologic habits of Aedes albopictus,for instant,its choice for sites to lay eggs and its flight;and on the effects of some watch-free factors.1.1 Aedes albopictus favors the environment with a lower illumination and dark back-ground water surface,especially for receptacle with rough-sufaces to lay its eggs.Accordingly,the cover and the supporter of the trap is designed with niger, while the trap body was transparent.This design poses dark-bright-dark layers from cover to bottom.The dark parts compose relatively higher volume,which accords with Aedes albopictus' biological characteristics of that it's easily attracted by dark materials.What's more,the lower part of the trap body,where Aedes albopictus rest on and lay eggs,is shadowed and consequently with lower temperature,which benefits their reproduction.Also,a dark sheath of the trap could be removed from the trap body to facilitate observation. 1.2.As Aedes albopictus lands off horizontally and takes off tilted,it's necessary to prevent those fell in the trap from escape.So three legs are configured to avoid tilt,it could keep steady and balanced even it's placed on uneven grass-thrived areas.1.3.Aedes albopictus is partially in indoor and partially in outdoor,lays eggs on humid rough surfaces,it's reasonable to avoid too much rain water from entering the trap,which interferes its functioning.To achieve this target,a floatable plastic screener mesh is placed on the water surface to support the filter paper where eggs are laid.2.Aedes- trap componentsThis instrument consists of four components:1,Black bowl cover.It has 4 big end up and cone shaped inward pop outs as mosquitoes entrances whose outer diameter is 81.0mm and height is 23.0mm;2,Transparent cup body.The transparent cup body fits right in with black bowl cover whose outer diameter is 75.4mm and height is 100.0mm;3,White plastic filter screen.The density of white plastic filter screen is less than water and the filter screen was placed in the transparent cup body whose bottom diameter is 9.4mm,top diameter is 30.0mm and height is 7.0mm.A piece of filter paper in same area must be placed on the plastic filter screen when it was applied to entrap mosquitoes.In order to lure aedes oviposit on the white filter paper,the white filter paper should be moist by contacting with the surface of water that the white plastic filter screen floated on.4,Black cup cover.The black cup cover with 3 legs covers the transparent cup body and its outer diameter is 82.0mm,its height excepts leg is 60.0mm,its big end up and cone shaped leg is 15mm high.3.Instruction of Aedes -trap3.1 First,putting the plastic filter apparatus into the transparent glass,then add 20ml tap water without chlorine and put a circular filter paper of 70mm diameter floating on the surface of the filter in this plastic cup,sealed the cover of the cup, sheathe the Cup entrusted.Finally,lay ID tags in the environment which is needed to be monitored.It is recommended that the storage time is 4 days.3.2 It is forbided that to add too much water in the cup,which is only allowed not to over the location of sets of this black glasses.Make sure that the cup is maintained steadily and avoid any inclination.4.The effects of trapping Aedes and eggs of Aedes- trap4.1 Calculation of effective index(1) Mosquito and ovipositor positive index is the deployment and recovery of each of 100 effective(not been knocked over or damaged) Aedes-traps or Mosq-ovitraps positive in adult aedes albopictus or eggs quantity.(2) Mosquito-trap positive index is the deployment and recovery of each of the 100 effective Aedes-traps or Mosq-ovitraps positive in adult aedes albopictus quantity.(3) Mosquito-trap density index means the average number of adult aedes albopictus that positive Aedes-traps or Mosq-ovitraps have captured.(4) Mosquito-trap effective index is multiply the Mosquito-trap positive index by the Mosquito-trap density index.(5) Oviposition index is the deployment and recovery of 100 effective Aedes-traps or Mosq-ovitraps positive in aedes albopictus eggs quantity.(6) Egg density index refers to positive Aedes-traps or Mosq-ovitraps collected the average number of eggs.(7) Oviposition effective index is multiply the Oviposition index by the Egg density index.(8) Rate of mosquito escapted from Aedes-traps or Mosq-ovitraps means the frequency of mosquitoes which have entered Aedes-traps or Mosq-ovitrap and then left,that is the percentage of the Aedes-traps or Mosq-ovitraps which aedes albopictus eggs positive but negative mosquitoes in all Aedes-traps or Mosq-ovitraps with mosquito and ovipositor positive.4.2 Experiments indoor:(1) Four Aedes- traps and four Mosq-ovitraps put in four comers of a large mosquito net(1.2×1.8×1.5m³).(2) After being fed mouse blood for 2 days,adult aedes albopictus were placed into the large mosquito net for 96 hours.Then count the number of the trapped adult mosquitoes and eggs. (3) The experiments were done for 2 times,and exchange the site of Aedes- traps and Mosq-ovitraps.4.3 Experiments outdoor(1) Experimental group and control group processingâ…°.Experiment group:In the Aedes-trap,infunde 20ml tap water without chlorine and put a sheet of 70mm filter paper on plastic filter screen, then head up and mark.â…±.Control group:In the bottom of Mosq-ovitraps,put a sheet of 85mm filter paper and infunde 20ml tap water with out chlorine,then head up and mark.(2) Two types mosquito trap groups were respectively put in underground garage and green belt of a campus of Guangzhou and a populated area of Foshan for 4 days.Different mosquito traps set at intervals of 20cm,and two close spots were at intervals of about 25m.The number of mosquito and egg were counted and exchanged the site of two types mosquito traps every 24 hours. Two experiments were carried out in the campus of Guangzhou,the populated area of Foshan experiments for 3 times,at equal pace investigated Breteau index of residential area,respectively,in August and October 2008,February 2009.Results1.Experiments indoorThe Aedes- trap group trapped 99 mosquitoes and 3220 eggs,while the control group caught 61 mosquitoes and 268 eggs after 96 hours.Statistical analysis showed that the numbers of mosquitoes(Z=-2.178,P=0.021) and eggs (Z=-2.021,P=0.043) trapped in the experiment group was higher than that of control group.2.Experiments outdoor in campus of Guangzhou(1) Field 1(The underground garage):After 4 days,MEI_Aedes in the Aedes- trap group was 130.00,MEI_Aedes in the Mosq-ovitrap group was 52.50;OEI_Aedes in the Aedes- trap group was 1728.57 and in the Mosq-ovitrap group was 360.00;The MEIs_Aedes(Z=-4.394,P=0.000) and OEIs_Aedes(Z=-2.400, P=0.016) of the Aedes- trap group were statistical higher than that in the Mosq-ovitrap group.MEI_culicine in Mosq-ovitrap group was 10 and no culicine be caught by the Aedes- trap group;Escape rate of the Aedes -trap group was 4.17%and the control group was no escape.(2) Field 2(The green belt):After 4 days,MEI_Aedes in the Aedes- trap group was 132.00 and in the Mosq-ovitrap group was 22.00;OEI_Aedes in the Aedes-trap group was 4598.00 and in the Mosq-ovitrap group was 460.00;The MEIs_Aedes(Z=-4.592,P=0.000) and OEIs_Aedes(Z=-3.641,P=0.000) of the Aedes- trap group were statistical higher than that in the Mosq-ovitrap group.Escape rate of the control group was 27.27%and the Aedes -trap group was no escape.There was no Culicine be captured by two groups.3.Field 3(The residential area experiment)results(1) The experiment results in August 2008:After 4 days,MEI_Aedes in the Aedes-trap group was 40.03 and in the Mosq-ovitrap group was 11.68,OEI_Aedes in the Aedes- trap group was 1442.76 and in the Mosq-ovitrap group was 334.13,MEI_culicine in the Aedes- trap group was 3.01 and in the Mosq-ovitrap group was 1.13;The MEIs_Aedes(Z=-7.529,P=0.000),OEIs_Aedes(Z=-6.058, P=0.000) and MEIs_culicine(Z=-2.484,P=0.013) of the Aedes- trap group were statistical higher than that in the Mosq-ovitrap group.Escape rate of the Aedes -trap group was 1.47%and there was no mosquito escapted from the control group.The indexs of Mosq-ovitrap method:MI_Aedes-trap was 25.30,MI_Mosq-ovitrap was 9.80;OI_Aedes-trap was 20.80,OI _Mosq-ovitrap was 6;MOI _{Aedes -trap} was 25.70,MOI _Mosq-ovitrap was 9.80;MDI _{Aedes -trap} was 1.56±1.00,MDI _Mosq-ovitrap was 1.19±0.49;EDI _{Aedes -trap} was 69.36±47.88,EDI _Mosq-ovitrap was 55.69±23.51; MI(χ²=21.922,P=0.000),OI(χ²=24.736,P=0.000),MOI(χ²=22.812 P=0.000) and MDI(Z=-2.059,P=0.039) of the Aedes -trap group were statistical higher than that in the Mosq-ovitrap group.EDIs between the Aedes- trap group and the Mosq-ovitrap group showed no difference (Z=-0.530,P=0.596)(2) The experiment results in October 2008:After 4 days,MEI_Aedes in the Aedes-trap group was 10.50 and in the Mosq-ovitrap group was 1.40,OEI_Aedes in the Aedes- trap group was 237.80 and no eggs be collected by in the Mosq-ovitrap group,MEI_culicine in the Aedes- trap group was 2.80 and in the Mosq-ovitrap group was 0.70;MEIs_Aedes(Z=-3.266,P=0.001) and MEIs _culicine(Z=-2.000,P=0.046) of the Aedes- trap group were statistical higher than that of the Mosq-ovitrap group.There were no aedes albopictus eggs be collected by the Mosq-ovitrap group and didn't analysis the OEIs_Aedes of two groups,and no mosquito escapted from two groups.The indexs of Mosq-ovitrap method:MOI_{Aedes -trap} and MI_{Aedes -trap} were 9.80,MOI_Mosq-ovitrap and MI_Mosq-ovitrap were 1.40;OI_Aedes-trap was 4.10,OI _Mosq-ovitrap was 0;MDI_Aedes-trap was 1.07±0.27,MDI_Mosq-ovitrap was 1.00±0.00; EDI_Aedes-trap was 58.00±27.98,EDI_Mosq-ovitrap was 0.MI,MOIof the Aedes- trap group were statistical higher than that in control group(χ²=8.011,P=0.005). MDIsbetween the Aedes- trap group and the Mosq-ovitrap group showed no difference(Z=-0.378,P=0.705).There was no aedes albopictus eggs be collected by the Mosq-ovitrap group and didn't analysis the EDI and OI of two groups.(3) The experiment results in February 2009:After 4 days,in the Aedes -trap group, there were 8 Aedes albopictus,96 Culex pipiens,and 388 eggs.MEI_Aedes was 4.11,OEI_Aedes was 168.26,MEI_culicine was 48.72,MOI was 3.60,MI was same with MOI,OI was 3.05,MDI was 1.14±0.38 and EDI was 55.17±23.86;In the control group,there were only 25 Culex pipiens,MEI_culicine was 12.69. Statistical analysis showed that the MEI_culicine in the Aedes -trap group was higher than that of control(Z=-6.194,P=0.000).It didn't analysis the MEIs _Aedes and OEIs _Aedes of two groups due to no Aedes albopictus be caught in the control group.(4) MEIs _Aedes of the Aedes- trap groups in the residential area in August,October 2008 and February 2009 were 40.03,10.50 and 4.11;the simultaneous OEIs _Aedes were 1442.76,237.80,168.26 and the MEIs_culicine were 3.01,2.80 and 48.72.The MEI_Aedes(χ²=54.762,P=0.000) and the OEI_Aedes(χ²=29.238,P =0.000) of the Aedes- trap groups in the residential area in August 2008 were the highest,followed by October 2008 and February 2009.However the MEI _culicine(χ²=25.070,P=0.000) of the Aedes- trap groups in the residential area in February 2009 was the highest,followed by August 2008 and October 2008.(5) By using binary logistic regression,the relationship between the positive Aedes-trap numbers and natural variables,as well as experiment during period were evaluated.The results showed that OR for natural temperature was 1.153 (95%CI,1.091～1.219),OR for experiment during period was 2.002 (95%CI,1.679～2.388).(6) The positive correlations were found between the MEIs_Aedes of the Aedes- trap and the Breteau Indexs(rp=0.244,P=0.000),and between the OEIs_Aedes in the Aedes -trap and Breteau Indexs(rp=0.256,P=0.000).Conclusions1.Our study,conducted in indoor and field experiments,showed that ensnaring Aedes albopictus and eggs applied with the Aedes- traps have better effect than that with Mosq-ovitraps,and its attraction to culex pipiens fatigans is also stronger than Mosq-ovitraps.Regarding its remarkable sensitivity and stability,it is a good apparatus to early warning for dengue fever or other disease mediumed by aedes.2.The correlation between the MEIs_Aedes of Aedes -trap and the breteau indexs of residential area were positive,in the same way the OEIs_Aedes of Aedes -trap compared with the breteau indexs of residential area were positive too.3.The new indexes that the Mosquito-trap effective index(MEI) and the Oviposition effective index(OEI) have more representative and more responsive for fluctuationsin in the density of mosquito-borne in environment than the Mosquito and oviposition positive index(MOI),the Mosquito-trap positive index(MI),the Oviposition index(OI),the Mosquito-trap density index(MDI) and the eggs density index(EDI).