Investigation Of Mosquito Distribution And Study On The Resistance Of Aedes Albopictus In Zhoushan

ObjectiveTo understand the composition of mosquito population from 2011 to 2017,to analyse seasonal fluctuations of mosquito,to understand mosquito density in different habitats,and then to provide scientific basis for mosquito control in Zhoushan city.To study the distribution of Aedes Albopictus,and to establish the basic database of Aedes Albopictus in Zhoushan.To investigate drug resistance of Aedes Albopictus to several common insecticides,and then learn to use pesticides scientifically and rationally to control mosquito-borne diseases.MethodsSurvey of mosquito population:one observation station was set in each county and district(Dinghai,Putuo,Lincheng,Daishan and Shengsi)in Zhoushan city for mosquito density monitoring,and Mosquito-lured Lamp Method in National Vector Monitoring Project was used from April to November during 2011-2017 period.Monitoring data were statistically analysed using SPSS 19.0 software.Investigations of mosquito breeding ground were done in counties and districts and some of the islands in Zhoushan using Pipette Method in GB 23797-2009 Mosquito Monitoring Methods.Data were then analysed using SPSS 19.0 software to understand the living environment,population composition,and competitiveness of mosquitoes in Zhoushan.Investigation of distribution of Aedes Albopictus:one observation station was set in each county and district(Dinghai,Putuo,Lincheng,Daishan and Shengsi)in Zhoushan city.Breteau Index Method in GB 23797-2009 Mosquito Monitoring Methods was used,and data were collected from May to October during 2015-2017 period,and then statistically analysed using SPSS 19.0 software.Study on drug resistance:larvae were collected and brought back to laboratory for breeding in four counties andone district mentioned above.The larvae dipping methodwas used on larvae,and resistance degree was determined by resistance multiples.Contactbarrelmethod was used on adults,andresistance degree was determined by bioassaymethod.ResultsSurvey of mosquito population:21618 mosquitoes were captured from 2011 to 2017.Culex pipiens pallens was the dominant species,accounting for 98.270%of the total number of mosquitoes.The peak density showedfrom June to August,and the average mosquito density was 2.206/(lamp · h).The highest density occured in June 2013,with a number of 6.567/(lamp · h).The proportion of Aedes Albopictus increased year by year,while the proportion of Culex Pipiens Pallens and Anopheles Sinensis decreased.There were at least 10 species of mosquitoes belonging to 5 genera and 2 subfamilies in Zhoushan,and top three species were Culex Pipiens Pallens(47.721%),Aedes Albopictus(28.534%),and Aedes aegypti(17.562%).Investigations of distribution of Aedes Albopictus:The Breteau Index map was unimodal in 2015,with the peak in July.The Breteau Index map was relatively flat in 2016-2017 period with no obvious peak.There was a significant difference in BI of 6 types of environment(χ2=127.425,P<0.001).There was a significant difference in Container Index of 6 types of environment(x2=44.505,P<0.001).The highest CI was found in tires(27.556%),and the indexes of tanks and idle containers were also high,with 18.642%and 16.512%,respectively.The lowest one was bonsai,with a CI of 1.706.Study on drug resistance:Aedes Albopictus larvae was sensitive to permethrin,deltamethrin,dichlorvos,and propoxur,with LC50 of 0.00439mg/L、0.00055mg/L、0.04364mg/L,and0.00412mg/Lrespectively.Compared with sensitive strains,Aedes Albopictus larvae had the highest resistance multiples in beta-cypermethrin as 3.27.Adults were sensitive to beta-cypermethrin,permethrin,deltamethrin,and propoxur,and were suspicious sensitive to malathion.ConclusionSurvey of mosquito population:Basically,the mosquito population composition and seasonal fluctuations were captured in Zhoushan.The density of mosquitoes in Zhoushan City remained at a relatively low level,but the proportion of Aedes Albopictus increased year by year.More publicity and education should be carried out,and the masses should be organized to regularly clean up waste water from tires to conduct comprehensive anti-mosquito operations before the peak season of mosquito density.Investigations of distribution of Aedes Albopictus:The density peak was concentrated from July to September in 2015-2017,suggesting the risk of dengue fever transmission.We must do a good job in monitoring the Breteau index.When the BI increased to more than 20,government agencies should be warned to carry out anti-mosquito elimination work.Study on drug resistance:Aedes Albopictus adults were resistant to malathion and larvae were resistant to beta-cypermethrin in Zhoushan.Insecticides should be used strategically to prevent and reduce the development of resistance.