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The Survey of Potential Risk Factors of Dengue Fever in Guanlei Port of Xishuangbanna, the Frontiers of Yunnan Province

Author: TanJun
Tutor: YangYaMing; ZhouHongNing
School: Dali University
Course: Pathogen Biology
Keywords: Dengue virus Aedes mosquitoes Virus infection Guanlei port ofYunnan
CLC: R181.3
Type: Master's thesis
Year: 2012
Downloads: 45
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Abstract

Objective: To investigate the species, ecological characteristics of dengue vectors,and their natural dengue virus infected rate as well as the dengue fever antibody ofhealthy residents in Guanlei port of Xishuangbanna, the frontiers of Yunnan province,providing effective evidences for dengue fever control in the frontiers orts of Yunnan.Method:(1) The investigation of the population density and ecologicalcharacteristic of dengue vectors. The densities of adult mosquitoes, from June toOctober in2011, we captured adult mosquitoes using man landing catches in thebamboo grove, within200meters near the village around Guanlei port, during16:30to18:30in the last ten days of each month. The habits of Aedes biting: from August toOctober, we set five points to collect Aede mosquitoes in Guanlei port during8:00to18:00in the last ten days of each month. Observers should rotate the site as as a5×5Latin square design every two hours, and adult mosquitoes were collected using manlanding catches. Meanwhile, we used the same method to observe the daytime(8:00-18:00) habits of adult aedes mosquitoes in bamboo grove near the village. Allthe adult mosquitoes were identified, counted, recorded and put into liquid nitrogenwith1.8ml microtubes, used for isolating and identifying virus in laboratory. For theinvestigation of larvae, from June to October, we surveyed various types of watercontainers nearby the survey sites in Guanlei port. The larvae or pupas in thecontainers were caught, recorded and identified. The densities of larvae were countedby house index (HI), container index (CI) and Breteau Index (BI).(2) Investigation ofthe dengue viruses antibody level for the healthy residents in Guanlei port. Wecollected100healthy people serums and detected the IgG antibody against denguevirus by using ELISA.(3) Investigation of the dengue viruses infected rate inmosquitoes. Dengue viruses were isolated from the adult mosquitoes captured fromthe field sites, and identified by RT-PCR. Results:(1) Condition of the population density and ecological characteristics ofdengue vectors. Total of910adult individual mosquitoes of21species from5genuseswere surveyed in this investigation. Among them, the number of Ae.albopictus was427, accounting for46.92%of total collected mosquitoes, which was the localpredominant species in the daytime. From June to October, the monthly densities ofAe.albopictus were8.33,15.33,2.8,5.2and1.92(person per hour), respectively. Thedensity peak was July and declined from August. The activity time of Ae.albopictus inthe bamboo grove and Guanlei port were15:00-17:00(bamboo grove),12:00-14:00and16:00-18:00(Guan port), respectively. From June to October, the monthlyindexes of Ae.albopictus larvae in Guanlei port were HI33.46, CI14.69and BI66.18.The peak of Ae.albopictus larvae densities were July and September. The rubberproducts container was the main breeding sites for Aede mosquito larvae, accountingfor43%of all the positive containers. In this survey, we only collected6larvae ofaedes aegypti.(2)100serum samples of healthy population from the areas weredetected by using ELISA. The positive rate of dengue viruses IgG antibody were6%.(3)10groups of Ae.albopictus (427),2groups of Ae.annandalei (74),4groups ofHe.reidi (177) and3groups of Ar.subalbatus (130) were detected by using RT-PCR,but non of dengue virus were detected.Conclusion:(1) The mosquitos’ species of Guanlei port in the daytime werecomplex and Ae.albopictus was the local predominant species. The density peak ofthis adult mosquito between bamboo grove (nearby the village) and Guanlei port weredifferent, which was July in bamboo grove, but were June and October in Guanleiport.(2) No dengue virus was detected from mosquitoes by using RT-PCR, though,the density of Ae.albopictus was still higher and wider distribution in Yunnan, it couldcause dengue fever epidemic ourbreak once dengue fever cases are imported fromneighboring countries.(3) Although the antibody positive level detected this time hasdeclined, the monitoring for dengue fever in this port should be enhanced since thehigher dengue virus susceptibility of healthy population, the increasing people ofentry and exit, as well as the severe situation of dengue fever epidemic in neighborcountries (Laos and Myanmar).

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