Study On The Dominant Anopheles (Diptera:Culicidae) And Explore Its Potential For Malaria Transmission In Chayu County, Tibet

ObjectiveTo describe the species composition and identify the morphology and molecular characters of Anopheles in Chayu County, the population survey, morphologic observation and molecular identification technology were used to data collection and analysis. After identified the dominant Anopheles in Chayu County, the data of human blood index, man biting rate and ratio of parous mosquitoes will be collected and analysis for explore the transmission capacity. These results will be expected to provide reference evidence for integrated malaria elimination program in Tibet.Methods1. Three villages were selected by altitude for mosquito investigation study sites in Chayu County. The population survey and density survey were conducted through light trapping and human trapping and cattle trapping.2. The morphologic observation and molecular identification on sequence ITS2and fragment28S-D3were conducted to identify the anopheles. The eggs lay from trapping adult anopheles were raised to larva to confirm the type of anopheles, the morphologic of eggs, larva and adult anopheles F1were recorded by tele-camera image as well.3. The data of human bit rate and vetcor capacity were collected through indoor and outdoor human trapping all night.4. Ratio of parous mosquitoes was calculated based on the data from morphologic observation on oval anatomy of trapped anopheles. Data of human blood index (HBI) was obtained through Multiplex Polymerase Chain Reaction (MPCR).Results1.1442anopheles were trapped by108light traps on13nights in the study,1228An. pseudowillmori (85.2%),5An. willmori (0.3%) and1An. Kochi (0.1%) were identified after morphologic observation. Based on these data, An. Pseudowillmori were considered to be the dominate anopheles in Chayu County.2. The morphologic characters of An. Pseudowillmori in different stages list as follow:2.1Eggs:long and thin eggs with thin top and blunt-round bottom. Then average length is deck and back deck divided by float device. The length of deck is average248μm. In the side view, the oval extends slightly concave with16ridges.2.2Larva:The head hair2-3C is straight with bifurcated side hair, the5-C is furcated into12-16branches. Ventral hairl-Ⅰ is common hair, furcated into3branches,1-Ⅲ-Ⅶ is well developed with palm shape and16-18leaves. The width of leaves is1/3-1/6of their length.2.3Pupa:There is no spot on elytron.The opening of the respirary tube is wide and deep, the colour of the basement is light. Ventral hair1-Ⅲ-Ⅳ furcated into4-6brances. The terminalia of male pupa has the same colour in the top and the bottom, while has a deep color band in the middle.2.4Adults:The length of top white ring is the same with the second one Tentacle, there are7white spottings in costal vein,2white white spottings in V1.2vague black spotting located in handle of V2.3black spottings in V3. V2.1is shorter than ante-fork.3. The crude HBI of An. pseudowillmori and An. willmori were0.35and0.29; the man bite rate of An. Pseudowillmori was8.9/person night.ConclusionBased on the study, there were three major type of anopheles in Chayu County; they were separately An. Pseudowillmori, An. Willmori and An. Kochithe. An. Pseudowillmori was considered to be the dominant anopheles. Although there were some slight morphologic difference in adult stage between An. Pseudowillmori trapped in Chayu County and An. Pseudowillmori reported in Guangxi and Yunnan, the morphologic identification in different stages and moleculer test results were confirmed. As An. Pseudowillmori were all night blood sucking, as well as the density, HBI and man bit rate of it were respectively higher than other types, it is indicated that the An. Pseudowillmori maybe the potential vectors of malaria in Chayu County.