Study On Risk Factor Analysis And Suitable Range Expansion Trend Of Bluetongue Vector In China

With the increase of global temperature,the suitable range of all kinds of vector insects is gradually expanding,and the vector-borne animal diseases pose more and more important threats to the health and safety of global livestock.Among them,bluetongue(BT)is such an acute infectious disease caused by bluetongue virus(BTV),which is mainly transmitted by Culicoides.Bluetongue threaten the health of wild and domestic ruminants and is one of the most harmful infectious diseases in sheep industry around the world.Because of its serious prevalence and difficult prevention and control,it is classified as OIE-Listed diseases that must be reported.At present,BT has been found all over the world except Antarctica.In China,since the first report in Yunnan Province in 1979,BTV has been detected in most provinces in China,and 11 serotypes have been isolated.For bluetongue,there is no effective treatment,so strengthening prevention is the key and effective method to control the outbreak of this disease.This paper starts with the study of the bluetongue vector,Culicoides,to collect and analyze the spatial distribution pattern,risk factors and potential habitats of a variety of Culicoides in China,so as to provide scientific reference for the monitoring management of bluetongue vector and the formulation of prevention and control measures for transmission of bluetongue virus.In this study,the data of the distribution points of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni in China from 1970 to 2019 were collected from the global biodiversity information network and published literature at home and abroad.The climate data and land use data under the current and four representative concentration pathway(RCP)scenarios of future were also collected.First,the spatial epidemiological method was used to explore the distribution and diffusion of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni in China.Then,the maximum entropy model was established to analyze the influence of various environmental variables on the distribution of Culicoides and to explore the current complete living area of three Culicoides in China.Finally,the expansion trend of three Culicoides suitable areas under climate change and land use change scenarios is predicted in 2030 and 2050.Based on this,the future transmission risk and epidemic trend of bluetongue in China are predicted and analyzed.The specific contents of the study include:(1)Through the analysis technology of global spatial autocorrelation and local spatial autocorrelation,the spatial distribution pattern of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni were analyzed,the aggregation and dispersion relationship were explored,and the current high-risk areas of bluetongue transmission were estimated.The results showed that there is no spatial autocorrelation in the distribution of Culicoides homotomus and Culicoides oxystoma in China during the study period,while the distribution of Culicoides actoni in China has local spatial autocorrelation,and local spatial autocorrelation detected two hot spots in Guangdong province and Taiwan Province,respectively.(2)Through the technology of centroid distribution and transfer,the direction of distribution and transfer of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni in China under three climate scenarios in the future were predicted.The results showed that the centroids of three Culicoides move to the south in RCP2.6,and to the north in RCP4.5 and RCP8.5.(3)Through the construction of MaxEnt model,the influence of various environmental factors on the distribution model of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni were analyzed,and the complete potential distribution risk map were drawn up.The results showed that the precipitation in the driest month,the highest temperature in the coldest month and the average precipitation in the coldest quarter were the most important environmental factors affecting the distribution of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni in China.The potentially highly suitable areas of three Culicoides are mainly distributed in Sichuan,Chongqing,Hubei and Anhui.(4)By predicting the environmental suitability of three Culicoides under the climate change scenarios in 2030 and 2050,the impacts of climate and land use change on the distribution of Culicoides were evaluated,and the future change of the transmission suitability of bluetongue virus in China was analyzed.The results showed that the niche of three Culicoides increased in different degrees in the future climate scenario compared with the current situation,and the Culicoides homotomus was mainly increasing along the edge of the current distribution area(North,middle and south of China);the Culicoides oxystoma will establish new environmental suitable areas in Inner Mongolia,Xinjiang and Gansu;and the suitable habitats of Culicoides actoni in Xinjiang,Sichuan and Guangxi increased more than other provinces.In summary,the following conclusions were drawn:(1)The distribution of Culicoides actoni in China has local spatial autocorrelation.Guangzhou province and Taiwan Province as well as the adjacent areas are the high aggregation areas of Culicoides actoni.(2)The precipitation in the driest month,the highest temperature in the coldest month and the average precipitation in the coldest quarter were the most important environmental factors affecting the distribution of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni in China.(3)The potential highly suitable areas of Culicoides homotomus,Culicoides oxystoma and Culicoides actoni mainly include Sichuan,Chongqing,Hubei and Anhui.In the future climate scenario,the niches of three Culicoides have increased in different degrees compared with the current one,and the center of mass move northward under the climate scenarios of RCP4.5 and RCP8.5.(4)At present,the high-risk areas of bluetongue transmission in China are mainly concentrated in Guangdong,Taiwan,Sichuan,Chongqing,Hubei and Anhui;in the future,the suitability areas for the transmission of bluetongue in China will increase,and Inner Mongolia,Xinjiang,Gansu and Guangxi may become new high-risk areas.