| Avian influenza is a serious and harmful infectious disease which probably impacts public health,social economy,and political stability.Recently,public health security and biological safety issues caused by avian influenza have attracted increasing attention.Domestic duck is the most important intermediate host of the bird flu virus.Its breeding process,health and epidemic prevention,transportation,and market transactions have important influence on the spread of the bird flu epidemic.Poyang Lake Plain(PLP),as the primary important rice planting area in Jiangxi Province,is also home to a large number of domestic duck breeders of different sizes,domestic goose ducks and wild duck domestication bases.At the same time,there are a large number of migratory birds in winter and spring season to inhabit and feed.It can be inferred that the probability of directly or indirectly spatial contact between domestic ducks(including goose ducks and wild ducks)and wintering migratory birds(such as through flowing water bodies)is increased on a time-space basis in the Poyang Lake Plain(PLP).It may also increase the chance of reassortment of wild bird avian influenza virus and poultry avian influenza virus.As a result,the risk of avian influenza in the PLP and its ecological safety cannot be underestimated.Take precautions of avian influenza is necessary,especially for the understanding the characteristics of duck breeding and analyses of the influencing factors of avian influenza in the study area.Scientifical understanding of the risks of avian influenza and its related ecological safety threatscontributes to maintaining the ecological security and stability in the lake area.In this study,the dikes data of PLP and survey data of domestic duck breeding from 2014 to 2017 were used to identify and monitor spatial patterns and changes of domestic duck breeding in 2014 and 2016 using the Google Earth image data.Landsat-8 OLI images acquired in 2014 and 2016,based on the supervised classification maximum likelihood method,were used to extract the spatial distribution of natural wetlands(rivers,main lake body of the Poyang Lake and sub-lakes)and artificial wetlands(paddy fields and ponds)in PLP.In addition,through field surveys and interviews with farmers,a total of 218 households' interviews of ducks(including goose ducks)in 13 county-level units were carried out to collect information on the risk factors of avian influenza at the farm level.Logistic regression analysis was used to evaluate the impact of different factors.Finally,using GIS spatial overlay analysis,the avian influenza risk in the lake area was spatially examined,and the Analytic Hierarchy Process and Pressure-State-Response(AHP-PSR)method was used to evaluate the ecological safety of bird flu in the lake area.The main results /conclusions are listed as follows:(1)The breeding scale of domestic duck in the PLP is large and the breeding phenomenon is common.Among them,the egg-laying ducks is the dominant type along with a small proportion of meat-type ducks,which are usually free-range.According to the households' interview,about 84.4% of the interviewed farmers raised the egg-laying ducks and 15.6% for raising the other type.The egg-laying ducks were mainly distributed in Nanchang County,Jinxian County,and Xinjian County,while the other is mainly concentrated in Poyang County,Yugan County,and Yongxiu County.Besides,about 44.1% of the surveyed farmers chose to freely raise ducks in the fields,while 45.4% of them kept the ducks completely in the sheds,and the left percentage of the interviewed farmers chose the both.The counties with a higher proportion of free-range ducks included Poyang County,Yugan County,Xinjian County,and Yongxiu County,with over 85% of the surveyed households.The lowest counties with less than 35% were Jinxian County and Nanchang County.(2)The occurrence of avian influenza in duck breeding in PLP is affected by many factors.The analyses of households' interviews including the basic conditions of farmers,characteristics of domestic duck breeding,feeding patterns,awareness of avian influenza risks,wild birds activities,health and epidemic prevention,market activities and transportation,showed that the health and epidemic prevention and wild birds activities were the leading factors for the control of the occurrence and spread of bird flu.At the same time,the individual's cultural level and awareness of avian influenza also played an important role in the prevention and control of avian influenza.The results of logistics regression analysis of risk factors of poultry flu in domestic duck breeding at the household level clearly showed that the importance of the above factors of decreased in the follow order,namely hygiene and epidemic prevention as the leading role,followed by farm households related factors,aquaculture and management factors,migratory bird activities and market and transport factors,respectively.(3)Affected by the domestic duck breeding,migratory birds activities,and live poultry market transactions,the PLP is facing varying degrees of avian influenza risk at county level.Among them,Nanchang County,Xinjian County,and Jinxian County held the highest risk level of avain influenza occurrence,as they have large-scale breeding of domestic ducks and relatively large-scale poultry and eggs trading markets.What's more,these counties are featured by most frequently imported and exported poultry and egg products.Secondly,because there are a large number of migratory birds and dense distribution of poultry markets,Yongxiu County,De'an County,Gongqingcheng City,Jiujiang City,Lushan City and Hukou County had the second highest risk level.In addition,several outbreaks of H5N1 highly pathogenic avian influenza were reported previously.Finally,due to the small proportion of duck breeding quantity and scatteredly distributed poultry markets,Poyang County,Yugan County and Duchang County had the lowest risk level of the occurrence of avian influenza.(4)In 2016,the ecological safety of the PLP related to the risk of bird flu occurrence was at a safe level with the safety index about 0.6327.The value is very close to the critical safety level ranging from 0.50 to 0.60.It may be easily turned to the critical safety level even the dangerous or unsafe level due to the increasingly impacts of other factors such as the size of domestic duck breeding,market transactions,seasonal migration of migratory birds,health and epidemic prevention,and global or regional bird flu epidemics. |
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