| Spatial heterogeneity of HFRS epidemic focus has the spatial criterion dependence. So the study of spatio-temporal dynamic of epidemics of HFRS should pay attention to spatial criterion.At present,there are many studies revealed spatio-temporal character of HFRS,including large spatial scale,middle spatial scale,Meso-micro scale,small scale.But spatio-temporal dynamics of HFRS virus and host in small area hasn't expounded by micro scale.The study on spatio-temporal dynamics of HFRS epidemics in small area has a great significance for working out practical prevention and control measures suited to the time and local conditions.For this reason,this study combines spatial epidemiology,community ecology,molecular biology,molecular genetics and spatial information statistics,based GIS.Longitudinal surveillance of host rats carried out in Jvnan County from Feb.2006 to Jan 2007,further expounding the relationship of spatio-temporal dynamic of HFRS various and host rats in small area.Results:1.Ecological characteristics of host ratsEcological environment influences community structure of host rat in experimental district.Rattus norvegicus and Mus musculus are major species,either in time niche or spatial niche.The ecological characteristics of host rat in experimental district as follow:①The community structure of host mice is different in experimental districts.②The season distribution of community structure is different.③Both time niche breadth and spatial niche breadth of Rattus norvegicus and Mus musculus are very high.Both time niche overlap index and spatial niche overlap index of Rattus norvegicus and Mus musculus are highest.④Shannon-Weiner S indiex,Niche Overlap index and ecological status of host mice in two experimental districts are difference due to natural condition and geographical factor.⑤Food niche overlap index and breed niche overlap index between species are high.2.The distribution character of host rat in small areaThe frist major specie is Mus musculus,second major specie is Rattus norvegicus in experimental districts.(1)Rat densities of seven villages in first experimental district are basically same.The constitutions of rat species in seven villages have different characteristics.The constitutions of rat species are basically similar in Xilandun village,Donglandun village,Qnliuhe village and Dashanqian village.The Rattus norvegicus is frist major specie,Mus musculus is second major specie in these four villages.The constitutions of rat species are basically similar in Houliangdian village,Dongliangdian village,Youzhuangzi village.The Mus musculus is frist major specie,Rattus norvegicus is second major specie in these three villages.(2)Rat densities of three villages in second experimental district are basically same, lower than first experimental district.The constitutions of rat species in three villages are similar.The Rattus norvegicus is frist major specie,Mus musculus is second major specie in Xidiantou village.The Mus musculus is frist major specie,Rattus norvegicus is second major specie in Wazi village and Zhongliangdian village.3.The season distribution of rat density in small areaThe rat densities in Feb,March,April,May,Nov,and Dec are high.Other months are low.The season distribution of rat density reflects host rat migration.From June to Oct,host rats move to field.In winter,host rats back to inside.4.Influence factors of host rats distributionThe spatial distribution shows clustered character.Regular deratization,cement anti-rat floor and methods used by residents are the main reasons for the decrease of rat density,while breeding livestock in yards and mixing up food,clothes and other goods are the main reasons for the increase of rats.5.The distribution character of parasitic miteIn experimental district,the amount of Rattus norvegicus infected are more than Mus musculus infected.Gamasid mite is major mite in experiment.6.The characteristics of the toxin-carrying rate of host ratsThe major hosts in experiment districts are Rattus norvegicus and Mus norvegicus. Although the number of Mus norvegicus preponderates over that of Rattus norvegicus, the toxin-carrying rate of the former is much higher than that of the latter.(1)In the captured rats in the first and the second experiment districts,there exist some toxin-carrying Apodemus.(2)The toxin-carrying rate in the first experiment district is high,although the rat density there is low.Thus,the condition of the outburst of HFRS exist as well.(3)The rat density and the toxin-carrying rate of host rat change according to the season.The toxin-carrying rates in February,May,September,October,and December are high.(4)There exist no differences in toxin-carrying rate and infection rate between Rattus norvegicus and Mus norvegicus.7.The spatial epidemiology characteristics of host animalsThe spatial autocorrelation analysis and spatial "hot spot" analysis are performed by using point pattern analysis based on GIS.(1)In the first experiment district:①The average radius of the first experiment district of host rat is 4.29 meters;The average radius of the strongest cluster district of host rat is 14.43 meters;The average radius of the biggest cluster district of host rat is 86.26 meters.The numbers of "hot spot" in different villages differ greatly.The undulation range of the first order is 3-8,and the undulation range of the second order is 0-1.②The average radius of the first experiment district of Mus norvegicus is 4.86 meters; The average radius of the strongest cluster district of Mus norvegicus is 21.14 meters; The average radius of the biggest cluster district of Mus norvegicus is 92.57 meters. The numbers of "hot spot" in different villages differ greatly.The undulation range of the first order is 1-12,and the undulation range of the second order is 0-2.③The average radius of the first experiment district of Rattus norvegicus is 5.00 meters;The average radius of the strongest cluster district of Rattus norvegicus is 32.71 meters; The average radius of the biggest cluster district of Rattus norvegicus is 93.86 meters. The numbers of "hot spot" in different villages differ greatly.The undulation range of the first order is 3-11,and there are no cluster hot spot of the second order.(2)In the second experiment district:①The average radius of the first experiment district of host rat is 3.30 meters;The average radius of the strongest cluster district of host rat is 13.67 meters;The average radius of the biggest cluster district of host rat is 83.00 meters.The numbers of "hot spot" in different villages differ greatly.The undulation range of the first order is 3-7,and the undulation range of the second order is 0-1.②The average radius of the first experiment district of Mus norvegicus is 3.67 meters;The average radius of the strongest cluster district of Mus norvegicus is 21.00 meters;The average radius of the biggest cluster district of Mus norvegicus is 79.67 meters.The numbers of "hot spot" in different villages differ greatly.The undulation range of the first order is 2-5,and the undulation range of the second order is 0-1.③The average radius of the first experiment district of Rattus norvegicus is 3.67 meters;The average radius of the strongest cluster district of Rattus norvegicus is 14.00 meters;The average radius of the biggest cluster district of Rattus norvegicus is 68.33 meters.The numbers of "hot spot" in different villages differ slightly.The undulation range of the first order is 2-4,and there are no cluster hot spot of the second order.(3)The "hot spot" analysis of NNH shows that there exist evident spatial clustered "hot spots" in rats in villages and clustered "disease foci" in rats of various species in villages.8.The analysis of virus sequence shows the movement track of host animals The spatial relationship of SEO viruses carded by different host rats is described by using phylogenetic tree and MST.The results show that:(1)The SEO viruses in different villages are relatively independent.(2)But SEO viruses carried by host rats in conterminous areas of villages are homogeneous to some extent.(3)The HFRS viruses in experiment districts show spatial structure to some extent.(4)The viruses carried by host rats in the same villages show some spatial structure and spatial heterogeneity.For instance,in Dashanqian village of the first experiment district,some viruses carried by host rats form obvious spread track.Conclusions:1.The ecological niche of host rats in experiment districts(1)The structure of community of host animals differ due to the differences of geographical ecological environments in different villages.But Rattus norvegicus and Mus norvegicus are still advantageous rats in villages.(2)The time niche,the spatial niche,the food niche,and the feed niche of host rats in different micro ecological environment show different characteristics,which reveals that the ecological population structures of HFRS host animals are very complex in micro scale.2.The distribution characteristics and related infection factors of host rats in experiment districtsIn small ecological environment,the rat density changes according to season evidently,and the spatial distribution shows clustered character.Regular deratization, cement anti-rat floor and methods used by residents are the main reasons for the decrease of rat density,while breeding livestock in yards and mixing up food,clothes and other goods are the main reasons for the increase of rats.3.Infection rates and indices of parasite acarid of different rats are different.Gamasid is the major mites in host animals in experiment district,and Rattus norvegicus is the main host of acarid.4.The infection characteristics of HFRS virus in host rat in experiment districtIn experiment district,although the rat density is low,the toxin-carrying rate is high. The toxin-carrying rate of Rattus norvegicus is higher than that of Mus norvegicus. Although the structure of host rats in villages differ greatly,the distribution characteristics of rat density in age,sex,and different season are similar.5.The spatial epidemiology characteristics of HFRS virus in host rat in experiment districtIn small site,the primary clustered range of host rats equates with the area of residents' room.The strongest cluster district centers in the area of 1-2 families;The average radius of the biggest cluster district of Mus norvegicus is 80 meters.The numbers of "hot spot" in different villages differ greatly.6.The spatial ecology and spatial epidemiology characteristics of toxin-carrying host rats(1)The relationship of SEO viruses in villages is obscure.(2)SEO viruses carried by host rats in conterminous areas of villages are homogeneous to some extent.It means that rats may be infected by others during the process of migrating to open country,and bring viruses back to rooms during the way back.(3)The HFRS viruses in experiment districts show spatial structure to some extent. That is to say the ecological barriers maybe exist between villages.(4)The viruses carried by host rats in the same villages show some spatial structure and spatial heterogeneity.For instance,in Dashanqian village of the first experiment district,some viruses carried by host rats form obvious spread track.The results show that there are both ecological barriers and ecological relationship inside villages.
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