| Echinococcosis is a worldwide lethal zoonosis,caused by tapeworms from the genus Echinococcus.Two forms of echinococcosis,cystic echinococcosis(CE)caused by infection with the metacestode of E.granulosus and alveolar echinococcosis(AE)caused by infection with the metacestode of E.multilocularis,were found to be endemic in the pasture areas of western China.Shiqu County in Ganze Tibetan Autonomous Prefecture,Sichuan Province,China,is located in the pasture areas of the eastern Tibetan Plateau,has been reported as one of the highest prevalence of echinococcsis with the prevalence of AE and CE was 6.2%and 6.8%,respectively.There was also a strain of E.shiquicus,which has not been reported currently as infecting humans.Coexisting of three Echinococcus species,E.granulosus,E.multilocularis and E.shiquicus in this area was a great risk to the health and production of pastoral Tibetan communities.In Shiqu County,sylvatic and anthropogenic cycles were two transmission ways of Echinococcus in different envoronments.Dogs and Tibetan foxes(Vulpes ferrilata)as definitive hosts play important roles in the transmission of E.multiloculairs and E.shiquicus.Eggs of Echinococcus spp.from canine feces were the main source of the pollution.Because of the close relationship between domestic dogs and humans,decrsesing the infection rate of Echinococcus spp.in domestic dogs has been considered to be the key to control human echinococcosis in pastoral areas.However,whether the sylvatic and anthropogenic transmission cycles of Echinococcus dominated by domestic dogs and Tibetan foxes in pastoral areas on the eastern Tibetan Plateau are independent of each other has been an important subject of debate.Therefore,understanding the role of dogs and Tibetan foxes as domestic and wild definitive hosts respectively in the transmission of E.multilocularis and E.shiquicus,exploring the transmission mechanism of E.multilocularis and E.shiquicus in sylvatic and anthropogenic environments is an important theoretical basis for the prevention and treatment of echinococcus in the pastoral area of the eastern Tibetan Plateau.This study was carried out from 2015 to 2017 in Shiqu County.The spatial pattern,species composition and the prevalence of Echinococcus spp.of each host in different transmission cycles were compared for discussing the role of dogs and Tibetan Fox in the transmission of Echinococcus.It provides an important theoretical basis for accurately understanding the transmission mechanism of Echinococcus spp.and comprehensive ecological controlling of echinococcosis in the epidemic areas of western China.The main findings were as follows:1.Rizha Valley and Eduoma Valley with artificial interference,Yongbo Valley and Eduoma side Valley without artificial interference were selecting to collected feces of Tibetan Fox using the methods of line transect in 2015-2016 between July and August,in Shiqu County.A total of 811 feces were recorded with 334 feces collected.The number of feces recorded and collected was no significant difference in slyvatic and anthropogentic environment respectively,in the same year(Rizha Valley vs Yongbo Valley,?~2=1.799,P=0.180;Eduoma Valley vs Eduoma side Valley,?~2=1.607,P=0.123).The minimum distance of feces from the edge of the village was256.496 m.The Wilcoxon Rank Sum test showed that the fecal spatial distribution density of Tibetan Fox was significantly different on scales of 500 m,1000 m,1500 m and 2000 m in slyvatic and anthropogentic environment(Rizha Valley vs Yongbo Valley,Z=2.637,P=0.008;Eduoma Valley vs Eduoma side Valley,Z=2.637,P=0.008).According to the detection of Copro-PCR,the prevalence of Echinococcus spp.in feces was 44.3%(148/334)with the prevalence of E.multilocularis and E.shiquicus,38.6%(129/334),18.3%(61/334),respectively.The?~2test indicated that the fecal prevalence of E.multilocularis(Rizha Valley vs Yongbo Valley,41/86 vs31/89,?~2=2.979,P=0.093;Eduoma Valley vs Eduoma side Valley,30/84 vs 27/75,?~2=0.295,P=0.628)and E.shiquicus(Rizha Valley vs Yongbo Valley,24/86 vs 28/89,?~2=0.624,P=0.624;Eduoma Valley vs Eduoma side Valley,7/84 vs 2/75,?~2=2.383,P=0.174)were no significant difference in sylvatic and anthropogenic environments.2.Dogs feces were collected in Rizha and Eduoma villages,Rizha Valley and Eduoma Valley with artificial interference,Yongbo Valley and Eduoma side Valley without artificial interference in 2015-2016 between July and August,in Shiqu County.A total of 109 dog feces were collected,including 75 of domestic dog feces and 30 unowned dogs feces in the village,and 4 dog feces from the anthropogenic environment.The detection results of the fecal prevenlece of Echinococcus spp.by Copro-PCR showed that the total prevenlence of Echinococcus was 29.5%(31/105),with the prevalence of E.multilocularis and E.shiquicus was 27.6%(29/105)and 14.3%(15/105).Significantly decreased from 51.2%(21/41)to 20%(3/15)between 2015and 2017 in Rizha(?~2=6.850,P=0.009).Only 4 dog feces collected in the sylvatic environment,and 1 collected in the valley of Eduoma side Valley was detected positive of E.multilocularis.3.Rizha Valley and Eduoma Valley with artificial interference,Yongbo Valley and Eduoma side Valley without artificial interference were selected to capture small mammals using four sampling quadrats(0.25 ha)with 500 m interval in each valley in2015-2016 between July and August,in Shiqu County.A total of 1209 small mammals were captured,including 22.3%(270/1209)of lagomorpha,77.7%(982/1209)of rodentia.Ochotona curzoniae,Lasiopodomys fuscus,Phaiomys leucurus were the main captured species.And there was no significant difference between their number in anthropogenic environment and sylvatic environment(Rizha Valley vs Yongbo Valley,417/422 vs 363/368,?~2=0.048,P=0.537;Eduoma Valley vs Eduoma side Valley,155/163 vs 245/256,?~2=0.086,P=0.437).Three lines transects of 2 km length were set using trace line methods to collect small mammal habitat using data in each valley.Combination with GIS geographic information system,the GAM(generalized additive model)was used to analysis the corelation between small mammal habitat using and environmental factors.The results of GAM showed that in the valley of Yongbo and Eduoma side without artificial interference,O.curzoniae burrow(Yongbo Valley,87.6%;Eduoma side Valley,64.8%)and vole burrows(Yongbo Valley,83.1%;Eduoma side Valley,61.4%)were the most important factors for the spatial distribution of their burrows.But these importance were diminished in Rizha Valley and Eduoma Valley with artificially disturbed.The overall prevalence of Echinococcus spp.detected by molecular methods in small mammals was 3.5%(42/1209,95%CI:2.4-4.5).Ana the prevanlence of E.multilocularis was(0.9%,11/1209,0.4-1.4)significant higher than E.shiquicus which was(2.6%,31/1209,1.7-3.5).The DNA of E.multilocularis and E.shiquicus in L.fuscus,O.curzoniae and P.leucurus were detected.4.The Echinococcus spp.mitochondrial cox1 gene sequences of each host in Shiqu County were obtained by using monoclonal sequencing.In Tibetan foxes,a total of 148 sequences,23 haplotypes of E.multilocularis cox1 gene and 7 sequences,4 haplotypes of E.shiquicus were obtained.In dogs,a total of 42 sequences,12haplotypes of E.multilocularis cox1gene and 2 sequences,1 haplotype of E.shiquicus cox1 gene were obtained.In small mammals,46 sequences,7 haplotypes haplotypes of E.multilocularis cox1 gene and 35 sequences,10 haplotypes of E shiquicus cox1gene were obtained.Haplotypes in the branches of Echinococcus Bayes didn't have significant geographical characteristics in canies and small mammals.And haplotypes from domestic dogs,Tibetan foxes and small mammals were found in each branch.In Bayes phylogenetic trees,there was no significant genetic structure differentiation between the haplotype of Echinococcus spp in canine and small mammals.And each branch has haplotypes from domestic dogs,Tibetan foxes and small mammals.5.Three male domestic dogs were selected to carry out the tracking of spatial activity at night using small GPS device in Eduoma in 2017 between July and August.The night tracking days of the three domestic dogs were 7 days,7 days,and 10 days,with a total of 24 days.The tracking duration of each domestic dog was 12.65(±2.32)h in each day and the average number of location points collected was 757.29(±137.99).The total tracking duration was 302.92 h,and the number of location points collected was 18,175.And the minimum convex polygon(MCP)method calculates the night dog's active area between 5.8-129.8 ha(100%MCP),when the maximum active distance from the release point was 1256.06 m.However,comparing the spatial range of the domestic dogs with the distribution of Tibetan Fox feces in Eduoma Valley,there was an overlap of 3.14%(100%MCP)between the two distributions.This study indicated the space behavior of free roaming domestic dogs may bring Echinococcus.spp in wild small mammals and Tibetan Fox into the anthropogenic environment.6.69 households with 84 owned dogs were surveyed for dog keeping information in the villages of Rizha and Eduoma in 2015-2017 between July and August,in Shiqu County.Variables based on household surveys and the the results of Echinococcus spp.prevalence by using Copro-PCR were included into a logistic regression model for significantly relevant factors to canine echinococcosis prevalence in dogs.The model shows that monthly deworming,leashing dogs all day,and the avoidance of dogs feeding on livestock viscera are significant measures to prevent canine echinococcosis infection in owned dogs.Carrying out a canine echinococcosis prevention and control program can significantly decrease the prevalence of Echinococcus spp.in dogs in Shiqu County.7.In conclusion,Tibetan Fox feces and small mammal burrows were widely distributed in both sylvatic and anthropogenic environments.Although domestic dogs were the inportant definitive host in the anthropogenic environment,there was a spatial overlapping area between the movement of domestic dogs and the distribution of Tibetan Fox feces.Ochotona curzoniae,L.fuscus,P.leucurus were the most important species in composition of the small mammal community,and also the main species infected with Echinococcus spp.Small mammals,dogs and Tibetan Fox were confirmed as the hosts of both E.multilocularis and E.shiquicus.And there was no significant genetic structure differentiation of the Echinococcus spp.cox1 gene in different hosts.Therefore,on the eastern Tibetan Plateau,domestic dogs were important defenitive hosts of Echinococcus spp in anthropogenic environment,and also palyed the important role in transmission of Echinococcus spp.from the sylvatic cycle to anthropogenic cycle. |
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