Investigation And Epidemic Characteristics Of Babesiasis In Southwest Yunling Mountains

Objective: Part of counties in the southwest of Yunling Mountains in Yunnan province as the spatial scope of the survey.Host animals(domestic animals and small mammals),vector ticks and specific population as the research objects.With the methods of etiology and molecular epidemiology,the infection situation of host animals,ticks and specific population in this area was investigated,and the 18 S rRNA gene sequence and genetic evolution of Babesia were analyzed,to provide scientific basis for the prevention and control of Babesiasis.Method:1.Anticoagulant blood vessels were used to collect venous blood samples of domestic animals.Small animals were captured by night trap method and rat cage method.After capture,they were taken back to the laboratory to collect liver and spleen samples.Free ticks were collected by flag method and parasitic ticks were collected by body surface collection method.Venous blood samples of patients with fever and anemia of unknown origin and blood samples of blood donors were collected from designated hospitals.2.The above samples were extracted with blood / tissue genomic DNA extraction kit,and 18 S rRNA of Babesia were amplified.The PCR amplified positive products obtained were used to sequenced in the company.the sequence in the NCBI web site(http://www.ncbi.nlm.nih.gov)BLAST,the obtained sequence homology analysis and construct phylogenetic tree analysis of genetic evolution.3.Blood smears were made from patients with fever and anemia of unknown origin for morphological examination.After Giemsa staining,the infection of Babesia in red blood cells was observed under microscope,and the image records were saved.Results:1.Sample collection: 498 samples of small mammals were collected from 3 counties(Yunlong County,Jianchuan County and Eryuan County)in southwestern YunlingMountains of Yunnan Province,belonging to 27 species,14 genera,8 families,4 orders.In 4 counties(Tengchong County,Gengma County,Yunlong County and Jianchuan County),a total of 1139 blood samples were collected from domestic animals(342 cattle blood,747 sheep blood,33 horse blood and 17 donkey blood),1003 tick samples(belonging to 9 species and 5 genera)were collected,and 1373 blood samples(811 fever of unknown cause,208 anemia patients and 354 blood donors)were collected from 4 counties(cities).2.The results of small mammal: A total of 55 positive samples were detected in 498 small mammals,with a positive rate of 11.04%,belonging to 7 small mammals.Babesia spp.was detected positive in small mammals in Yunlong County and Jianchuan County.The positive rates were 31.58%(54/171)and 0.47%(1/212),respectively.Babesia spp.wasn’t detected positive in small mammals in Eryuan County.3.The results of domestic animals: A total of 55 positive samples were detected from 1139 blood samples of domestic animals,with a positive rate of 4.83%.The positive rates were 2.05%(7/342)and 6.43%(48/747)in blood samples of cattle and sheep,but not in horses and donkeys.They are distributed in 4 counties,the positive rates from high to low was 22.61%(26/115)in Jianchuan County,7.55%(16/212)in Yunlong County,1.85%(1/54)in Gengma County and 1.58%(12/758)in Tengchong City.4.The results of ticks: 58 ticks were positive in 1003 tick samples,the positive rate was 5.78%.Babesia spp.were detected from 4 ticks(I.granulatus,I.ovatus,R.microplus and H.montgomeryi),and the positive rates were 17.31%(9/52),8.46%(17/201),6.64%(30/452)and 0.81%(1/123),respectively.The positive rates of ticks collected from 4 counties(cities)was 9.63%(18/187)in Gengma County,6.30%(8/127)in Yunlong County,4.93%(14/284)in Jianchuan County and 4.44%(18/405)in Tengchong City.5.The results of human: 28 positive samples were detected in 1373 blood samples of specific population,and the total positive rate was 2.04%,all of them were anemia patients.28 cases of positive peripheral blood smear staining microscopic examination,21 cases of which were observed of Babesia infection of red blood cells.Conclusion:1.The infection of Babesia exists in host animals,vector ticks and specific populations in southwestern Yunling Mountains of Yunnan Province.2.The host animals and vector ticks of Babesia were complex and diverse in the surveyarea.Babesia app.was detected in cattle,sheep,7 species of small mammals,and 4 tick species,respectively.In N.excelsior and S.leucops infections were first reported.B.microti was detected in I.granulatus,R.microplus and H.montgomeryi,which has not been reported before.3.Babesia app.detected in the survey area had high diversity.A total of 8 species of Babesia have been detected,including B.microti,B.venatorum and B.bigemina,which are associated with human diseases.Otsu type of B.microti was detected in the host animals,and Kobe type was detected in the vector ticks.Two Babesia spp.(Otsu type of B.microti and Babesia venatorum Tianzhu strain)have been detected among anaemia patients.4.Tengchong City of Yunnan Province may be the natural foci of Babesiosis.The sequence similarity of 18 S rRNA gene of B.microti from host animals,vector ticks and specific populations was 94.4% ~ 99.7%.The genetic evolution analysis was in the same branch and had a common ancestor,indicating that there was a transmission chain of pathogens between hosts,vectors and human beings in this area.In this study,molecular epidemiological investigation was used to confirm that the host animals and vector ticks of Babesia are various and widely distributed,and Babesia app.has high diversity in the southwest of Yunling mountains in Yunnan Province,and confirmed the existence of Babesia infection in specific population.Due to the limited time of this project,characteristics of pathogens and human infection is still in progress.The results laid a foundation for the preliminary study of Babesia natural foci in the southwest of Yunling mountains,Yunnan Province.