| Objective:Part of counties in the western Yunnan province were taken as the spatial scope of the survey.Host Animals(domestic animals and small mammals),vectors and patients with arthritis symptoms were severed as research objects.Molecular epidemiology and immunology methods were used to understand Borrelia burgdorferi sensu lato infection and genepolymorphism among host animals and vectors in western Yunnan and provide scientific evidence for developing control measures.Method:1.Venous blood of domestic animals was collected by vacuum blood collection tube,small mammals were captured by night trapping method and rat cage method,then liver,kidney and spleen samples were collected;free ticks were collected by flag method,and parasitic ticks were collected on the skin surface of animals;the blood of arthritis patients who had excluded rheumatism and rheumatoid diseases were collected and separated serum.2.The DNA of livestock blood samples,small animal organs,tick samples were extracted by blood/tissue genomic DNA extraction kit,and The 5S~23S rRNA spacer gene,Fla gene and 16 S rRNA gene of Borrelia burgdorferi were amplified.Homology analysis was carried out on the obtained sequences and phylogenetic tree was constructed for genetic evolution analysis.3.The serum IgG antibody detection kit(ELISA)of Borrelia burgdorferi was used for antibody detection.4.The results were analyzed by SPSS17.0 software and compared by chi-square test.Results:1.Sample collection: A total of 1927 blood samples of domestic animals from 5 kinds(cattle,sheep,dogs,horses and donkeys)were collected in 16 counties.3659 samples of small animals belonging to 57 species,29 genera and 10 families from 5 orders were collected in 23 counties.737 tick samples belonging to 10 species,4 genera were collected in 9 counties.281 serum samples were collected from patients with arthritis in 4 counties.2.The results of domestic animals: 1927 blood samples of livestock(554 cattle blood,636 sheep blood,33 horse blood,17 donkey blood and 687 dog blood)were detected.52 samples were detected positive for Borrelia burgdorferi,the positive rate was 2.70%.They belonged to three genotypes: B.afzelii,B.burgdorferi and B.garinii,mainly B.afzelii(90.38%).Cattle,sheep,dogs and horses were detected positive.The positive rate of dog blood was the highest(6.26%)and donkey blood was detected negative.Eight of the 16 counties(cities)were positive.The highest positive rate was Deqin(10.33%),followed by Lanping(3.33%)and Gengma(2.94%).3.The results of small mammal: 3659 small mammal samples were detected,belonging to 57 species,29 genera,10 families,5 orders.A total of 146 samples were positive in 30 small mammals,the positive rate was 3.99%.They belonged to 5 genotypes: B.afzelii,B.burgdorferi sensu stricto,B.garinii,B.japonica and B.valaisiana,with B.afzelii as the main genotype(56.84%).Among 23 counties,14 counties were positive,mainly distributed in the northwestern Yunnan Province.The infection rate of small animals was the highest in forest areas above 2500 m altitude.4.The results of ticks: 737 ticks belonging to 10 species,4 genera were collected,103 ticks were positive,the positive rate was 13.98%.Six genotypes of Borrelia burgdorferi(B.afzelii,B.garinii,B.japonica,B.valaisiana,B.burgdorferi sensu stricto,B.sinica)were detected from five ticks(H.nepalensis,I.ovatus,I.granulatus,R.microplus and H.kolonini),with B.garinii as the dominant species(47.57%).Among 9 counties,6 counties were positive,mainly distributed in the western of Yunnan Province.5.The results of population: 281 sera of arthritis patients from 4 counties(cities)were tested,111 of them were positive for Lyme disease IgG antibody,the total positive rate was 39.50%.Conclusion:1.The infection of Borrelia burgdorferi exists in domestic animals,small mammal and ticks in Western Yunnan Province,which mainly distributed in northwest Yunnan The positive rates were 2.70% in domestic animals,3.99% in small mammals and 13.98% in ticks.2.The host animals and vectors of Borrelia burgdorferi in Western Yunnan Province were complex and diverse.Cattle,sheep,dogs and horses were detected positive,among which cattle,sheep and horse infections were first reported in Yunnan Province;30 species of small mammals were detected positive,among which 20 species were first reported;and 5 species ticks(2 Ixodes,2 Haemaphysalis and 1 Rhipicephalus)were detected positive.3.The infections of Borrelia burgdorferi in host and vector from the investigated area had high diversity.Eight genotypes of Borrelia burgdorferi were detected,five were detected in host animals and six were detected in ticks,two of which were undetermined genotypes.B.japonica was detected in Apodemus draco,Niviventer excelsior and I.granulosus,B.sinica was detected in H.kolonini(new tick species)for the first time,and B.sinica was detected in I.ovata for the first time in Yunnan Province.4.Some areas in Western Yunnan may be the focus of Lyme disease.B.afzelii and B.garinii were the main genotypes of Borrelia burgdorferi detected in hosts and vectors,which were recognized to be pathogenic to humans.The homology between the detected gene sequences and those registered in GenBank was 98-99%.The sequence homology of B.afzelii detected from livestock,small mammals and ticks in the same area(Deqin County)ranged from 98 to 99%,indicating that there was a transmission chain of pathogens between hosts and vectors in this area.At the same time,Lyme disease serum antibody was positive,the total positive rate of IgG antibody was 39.50%.In this study,molecular epidemiological investigation was used to confirm that host animals and vectors of Borrelia burgdorferi in Western Yunnan are various and widely distributed,and the genetic diversity of pathogens is high and the pathogenicity is strong.Serology confirmed that infection exists in specific populations.Due to the limited time,the situation of population infection,isolation of pathogens and diagnosis of patients is still in progress.This study provides a preliminary research basis for the confirmation of the natural focus of Lyme disease in Yunnan Province. |
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