| Objective:1?To understand epidemiological characteristics of SFTSV in livestock animals,rodents,ticks and humans,and explore SFTSV possible circulatory transmission mode.2?To analyze genetic evolution characteristics of the isolates from different genera and other regions and domestic and foreign strains.Methods:1?Through the epidemiological survey,analyze the distribution and clinical characteristics of SFTS cases from 2011 to 2016 in Hubei province.2?The serological and carrying rates of rodents and domestic animals and healthy popularti on were studied by RT-PCR and ELISA.The positive fragments were amplified and seque ncing,and sequence assembly,homology comparison,phylogenetic tree and recombination are analyzed by DNAStar,MEGA6.06 and RDP4 software.Results:1?Epidemiological characteristics of SFTS CasesThe distribution characteristics,pathogenicity and clinical features of SFTS cases were systematically analyzed from 2011 to 2016 in Hubei province.The main population was famers,and the mortality rate was 4.34%,and the main epidemic season was from April to October,and the peak was May,and the main morbidity areas in our province were the highest in the Dabie mountains closing to Henan and Anhui province.The median incidence of cases with different regions were significantly different(X2=821.22,p<0.05).The differences of the case fatality rate are statistically significant(X2=25.417,p<0.05).The age of the cases was mainly between 40 and 80 years old.The highest age group was 55-59 years old and 60-64 years old.The differences of the mortality with different age groups are statistically significant(X2=34.835,p<0.05).The incidence of SFTSV in our province increased year by year,and the reported cases and confirmed cases were significantly higher,especially in 2016,the incidence of disease for the first time was the higest in the country,up to 1.0954/100000,and was the first time more than Henan Province.The positive rate of SFTSV and Hantavirus(HV)from SFTS cases were 54.61%and 1.4%byPCR respectively.The effects of the sampling time for the detection rate after the onset of the disease were investigated.After the onset of the first week,the positive rate of SFTSV-PCR and SFTSV-ELISA-IgM were 69.05%and 47.6%respectively,and after the onset of the second week,the positive rate of SFTSV-PCR andSFTSV-ELISA-IgM were 50%and 52.5%respectively.The positive rate of SFTSV-PCR was higher than that of SFTSV-ELISA-IgM in the first weeks after onset,and the positive rate of SFTSV-ELISA was higher than that of SFTSV-PCR in the second week after onset of illness.However,there was no significant difference between the first week and the second week after the onset of illness(X2=0.974,p>0.05),and the consistency of the positive rate for SFTSV-PCR and SFTSV-ELISA-IgM was 51.2%.The positive rate combination ELISA-IgM with qRT-PCR were up to 79.2%.2?Investigation on serum antibody level in healthy populationIn a total of 603 serum samples,the SFTSV-IgG antibody positive rate was 5.97%,and the farmers accounted for 10.56%,which was higher than students group and other occupations group.The positive rate of SFTSV antibody was significantly different among occupation groups(X2=26.113,p<0.05).The SFTSV-IgG antibody positive rate of epidemic areas were higher than that of non-epidemic areas between different areas,and the differences were statistically significant(X2=13.722,p<0.05).3?Investigation on epidemiology and carrying virus rate of domestic animals and RodentsIn a total of 98 sheep serum samples,the total antibody and nucleic acid positive of sheep was 81.63%and 3.06%respectively.In a total of 58 cows samples of cows samples,the total antibody and nucleic acid positive rate was 67.24%and 5.17%respectively.In a total of 19 dog serum samples were collected,the total antibody positive rate was 63.16%.In a total of 369 mice samples were collected,4 mice were the positive of the total antibody,which was 1.08%,and there was 1 positive in Suizhou,1 in Yicheng and 2 in Qianjiang and there was no viral RNA positive for mice by qRT-PCR.One SFTSV strains(HB3-sheep03)was isolated from sheep sera and three SFTSV strains were isolated from the sera of local patients,and finished their whole genome sequencing,and the homology for HB3-sheep03 strain,compared to virus from the local isolates and other provinces.The results showed that the nucleotide identity of the S fragment was 94.4%-96.3%,and the amino acid identity was 85.8%-93.3%with that of sheep,cattle,dog and tick isolated Shandong province and Jiangsu province.The HB154 strain,HB156 strain and HB155 strain isolated from the sera and the HB3-sheep03 strain isolated from the sheep were distributed in the same subfamily,and the nucleotide identity of S fragment was 97.6%-97.7%,the amino acid identity was 94.2%-94.4%,and the nucleotide identity of M fragment was 98.6%-98.7%,the amino acid identity was 98.9%-99%,and the nucleotide identity of L fragment was 98.1%,the amino acid identity was 96.8%-97%,and compared with Shandong province,Henan province and Anhui province,the nucleotide identity of the S fragment was 94%-100%,the amino acid identity was 86%-100%,and the nucleotide identity of the M fragment was 92.8%-100%,the amino acid identity was 96%-100%,and the nucleotide identity of L fragment was 95.0%-100%,and the amino acid identity was 95.2%-100%.4?Investigation of ticks carrying virusIn a total of 683 ticks samples were collected,the viral RNA positive rate was 1.32%,and one SFTSV from ticks was successfully isolated(HB2016-P35 strain),and completed whole genome sequence,which compared with Hubei,Henan and Shandong provinces,as well as in Japan and Korea,and the results showed that the homology of the nucleotide identity was 93.3%-99.8%and the identity of the amino acid was 83.1%-100%,which was the closest to HBGS13 strains(KY440772),HB2014-10 strains and 2013052Sstrains from our province and Henan province,and compared with HBGS13 strains,and the identity of the nucleotide and amino acid were 99.7%and 98.7%respectively,and compared with 2013052S strains,and the identity of the nucleotide and amino acid were 99.8%and 100%respectively,and compared with the HB2014-10 strains,and the homology of the nucleotide and amino acid was 99.5%and 99%respectively.The identity of nucleotide was 94.8%-98.8%and the amino acid was 83.4-97.6%respectively,and compared with tick strains for sheep isolated Shandong and Jiangsu.5?Genetic evolution and recombination analysisSince 2010-2016,In a total of 98 SFTSV strains were isolated from our province,two recombinant strains were discovered,one strain was isolated from tick and one strain was isolated from patient serum.and a total of 44 SFTSV strains were finished for whole sequencing.Although they were high homologous,they could still be divided into A-F subgroups.The identity of nucleotides of the strain S,M,L isolated from our province was 94%-100%,93.4%-100%and 95.4%-99.9%respectively,and the homology of amino acid was 89.1-100%,93.3%-100%and 95.4%-99.9%respectively,compared with domestic and abroad,the identity of nucleotides of S,M and L was 93.2%-100%,93.1%-100%and 95.4%-100%respectively,and the identity of amino acid was 82.4%-99.7%,82.7%-99.9%and 95.1%-99.9%respectively.Conclusion1?The study have the systematic analyzed for distribution of SFTS cases in our province and national level and explored for the potential of other pathogenic spectrumcharacteris tics ofSFTS cases in our province,which has very important clinical and practical significance.2?The invisible infection of SFTSV existed in healthy people in Hubei province,the antibody levels of epidemic areas have significantly higher than that of non endemic areas,the differences were statistically significant and the antibody levels of the different occupational population were significantly different,mainly because contact ticks opportunity is different,and need to strengthen the prevention of SFTSV infectiable group consciousness and SFTSV rapid diagnostic ability.3?SFTSV strains firstly isolated from Haemaphysalis longicornis,and firstly discovered restructuring SFTSV strains from sheep serum,and its parents were from human strain.These results confirmed that the sheep and Haemaphysalis longicornis might be SFTSV medium and host from the perspective of pathogenic biology.The cattle,sheep,dogs and rats had detected the anti-SFTSV total antibody specificity,and confirmed its as a host of possibilities from serology.From mice and dogs failed to detect specific nucleic acid for SFTSV.4?It is higher homology among strains by genetic evolution characteristics analysis at home and abroad.SFTSV strains still can be divided into total of six sublineage from A-F.Between strains were high homologydifferent regions,different years,different times and different sources,and have no significant difference.There were also no significantdifference between strains from the different clinical symptoms about the light and heavy and death cases.5?Recombinant SFTSV strains for sheep have firstly discovered from parent human SFTSV strain,sheep may have played an important role in the exchange,and may be SFTSV medium and host,and provides for the new messages of infection for SFTSV transmission cycle mode and route of transmission mechanism,and explore the restructuring different strain subline changes in our province and other areas,which will lead to a transformation of antigen sites and drift,and may cause more SFTSV severe cases and deaths. |
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