中国内蒙古、新疆部分地区鼠类自然感染恙虫病东方体的调查

Investigation on rodents' natural infection of Orientia tsutsugamushi in some areas of Inner Mongolia and Xinjiang, China

目的了解中国内蒙古、新疆自治区部分地区鼠类自然感染恙虫病东方体(Ot)的情况。方法采用鼠夹捕鼠,从鼠脾中提取DNA,应用巢式PCR(nPCR)检测Ot-Sta56基因;对部分阳性标本测序,用Clustal X(5．0)和DNA Club软件对序列进行比较分析。结果内蒙古地区捕获各种鼠类共计90只,其中6只nPCR检测阳性,总阳性率为6．67％,不同鼠种间阳性率有差别,但无统计学意义(X2=8．898,P=0．148);新疆地区捕获各种鼠类共计20只,其中1只nPCR检测阳性,阳性率为5．00％。不同地区间阳性率比较虽略有差别,但无统计学意义(X2=0．076,P=0．782)。内蒙古、新疆部分地区从农田中捕获的鼠类标本为9只,占8．18％,无阳性标本;从草原捕获的鼠类标本为101只,占91．82％,其中阳性标本为7只,草原鼠标本Ot感染率为6．93％。序列分析结果:N59(内蒙古莫氏田鼠)、N69(内蒙古黑线仓鼠)、X33(新疆普通仓鼠)3份标本nPCR产物碱基序列与Karp株相应DNA片段的碱基序列同源性最高,均为99％,应属于Karp型;N65(内蒙古黑线仓鼠)及N88标本(内蒙古黑线姬鼠)nPCR产物碱基序列与中国台湾Taitung-2株和TW461株相应DNA片段的碱基序列同源性最高,均为94％;N90(内蒙古黑线姬鼠)与日本Oishi株相应DNA片段的碱基序列同源性最高,为96％。系统发育分析表明,N59、N69、X33位于Karp株所在的分支,而N65、N88、N90与Taitung-2株、TW461株、Yonchon株、Sxh951株、Oishi株、Kanda株属同一支系。结论研究证实内蒙古、新疆部分地区鼠类存在Ot自然感染,其基因型较为复杂。这为进一步深入进行恙虫病疫源地的调查奠定了基础。

Objective To investigate rodents＇ natural infection of Orientia tsutsugamushi （Ot） in some areas of Inner Mongolia and Xinjiang, China. Methods DNAs were extracted from spleens of the captured mice and nested-polymerase chain reaction （nPCR） technique was used to detect the Ot-Sta56 gene. Six positive samples were sequenced and analyzed by Ctustal X （5.0） and DNA Club software. Results A total of 90 rodents were captured in Inner Mongolia, and the overall prevalence of Ot was 6.67%. There was no significant difference in infection rates among the positive rodents species. 20 rodents were captured in Xinjiang, and the prevalence of Ot was 5.00 %. The geographical difference in infection rates was not statistically significant between Inner Mongolia and Xinjiang. 9 rodents were captured in farmlands of Inner Mongolia and Xinjiang but there was no positive samples found. 101 rodents were captured in grasslands, and the prevalence of Ot was 6.93%. The Sta56 gene nucteotide sequence homology to Karp strain of N59 （ from Mierotus rnaxirnowiczii ）, N69 （ from Cricetulus barabensis ） and X33 （from Cricetus cricetus） was 99 %. The sequence homology to Taitung-2 strain and TW461 strain of N65 （from C. barabensis ） was 94 %, and the sequence homology to Taitung-2 strain and TW461 strain of N88（from Apodernus agrarius ） was also 94%. The sequence homology to Oishi strain of N90 （from A. agrarius） was 96.00 %. Conclusion Our findings indicated that infections of Ot did exist in rodents captured from Inner Mongolia and Xinjiang. The genotypes of Ot in Inner Mongolia and Xinjiang were quite complex, with some of them belonged to Karp type, and the others belonged to Taitung-2, TW461 and Oishi types which providing evidence for further investigation on the scrub typhus fuci in the two areas.