Abstract: Objective To investigate the difference in the positive rate of Orientia tsutsugamushi between different organs of small mammals, and to provide a reference for the pathogen monitoring of scrub typhus. Methods Liver, spleen, lung, kidney, and ear samples were collected from 105 small mammals collected in Yongcheng city of Henan province, China in October 2017, and liver, spleen, and ear samples were collected from 324 small mammals collected in Pinggu district of Beijing, China from September to November 2018. DNA was extracted, and nested PCR amplification was used to detect the nucleic acid fragment of the 56 kDa protein gene of O. tsutsugamushi. The specimens with specific bands were genotyped by comparison of nucleotide sequence, and the positive rate was calculated. Results The positive rate of O. tsutsugamushi in small mammals was 10.48% in Yongcheng city and 12.96% in Pinggu district, with no significant difference (χ²=0.494, P=0.504). The positive rate of O. tsutsugamushi in different organs within the same site was 0.98%-14.81%; pairwise comparison showed that the positive rate of O. tsutsugamushi in the ear of the small mammals in Yongcheng city was higher than that in the other four organs, and the positive rate of O. tsutsugamushi in the liver of the small animals in Pinggu district was significantly higher than that in the spleen (χ²=5.818, P=0.022). The comparison of the two places showed that the positive rate of O. tsutsugamushi in the ear of the small mammals in Yongcheng city was significantly higher than that in Pinggu district (χ²=6.525, P=0.011). For the small mammals in Pinggu district, the positive rate of Shimokoshi-type O. tsutsugamushi in the spleen was lower than that in liver and the ear, while there was no significant difference in the positive rate of Kawasaki-type O. tsutsugamushi between the different organs (χ²=1.560, P=0.455). The pooled analysis of the detection results of the liver and the spleen in Yongcheng city and Pinggu district showed that the positive rate of O. tsutsugamushi in the liver was higher than that in the spleen. The results of consistency test showed no significant difference (Kappa=0.015, P=0.744), with poor consistency of positive infection in the liver and the spleen. Conclusion There are no significant differences in the positive rates of Kawasaki-type O. tsutsugamushi in the liver, spleen, lung, and kidney of small mammals between Yongcheng city and Pinggu district, while the positive rate of Shimokoshi-type O. tsutsugamushi in the liver and the ear is higher than that in the spleen. Detection of O. tsutsugamushi in the organ of various small mammals or in multiple organs can improve the detection rate of O. tsutsugamushi, and rodent ears can also be used as samples for the pathogen monitoring of scrub typhus.

Key words: Small mammal, Orientia tsutsugamushi, Organ, Positive rate

摘要： 目的 探究小型兽类不同器官恙虫病东方体阳性率有无差别，为恙虫病的病原学监测提供参考依据。方法 分别选取2017年10月在河南省永城市采集的105只小型兽类的肝、脾、肺、肾、耳样本和2018年9－11月在北京市平谷区采集的324只小兽的肝、脾、耳样本，提取组织DNA，采用巢式PCR扩增检测恙虫病东方体56 kDa蛋白基因核酸片段，出现特异性条带标本通过核酸序列比对确定基因分型并计算阳性率。结果 永城市和平谷区小兽阳性率分别为10.48%和12.96%，二者差异无统计学意义（χ²=0.494，P=0.504）。相同地点小兽不同器官阳性率在0.98%～14.81%，经两两比较χ²检验，永城市小兽耳的阳性率高于其他4种器官，平谷区肝脏的阳性率高于脾脏，差异有统计学意义（χ²=5.818，P=0.022）。两地之间比较，永城市小兽耳的阳性率高于平谷区，差异有统计学意义（χ²=6.525，P=0.011）。平谷区小兽脾的Shimokoshi型阳性率低于肝和耳，Kawasaki型不同器官阳性率差异无统计学意义（χ²=1.560，P=0.455）。两地肝、脾检测结果合并后配对结果显示肝脏的阳性率高于脾脏。一致性检验结果无统计学意义（Kappa=0.015，P=0.744），肝脏、脾脏阳性感染一致性差。结论 永城市和平谷区小兽Kawasaki型的肝、脾、肺、肾恙虫病东方体阳性率差异无统计学意义，而Shimokoshi型肝、耳高于脾。检测多种小兽脏器或多种器官混合可提高恙虫病东方体检出率，兽耳也可作为病原学检测样本。

关键词: 小型兽类, 恙虫病东方体, 器官, 阳性率