Molecular epidemiology of relapsing fever and prevention of Borrelia infection

通过血玻片检查、巢式PCR检测媒介蜱虫和人类血液样本，对坦桑尼亚中部一个村庄的人口进行了螺旋体疏螺旋体调查。PCR在检测感染方面的敏感性是前者的两倍，在11.1%的发烧儿童和4.2%的其他健康儿童中发现伯氏疏螺旋体。对18例感染的伯氏疏螺旋体进行基因分型，鉴定出杜顿氏疏螺旋体和一种新的未命名物种，未从人类或其他脊椎动物中发现。该疏螺旋体的系统发育分析与新世界复发热疏螺旋体相似。这是坦桑尼亚中部蜱传回归热的一种新病原体，以前从感染房屋的猪鸟蜱中分离出来。在坦桑尼亚Dodoma附近的Mvumi Mission村的房屋中也收集到了蜱虫。采用基于鞭毛蛋白基因的巢式聚合酶链反应检测所有蜱是否感染伯氏疏螺旋体。所有房屋均有大量蜱虫，收集到的蜱虫均为猪鸟蜱。120只蜱中51只感染了螺旋体，鞭毛蛋白基因序列比较表明，大多数螺旋体属于杜顿疏螺旋体，该螺旋体是东非蜱传回归热的病原体。其余螺旋体与duttonii有较大差异。这表明新的伯氏疏螺旋体在该地区分布，是回归热的病原体。利用16S核糖体RNA基因序列进行的系统发育分析也支持该螺旋体是一个不同于先前描述的伯氏疏螺旋体属成员的种。

The population of a central Tanzanian village were investigated for Borrelia sp. spirochaetes by blood slide examination, nested PCR for vector ticks and human blood samples. PCR was twice as sensitive in detecting infections, revealing Borrelia sp. in 11.1% of children with fever, and 4.2% of otherwise healthy children. Genotyping Borrelia sp. from 18 infections identified Borrelia duttonji and a new unnamed species, not known from humans or other vertebrates. Phylogenetic analysis of this Borrelia was resembled New World relapsing fever borreliae. Previously isolated from Ornithodoros porcinus ticks infesting houses, this is a new causative agent of tick-borne relapsing fever in Central Tanzania. Ticks were also collected from the houses in Mvumi Mission village, near Dodoma, Tanzania. All ticks were examined for Borrelia infestation by flagellin gene-based nested polymerase chain reaction. All houses were highly infested with ticks, and all ticks collected were of the Ornithodoros porcinus species. Fifty-one out of 120 ticks were infected with spirochetes, and a flagellin gene sequence comparison showed that most of the spirochetes belonged to Borrelia duttonii, which is the causative agent of tick-borne relapsing fever in East Africa. The rest of the spirochetes were quite different from B. duttonii. This indicates the new Borrelia is distributed and is causative agent of relapsing fever in the area. Phylogenetic analysis using 16S ribosomal RNA gene sequences also supported that the spirochete was a Borrelia species distinct from previously described members of the genus.