McCall P J, Hume Jen C C, Motshegwa Kefentse, Pignatelli Patricia, Talbert Alison, Kisinza William
Vector Group, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
Vector Borne Zoonotic Dis. 2007 Winter;7(4):659-66. doi: 10.1089/vbz.2007.0151.
Tick-borne relapsing fevers (TBRF) are caused by infection with Borrelia spirochetes and transmitted to humans by ticks. All except East African TBRF, caused by Borrelia duttonii, are known zoonoses. This widespread, endemic and pathogenic infection has only been found in humans and the Ornithodoros sp. soft tick vectors. We investigated the role of domestic animals as possible reservoirs of infection in a TBRF endemic region. Tick infestations in households and pigpens were investigated in the villages near Mvumi hospital in central Tanzania. Blood from chickens and pigs was examined by PCR and flagellin gene sequencing was performed on any Borrelia sp. infections detected. A mark-recapture experiment investigated tick movement between pigpens and houses. The acceptability of chickens as tick hosts was also investigated. Tick infestation of the 122 houses investigated was high (47%). Pigpens also were tick infested (16%) and were more likely to be so if they were located close to tick infested households (p<0.001). PCR screening of peripheral blood found Borrelia infections in both chickens and pigs (11% and 8.9% respectively). Sequencing of a subset of positive samples revealed that the amplified Borrelia sp. flagellin gene fragments shared greatest homology with B. duttonii. In a mark-recapture experiment, ticks released in pigpens were recaptured inside human bedrooms. When offered chickens as hosts, over 20% of ticks fed. For the first time in East Africa, we record natural infections of Borrelia in domestic animals and show that tick populations may act as bridging vectors between animals and humans. These results, from villages where B. duttonii is already known to be prevalent and a major cause of illness in humans, and where it has been found at high levels in ticks, strongly support the case that it is a zoonosis. This increases understanding of the epidemiology and control of this important but neglected human disease.
蜱传回归热（TBRF）由感染疏螺旋体属螺旋体引起，并通过蜱传播给人类。除了由达顿疏螺旋体引起的东非蜱传回归热外，其余均为人畜共患病。这种广泛流行、地方性且具有致病性的感染仅在人类和钝缘蜱属软蜱媒介中发现。我们在一个蜱传回归热流行地区调查了家畜作为可能感染源的作用。在坦桑尼亚中部姆武米医院附近村庄的家庭和猪圈中调查了蜱虫侵扰情况。通过聚合酶链反应（PCR）检测鸡和猪的血液，并对检测到的任何疏螺旋体属感染进行鞭毛蛋白基因测序。一项标记重捕实验研究了蜱在猪圈和房屋之间的移动情况。还调查了鸡作为蜱宿主的可接受性。在所调查的122户家庭中，蜱虫侵扰率很高（47%）。猪圈也有蜱虫侵扰（16%），如果靠近有蜱虫侵扰的家庭，则更有可能出现这种情况（p<0.001）。对外周血进行PCR筛查发现鸡和猪均有疏螺旋体感染（分别为11%和8.9%）。对一部分阳性样本进行测序显示，扩增的疏螺旋体属鞭毛蛋白基因片段与达顿疏螺旋体的同源性最高。在一项标记重捕实验中，在猪圈中释放的蜱在人类卧室中被重新捕获。当提供鸡作为宿主时，超过20%的蜱会叮咬。在东非，我们首次记录到家畜感染疏螺旋体的自然情况，并表明蜱虫种群可能充当动物与人类之间的桥梁媒介。这些结果来自已知达顿疏螺旋体流行且是人类主要致病原因、蜱虫中含量很高的村庄，有力地支持了它是一种人畜共患病的观点。这增进了我们对这种重要但被忽视的人类疾病的流行病学和控制的理解。
