云南新发蜱传螺旋体分离鉴定及其自然疫源地调查研究

Ticks are widely-spread arachnids in nature and known as a vector implicated in the transmission of a number of infections caused by pathogens such as bacteria, viruses and protozoa. In recent years, emerging infectious diseases associated with these arachnids caused a world-wide concern. In China, a typical tick-borne pathogen, Borrelia burgdorferi, which causes the famous Lyme disease and is notorious as so-called "AIDS No.2", has been identified in 20 provinces. More pathogens are found to be new types and strains and more concern was aroused. Yunnan, as China’s most diverse province ecologically and biologically, contains various natural conditions suitable for the agents of many natural focus diseases. This study aims to separate and identify the Borrelia burgdorferi and Borrelia miyamotoi which have been detected from the host animals and ticks collected in Yunnan Province in previous study. Based on the characters of topography, climate and forest vegetation zone, representative areas will be selected to focus on ticks, small mammals and livestock, thus identifying natural foci of this disease. In the meantime, sentinel hospitals will be established to carry out case investigation on the patients bitten by ticks, thus revealing the relationship between the type of borrelia and geographical environment. The risk of infection in local inhabitants will be estimated. Overall, this study will be undertaken to isolate and identify tick-borne spirochetes, known and unknown, in Yunnan Province. The results from this study will contribute to enrich China’s resource library of spirochetes and provide scientific basis for the prevention and control of this disease in China.

蜱虫是目前传播病原体类别最多、分布最广的一类媒介生物。近年新发蜱媒病不断出现，各国普遍关注。蜱传螺旋体的典型代表——引起素有 “第二艾滋病”之称莱姆病的伯氏疏螺旋体，其种类、型别复杂多样，在我国广泛分布。近年还有新的蜱传螺旋体被发现。云南具有中国最复杂多样的生态环境，构成了多种虫媒和自然疫源性疾病长期保存、发生和流行的自然条件。本研究拟在前期工作在云南部分地区筛检出新型伯氏疏螺旋体和回归热螺旋体线索的基础上，进一步进行病原体的分离和鉴定；基于云南地理气候环境和森林植被带，选择代表性样区，围绕蜱类、小型兽类、家畜开展自然疫源地的深入调查；并针对当地哨点医院蜱虫叮咬和接触的疑似患者，开展个案和致病性调查。从而掌握云南新发蜱传螺旋体的类型、空间分布特征及其与地理环境因素间的关系，人群被感染风险；分离新型蜱传螺旋体，丰富我国的螺旋体资源库，为我国新发蜱传螺旋体病的防控提供科学依据。

本研究以云南西部为主要调查研究的空间范围，对代表性样区重点人群、宿主动物和媒介蜱进行了样本采集和蜱传螺旋体等蜱传疾病的调查。共完成采自32个（市）、分属5目12科32属68种小型兽类5044只、16个县（市）的5种家养动物血液1927份、14个县（市）分属5属14种的蜱虫1507只的分子生物学检测；采自6个县（市）的5种蜱950只及大量蜱卵分260组进行了螺旋体分离培养。调查结果证实，云南省可能存在莱姆病自然疫源地，宿主动物和媒介蜱种类丰富，牛、羊、犬、马、30种小型兽类和5个蜱种中检出6种基因型伯氏疏螺旋体，具有较高的基因多样性特征，B.burgdorferi sensu stricto、B.japonica、B.sinica和B.valaisiana为云南首次道；B.afzellii、B.garinii为优势基因型，检出的序列与国内外患者中检出的序列高度同源。且同一地区在宿主和媒介中检出的序列高度同源，部分地区的重点人群中血清抗体滴度、阳性率较高，存在宿主、媒介、人群间传播链的可能。首次证实云南省家畜和媒介蜱携带多种回归热螺旋体，分属两种：一种为B.miyamotoi西伯利亚型和可能变异新基因型；另一种与现有报道的回归热螺旋体差异较大，可能为一新种疏螺旋体，暂命名为Borrelia dali。本次检出的回归热螺旋体宿主动物可能为牛、羊、犬等大型哺乳动物，小型兽类可能不是其主要宿主，5种蜱检出阳性。该结果与国内在东北的调查结果一致，但与国外调查认为小型兽类是主要宿主动物存在差异。检出阳性的蜱种、地区分布与伯氏疏螺旋体基本一致。本研究结果对于了解该地区蜱传螺旋体等媒媒传染病的情况、优势基因种/型、掌握人群感染风险进而制定科学的防治措施提供了科学依据。同时也显示，云南省蜱传螺旋体等蜱媒病原体及宿主、媒介种类均具有高度多样性和复杂性的特征，蜱媒病是该地区不容忽视的虫媒传染病。项目实施期间发表标注该项目资助的学术论文16篇，其中SCI论文3篇。