Risk factors for human Mycobacterium bovis infections in an urban area of Brazil

BACKGROUND The World Health Organization (WHO) has classified human zoonotic tuberculosis (TB) due to Mycobacterium bovis as a neglected issue in the developing world. In a recent cross-sectional study in Brazil, three of 189 TB patients presented with a coinfection of M. bovis and M. tuberculosis and were selected as cases for this study. OBJECTIVE The aim was to evaluate risk factors (RF) for zoonotic TB in an urban area of Brazil in order to guide preventive programmes. METHODS A matched case-control study was carried out nested within a cross-sectional study. For each of the three cases, 14 age- and sex-matched controls (TB due to M. tuberculosis) were selected. FINDINGS Zoonotic potential exposures (ZE) and extrapulmonary TB (EPTB) were independently associated with zoonotic TB in multivariate analyses. CONCLUSIONS ZE by occupation and consumption of raw milk and derivative products that place individuals in direct and indirect contact with animals and their excretions/secretions increase the risk for zoonotic TB in Brazil, especially among those with EPTB. Therefore, measures such as efficient control of bovine TB, distribution of pasteurised milk and its derivative products, and the diagnosis and monitoring of zoonotic TB in humans are essential steps, especially in developing countries where bovine TB is enzootic, and further studies are necessary.

【背景】世界卫生组织（World Health Organization, WHO）已将牛分枝杆菌（Mycobacterium bovis）所致人类人畜共患结核病（zoonotic tuberculosis, TB）归类为发展中国家被忽视的公共卫生问题。近期在巴西开展的一项横断面研究（cross-sectional study）中，189名结核病患者中有3名同时合并感染牛分枝杆菌与结核分枝杆菌（Mycobacterium tuberculosis），遂将其纳入本次研究的病例组。
【研究目的】本研究旨在评估巴西某城区人畜共患结核病的危险因素（risk factors, RF），以期为相关防控规划提供科学指导。
【研究方法】本研究为一项嵌套于横断面研究的匹配式病例对照研究（matched case-control study）。针对每例病例，选取14名年龄与性别相匹配的对照者（均为结核分枝杆菌所致结核病患者）。
【研究结果】多变量分析显示，人畜共患暴露风险（zoonotic potential exposures, ZE）与肺外结核（extrapulmonary TB, EPTB）均与人畜共患结核病存在独立相关性。
【研究结论】因职业暴露及饮用生乳及其衍生制品导致的人畜共患暴露风险，会使个体直接或间接接触动物及其排泄物/分泌物，进而升高巴西人群罹患人畜共患结核病的风险，该风险在肺外结核患者中尤为显著。因此，诸如高效管控牛结核病、推广巴氏消毒乳及其衍生制品、开展人类人畜共患结核病的诊断与监测等措施，均为必要之举；在牛结核病呈地方性流行的发展中国家，此类举措尤为关键，且仍需开展进一步相关研究。