Hansen Martin Rune Hassan, Schullehner Jörg, Gyldenkærne Steen, Omland Øyvind, Frohn Lise Marie, Sigsgaard Torben, Schlünssen Vivi
Research Unit for Environment, Work and Health, Department of Public Health, Aarhus University, Bartholins Allé 2, Building 1260, Aarhus C, DK-8000, Denmark.
Department of Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, Aarhus N, DK-8200, Denmark.
Infection. 2025 Sep 8. doi: 10.1007/s15010-025-02629-2.
Livestock-MRSA (methicillin-resistant Staphylococcus aureus) can cause infections in persons without known contact to livestock, but the route of transmission is unclear. We investigated whether the risk of livestock-MRSA infection among persons with no known contact to livestock is associated with the number of pig farms near the home, and whether this association is affected by the upwind/downwind location of the farms.
Register-based case-control study of 518 persons from Denmark with clinical infections with livestock-MRSA in 2016-2021 and no known exposure to livestock, and 4,944 matched controls. Distances and angles from home addresses to all pig farms within a distance of 25 km were calculated, and compared with the mean wind direction in the area.
The mean number of pig farms within 13,127 m of the home address was 3.3 [0.3; 6.3] higher for cases (60.5) than controls (57.1), with a larger difference for farms upwind than downwind. The primary analysis showed that the livestock-MRSA exposure from a downwind farm was 59% [40%; 178%] of the exposure from an upwind farm, but the difference disappeared after confounder adjustment. In a post-hoc analysis, cases were surrounded by more pig farms at 50 - 6,250 m from the home address, and in the interval 1,250-6,250 m the difference was only seen in the upwind directions.
The risk of livestock-MRSA infection among persons without known livestock contact was influenced by the number of and distance to pig farms. In an exploratory post-hoc analysis, but not the main analysis, the risk was also influenced by mean wind direction.
家畜耐甲氧西林金黄色葡萄球菌（Livestock-MRSA）可在无明确家畜接触史的人群中引起感染，但其传播途径尚不清楚。我们调查了无明确家畜接触史的人群中家畜-MRSA感染风险是否与家附近的猪场数量有关，以及这种关联是否受猪场的上风/下风位置影响。
基于登记的病例对照研究，研究对象为2016年至2021年丹麦518例临床感染家畜-MRSA且无明确家畜接触史的患者，以及4944例匹配对照。计算从家庭住址到25公里范围内所有猪场的距离和角度，并与该地区的平均风向进行比较。
病例组（60.5）家庭住址13127米范围内的猪场平均数量比对照组（57.1）多3.3[0.3；6.3]，上风方向的猪场差异比下风方向更大。初步分析显示，下风方向猪场的家畜-MRSA暴露量是上风方向猪场的59%[40%；178%]，但在调整混杂因素后差异消失。在一项事后分析中，病例组在距家庭住址50至6250米范围内被更多猪场包围，在1250至6250米区间，差异仅在上风方向出现。
无明确家畜接触史的人群中家畜-MRSA感染风险受猪场数量和距离影响。在一项探索性事后分析中（而非主要分析），风险也受平均风向影响。
