Moriarty Kathleen, Champetier Antoine, Galli Francesco, Dürr Salome, Chitnis Nakul
University of Basel, Basel, Switzerland.
Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
PLoS One. 2025 Aug 22;20(8):e0329714. doi: 10.1371/journal.pone.0329714. eCollection 2025.
Infectious diseases in livestock have detrimental effects on the health of animals, the livelihood of farmers, and the meat industry. Understanding the specific pathways of disease spread and evaluating the effectiveness of surveillance measures is critical to preventing large outbreaks. Direct livestock transport, transport tours-where a single truck moves livestock between multiple farms in a single journey-and contacts that livestock have with their surrounding environment have been identified as drivers of disease dissemination. The objective of this study was to assess the role of these different pathways in the transmission of several swine pathogens and to evaluate the efficacy of surveillance strategies in identifying outbreaks. To achieve this, we built contact networks for these modes of disease transmission based on empirical data from the Swiss swine production sector. We developed a stochastic, susceptible-infectious-recovered (SIR) type, herd-based model to simulate the spread of multiple pathogens within farms and between farms along the networks. We parameterized the model for Porcine Reproductive and Respiratory Syndrome (PRRS) virus, African Swine Fever (ASF) virus, and Actinobacillus pleuropneumonia (APP): three pathogens with distinct clinical patterns, modes of transmission, and contact transmission rates. The model provides insight into the contribution of different contact types to disease dispersion. Our findings highlight that direct truck transport and local spread are the main routes of between-farm transmission. In addition, we analyzed the ability of surveillance measures to detect outbreaks from these distinct pathogens spreading along the contact networks. Farmer-based surveillance programs were the only measures that consistently identified outbreaks of APP and PRRS, and they were able to identify ASF outbreaks almost 8 weeks or more before active slaughterhouse- and network-based surveillance. Our model outcomes give evidence of the prominent transmission pathways and surveillance measures, which could help establish programs to prevent the spread of swine infectious diseases.
家畜传染病会对动物健康、农民生计以及肉类行业产生不利影响。了解疾病传播的具体途径并评估监测措施的有效性对于预防大规模疫情爆发至关重要。已确定直接的家畜运输、运输行程（即一辆卡车在单次行程中在多个农场之间运输家畜）以及家畜与其周围环境的接触是疾病传播的驱动因素。本研究的目的是评估这些不同途径在几种猪病原体传播中的作用，并评估监测策略在识别疫情方面的功效。为实现这一目标，我们基于瑞士养猪业的经验数据构建了这些疾病传播模式的接触网络。我们开发了一种基于群体的随机易感 - 感染 - 恢复（SIR）型模型，以模拟多种病原体在农场内部以及沿着网络在农场之间的传播。我们为猪繁殖与呼吸综合征（PRRS）病毒、非洲猪瘟（ASF）病毒和胸膜肺炎放线杆菌（APP）对模型进行了参数化：这三种病原体具有不同的临床模式、传播方式和接触传播率。该模型深入了解了不同接触类型对疾病传播的贡献。我们的研究结果表明，直接的卡车运输和局部传播是农场间传播的主要途径。此外我们分析监测措施从这些沿着接触网络传播的不同病原体中检测疫情的能力。基于农民的监测计划是唯一能够持续识别APP和PRRS疫情的措施，并且它们能够在基于屠宰场和网络的主动监测之前近8周或更长时间识别出ASF疫情。我们的模型结果证明了突出的传播途径和监测措施，这有助于制定预防猪传染病传播的计划。
