INRA, ONIRIS, UMR1300 Bioagression, Epidémiologie et Analyse de Risque, BP 40706, F-44307 Nantes, France.
J Dairy Sci. 2010 Oct;93(10):4455-70. doi: 10.3168/jds.2010-3139.
Epidemiological models have been developed to test hypotheses on Mycobacterium avium ssp. paratuberculosis (Map) transmission in a herd, and to compare different paratuberculosis control strategies and alternatives for certification-and-surveillance schemes. The models are simplified representations of existing biological processes tailored to the questions they are intended to answer. Such models depend on available knowledge about the underlying processes, notably in relation to pathogen transmission. All decisions relating to integration of specific aspects of the herd structure and transmission mechanisms as well as modeling objective will influence model behavior and simulation results. This paper examines assumptions on pathogen transmission and risk mitigation represented in 8 epidemiological models of within-herd Map transmission in dairy cattle. We describe available models' structure and examine them in the context of current knowledge about host infection and pathogen transmission pathways. We investigate how population structure and herd management are modeled with regard to their influence on contact structure and pathogen transmission. We show that assumptions about routes of transmission and their contribution within a herd vary greatly among models. Gaps of knowledge that are pivotal to defining transmission equations and parameters, such as variation of susceptibility with age and variability of pattern of shedding, are identified. Quantitative estimates of this incomplete information should be targeted by future research. Existing models could be improved by considering indirect transmission via the environment taking account of Map survival and contact structure between animals in a herd, and by including calf-to-calf transmission, which has recently been proven as being important.
已开发出流行病学模型来检验分枝杆菌副结核亚种（Map）在牛群中传播的假设，并比较不同的副结核病控制策略和认证-监测计划的替代方案。这些模型是对现有生物过程的简化表示，旨在回答他们要回答的问题。此类模型取决于有关潜在过程的可用知识，特别是与病原体传播有关的知识。与牛群结构和传播机制的特定方面的整合以及建模目标有关的所有决策都将影响模型行为和模拟结果。本文检查了 8 种奶牛群内 Map 传播的流行病学模型中所代表的病原体传播和风险缓解假设。我们描述了可用模型的结构，并根据宿主感染和病原体传播途径的现有知识对其进行了检查。我们研究了如何对种群结构和牛群管理进行建模，以了解其对接触结构和病原体传播的影响。我们表明，模型之间对传播途径及其在牛群中的贡献的假设差异很大。确定了传播方程和参数的关键知识空白，例如年龄相关的易感性变化和脱落模式的可变性。应针对此不完整信息进行未来研究。通过考虑环境中的间接传播并考虑到 Map 的存活和牛群中动物之间的接触结构，以及包括最近已被证明很重要的犊牛间传播，可以改进现有的模型。
