Centre for Veterinary Epidemiology and Risk Analysis, UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin, D04 W6F6, Ireland.
INRAE, Oniris, BIOEPAR, 44300, Nantes, France.
Vet Res. 2022 Jun 22;53(1):45. doi: 10.1186/s13567-022-01066-5.
Bovine paratuberculosis is an endemic disease caused by Mycobacterium avium subspecies paratuberculosis (Map). Map is mainly transmitted between herds through movement of infected but undetected animals. Our objective was to investigate the effect of observed herd characteristics on Map spread on a national scale in Ireland. Herd characteristics included herd size, number of breeding bulls introduced, number of animals purchased and sold, and number of herds the focal herd purchases from and sells to. We used these characteristics to classify herds in accordance with their probability of becoming infected and of spreading infection to other herds. A stochastic individual-based model was used to represent herd demography and Map infection dynamics of each dairy cattle herd in Ireland. Data on herd size and composition, as well as birth, death, and culling events were used to characterize herd demography. Herds were connected with each other through observed animal trade movements. Data consisted of 13 353 herds, with 4 494 768 dairy female animals, and 72 991 breeding bulls. We showed that the probability of an infected animal being introduced into the herd increases both with an increasing number of animals that enter a herd via trade and number of herds from which animals are sourced. Herds that both buy and sell a lot of animals pose the highest infection risk to other herds and could therefore play an important role in Map spread between herds.
牛型副结核病是一种由牛分枝杆菌副结核亚种（Map）引起的地方病。Map 主要通过感染但未被发现的动物在畜群之间传播。我们的目的是调查观察到的畜群特征对爱尔兰全国范围内 Map 传播的影响。畜群特征包括畜群规模、引入的繁殖公牛数量、购买和销售的动物数量，以及焦点畜群从哪些畜群购买和销售给哪些畜群。我们根据其感染和向其他畜群传播感染的可能性对畜群进行分类。我们使用随机个体基础模型来代表爱尔兰每个奶牛畜群的畜群动态和 Map 感染动力学。使用畜群规模和组成以及出生、死亡和淘汰事件的数据来描述畜群动态。畜群通过观察到的动物贸易流动相互连接。数据包括 13353 个畜群，4494768 头奶牛和 72991 头繁殖公牛。我们表明，通过贸易进入畜群的动物数量以及动物来源的畜群数量增加，感染动物被引入畜群的概率也会增加。既购买又销售大量动物的畜群对其他畜群构成最高的感染风险，因此在畜群之间的 Map 传播中可能发挥重要作用。
