Data from: Contact and contagion: bighorn sheep demographic states vary in probability of transmission given contact

1. Understanding both contact and probability of transmission given contact are key to managing wildlife disease. However, wildlife disease research tends to focus on contact heterogeneity, in part because probability of transmission given contact is notoriously difficult to measure. Here we present a first step toward empirically investigating probability of transmission given contact in free-ranging wildlife.
2. We used measured contact networks to test whether bighorn sheep demographic states vary systematically in infectiousness or susceptibility to Mycoplasma ovipneumoniae, an agent responsible for bighorn sheep pneumonia.
3. We built covariates using contact network metrics, demographic information, and infection status, and used logistic regression to relate those covariates to lamb survival. The covariate set contained degree, a classic network metric describing node centrality, but we also built covariates that broke the network metrics into particular categories that differentiated between contacts with yearlings, ewes with lambs, and ewes without lambs, and animals with and without active infections.
4. Yearlings, ewes with lambs, and ewes without lambs showed similar group membership patterns, but direct interactions involving touch occurred at a rate two orders of magnitude higher between lambs and reproductive ewes than between any classes of adults or yearlings, and one order of magnitude higher than direct interactions between lambs.
5. Although yearlings and non-reproductive bighorn ewes regularly carried Mycoplasma ovipneumoniae, our models suggest that a contact with an infected reproductive ewe had approximately five times the odds of producing a lamb mortality event of an identical contact with an infected dry ewe or yearling. Consequently, management actions targeting infected animals might lead to unnecessary removal of young animals who carry pathogens but rarely transmit.
6. This analysis demonstrates a simple logistic regression approach for testing a priori hypotheses about variation in odds of transmission given contact for free-ranging hosts, and may be broadly applicable for investigations in wildlife disease ecology.

1. 接触行为与接触后传播概率（probability of transmission given contact）的综合认知，是野生动物疫病防控的核心要点。然而，当前野生动物疫病研究多聚焦于接触异质性，部分原因在于接触后传播概率的量化难度极高。本研究针对自由放养野生动物的接触后传播概率开展实证探索，迈出了关键的第一步。
2. 本研究利用实测接触网络，验证大角羊的种群状态是否与其对绵羊肺炎支原体（Mycoplasma ovipneumoniae）——一种引发大角羊肺炎的病原——的感染性或易感性存在系统性差异。
3. 本研究基于接触网络指标、种群统计信息与感染状态构建协变量，并通过逻辑回归模型关联协变量与羊羔存活率。协变量集合包含描述节点中心性的经典网络指标——度（degree），同时还将网络指标拆解为特定类别：区分与周岁羊、带羔母羊、无羔母羊的接触，以及与活动性感染个体和非感染个体的接触。
4. 周岁羊、带羔母羊与无羔母羊展现出相似的群体归属模式，但羊羔与繁殖母羊间的肢体接触类直接互动频率，较成年个体类群间或周岁羊间的互动高出两个数量级，较羊羔间的直接互动也高出一个数量级。
5. 尽管周岁羊与非繁殖大角羊母羊常携带绵羊肺炎支原体，但本研究模型显示：与感染繁殖母羊的接触，其引发羊羔死亡事件的优势比约为与感染无羔母羊或周岁羊接触的5倍。据此，针对感染个体的防控措施，可能会误将携带病原体却极少发生传播的幼年个体纳入移除范围。
6. 本分析提出了一种简易的逻辑回归方法，用于验证关于自由活动宿主接触后传播概率优势比变异的先验假设，该方法可广泛应用于野生动物疫病生态学相关研究。