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. 明晰宿主间接触行为与接触前提下的传播概率，是野生动物疫病防控的核心所在。然而当前野生动物疫病研究多聚焦于接触异质性，部分原因在于接触前提下的传播概率向来难以精准测定。本研究针对自由活动野生动物的接触前提下传播概率开展实证调查，迈出了相关研究的第一步。
2. 本研究利用实测接触网络，检验大角羊的种群特征是否在绵羊肺炎支原体（Mycoplasma ovipneumoniae，该病原体可引发大角羊肺炎）的感染性或易感性上存在系统性差异。
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，并通过逻辑回归将这些协变量与羔羊存活率关联。协变量集合包含节点度（degree）——一种描述节点中心性的经典网络指标，同时还构建了将网络指标按特定类别拆分的协变量，以区分与亚成体（yearling）、带羔母羊、无羔母羊的接触，以及与存在活跃感染和无活跃感染个体的接触。
4. 亚成体、带羔母羊与无羔母羊的群体归属模式相似，但羔羊与繁殖母羊间的直接肢体互动频率，较成年个体任意类群间或亚成体间的互动频率高出两个数量级，较羔羊间的直接互动频率高出一个数量级。
5. 尽管亚成体与非繁殖期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引发羔羊死亡事件的发生比约为与感染空怀母羊或亚成体接触的5倍。据此，针对感染个体的防控措施可能会不必要地捕杀携带病原体但极少发生传播的幼年个体。
6. 本分析提出了一种简易的逻辑回归方法，用于检验关于自由活动宿主接触前提下传播发生比变异的先验假设，该方法或可广泛应用于野生动物疫病生态学相关研究。