BACKGROUND Infectious respiratory disease is common in young horses and can impact athletic performance and long-term health. Significant variation in the duration of clinical disease has been observed, even in the absence of secondary complications. The determination of factors associated with disease chronicity may facilitate clinical decision-making and the development of improved biosecurity protocols. OBJECTIVE To investigate contact network characteristics, and demographic variables associated with time to clinical recovery from Equine Rhinitis A virus respiratory disease. STUDY DESIGN Prospective cohort study. METHODS Yearling Standardbred racehorses (n = 58) housed in a multi-barn training facility in Southern Ontario were included. Horses were monitored daily for clinical signs of acute respiratory disease over a 41-day period in Autumn 2017. Contact patterns between horses, including older racehorses, were determined through use of proximity loggers attached to halters during the initial 7-day of the study. Associations between duration of disease, demographic factors (birth month, gait, sex and yearling sale), serologic titres and network metrics (degree, betweenness and Eigenvector centrality) were investigated using a Cox proportional hazard model. RESULTS Yearling attack rate for infectious respiratory disease was 87.9% (n = 51). Median time to recovery was 6 days (IQR = 1-32) and 17 horses were censored due to early withdrawal or failure to recover during the study period. In those yearlings born February-May, birth month was significant in the Cox proportional hazard model (Hazard Ratio 0.7, 95% CI 0.49-1, P = 0.05). MAIN LIMITATION Probability of censoring was not independent of outcome which necessitated use of sensitivity analysis. CONCLUSIONS These findings suggest late born foals are less likely to recover quickly from infectious respiratory disease.

中文翻译：

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马鼻炎A病毒呼吸道疾病持续时间的危险因素。

背景传染性呼吸道疾病在幼马中很常见，并且会影响运动表现和长期健康。即使在没有继发并发症的情况下，也观察到临床疾病持续时间的显着变化。确定与疾病慢性相关的因素可能有助于临床决策和改进生物安全方案的开发。目的 调查接触网络特征，以及与马鼻炎 A 病毒呼吸道疾病临床恢复时间相关的人口统计学变量。研究设计 前瞻性队列研究。方法 包括安置在安大略省南部一个多谷仓训练设施中的一岁马标准种马（n = 58）。在 2017 年秋季的 41 天期间，每天监测马匹的急性呼吸道疾病临床症状。在研究的最初 7 天期间，通过使用附在缰绳上的接近记录器来确定马匹之间的接触模式，包括较老的赛马。使用 Cox 比例风险模型研究了疾病持续时间、人口统计学因素（出生月份、步态、性别和一岁销售）、血清学滴度和网络指标（度、介数和特征向量中心性）之间的关联。结果 传染性呼吸道疾病的一岁鸽发病率为 87.9%（n = 51）。恢复的中位时间为 6 天（IQR = 1-32），17 匹马由于在研究期间过早退出或未能恢复而被审查。在 2 月至 5 月出生的一岁鸽中，出生月份在 Cox 比例风险模型中是显着的（风险比 0.7，95% CI 0.49-1，P = 0.05）。主要限制 审查的概率并不独立于需要使用敏感性分析的结果。结论 这些研究结果表明，出生较晚的小马驹不太可能从传染性呼吸道疾病中快速恢复。