Pooled milk is used for the surveillance of several diseases of livestock. Previous studies demonstrated the detection of foot-and-mouth disease virus (FMDV) in the milk of infected animals at high dilutions, and consequently, the collection of pooled milk samples could be used to enhance FMD surveillance. This study evaluated pooled milk for FMDV surveillance on a large-scale dairy farm that experienced two FMD outbreaks caused by the A/ASIA/G-VII and O/ME-SA/Ind-2001d lineages, despite regular vaccination and strict biosecurity practices. FMDV RNA was detected in 42 (5.7%) of the 732 pooled milk samples, and typing information was concordant with diagnostic reports of clinical disease. The FMDV positive milk samples were temporally clustered around reports of new clinical cases, but with a wider distribution. For further investigation, a model was established to predict real-time RT-PCR (rRT-PCR) CT values using individual cattle movement data, clinical disease records and virus excretion data from previous experimental studies. The model explained some of the instances where there were positive results by rRT-PCR, but no new clinical cases and suggested that subclinical infection occurred during the study period. Further studies are required to investigate the effect of vaccination on FMDV excretion in milk, and to evaluate more representative sampling methods. However, the results from this pilot study indicate that testing pooled milk by rRT-PCR may be valuable for FMD surveillance and has provided evidence of subclinical virus infection in vaccinated herds that could be important in the epidemiology of FMD in endemic countries where vaccination is used.

中文翻译：

---

在流行环境中的大型奶牛场使用混合牛奶进行口蹄疫监测。

混合奶用于监测多种家畜疾病。以前的研究表明，在高稀释度的受感染动物的乳汁中检测到口蹄疫病毒 (FMDV)，因此，收集合并的牛奶样本可用于加强 FMD 监测。本研究评估了大型奶牛场的 FMDV 监测混合奶，该奶牛场经历了两次由 A/ASIA/G-VII 和 O/ME-SA/Ind-2001d 谱系引起的口蹄疫爆发，尽管定期接种疫苗并采取严格的生物安全措施。在 732 份汇集的牛奶样本中，有 42 份（5.7%）检测到 FMDV RNA，分型信息与临床疾病的诊断报告一致。FMDV 阳性牛奶样本暂时聚集在新临床病例的报告周围，但分布范围更广。为了进一步调查，建立了一个模型来预测实时 RT-PCR (rRT-PCR) CT 值，使用个体牛的移动数据、临床疾病记录和来自先前实验研究的病毒排泄数据。该模型解释了一些 rRT-PCR 有阳性结果但没有新的临床病例的情况，并表明在研究期间发生了亚临床感染。需要进一步的研究来调查疫苗接种对牛奶中 FMDV 排泄的影响，并评估更具代表性的采样方法。然而，这项试点研究的结果表明，通过 rRT-PCR 检测合并的牛奶可能对 FMD 监测有价值，并提供了接种牛群中亚临床病毒感染的证据，这对于使用疫苗接种的流行国家的 FMD 流行病学可能很重要.