An observational study describes an outbreak of bovine viral diarrhea virus (BVDV) in a dairy herd in Spain. The herd was subjected to a voluntary control program. In a sampling carried out in June 2020, bulk tank milk antibody levels increased compared to the previous sampling. Additionally, serum samples from 4 young heifers also tested positive for antibodies. Since the results were consistent with a recent infection, we proceeded to detect possible persistently infected (PI) animals using antigen ELISA (on serum/ear-notch samples), following the program guidelines. From this moment on, 42 animals tested positive for BVDV antigen, of which 17 were under typical acute infection (AI), 13 were deemed as PI, and eight died early on the farm before having information to determine their status. The remaining 4 showed intriguing test results consistent with a long-term AI since they tested BVDV positive in at least two antigen tests more than 3 weeks apart. Thus, one animal was positive until 80 days of age in serum, and others even for longer periods in ear-notch samples, until they finally tested negative for BVDV. Based on these results, longer follow-up may be necessary in BVDV positive animals to accurately confirm persistent infection.

一项观察性研究描述了西班牙奶牛场爆发的牛病毒性腹泻病毒 (BVDV)。该牛群接受了自愿控制计划。在 2020 年 6 月进行的抽样中，散装罐奶抗体水平与之前的抽样相比有所上升。此外，4头小母牛的血清样本也检测出抗体呈阳性。由于结果与最近的感染一致，我们按照计划指南，使用抗原 ELISA（在血清/耳切口样本上）检测可能持续感染 (PI) 的动物。从此时起，42只动物的BVDV抗原检测呈阳性，其中17只处于典型急性感染（AI）状态，13只被视为PI，8只在获得确定其状况的信息之前就在农场提前死亡。其余 4 例显示出与长期 AI 一致的有趣测试结果，因为他们在相隔超过 3 周的至少两次抗原测试中检测出 BVDV 阳性。因此，一只动物在血清中直到 80 天时才呈阳性，而其他动物的耳切口样本中的阳性时间甚至更长，直到它们最终检测出 BVDV 呈阴性。根据这些结果，可能需要对 BVDV 阳性动物进行更长时间的随访，以准确确认持续感染。