Dept. of Agriculture, Food and the Marine, Surveillance, ABP, TSE Division, Backweston Laboratory Complex, Celbridge, Co. Kildare, W23 X3PH, Ireland.
UCD Centre for Veterinary Epidemiology and Risk Analysis, School of Veterinary Medicine, University College Dublin, Dublin D04 V1W8, Ireland.
Prev Vet Med. 2020 Jun;179:104990. doi: 10.1016/j.prevetmed.2020.104990. Epub 2020 Apr 18.
A compulsory national BVD eradication programme commenced in Ireland in 2013. Since then considerable progress has been made, with the animal-level prevalence of calves born persistently infected (PI) falling from 0.67 % in 2013 to 0.06 % in 2018. The herd-level prevalence fell from 11.3 % in 2013 to 1.1 % in 2018. In the Irish programme, herds in which all animals have a known negative status and which have not contained any PI animals for 12 months or more are assigned a negative herd status (NHS). While considerable progress towards eradication has been made, PI calves have been identified in a small proportion of herds that had previously been assigned NHS. Given this context, a case-control study was conducted to investigate potential risk factors associated with loss of NHS in 2017. 546 herds which had NHS on 1 January 2017 and lost that status during 2017 (case herds) were matched with 2191 herds (control herds) that retained their NHS status throughout 2017. Previous history of BVD infection, herd size, herd expansion, the purchase of cattle including potential Trojan cattle and the density of BVD infection within 10 km of the herd emerged as significant factors in a multivariable logistic regression model. This work adds to the evidence base in support of the BVD eradication programme, particularly establishing why BVD re-emerged in herds which had been free of BVD for at least the previous 12 months prior to the identification of a BVD positive calf. This information will be especially important in the context of identifying herds which may be more likely to contain BVD positive animals once the programme moves to herd-based serology status for trading purposes in the post-eradication phase.
2013 年，爱尔兰启动了一项强制性全国牛病毒性腹泻病根除计划。自那时以来，已经取得了相当大的进展，持续感染（PI）小牛的动物水平流行率从 2013 年的 0.67%降至 2018 年的 0.06%。牛群水平流行率从 2013 年的 11.3%降至 2018 年的 1.1%。在爱尔兰的计划中，所有动物都有已知阴性状态且在 12 个月或更长时间内未出现 PI 动物的牛群被赋予阴性牛群状态（NHS）。尽管在根除方面取得了相当大的进展，但在先前被分配 NHS 的一小部分牛群中仍发现了 PI 小牛。考虑到这种情况，进行了一项病例对照研究，以调查与 2017 年 NHS 丧失相关的潜在风险因素。2017 年 1 月 1 日 NHS 为阳性但在 2017 年期间丧失 NHS 状态的 546 个牛群（病例牛群）与 2191 个在 2017 年期间保持 NHS 状态的牛群（对照牛群）相匹配。先前的 BVD 感染史、牛群规模、牛群扩张、牛的购买，包括潜在的特洛伊牛以及牛群周围 10 公里内 BVD 感染的密度，在多变量逻辑回归模型中成为显著因素。这项工作增加了支持 BVD 根除计划的证据基础，特别是确定了为什么在 BVD 阳性小牛被发现之前，至少在前 12 个月内没有 BVD 的牛群中 BVD 再次出现的原因。在根除阶段，一旦该计划转向用于交易目的的基于牛群的血清学状态，该信息对于确定可能更有可能包含 BVD 阳性动物的牛群将特别重要。
