French Agency for Food, Environmental and Occupational Health and Safety (Anses), Ploufragan-Plouzané-Niort Laboratory, Unit Pathology and Welfare of Ruminants, National Reference Laboratory for IBR, Niort, France.
French Agency for Food, Environmental and Occupational Health and Safety (Anses), Ploufragan-Plouzané-Niort Laboratory, Unit Pathology and Welfare of Ruminants, National Reference Laboratory for IBR, Niort, France.
Prev Vet Med. 2019 Nov 1;171:104743. doi: 10.1016/j.prevetmed.2019.104743. Epub 2019 Aug 13.
Within the framework of the national voluntary eradication program for Bovine alphaherpesvirus 1 (BoHV1) in France, the proportion of certified-free herds which experienced no more than two positive animals (termed singleton reactors) steadily increased to reach up to 95% in 2015. The aim of this study was to collate and evaluate serological data to gain insight into these epidemiological questionable BoHV1 seropositive animals. Preliminary evaluation of the performances of BoHV1 ELISA kits using a collection of 997 field sera with well-defined status revealed a relatively low specificity of the two gB blocking ELISAs most used in France for confirmatory testing (93.2% and 97.5% for gB-IDVet and gB-Idexx, respectively). In both ELISAs, the suboptimal specificity was associated with the presence of antibodies against BoHV2. Reassessment of the cut-offs led to a specificity and a sensitivity higher than 99.3%. Consequently, a comprehensive analysis of gB-positive sera from 2551 singleton reactors was performed by using gB ELISAs with optimized cut-offs, combined with viral neutralization test (campaign 2014-2015) or gE ELISA (campaign 2015-2016). Fifty percent of the 728 sera collected in 2014-2015 reacted below the optimized cut-offs in both gB ELISAs. Analysis of new blood samples collected at a minimum 6-week interval showed that these weak-positive reactions did not increase with time and could not be confirmed by confirmatory tests. Among the 1823 sera collected in 2015-2016, only 84 samples tested positive by gE ELISA, most of them corresponding to sera with reactivity above the optimized cut-offs in gB ELISAs. Screening for BoHV2 antibodies revealed a significantly increased prevalence among herds with singleton reactors, compared with the between-herd prevalence in French cattle herds. Altogether, these results provided suitable analytical strategies to limit the occurrence of false-positive BoHV1 reactions and inappropriate withdrawal of the BoHV1-free status, without alteration of diagnostic costs and reliability of eradication programs.
在法国国家牛疱疹病毒 1 （BoHV1）自愿根除计划的框架内，无更多阳性动物（称为单发性反应者）的认证无病牛群比例稳步上升，到 2015 年达到 95%。本研究旨在汇总和评估血清学数据，以深入了解这些具有流行病学疑问的 BoHV1 血清阳性动物。使用 997 份具有明确状态的现场血清样本对 BoHV1 ELISA 试剂盒进行初步评估，结果显示，法国最常用的两种 gB 阻断 ELISA （gB-IDVet 和 gB-Idexx）的特异性相对较低（分别为 93.2%和 97.5%）。在这两种 ELISA 中，次优特异性与针对 BoHV2 的抗体的存在有关。重新评估截止值可使特异性和敏感性均高于 99.3%。因此，使用优化截止值的 gB ELISA 对来自 2551 名单发性反应者的 gB 阳性血清进行了全面分析，并结合病毒中和试验（2014-2015 年运动）或 gE ELISA（2015-2016 年运动）进行分析。在 2014-2015 年收集的 728 份血清中，有 50%在两种 gB ELISA 中均低于优化截止值。对至少间隔 6 周采集的新血液样本的分析表明，这些弱阳性反应并未随时间增加，并且不能通过确认性试验来确认。在 2015-2016 年收集的 1823 份血清中，只有 84 份样品通过 gE ELISA 呈阳性，其中大多数与 gB ELISA 中优化截止值以上的反应性血清相对应。针对 BoHV2 抗体的筛选显示，与法国牛群的群间流行率相比，单发性反应者牛群的流行率显著增加。总的来说，这些结果提供了合适的分析策略，可以限制假阳性 BoHV1 反应的发生，并避免不合理地取消 BoHV1 无病状态，而不会改变诊断成本和根除计划的可靠性。
