Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
Kreavet, Hendrik Mertensstraat 17, 9150, Kruibeke, Belgium.
Vet Parasitol. 2020 Dec;288:109280. doi: 10.1016/j.vetpar.2020.109280. Epub 2020 Nov 2.
The lungworm Dictyocaulus viviparus can have a major impact on bovine health and productivity. Enzyme-Linked Immunosorbent Assays (ELISA), based on a recombinant Major Sperm Protein (MSP), have been developed to detect D. viviparus-specific antibodies in bulk tank milk (BTM). The objectives of this study are to assess the association between BTM optical density ratio's (ODR) and farmer-reported lungworm outbreaks based on the clinical sign "coughing" throughout the grazing season and to compare the sensitivity and specificity of two ELISAs under field conditions. The Hannover MSP-ELISA and the prototype Svanova MSP-ELISA were used for the detection of D. viviparus antibodies in BTM samples on 717 dairy farms during the 2018 grazing season. Assuming all herds to be truly lungworm infected, the results show that the Svanova ELISA had a lower sensitivity (40-65%) and specificity (75-90%) for the detection of D. viviparus infections in BTM compared to the Hannover ELISA, which had a sensitivity of 42% and 74% and specificity of 100% and 98% at a cut-off of 0.41 ODR and 0.25 ODR, respectively. Therefore, analyses of the associations between milk antibody levels and farmer-reported outbreaks during the 2018 and 2019 grazing season were assessed using the Hannover ELISA, on 717 and 634 farms, respectively. A positive association was found between a farmer-reported outbreak and having at least two consecutive positive BTM ODR's at a cut-off of 0.41 in 2018 (Odds Ratio (OR) = 5.5) and 2019 (OR = 2.8). Furthermore, there was a significant association between a farmer-reported outbreak and having a positive BTM ODR in August (OR 2018 = 4.4; OR 2019 = 2.8) and October (OR 2018 = 3.7; OR 2019 = 1.8). On the farms with a farmer-reported outbreak and positive BTM samples, over half (2018 = 77%; 2019 = 57%) of the positive ODR's were situated before the outbreak and 47% (2018) and 42% (2019) within 12 weeks before the outbreak. In conclusion, there is a positive association between farmer-reported outbreaks and the occurrence of a positive BTM sample at the cut-off of 0.41 ODR using the Hannover ELISA.
细颈囊尾蚴（Dictyocaulus viviparus）对牛的健康和生产力有重大影响。酶联免疫吸附试验（ELISA）基于重组主要精子蛋白（MSP），已被开发用于检测批量奶（BTM）中的细颈囊尾蚴特异性抗体。本研究的目的是评估 BTM 光密度比（ODR）与放牧季节中基于“咳嗽”临床症状的农民报告的肺蠕虫病暴发之间的关联，并在田间条件下比较两种 ELISA 的敏感性和特异性。汉诺威 MSP-ELISA 和原型斯瓦诺瓦 MSP-ELISA 用于检测 2018 年放牧季节期间 717 个奶牛场 BTM 样本中的细颈囊尾蚴抗体。假设所有牛群都被真正感染了肺蠕虫，结果表明，与汉诺威 ELISA 相比，斯瓦诺瓦 ELISA 检测 BTM 中细颈囊尾蚴感染的敏感性（40-65%）和特异性（75-90%）较低，汉诺威 ELISA 的敏感性为 42%，特异性为 100%和 98%，在 0.41 ODR 和 0.25 ODR 截止值下。因此，在 2018 年和 2019 年放牧季节，使用汉诺威 ELISA 分别在 717 家和 634 家奶牛场评估了牛奶抗体水平与农民报告的暴发之间的关联。在 2018 年（优势比（OR）= 5.5）和 2019 年（OR = 2.8），在 0.41 截止值下，农民报告的暴发与至少连续两次 BTM ODR 呈阳性之间存在阳性关联。此外，在农民报告的暴发和 8 月 BTM ODR 阳性（OR 2018 = 4.4；OR 2019 = 2.8）和 10 月（OR 2018 = 3.7；OR 2019 = 1.8）之间存在显著关联。在有农民报告的暴发和 BTM 样本阳性的农场中，超过一半（2018 = 77%；2019 = 57%）的阳性 ODR 位于暴发之前，47%（2018 年）和 42%（2019 年）在暴发前 12 周内。总之，在使用汉诺威 ELISA 时，在 0.41 ODR 截止值下，农民报告的暴发与 BTM 样本阳性之间存在正相关。
