Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
Kreavet, Hendrik Mertensstraat 17, 9150, Kruibeke, Belgium.
Vet Parasitol. 2021 Apr;292:109414. doi: 10.1016/j.vetpar.2021.109414. Epub 2021 Mar 15.
Dictyocaulus viviparus, the causative agent of bovine parasitic bronchitis, is an important parasite of dairy cattle. Infections can lead to substantial economic losses, due to mortality, reduced weight gain and milk production and treatment costs. There have been relatively few studies investigating herd management risk factors for infections with D. viviparus and lungworm-associated production losses. The aims of this study were (1) to assess the impact of (sub)clinical lungworm infections on productivity in dairy cows and, (2) to identify or confirm risk factors, related to herd management, for infections in grazing dairy cattle. Using a recombinant Major Sperm Protein (MSP)-based ELISA, the presence of D. viviparus antibodies in bulk tank milk (BTM) samples was evaluated on 717 and 634 farms at two-week intervals during two grazing seasons (2018 and 2019). Associations between milk antibody levels and production data (mean milk yield in kg/cow/day, percentage of fat and protein) were assessed, as well as associations with putative risk factors in the herd management, gathered through a questionnaire survey. In both years, there was a substantial, but non-significant, difference in the annual mean milk yield on farms with at least one BTM sample above the cut-off of 0.41 ODR, compared with the mean milk yield on farms that stayed under this threshold on each sampling day (-0.17 and -0.70 kg milk/cow/day in 2018 and 2019, respectively). In 2019, this association was stronger, and significant, when the cut-off was exceeded in at least two consecutive BTM samples (-1.74 kg milk/cow/day). BTM results were also significantly negatively associated with the closest milk production data during the two-weekly BTM sampling intervals in 2019. A single or two consecutive positive tests were used in the risk factor analysis as a proxy for lungworm-associated milk yield losses. Purchase of new animals (Odds Ratio (OR) = 2.68) and the proportion of the first grazing season covered by preventive anthelmintic treatment (OR up to 3.88, depending on proportion) were positively associated with lungworm-associated milk yield losses, while mowing at least 50 % of the pastures (OR = 0.57) was negatively associated with lungworm-associated milk yield losses. Our results suggest that the ELISA holds promise to identify herds with significant production losses due to lungworm infections, under the condition that BTM sampling is done repeatedly during the grazing season. Based on the confirmed risk factors, adjustments of the farm management could perhaps mitigate these losses.
细颈囊尾蚴，牛寄生性支气管炎的病原体，是奶牛的一种重要寄生虫。感染会导致大量的经济损失，因为感染会导致死亡率上升、体重增加和牛奶产量减少以及治疗费用增加。关于细颈囊尾蚴感染和与肺线虫相关的生产损失，对放牧奶牛群管理风险因素的研究相对较少。本研究的目的是：(1)评估临床和亚临床肺线虫感染对奶牛生产力的影响；(2)确定与放牧奶牛感染相关的、与 herd management 相关的风险因素。使用基于重组主要精子蛋白(MSP)的 ELISA，在两个放牧季节(2018 年和 2019 年)，每隔两周评估 717 个和 634 个牧场的牛奶样本中细颈囊尾蚴抗体的存在情况。评估了牛奶抗体水平与生产数据(每头奶牛每天的平均牛奶产量、脂肪和蛋白质的百分比)之间的关系，以及与 herd management 中通过问卷调查收集的潜在风险因素之间的关系。在这两年中，在每年至少有一个牛奶样本抗体水平超过 0.41 ODR 截止值的农场中，与每年都低于此阈值的农场相比，平均牛奶产量存在显著但无统计学意义的差异(-0.17 和-0.70 kg 牛奶/奶牛/天，2018 年和 2019 年)。在 2019 年，当至少两个连续的 BTM 样本超过截止值时，这种关联更强，且具有统计学意义(-1.74 kg 牛奶/奶牛/天)。2019 年，在两周的 BTM 采样间隔期间，BTM 结果与最接近的牛奶生产数据也呈显著负相关。在风险因素分析中，单次或连续两次阳性检测被用作与肺线虫相关的牛奶产量损失的替代指标。购买新动物(优势比(OR)=2.68)和第一个放牧季节中预防性驱虫治疗的比例(取决于比例，最高可达 3.88)与肺线虫相关的牛奶产量损失呈正相关，而至少刈割 50%的牧场(OR=0.57)与肺线虫相关的牛奶产量损失呈负相关。我们的研究结果表明，在放牧季节期间重复进行 BTM 采样的情况下，ELISA 有希望识别出因肺线虫感染而导致重大生产损失的牛群。基于已确认的风险因素，对农场管理进行调整可能会减轻这些损失。
