University of Liverpool, Department of Epidemiology and Population Health, Institute of Infection and Global Health, Liverpool CH64 7TE, UK.
University of Liverpool, Department of Infection Biology and Microbiomes, Institute of Infection, Veterinary and Ecological Sciences, Liverpool CH64 7TE, UK; University of Bristol, School of Veterinary Sciences, Langford House, Langford, North Somerset BS40 5DU, UK.
Vet Parasitol. 2022 Sep;309:109770. doi: 10.1016/j.vetpar.2022.109770. Epub 2022 Jul 22.
Outbreaks of cattle lungworm disease (Dictyocaulus viviparus) are explosive and costly. The unpredictability of the disease often encourages farmers to apply blanket anthelmintic treatments to the herd, which impede the acquisition of immunity, increase the risk of drug resistance, and interfere with efforts to reduce anthelmintic use against ubiquitous gastrointestinal nematodes. Improving our understanding of the factors which lead to a high risk of infection with lungworm, (including climatic pressure), would support a more targeted management. We present GLOWORM-FL-DV, the first mathematical model of the free-living stages of D. viviparus. The ecology of D. viviparus is unique compared with other strongylid nematodes due to its relationship with Pilobilus spp. fungi, which enhance the transmission potential. The role of the fungi was therefore incorporated into the model framework, informed by laboratory observations of Pilobolus spp. development and sporulation. The thermal niche of D. viviparus was characterised based on published and laboratory observations. Mortality of parasitic larvae increased significantly below 0C, and larval development occurred above 1.4C, whereas the estimated minimum temperature for migration via Pilobolus spp. was 8.8C. Model predictions were compared with antibody levels in bulk milk tank samples collected at two-weekly intervals from eight dairy herds across Great Britain over two grazing seasons. The model predicted high levels of larval abundance on pasture 46 days (38-52 days) before a rise in antibody levels and 22-26 days before the onset of clinical signs. The model assesses the impact of climate and weather on lungworm larval availability at pasture and provides a framework for the development of a risk forecasting system. This could help to focus vigilance for clinical signs at high-risk times and facilitate the targeted use of anthelmintics to prevent outbreaks, in support of sustainable parasite control.
牛肺线虫病（Dictyocaulus viviparus）爆发具有爆发性和高成本的特点。该疾病的不可预测性常常促使农民对整个畜群进行全面驱虫处理，这不仅阻碍了免疫的获得，增加了药物耐药性的风险，还干扰了减少普遍存在的胃肠道线虫驱虫药物使用的努力。提高我们对导致感染肺线虫高风险的因素（包括气候压力）的认识，将有助于更有针对性的管理。我们提出了 GLOWORM-FL-DV，这是第一个 D. viviparus 自由生活阶段的数学模型。与其他强旋线虫相比，D. viviparus 的生态学是独特的，因为它与 Pilobilus 属真菌有关，真菌增强了其传播潜力。因此，该模型框架纳入了真菌的作用，这是基于对 Pilobolus 属真菌发育和孢子形成的实验室观察得出的。根据已发表的和实验室观察结果，确定了 D. viviparus 的热生态位。寄生幼虫的死亡率在 0°C 以下显著增加，幼虫发育发生在 1.4°C 以上，而通过 Pilobolus 属真菌迁移的估计最低温度为 8.8°C。模型预测结果与从英国八个奶牛场采集的每隔两周的牛奶罐样本中的抗体水平进行了比较，该样本采集了两个放牧季节。该模型预测，在抗体水平升高前 46 天（38-52 天），以及在临床症状出现前 22-26 天，牧场上幼虫丰度会很高。该模型评估了气候和天气对牧场上肺线虫幼虫可用性的影响，并为开发风险预测系统提供了框架。这有助于在高风险时期集中警惕临床症状，并促进驱虫药物的靶向使用，以预防疫情爆发，支持寄生虫的可持续控制。
