Norwegian Veterinary Institute, P.O. Box 64, NO-1431, Ås, Norway; Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066, Blindern, NO-0316, Oslo, Norway.
Norwegian Veterinary Institute, P.O. Box 64, NO-1431, Ås, Norway.
Prev Vet Med. 2021 Nov;196:105497. doi: 10.1016/j.prevetmed.2021.105497. Epub 2021 Sep 20.
Reindeer pastoralism is a widespread practise across Fennoscandia and Russia. An outbreak of chronic wasting disease (CWD) among wild reindeer (Rangifer tarandus) poses a severe threat to the semi-domestic reindeer herding culture. Establishing surveillance is therefore key, but current models for surveillance of CWD are designed for wild cervids and rely on samples obtained from recreational hunters. Targeting animal groups with a higher infection probability is often used for more efficient disease surveillance. CWD has a long incubation period of 2-3 years, and the animals show clinical signs in the later stages of the infection i.e. 1-4 months prior to death. The semi-domestic reindeer are free-ranging most of the year, but during slaughtering in late fall, herders stress the animals in penned areas. This allows removal of animals with deviant behaviour or physical appearance, and such removals are likely to include animals in the clinical stages of CWD if the population is infected. In Norway, the semi-domestic reindeer in Filefjell is adjacent to a previously CWD infected wild population. We developed a risk-based surveillance method for this semi-domestic setting to establish the probability of freedom from infection over time, or enable early disease detection and mitigation. The surveillance scheme with a scenario tree using three risk categories (sample category, demographic group, and deviations in behaviour or physical appearance) was more effective and less invasive as compared to the surveillance method developed for wild reindeer. We also simulated how variation in susceptibility, incubation period and time for onset of clinical signs (linked to variation in the prion protein gene, PRNP) would potentially affect surveillance. Surveillance for CWD was mandatory within EU-member states with reindeer (2018-2020). The diversity of management systems and epidemiological settings will require the development of a set of surveillance systems suitable for each different context. Our surveillance model is designed for a population with a high risk of CWD introduction requiring massive sampling, while at the same time aiming to limit adverse effects to the populations in areas of surveillance.
驯鹿放牧在芬诺斯堪的亚和俄罗斯广泛存在。野生驯鹿（Rangifer tarandus）中慢性消耗病（CWD）的爆发对半驯化的驯鹿放牧文化构成了严重威胁。因此，建立监测至关重要，但目前用于监测 CWD 的模型是为野生鹿科动物设计的，依赖于从娱乐性猎人那里获得的样本。针对具有更高感染概率的动物群体，通常用于更有效地进行疾病监测。CWD 的潜伏期为 2-3 年，动物在感染的后期阶段即死亡前 1-4 个月出现临床症状。半驯化的驯鹿在一年中的大部分时间都是自由放养的，但在秋季末期进行屠宰时，牧民会将动物圈养在围栏区域。这允许移除行为异常或外观异常的动物，如果种群受到感染，这些移除很可能包括处于 CWD 临床阶段的动物。在挪威，Filefjell 的半驯化驯鹿与先前感染过 CWD 的野生种群相邻。我们为这种半驯化环境开发了一种基于风险的监测方法，以确定随着时间的推移是否存在无感染的可能性，或能够进行早期疾病检测和缓解。与为野生驯鹿开发的监测方法相比，使用三个风险类别（样本类别、人口统计群体以及行为或身体外观上的偏差）的情景树的监测方案更有效且侵入性更小。我们还模拟了易感性、潜伏期和临床症状出现时间（与朊病毒蛋白基因 PRNP 的变异有关）的变异如何潜在地影响监测。欧盟成员国（2018-2020 年）强制对 CWD 进行监测。管理系统和流行病学环境的多样性将需要开发一套适合每个不同情况的监测系统。我们的监测模型是为具有高 CWD 引入风险的种群设计的，需要大规模采样，同时旨在限制监测区域种群的不利影响。
