Norwegian Institute for Nature Research, PO Box 5685, Torgarden NO-7485 Trondheim, Norway.
Virus Surveillance Unit, Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK.
J Wildl Dis. 2021 Apr 1;57(2):282-291. doi: 10.7589/JWD-D-20-00068.
In Norway, the Willow Ptarmigan (Lagopus lagopus lagopus) is experiencing population declines and is nationally Red Listed as Near Threatened. Although disease has not generally been regarded as an important factor behind population fluctuations for Willow Ptarmigan in Norway, disease occurrence has been poorly investigated. Both louping-ill virus (LIV) and the closely related tick-borne encephalitis virus are found along the southern part of the Norwegian coast. We assessed whether and where Norwegian Willow Ptarmigan populations have been infected with LIV. We expected to find infected individuals in populations in the southernmost part of the country. We did not expect to find infected individuals in populations further north and at higher altitudes because of the absence of the main vector, the sheep tick (Ixodes ricinus). We collected serum samples on Nobuto filter paper and used a hemagglutination inhibition assay for antibodies against LIV. We collected data at both local and country-wide levels. For local sampling, we collected and analyzed 87 hunter-collected samples from one of the southernmost Willow Ptarmigan populations in Norway. Of these birds, only three positives (3.4%) were found. For the country-wide sampling, we collected serum samples from 163 Willow Ptarmigan carcasses submitted from selected locations all over the country. Of these birds, 32% (53) were seropositive for LIV or a cross-reacting virus. Surprisingly, we found seropositive individuals from locations across the whole country, including outside the known distribution of the sheep tick. These results suggest that either LIV or a cross-reacting virus infects ptarmigan in large parts of Norway, including at high altitudes and latitudes.
在挪威，柳雷鸟（Lagopus lagopus lagopus）的数量正在减少，被国家列为近危物种。尽管疾病通常不被认为是导致挪威柳雷鸟数量波动的重要因素，但对该病的发生情况研究甚少。在挪威南部沿海地区，既有卢氏细螺旋体病毒（LIV），也有与之密切相关的蜱传脑炎病毒。我们评估了挪威柳雷鸟种群是否感染了 LIV 病毒，以及感染发生的地点。我们预计在该国最南部的种群中会发现感染个体。我们预计在更北和更高海拔的种群中不会发现感染个体，因为缺乏主要的传播媒介绵羊蜱（Ixodes ricinus）。我们使用诺布托滤纸收集血清样本，并采用血凝抑制试验检测针对 LIV 的抗体。我们在地方和全国两个层面上收集数据。在地方采样中，我们从挪威最南部的柳雷鸟种群之一收集并分析了 87 份猎鸟采集的样本。这些鸟类中只有 3 个呈阳性（3.4%）。在全国范围的采样中，我们从全国选定地点提交的 163 只柳雷鸟尸体中采集了血清样本。这些鸟类中，53 个（32%）对 LIV 或交叉反应病毒呈血清阳性。令人惊讶的是，我们在全国各地的地点都发现了血清阳性个体，包括已知绵羊蜱分布范围之外的地点。这些结果表明，LIV 或交叉反应病毒感染了挪威大部分地区的雷鸟，包括高海拔和高纬度地区。
