Norwegian Veterinary Institute, P.O. Box 64, NO-1431 Ås, Norway.
Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Torgarden, NO-7485 Trondheim, Norway.
J Gen Virol. 2024 Jan;105(1). doi: 10.1099/jgv.0.001952.
Transmissible spongiform encephalopathies or prion diseases comprise diseases with different levels of contagiousness under natural conditions. The hypothesis has been raised that the chronic wasting disease (CWD) cases detected in Nordic moose () may be less contagious, or not contagious between live animals under field conditions. This study aims to investigate the epidemiology of CWD cases detected in moose in Norway, Sweden and Finland using surveillance data from 2016 to 2022.In total, 18 CWD cases were detected in Nordic moose. All moose were positive for prion (PrP) detection in the brain, but negative in lymph nodes, all were old (mean 16 years; range 12-20) and all except one, were female. Age appeared to be a strong risk factor, and the sex difference may be explained by few males reaching high age due to hunting targeting calves, yearlings and males.The cases were geographically scattered, distributed over 15 municipalities. However, three cases were detected in each of two areas, Selbu in Norway and Arjeplog-Arvidsjaur in Sweden. A Monte Carlo simulation approach was applied to investigate the likelihood of such clustering occurring by chance, given the assumption of a non-contagious disease. The empirical -value for obtaining three cases in one Norwegian municipality was less than 0.05, indicating clustering. However, the moose in Selbu were affected by different CWD strains, and over a 6 year period with intensive surveillance, the apparent prevalence decreased, which would not be expected for an ongoing outbreak of CWD. Likewise, the three cases in Arjeplog-Arvidsjaur could also indicate clustering, but management practices promotes a larger proportion of old females and the detection of the first CWD case contributed to increased awareness and sampling.The results of our study show that the CWD cases detected so far in Nordic moose have a different epidemiology compared to CWD cases reported from North America and in Norwegian reindeer (). The results support the hypothesis that these cases are less contagious or not contagious between live animals under field conditions. To enable differentiation from other types of CWD, we support the use of sporadic CWD (sCWD) among the names already in use.
传染性海绵状脑病或朊病毒病包括在自然条件下具有不同传染性水平的疾病。有人提出假设，在北欧驼鹿中检测到的慢性消耗病（CWD）病例可能传染性较低，或者在野外条件下活动物之间没有传染性。本研究旨在利用 2016 年至 2022 年的监测数据，调查挪威、瑞典和芬兰驼鹿中检测到的 CWD 病例的流行病学。共有 18 例 CWD 病例在北欧驼鹿中被检测到。所有驼鹿的大脑中均检测到朊病毒（PrP）呈阳性，但淋巴结呈阴性，所有驼鹿均为老年（平均 16 岁；范围 12-20 岁），除 1 例外，均为雌性。年龄似乎是一个强有力的风险因素，而性别差异可能是由于狩猎针对小牛、幼鹿和雄性，导致很少有雄性达到高龄所致。病例在地理上分散，分布在 15 个市。然而，在挪威的塞尔布和瑞典的阿尔耶普卢格-阿尔维德佐尔有三个地区各发现了三个病例。应用蒙特卡罗模拟方法来调查在假设疾病无传染性的情况下，这种聚类是否由偶然发生的可能性。在一个挪威市获得三个病例的经验值小于 0.05，表明存在聚类。然而，塞尔布的驼鹿受到不同的 CWD 株的影响，并且在六年的密集监测期间，明显的患病率下降，这不符合 CWD 持续爆发的预期。同样，在阿尔耶普卢格-阿尔维德佐尔的三个病例也可能表明聚类，但管理实践促进了更多的老年雌性，并且首例 CWD 病例的发现提高了人们的认识和采样。我们的研究结果表明，迄今为止在北欧驼鹿中检测到的 CWD 病例与北美和挪威驯鹿中报告的 CWD 病例的流行病学有很大不同（）。结果支持这些病例在野外条件下在活动物之间传染性较低或没有传染性的假设。为了能够与其他类型的 CWD 区分开来，我们支持在已使用的名称中使用散发性 CWD（sCWD）。
