Department of Wildlife, Fish and Environmental Studies, Faculty of Forest Sciences, Swedish University of Agricultural Sciences, 90183, Umeå, Sweden.
Swedish Association for Hunting and Wildlife Management, Öster Malma, 611 91, Nyköping, Sweden.
Acta Vet Scand. 2021 Jun 2;63(1):23. doi: 10.1186/s13028-021-00588-w.
The parasitic fauna of beavers (Castor fiber and C. canadensis) has been well studied in many parts of their respective areas of distribution. In Scandinavia there have, however, been limited investigations conducted on the parasites of beavers in recent times. The present study is the first quantitative survey of parasites on beavers living in Sweden and elsewhere in Scandinavia. We investigated the parasitic fauna of the Eurasian beaver (C. fiber) in a North-South gradient in Sweden. The aim of the study was to investigate parasite distribution and prevalence in particular, related to average yearly air temperature and different age groups of beavers. A total of 30 beavers were sampled at eight localities, spanning a 720 km North-South gradient during the springs of 1997 and 1998.
Five parasite taxa were identified. Four of these were present in all of the examined beavers, Stichorchis subtriquetrus (trematode), Travassosius rufus (nematode), Platypsyllus castoris (coleopteran), and Schizocarpus spp. (arachnid). A higher number of new infections of S. subtriquetrus, and more adults of T. rufus, were seen in beavers in southern Sweden where temperatures are higher. One-year old beavers had a higher infestation of S. subtriquetrus, but not of T. rufus, than older individuals.
The parasite fauna of Swedish beavers mirrored the impoverished parasite fauna of the original Norwegian population, and the high prevalence of parasites could be due to low major histocompatibility complex (MHC) polymorphism. Young beavers had a higher load of trematodes, probably depending on behavioural and ecological factors. Warmer temperatures in southern localities likely contributed to increased endoparasite loads.
在其分布区域的许多地方，人们对海狸（Castor fiber 和 C. canadensis）的寄生动物群进行了很好的研究。然而，在斯堪的纳维亚半岛，最近对海狸寄生虫的研究有限。本研究是对生活在瑞典和斯堪的纳维亚其他地区的海狸寄生虫进行的首次定量调查。我们在瑞典进行了南北梯度调查，研究了欧亚海狸（C. fiber）的寄生动物群。该研究的目的是调查寄生虫的分布和流行情况，特别是与海狸的平均年空气温度和不同年龄组有关的情况。1997 年和 1998 年春季，在 8 个地点共采集了 30 只海狸样本，跨越了 720 公里的南北梯度。
共鉴定出 5 种寄生虫。其中 4 种在所有检查的海狸中都存在，即 Stichorchis subtriquetrus（吸虫）、Travassosius rufus（线虫）、Platypsyllus castoris（鞘翅目）和 Schizocarpus spp.（蛛形纲）。在温度较高的瑞典南部，新感染 S. subtriquetrus 的海狸数量更多，成年 T. rufus 的数量也更多。一岁的海狸比年长的个体感染 S. subtriquetrus 的情况更严重，但感染 T. rufus 的情况则相反。
瑞典海狸的寄生虫群反映了原始挪威种群中寄生虫群的贫瘠，高寄生虫流行率可能是由于主要组织相容性复合体（MHC）多态性低。年幼的海狸有更高的吸虫负荷，可能取决于行为和生态因素。南部地区温暖的气温可能导致内寄生虫负荷增加。
