School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Canada.
Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
Chemosphere. 2020 Jun;248:126011. doi: 10.1016/j.chemosphere.2020.126011. Epub 2020 Jan 25.
The Giant Mine is an abandoned gold mine in Yellowknife, Northwest Territories, Canada. Throughout its operation from 1948 to 2004, the Giant Mine released heavy amounts of arsenic trioxide into the environment, thus contaminating the soil and surface water within and around the vicinity of the mine site. Chronic arsenic (As) poisoning negatively impacts wildlife health and can induce multi-organ damages including neurodegeneration and visual dysfunction depending on concentration and duration of exposure. The aim of the current study was to comparatively assess retina layer changes and prevalence of ocular lesions in wild rodent populations (i.e. muskrats and red squirrels) breeding in arsenic endemic areas of Yellowknife, near the vicinity of the abandoned Giant mine site (∼2 km radius), at an intermediate location (approximately 20 km from the mine area) as well as a reference location (spanning 52-105 km from the city of Yellowknife, Canada). Eye globes were removed from euthanized muskrats and squirrels from the three sampling locations with increasing distance from the Giant mine area. Optical Coherence Tomography (OCT) was used to attempt a pan-retinal layer assessment, and histologic examination was utilized for assessment and confirmation of ocular lesions. The retinal layers were measured and statistically compared between the groups based on sampling locations to enhance the scope of histologic evaluations. The preliminary results revealed that thicknesses of ganglion cell layer (GCL), retina nerve fibre layer (NFL), and inner retina layer (IR) were statistically reduced in the muskrats from arsenic endemic area, particularly near the vicinity of the Giant mine compared to the control group. Generalized ocular pathology was histologically confirmed in all the muskrats from the arsenic endemic areas with the manifestation of moderate to severe lymphocytic plasmacytic uveitis (LPU), keratitis and subcapsular cataracts. Inner retinal degeneration was also observed in all the muskrats from the arsenic endemic areas, while muskrats from the control group were predominantly normal. Three muskrats from the control group were noted to have a mild LPU and keratitis. Significant histopathologic changes were not detected in the squirrel eyes from the three groups except for incidental mild cornea scars from all the locations. In general, these preliminary findings confirm the presence of ocular lesions and retina abnormalities in wild muskrats in the Yellowknife area and provide the first evidence of visual dysfunction and impairment in wildlife inhabiting arsenic endemic areas of Canada.
巨矿是加拿大西北地区耶洛奈夫的一个废弃金矿。从 1948 年到 2004 年运营期间，巨矿向环境中释放了大量的三氧化二砷，从而污染了矿区及其周围的土壤和地表水。慢性砷（As）中毒会对野生动物的健康产生负面影响，并可能导致多器官损伤，包括神经退行性变和视觉功能障碍，具体取决于暴露的浓度和持续时间。本研究的目的是比较评估在耶洛奈夫受砷影响地区（即麝香鼠和红松鼠）繁殖的野生啮齿动物种群（麝香鼠和红松鼠）的视网膜层变化和眼部病变的发生率，这些地区靠近废弃的巨矿（大约 2 公里半径），在一个中间位置（距离矿区大约 20 公里）以及一个参考位置（距离加拿大耶洛奈夫市 52-105 公里）。从三个采样地点安乐死的水貂和松鼠中取出眼球。光学相干断层扫描（OCT）用于尝试进行全视网膜层评估，并用组织学检查评估和确认眼部病变。根据采样地点测量并比较视网膜层的厚度，并在统计学上比较各组之间的差异，以增强组织学评估的范围。初步结果表明，与对照组相比，来自受砷影响地区的水貂的神经节细胞层（GCL）、视网膜神经纤维层（NFL）和内视网膜层（IR）的厚度明显变薄，尤其是在靠近巨矿的地方。所有来自受砷影响地区的水貂均经组织学证实存在广泛的眼部病理学，表现为中度至重度淋巴细胞浆细胞性葡萄膜炎（LPU）、角膜炎和囊下白内障。所有来自受砷影响地区的水貂均观察到内视网膜变性，而对照组的水貂主要正常。对照组的 3 只水貂被发现患有轻度 LPU 和角膜炎。除了所有部位的轻微角膜疤痕外，三组松鼠的眼睛均未发现明显的组织病理学变化。总的来说，这些初步发现证实了耶洛奈夫地区野生水貂存在眼部病变和视网膜异常，并为加拿大受砷影响地区野生动物的视觉功能障碍和损伤提供了首例证据。
