Chronic arsenicosis and cadmium exposure in wild snowshoe hares (Lepus americanus) breeding near Yellowknife, Northwest Territories (Canada), part 2: Manifestation of bone abnormalities and osteoporosis

Various bone abnormalities, including osteoporosis, have been associated with chronic arsenic and cadmium exposure in experimental animal models, but information regarding the bone pathology of wild population of small mammals breeding in contaminated environment is limited. This present study was conducted to comparatively assess the prevalence and pattern of skeletal abnormalities in free ranging snowshoe hares inhabiting an area heavily contaminated by arsenic and other trace metals, near the vicinity of the abandoned Giant mine, and in a reference location approximately 20km from the city of Yellowknife, Northwest Territories, Canada. The femur and vertebrae of snowshoe hares from the mine area and reference location were subjected to bone densitometry examination and biomechanical testing using dual energy X-ray absorptiometry (DXA) and 3-point bending test. t-test results indicated that femoral densitometry parameters such as bone mineral density (BMD) (p=0.5), bone mineral content (BMC) (p=0.675), bone area (BA) (p=0.978) and tissue area (TA) (p=0.549) were not significantly different between locations. All densitometry parameters of the vertebrae (BMD, BA and TA) differed between locations (p<0.05), except for BMC (p=0.951) which showed no significant difference between the two locations. Vertebrae from the mine area also showed relatively lower BA and TA compared to the reference location. A constellation of skeletal abnormalities were also observed along the axial and appendicular bones respectively. Specifically, growth defects, osteoporosis, cortical fractures, sclerosis, and cyst like changes were commonly observed in the femurs and vertebrae of hares from both locations. With respect to biomechanical properties, only bone stiffness and peak load tended to be relatively reduced in specimens from the mine area, whereas work to failure was notably increased in specimens from the reference site compared to those from the mine area. Taken together, the results of this preliminary study suggest that chronic concomitant exposure to arsenic and cadmium may be involved in the etiology of various bone abnormalities, including osteoporosis in wild population of snowshoe hares from the Yellowknife area. The result presented in this study represent the first evaluation of osteological effects in free-ranging furbearers (snowshoe hares) diagnosed with arsenicosis, and concomitantly exposed to environmental levels of cadmium.