Reports of elk (Cervus elaphus) with lameness and severely deformed or missing hooves increased dramatically in southwest Washington State during the late winter and early spring of 2008. The geographic distribution of reports of the disease has continued to expand since then, and at this time is estimated to encompass a core area of approximately 10,500 km2 (4,000 mi2). A diagnostic investigation to determine the cause was initiated in 2009. Radiography, bacteriology, virology, serology, and trace mineral analysis failed to reveal a cause of the disease.2 Histopathology and silver staining of lesions from affected hooves demonstrated the presence of deeply invasive spirochetes accompanied by significant inflammation. Furthermore, Treponema phagedenis-like and Treponema medium-like spirochetes were isolated from diseased elk hooves. These isolated Treponema sp. represent two of the three phylotypes known to be highly associated with hoof diseases in domestic animals: bovine digital dermatitis in cattle1 and contagious ovine digital dermatitis in sheep3. Based on findings to date, it appears that Treponema spp. may have a causal role in the emergence of a significant disease of free-ranging elk in the Pacific Northwest of North America.
The authors thank the staff of the Washington Department of Fish and Wildlife for their assistance with elk collections.
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