Treponeme-associated hoof disease of wild elk (Cervus elaphus spp.) in southwestern Washington State, USA

Authors: HAN, SUSHAN - Colorado State University; MANSFIELD, KRISTIN - Washington Department Of Fish & Wildlife; HALDORSON, GARY - Washington State University; BRADWAY, DAN - Washington State University; BESSER, TOM - Washington State University; REED, DERYCK - University Of California, Davis; Alt, David; Wilson-Welder, Jennifer

Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2017
Publication Date: 9/24/2018
Citation: Han, S., Mansfield, K., Haldorson, G., Bradway, D., Besser, T., Reed, D., Alt, D.P., Wilson-Welder, J.H. 2018. Treponeme-associated hoof disease of wild elk (Cervus elaphus spp.) in southwestern Washington State, USA. Veterinary Pathology. https://doi.org/10.1177/0300985818798108.
DOI: https://doi.org/10.1177/0300985818798108

Interpretive Summary: In southwest Washington State wild free-ranging elk have developed a severe hoof disease with many similarities to digital dermatitis of livestock including presence of several Treponema spirochetes. An investigation was undertaken to examine 9, 7 and 3 month old elk with early or developing lesions to gain insights into lesion cause and pathogenesis. Animals at 9 months old showed chronic severe changes similar to adult animals previously captured. 7 month old elk had minor lesions at the top of the hoof horn and 3 month old elk showed minimal visible or histological changes but Treponemes were detected by molecular methods indicating that they may be starting to develop lesions. The presence of the Treponemes and significant host responses (antibody) to them confirm the pathogenic role of Treponema in this hoof disease of wild animals as well as livestock.

Technical Abstract: An outbreak of novel hoof disease in wild southwest Washington state elk (Cervus elaphus spp.) emerged in 2008 and significantly spread throughout the region. Initial studies showed adult elk had chronic hoof overgrowth, sole ulcers and sloughed hooves, but a cause was not determined. To identify possible etiologies, 9-, 7- and 3-month-old elk were collected. Nine-month-old elk had sole ulcers (3/9 elk, 33%), and sloughed or overgrown hooves (4/9 elk, 44%) similar to adults. Histologically, lesions consisted of dissecting ulcers, suppurative necrotizing inflammation, epithelial hyperplasia and deeply invasive spirochetes identified as Treponema sp. via immunohistochemistry (IHC) and confirmed by polymerase chain reaction (PCR). Seven-month-old elk had ulcers of the coronary band, heel and interdigital space with underrunning of the hoof wall (6/8 elk, 75%), with Treponema sp. identified in all lesions. Three month-old calves had superficial coronary erosions that lacked inflammation and identifiable spirochetes (3/5 elk, 60%), but were culture and PCR positive for Treponema sp., suggesting a possible early lesion. Lesions from 9- and 7-month-old elk included mixtures of aerobic and anaerobic bacteria, many of which are specifically associated with infectious foot disease in livestock. Antibody ELISA of 7- and 3-month-old elk from the enzootic region showed trend toward an increase in Treponema homogenate titers compared to healthy elk from outside the region, further supporting the significance of Treponema in the pathogenesis of hoof disease. Treponema associated hoof disease (TAHD) in elk, a debilitating and progressive condition, shares many similarities to bovine digital dermatitis and contagious ovine digital dermatitis.