Characterization and progression of treponeme-associated hoof disease (TAHD) lesions in individual elk (Cervus elaphus) in southwest Washington, USA

Treponeme-associated hoof disease (TAHD) has emerged as a significant disease of elk (Cervus elaphus) in southwest Washington over the past decade. In order to describe the progression of the disease in individual elk and to... [ view full abstract ]

Treponeme-associated hoof disease (TAHD) has emerged as a significant disease of elk (Cervus elaphus) in southwest Washington over the past decade. In order to describe the progression of the disease in individual elk and to investigate potential relationships between severity of hoof disease and individual and population health parameters, 30 radio-collared elk were initially examined in February 2015, and again 10 months later in December 2015. Hoof lesions were assigned Grades ranging from 1 (erythematous to ulcerative lesion limited to the skin) to 4 (sloughing of the hoof capsule) at each examination. In addition, hoof swabs were collected from both negative control and diseased animals and examined under dark field microscopy for the presence of spirochetes. At initial examination, 18 animals were TAHD-positive and 12 animals were classified as negative controls. Ten months later, one initially TAHD-positive animal with a Grade 1 lesion on one hoof had recovered; while disease remained the same (n=5) or progressed to a more severe grade (n=12) in the remaining TAHD-positive animals. Of the 12 animals initially classified as negative controls, 9 maintained their negative control status, while 3 developed TAHD. Of the 21 animals ultimately diagnosed with TAHD, lesions were limited to the hind hooves in all but 3. Hoof lesions were strongly associated with the detection of spirochetes via dark field microscopy. Findings to date suggest that TAHD is a rapidly progressive disease with little evidence thus far of recovery from advanced stages, and provide further evidence for the role of pathogenic spirochetes in the etiology of TAHD.