Detection of treponemes in canker lesions of horses by 16S rRNA clonal sequencing analysis.

Equine canker is a chronic pododermatitis of the hoof in horses. Although spirochetes are detectable histopathologically in the lesions, the precise etiology remains unclear. This study reports the 16S rRNA gene sequencing of randomly selected clones based on PCR with Treponema-specific primers, using the canker lesions from two horses and healthy frog and sole from a horse. A total of 114 clones were obtained from the lesions, but no clones were detected in the healthy hoof tissues. The clones from the canker lesions examined were grouped into 19 operational taxonomic units, such as treponemal phylotypes originating from papillomatous digital dermatitis lesions of dairy cattle and as-yet uncultured human oral treponemes, indicating the presence of multiple treponemes in the lesions.