LAUSR

The three pathogenic treponemes associated with bovine digital dermatitis (DD), Treponema medium, Treponema phagedenis and Treponema pedis, have been reported to infect a variety of tissues and structures in cattle, including pressure sores (Clegg and others 2016c), hock lesions (Clegg and others 2016a), the so-called ‘non-healing’ hoof disorders (evans and others 2011), and ischaemic teat necrosis lesions (Clegg and others 2016b). In sheep, these DD treponemes are strongly associated with the disease contagious ovine digital dermatitis (CODD) (Sullivan and others 2015) and are now considered a necessary cause of disease. We wish to report a case of a sheep that had a non-healing lesion from which we were able to identify these pathogenic treponemes. The sheep was one of a group of 40 yearling ewes housed on straw, of which 21 had at least one foot exhibiting clinical signs of CODD (Angell and others 2015). The sheep in question did not, at the time, have lesions consistent with CODD, although it did have lesions consistent with footrot on both front feet and an interdigital dermatitis lesion on the left hind foot. Upon further examination, this sheep also had a 2 cm diameter hairless, reddened and thickened lesion, with a central 0.5 cm hole over the left carpal joint from which a sparse, flocculent, serosanguineous discharge could be aspirated. The clinical signs and gross pathology clearly indicated the chronicity of this lesion, although a precise duration could not be established and it was considered to be most likely caused by feeding from a kneeling position (ie, a pressure sore) because of pain caused by the footrot present. Sterile cotton swabs were used to sample the discharge from this lesion and these were processed for culture and PCR using standard methods (evans and others 2009). Both T medium and T phagedenis DNA were detected by PCR directly from the swabs. While DD treponeme isolation attempts did not produce a pure isolate, T phagedenis DNA was detected from the bacterial culture and spirochaetes were observed by phase contrast microscopy. We believe that this is the first report of DD treponeme phylogroups in a nonfoot lesion from a sheep, and it highlights that these organisms should be considered as potential secondary invaders, not only in cattle but also in other species, particularly in lesions that do not heal rapidly. We would be interested to know if other practitioners have seen similar lesions in sheep.