Abstract
Verrucous dermatitis and digital papillomatosis caused by Treponema-like spirochetes occurred in 43 dairy cattle on a farm in the Ishikari district, Hokkaido. Located mainly on the hind limb, the almost circular, raised lesions encrusted the plantar aspect of the pastern. Inflicted animals frequently demonstrated signs of lameness in the hind limb. The lesions were malodorous and very painful when touched. In the keratinized outer layer of the epidermis, histopathological examination revealed hyperkeratosis and parakeratosis with multiple foci of bacterial infection associated with perivascular infiltration of mononuclear cells in the dermis. Levaditi silver impregnation and Warthin-Starry staining of histological sections detected organisms with spirochete morphology in the shallower region of the epidermis. In terms of immunohistochemistry, the organisms reacted positively to the anti-Treponema pallidum polyclonal antibody. The ultrastructural morphology of the spirochetes resembled that of the Treponema sp. Though they responded strongly to antibiotic treatment with tetracycline, cefazolin, and chloramphenicol, in many cases, the lesions recurred in from 1 to 3 months after therapy. We failed to isolate the pathogen from the lesions.
