[First case description of contagious ovine digital dermatitis in Switzerland]

Contagious ovine digital dermatitis (CODD) is an emerging infectious foot disease in sheep. To date, CODD has been described in Great Britain, Ireland, Sweden and Germany and now in Switzerland for the first time. Unlike foot rot, the CODD lesions do not spread from the interdigital space, but usually begin at the dorsal/abaxial coronary band. The changes can spread to the hoof wall and the sole and finally can lead to exungulation, similar to foot rot. Treponema spp. are often found in CODD lesions analogous to digital dermatitis (Mortellaro's disease) in cattle. Involvement of Dichelobacter nodosus (D. nodosus) is considered a risk factor, but the presence of the bacterium is not mandatory. In February 2022, ulcerative lesions in the dorso-axial coronary band area were noticed on both claws of the left forelimb in an ewe. Histology of the biopsy showed hyperkeratosis and erosion with exocytosis and crust formation. Treponema spp. PCR and fluorescence in situ hybridization (FISH) were positive for Treponema phylotype 1 (PT1). In addition, D. nodosus and Porphyromonas levii could be detected in the biopsy using PCR. A single local application of chlortetracycline spray led to clinical healing within two weeks, no recurrence was seen within the following two months. Three control sheep, which were kept together with the diseased sheep, did not show any clinical signs of CODD. Treponema spp could not be found in interdigital and coronary band biopsies by PCR or FISH. This is the first description of CODD in Switzerland and aims to sensitize veterinarians to CODD as a differential diagnosis for foot diseases in sheep.