First report on outbreaks of contagious ovine digital dermatitis in Sweden

BACKGROUND: Contagious ovine digital dermatitis (CODD) is considered widespread in the United Kingdom but was only recently reported in mainland Europe, as one outbreak in Germany. The disease can cause severe lameness in sheep and, if left untreated, can lead to total avulsion of the hoof capsule. CODD is considered to have multifactorial and polymicrobial aetiology, in which Treponema medium/Treponema vincentii phylogroup, Treponema phagedenis phylogroup and Treponema pedis are believed to play a significant role. Footrot and CODD have a close connection and footrot is considered an important risk factor for CODD. CASE: Lameness, mainly in lambs aged 1.5 months, was reported on a farm in Sweden in spring 2018. The animals showed no signs of footrot and the causative agent, Dichelobacter nodosus, was not found. CODD was suspected but not confirmed, and the clinical signs subsided when the animals were turned out to pasture. In February 2019, young lambs and ewes were lame again and this time CODD was diagnosed. After treatment, the whole flock was slaughtered later in 2019 due to CODD. In autumn 2020, CODD was diagnosed on another Swedish farm, this time as part of a mixed infection with D. nodosus. The animals were treated with footbaths in zinc sulphate 10% by the farmer, but lameness recurred soon afterwards. The animals were treated, but ultimately the whole flock was slaughtered. No connection was found between the two farms. CONCLUSION: The first two outbreaks of CODD in Sweden have been diagnosed and are described in this case report. If it spreads, CODD could have a negative impact on the Swedish sheep industry in terms of animal welfare, production and antibiotic use.