Corynebacterium diphtheriae and non-toxigenic C. ulcerans at a horse stable in Finland, 2021. Corynebacterium diphtheriae and non-toxigenic C. ulcerans, WGS

Abstract Corynebacterium diphtheriae and C. ulcerans, when toxin producing, are the cause of diphtheria, a potentially life-threatening illness in humans. Horses are known to be susceptible to infection that may manifest clinically on rare occasions. In late 2021 and early 2022 specimens from five horses at a two different stables with several horses suffering from mud fever-type lesions were cultured at the Laboratory of clinical microbiology at the University of Helsinki Faculty of veterinary medicine. C. diphtheriae and/or C. ulcerans was recovered from all of these. Objectives To describe the outbreak and identify possible sources of the infection and how it spread. Further, to analyse the bacterial isolates by WGS analysis.