Lack of Detectable Anti-Diphtheria Toxin Antibodies in European Hedgehogs (Erinaceus europaeus) from a Corynebacterium ulcerans Hotspot

Abstract

Corynebacterium ulcerans is a zoonotic pathogen causing cutaneous diphtheria. In Belgium, the bacterium is the cause of hedgehog diphtheric disease (HDD) that appears to have emerged from an endemic state within the European hedgehog (Erinaceus europaeus) population. In spring 2025, 11 hedgehogs admitted to a wildlife rehabilitation center were euthanized due to their severe condition. Blood was collected for anti-diphtheria toxin antibody detection, and lesion swabs (if present) and oral cavity swabs were taken, followed by necropsy. Of nine hedgehogs exhibiting HDD-like lesions, five were confirmed positive for C. ulcerans, with four animals harboring toxigenic strains. None of the 11 hedgehogs had detectable anti-diphtheria toxin titers. These findings suggest that although European hedgehogs in HDD-endemic regions are frequently exposed to C. ulcerans, the development of systemic antitoxin immunity remains uncertain and should be explored in larger studies that include healthy animals.