Equine neuroborreliosis in Scandinavia: cerebrospinal fluid PCR confirmation and successful treatment in a mare

Abstract Background Lyme borreliosis (LB), caused by Borrelia burgdorferi , is an emerging concern in human medicine, and is a controversial topic in equine medicine. Neuroborreliosis (NB), a neurologic manifestation of LB, remains challenging to diagnose due to nonspecific clinical signs and the lack of definitive diagnostic methods. This report describes the first documented case of equine NB in Scandinavia. Case presentation: An 11-year-old mare presented with progressive weight loss, ataxia, muscle atrophy, and hyperesthesia. Cerebrospinal fluid (CSF) analysis revealed neutrophilic pleocytosis, elevated protein and a positive PCR result for Borrelia spp . The mare showed clinical improvement and long-term recovery following prolonged doxycycline therapy. Conclusions: This case is the first reported case of neuroborreliosis in a horse in Scandinavia and supports the diagnostic relevance of CSF PCR in conjunction with clinical and cytological findings. It also underscores the potential for recovery in equine NB when early antimicrobial treatment is initiated.