Acta veterinaria Scandinavica2026; 68(1); 38; doi: 10.1186/s13028-026-00879-0

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

Ruiz, S
·
Øverlie, M
·
Bergren, A
·
Risnes Hellings, I

Abstract: Lyme borreliosis (LB), caused by Borrelia burgdorferi sensu lato, 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. Methods: 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.

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Publication Date: 2026-09-01 PubMed ID: 42786515PubMed Central: 3123645DOI: 10.1186/s13028-026-00879-0Google Scholar: Lookup

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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Equine neuroborreliosis (NB), a neurological condition caused by Lyme borreliosis bacteria, was confirmed for the first time in Scandinavia using cerebrospinal fluid PCR testing in a mare, which subsequently recovered after prolonged antibiotic treatment.

Background and Significance

Lyme borreliosis (LB) is an infection caused by Borrelia burgdorferi sensu lato bacteria, primarily recognized as an emerging concern in human health.
In horses, LB and its neurological form, neuroborreliosis (NB), are controversial and challenging to diagnose due to non-specific symptoms and lack of definitive diagnostic tools.
This study reports the first confirmed case of equine neuroborreliosis in Scandinavia, filling a gap in veterinary infectious disease knowledge for that region.

Case Description

Patient: An 11-year-old mare presented with several clinical signs including:
- Progressive weight loss
- Ataxia (loss of coordination)
- Muscle atrophy
- Hyperesthesia (increased sensitivity to stimuli)
Neurological signs suggested involvement of the central nervous system, raising suspicion for NB.

Diagnostic Approach

Cerebrospinal fluid (CSF) was collected to investigate the neurological symptoms further.
Laboratory analyses on CSF revealed:
- Neutrophilic pleocytosis – increased neutrophils indicating inflammation or infection.
- Elevated protein levels – suggesting a disrupted blood-CSF barrier or inflammation.
- Positive PCR result for Borrelia species – molecular confirmation of infection in the central nervous system.
The combination of clinical signs, cytological findings, and CSF PCR confirmed the diagnosis of neuroborreliosis.

Treatment and Outcome

The mare was treated with prolonged doxycycline therapy, an antibiotic effective against Borrelia bacteria.
Clinical improvement was observed over time, indicating that early antimicrobial treatment can be effective even in neurological Lyme disease in horses.
The mare achieved long-term recovery, demonstrating a positive prognosis with appropriate management.

Conclusions and Implications

This study establishes the diagnostic value of CSF PCR alongside clinical and cytological assessments in confirming equine neuroborreliosis.
The first documented Scandinavian case highlights the geographic spread and need for awareness of NB in horses in this region.
Early recognition and treatment of equine NB can lead to successful recovery, emphasizing the importance of prompt diagnosis and antimicrobial intervention.
The findings may encourage veterinarians to consider NB as a differential diagnosis in horses exhibiting neurological signs, particularly in endemic or emerging areas.

Cite This Article

APA

Ruiz S, Øverlie M, Bergren A, Risnes Hellings I. (2026). Equine neuroborreliosis in Scandinavia: cerebrospinal fluid PCR confirmation and successful treatment in a mare. Acta Vet Scand, 68(1), 38. https://doi.org/10.1186/s13028-026-00879-0

Publication

Acta veterinaria Scandinavica

ISSN: 1751-0147

NlmUniqueID: 0370400

Country: England

Language: English

Volume: 68

Issue: 1

PII: 38

Researcher Affiliations

Ruiz, Sofia

Dobloug & Ruiz Veterinærtjenester AS, Sankt Mikaels Veg 285, Vang På Hedmarken, 2324, Norway. sofiavalenciaruiz10@gmail.com.

Øverlie, Marianne

Bjerke Dyrehospital, Refstadveien 1, Oslo, 0589, Norway.

Bergren, Amanda

Bjerke Dyrehospital, Refstadveien 1, Oslo, 0589, Norway.

Risnes Hellings, Ingunn

Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine and Biosciences, Norwegian University of Life Sciences, Postboks 5003, Ås, 1432, Norway.

MeSH Terms

Animals
Horses
Female
Horse Diseases / drug therapy
Horse Diseases / diagnosis
Horse Diseases / microbiology
Horse Diseases / cerebrospinal fluid
Polymerase Chain Reaction / veterinary
Anti-Bacterial Agents / therapeutic use
Doxycycline / therapeutic use
Lyme Neuroborreliosis / veterinary
Lyme Neuroborreliosis / drug therapy
Lyme Neuroborreliosis / diagnosis
Lyme Neuroborreliosis / cerebrospinal fluid
Scandinavian and Nordic Countries

Conflict of Interest Statement

Declarations. Ethical approval: This case report did not require official or institutional ethical approval. The animal was handled according to high ethical standards and national legislation. Consent for publication: The owner of the horse has given approval for publication of this case. Prior publication: Data have not been published previously. Competing interests: The authors declare no competing interests.

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