Effect of Long-Term Freezing on Indirect Fluorescent Antibody Titers for the Diagnosis of Equine Protozoal Myeloencephalitis.
Abstract: Long-term freezing storage can alter the stability of proteins, thereby compromising accurate determination of indirect fluorescent antibody test (IFAT) titers that support the diagnosis of equine protozoal myeloencephalitis. Objective: Assess the effect of long-term storage at -80°C on IFAT against S. neurona and N. hughesi in equine serum and cerebrospinal fluid (CSF). Methods: Paired serum and CSF (n = 46), and serum only (n = 25) samples. Methods: Prospective study of samples stored 6-12, 13-18, and 19-24 months. Comparing antibody titers across time points, McNemar and Wilcoxon rank tests were used for statistical analysis. Results: After long-term freezing storage for 19-24 months, N. hughesi IFAT results for CSF were significantly different compared with their fresh-testing time point (p = 0.04), but a similar difference was not observed for serum samples. No statistical differences were observed for serum or CSF samples tested for S. neurona after 6-12, 13-18, or 19-24 months compared with their original fresh testing results. However, the serum to CSF ratio cutoff of ≤ 64 in support of disease changed in 41% (19 of 46) of paired samples. Conclusions: Freezing samples at -80°C for more than 18 months might alter test results, leading to possible changes in serum to CSF ratio calculations and affecting the interpretation of results for clinical and research purposes.
© 2025 The Author(s). Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
Publication Date: 2025-08-30 PubMed ID: 40873183PubMed Central: PMC12391721DOI: 10.1111/jvim.70225Google Scholar: Lookup
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Cite This Article
APA
Valderrama-Martinez C, Packham A, Smith W, Mendoza-Flores JE, Zheng S, Chigerwe M, Plancarte M, Aleman M.
(2025).
Effect of Long-Term Freezing on Indirect Fluorescent Antibody Titers for the Diagnosis of Equine Protozoal Myeloencephalitis.
J Vet Intern Med, 39(5), e70225.
https://doi.org/10.1111/jvim.70225 Publication
Researcher Affiliations
- Departamento de Salud Animal, Facultad de Medicina Veterinaria y Zootecnia. Universidad Nacional de, Bogotá, Colombia.
- One Health Institute, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- One Health Institute, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- One Health Institute, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
MeSH Terms
- Animals
- Horses
- Horse Diseases / diagnosis
- Horse Diseases / parasitology
- Horse Diseases / blood
- Horse Diseases / cerebrospinal fluid
- Freezing
- Fluorescent Antibody Technique, Indirect / veterinary
- Encephalomyelitis / veterinary
- Encephalomyelitis / diagnosis
- Encephalomyelitis / parasitology
- Encephalomyelitis / cerebrospinal fluid
- Encephalomyelitis / blood
- Prospective Studies
- Antibodies, Protozoan / blood
- Antibodies, Protozoan / cerebrospinal fluid
- Sarcocystosis / veterinary
- Sarcocystosis / diagnosis
- Time Factors
- Neospora / immunology
Grant Funding
- PD1001 / The Seed for International Activities Program, sponsored by Global Affairs at UCD
- V435AM2 / Gifts from anonymous donors towards the Equine and Comparative Neurology Research Group
Conflict of Interest Statement
Authors declare no off‐label use of antimicrobials. Munashe Chigerwe serves as Associate Editor for the Journal of Veterinary Internal Medicine. He was not involved in the review of this manuscript. The other authors declare no conflicts of interest.
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