A comparative study evaluating three line immunoassays available for serodiagnosis of equine Lyme borreliosis: Detection of Borrelia burgdorferi sensu lato-specific antibodies in serum samples of vaccinated and non-vaccinated horses.
Authors: Broeckl Cornelia V, Hiereth Stephanie, Straubinger Reinhard K
Journal: PloS one
Summary
# Editorial Summary: Line Immunoassay Comparison for Equine Lyme Disease Diagnosis Diagnosing equine Lyme borreliosis presents a genuine clinical challenge: the disease causes non-specific signs that overlap with many conditions, serological testing lacks standardisation, and vaccination complicates interpretation by producing antibodies indistinguishable from natural infection. Broeckl and colleagues evaluated three commercially available line immunoassays (LIAs) against 393 serum samples from 131 horses with known infection or vaccination status, including non-vaccinated controls, vaccinated animals (two doses), and those receiving a booster immunisation at 180 days. Agreement between the three tests proved disappointing, with kappa coefficients ranging from poor to moderate depending on the assay and sampling timepoint, revealing significant inconsistencies in how individual antigen signals—particularly outer surface protein A (OspA) and VlsE—were detected and interpreted across platforms. For equine practitioners relying on two-tier testing protocols (screening ELISA/IFA followed by confirmatory LIA), these findings highlight a critical gap: the current generation of commercial LIAs lacks sufficient standardisation and sensitivity for reliable differentiation between vaccinated and naturally infected horses, potentially leading to both false negatives and diagnostic confusion. The authors recommend that manufacturers recalibrate antigen signal sensitivity and specificity for equine samples and establish standardised interpretation criteria—essential steps before these tests can be considered trustworthy for clinical decision-making or epidemiological surveillance in horses at risk of Lyme borreliosis.
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Practical Takeaways
- •Lyme borreliosis serology in horses is unreliable across available commercial tests — insist on a standardized two-tier testing protocol and be cautious interpreting single LIA results, especially in vaccinated horses.
- •OspA and VlsE antigen results are particularly inconsistent between tests; correlate serology with clinical signs and exposure history rather than relying on antibody titers alone.
- •When submitting samples for LB testing, document vaccination status clearly and consider repeat testing at different timepoints, as single-point serology may be misleading due to poor inter-test agreement.
Key Findings
- •Three line immunoassays (LIAs) showed poor to moderate agreement (Fleiss' kappa) for detecting B. burgdorferi antibodies in equine serum, varying by group and sampling timepoint.
- •Vaccine-induced antibodies complicate diagnosis; vaccinated horses showed different serological patterns compared to non-vaccinated horses at days 0, 135, and 210.
- •Deficient antigen sensitivity was observed across LIAs, particularly for OspA and VlsE signals, with inappropriate OspA signal interpretation in some tests.
- •All three LIAs had similar user-friendliness, with two offering scanner-based evaluation; improved standardization of antigen signals and evaluation protocols is needed.