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.

The study is a comparative analysis of three line immunoassays for serodiagnosing equine Lyme borreliosis. Specifically, it evaluates how these tests detect Borrelia burgdorferi sensu lato-specific antibodies in serum samples of both vaccinated and non-vaccinated horses.

Research Background

• The study discusses challenges in diagnosing equine Lyme borreliosis (LB), an infection characterized by nonspecific clinical signs and caused by the Borrelia burgdorferi sensu lato complex (Bbsl). The presence of vaccine-induced antibodies further complicates detection.
• The standard two-tier test system for detecting specific Bbsl antibodies involves an enzyme-linked immunosorbent assay (ELISA) or indirect fluorescent antibody test (IFA) for initial antibody screening, followed by a confirming line immunoassay (LIA).

Methodology

• The researchers compared three available LIAs for finding antibodies in equine serum samples.
• They used 393 serum samples from 131 horses with known serostatus. Some horses were non-vaccinated, while others were either vaccinated against LB on days 0 and 14, or given an initial vaccination plus a booster on day 180.
• Serum was collected on days 0, 135, and 210 of the study.
• Outcomes were based on the tests’ sensitivity, specificity, diagnostic outcome, and operability.
• The researchers looked at the diagnostic results agreement for overall test results and individual antigen-antibody complex signal results, represented by the Fleiss’ kappa coefficient. These agreement scores varied from poor to moderate, depending on the group and blood sample collection time-point.

Findings

• The researchers observed deficiencies depending on the LIA used. Specifically, certain antigen signals on the LIA strip had insufficient sensitivity, especially for outer surface protein (OspA) or variable major protein-like sequence expressed (VlsE).
• Test interpretation of the OspA signal was sometimes inappropriate.
• Operationally, all three LIAs were user-friendly, with some minor variations. Two of the LIAs offered simplified test evaluation via a bundled scanner and evaluation software.

Recommendations

• To improve the functionality of available LIAs for equine serum samples, the study recommends adjusting the sensitivity and specificity of individual test antigen signals.
• It also advises establishing suitable evaluation protocols.