Comparison between available serologic tests for detecting antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi in horses in Canada.

This research investigates the consistency between different serologic tests for detecting antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi in horses. The study suggests that inconsistencies in test results may arise from various factors, and proposes that screening of horses for exposure to tick-borne diseases in non-endemic areas may not be necessary.

Research Methodology

• The researchers examined 50 serum samples from horses of unknown clinical status and at low risk for infection.
• Several serologic tests were assessed, including a point-of-care enzyme-linked immunosorbent assay (pocELISA), 2 indirect fluorescent antibody tests for Anaplasma, and an antibody test, an ELISA confirmed with Western blot, and a Lyme multiplex assay for Borrelia.

Key Findings

• The results show a significant difference in the proportion of seropositive results in each pairwise comparison of tests for detection of antibodies against Anaplasma phagocytophilum.
• For Borrelia burgdorferi, a similar significant discrepancy was observed between the pocELISA and IFAT, and between the pocELISA and Lyme multiplex assay.
• The agreement measures, such as kappa, varied from poor to fair. However, when evaluating a prevalence-adjusted, bias-adjusted kappa, the agreement between tests improved.

Possible Explanations for the Observed Inconsistency

• The researchers suggested a few reasons for the lack of agreement between the tests. These include differences in methodology between the evaluated tests, potential cross-reactivity or the occurrence of false-positive and false-negative test results.

Implications of the Research

• The observed inconsistencies in test results trigger questions about the reliability of these tests in detecting tick-borne diseases in horses, particularly in non-endemic areas.
• The study proposes that screening of horses for exposure to such diseases in regions where these are not prevalent may not be necessary, especially considering the limitations of interpreting serologic test results in the absence of clinical disease.