Interpretation of serum antibody response to Anoplocephala perfoliata in relation to parasite burden and faecal egg count.
Authors: Kjaer L N, Lungholt M M, Nielsen M K, Olsen S N, Maddox-Hyttel C
Journal: Equine veterinary journal
Summary
# Editorial Summary: Serum Antibody Response to *Anoplocephala perfoliata* — Practical Diagnostic Interpretation Diagnosing equine tapeworm infection reliably remains challenging, prompting Kjaer and colleagues to evaluate how serum antibody levels correlate with actual parasite burden. Using 84 horses presented for slaughter at a Danish abattoir, researchers compared counts of recovered tapeworms and their developmental stages against concurrent serum ELISA results and faecal egg counts, employing receiver operating characteristic analysis to determine optimal diagnostic thresholds. Faecal egg counting proved substantially more sensitive (89%) when targeting horses harbouring more than 20 worms, with a moderate correlation (0.71) between worm burden and egg shedding; however, the standard ELISA cut-off previously suggested failed to reliably distinguish infected from uninfected horses, necessitating adjustment to an optical density value of 0.7 for improved sensitivity (0.68) and specificity (0.71). For practitioners managing individual horses, faecal analysis appears more informative than serum antibody testing, particularly when infection intensity is likely to be high, whilst the revised ELISA interpretation may prove more useful in population-level screening or when faecal samples are unavailable. These findings highlight the importance of contextualising diagnostic results within the clinical picture—neither test performs perfectly in isolation, and treatment decisions should reflect the quantitative relationship between diagnostic output and true infection risk.
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Practical Takeaways
- •Faecal egg counts are more reliable than ELISA for diagnosing potentially pathogenic A. perfoliata infections in individual horses, particularly when parasite burden is high
- •Use an ELISA optical density threshold of 0.7 to identify horses requiring anti-tapeworm treatment in Danish horse populations, recognizing substantial individual variation in antibody response
- •Neither diagnostic method alone is perfectly sensitive; consider parasite burden when interpreting negative results, as light infections may be missed by both faecal counts and serology
Key Findings
- •Macroscopically visible A. perfoliata detected in 29% (24/84) of horses at slaughter
- •Faecal egg count sensitivity was 0.46 overall but increased to 0.89 when worm burden exceeded 20 tapeworms
- •Correlation of 0.71 found between worm burden and faecal egg count
- •Serum ELISA at OD cutoff of 0.7 achieved sensitivity of 0.68 and specificity of 0.71, with significant correlation to infection intensity