Comparison of morphological and molecular Strongylus spp. identification in equine larval cultures and first report of a patent Strongylus asini infection in a horse.
Authors: Diekmann Irina, Blazejak Katrin, Krücken Jürgen, Strube Christina, von Samson-Himmelstjerna Georg
Journal: Equine veterinary journal
Summary
# Editorial Summary German researchers directly compared morphological and molecular diagnostic methods for identifying Strongylus species in equine faecal cultures, analysing 594 samples positive for nematode DNA obtained from routine diagnostic submissions in 2018. Morphological and PCR-based identification showed substantial disagreement, with particularly poor concordance for *S. vulgaris* (0% morphological versus 0.8% molecular detection) and *S. equinus* (2.0% versus 0.2%), though fair agreement was achieved for *S. edentatus*. Notably, molecular analysis identified a case of *S. asini* infection in a domestic horse—the first reported patent infection in equids—though the clinical and epidemiological significance of this species remains unclear. For practitioners, these findings highlight that routine morphological larval culture identification may substantially underestimate or misidentify Strongylus species prevalence, with implications for targeted anthelmintic strategies, particularly where *S. vulgaris* control is a priority; however, the authors acknowledge that neither method is yet established as a reliable gold standard, and further validation of cost-effective diagnostic approaches is needed before major changes to laboratory protocols can be confidently recommended.
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Practical Takeaways
- •Morphological larval culture examination alone may underestimate prevalence of S. vulgaris and other Strongylus species; molecular confirmation should be considered for routine diagnostic surveillance
- •Be aware that S. asini, rarely reported in domestic horses, may be present in equine populations; consider molecular screening if clinical signs persist despite targeted anthelmintic treatment
- •Current routine diagnostic methods have variable reliability depending on species; standardized protocols combining both morphological and molecular approaches may improve parasite control targeting in practice
Key Findings
- •Among 594 nematode DNA-positive samples, morphological and molecular identification methods showed fair agreement for S. edentatus (0.3% vs 1.5%), slight agreement for S. equinus (2.0% vs 0.2%), and poor agreement for S. vulgaris (0% vs 0.8%)
- •First documented patent S. asini infection in a domestic horse, confirmed by sequencing, identified through molecular PCR analysis
- •Morphological examination failed to detect S. vulgaris in any samples while molecular PCR detected it in 0.8% of samples, indicating significant diagnostic method discrepancy
- •Results demonstrate that morphological and molecular identification methods produce substantially different species frequency data and reliability varies considerably by Strongylus species