Changes in Serum Strongylus Vulgaris-Specific Antibody Concentrations in Response to Anthelmintic Treatment of Experimentally Infected Foals.
Authors: Nielsen Martin Krarup, Scare Jessica, Gravatte Holli Sullivan, Bellaw Jennifer Lynn, Prado Julio C, Reinemeyer Craig Robert
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Strongylus vulgaris Serology and Treatment Timing Strongylus vulgaris remains a significant threat to equine health despite modern management practices, with its larval migration through mesenteric vessels capable of causing fatal colic. A serum ELISA has been developed to detect migrating larvae, yet the diagnostic value of this test in relation to treatment timing remains poorly characterised. This experimental study tracked antibody responses in fifteen foals following controlled S. vulgaris infection and either early (Day 56) or delayed (Day 112) ivermectin treatment, with untreated controls, collecting paired serum and faecal samples throughout a 196-day observation period. Both treated groups showed acute increases in ELISA values post-treatment, but foals receiving early intervention had significantly lower cumulative antibody concentrations from Day 140 onwards compared to delayed-treatment and control cohorts, indicating that S. vulgaris-specific antigens are generated continuously throughout arterial infection rather than exclusively during larval migration phases. For practitioners, these findings suggest that serological monitoring with S. vulgaris ELISA may help identify persistent or recent infections, and that treatment timing substantially influences the antigen load generated over an infection's course—with implications for both diagnostic interpretation and strategic anthelmintic scheduling in at-risk populations.
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Practical Takeaways
- •Early ivermectin treatment of young horses infected with S. vulgaris reduces the overall parasitic burden and associated disease risk; treating foals around 8 weeks of age may be more effective than delayed treatment
- •A temporary rise in serum antibody levels after ivermectin treatment is expected and indicates drug efficacy against migrating larvae—this is a positive prognostic sign, not a treatment failure
- •Serum ELISA testing can help monitor S. vulgaris infection status in foals, though rising antibody titers following treatment require clinical interpretation in context of treatment timing
Key Findings
- •Early ivermectin treatment (Day 56) significantly reduced serum S. vulgaris-specific antibody concentrations compared to late treatment (Day 112) or untreated controls by Days 140-196
- •Both treated groups showed increased ELISA values immediately following ivermectin administration, indicating acute antigen release from dying parasites
- •S. vulgaris-specific antigen is produced continuously throughout arterial migration, not only in late larval stages as previously thought
- •Early parasite elimination reduces cumulative antigen burden even though diagnostic antigen persists throughout infection course