SvSXP: A Strongylus vulgaris antigen with potential for prepatent diagnosis

Ulla V. Andersen, Daniel K. Howe, Sriveny Dangoudoubiyam, Nils Toft, Craig R. Reinemeyer, Eugene T. Lyons, Susanne N. Olsen, Jesper Monrad, Peter Nejsum, Martin K. Nielsen

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Background: Strongyle parasites are ubiquitous in grazing horses. Strongylus vulgaris, the most pathogenic of the large strongyles, is known for its extensive migration in the mesenteric arterial system. The lifecycle of S. vulgaris is characterised by a long prepatent period where the migrating larvae are virtually undetectable as there currently is no test available for diagnosing prepatent S. vulgaris infection. Presence of S. vulgaris larvae in the arterial system causes endarteritis and thrombosis with a risk of non-strangulating intestinal infarctions. Emergence of anthelmintic resistance among cyathostomins has led to recommendations of reduced treatment intensity by targeting horses that exceed a predetermined strongyle faecal egg count threshold. One study suggests an apparent increase in prevalence of S. vulgaris on farms where reduced anthelmintic treatment intensity has been implemented. These issues highlight the need for an accurate and reliable assay for diagnosing prepatent S. vulgaris infection. Methods. Immunoscreening of a larval S. vulgaris cDNA library using hyperimmune serum raised against S. vulgaris excretory/secretory antigens was performed to identify potential diagnostic antigens. Immunoreactive clones were sequenced, one potential antigen was characterised, expressed as a recombinant protein, initially evaluated by western blot (WB) analysis, the diagnostic potential of the IgG subclasses was evaluated by ELISA, and the diagnostic accuracy evaluated using serum from 102 horses with known S. vulgaris infection status. Results: The clone expressing the potential antigen encoded a S. vulgaris SXP/RAL2 homologue. The recombinant protein, rSvSXP, was shown to be a potential diagnostic antigen by WB analysis, and a target of serum IgGa, IgG(T) and total IgG in naturally infected horses, with IgG(T) antibodies being the most reliable indicator of S. vulgaris infection in horses. Evaluation of diagnostic accuracy of the ELISA resulted in a sensitivity of 73.3%, a specificity of 81.0%, a diagnostic odds ratio of 11.69; a positive likelihood ratio (LR) of 3.85 and a negative LR was 0.33. The area under the ROC curve was 0.820. Conclusion: IgG(T) antibodies to recombinant SvSXP show potential for use as an antigen for prepatent diagnosis of migrating stages of S. vulgaris with moderate to good diagnostic accuracy.

Original languageEnglish
Article number84
JournalParasites and Vectors
Issue number1
StatePublished - 2013

Bibliographical note

Funding Information:
The authors wish to thank the Denmark-America Foundation for generous support of the research stay at the M.H. Gluck Equine Research Center, University of Kentucky, USA. Additional financial support was provided by Foreningen Kustos af 1881, Hesteafgiftsfonden, Oticon Fondet, HP. Olsen & Hustru, Godsejer Victor A. Goldschmidts legat and Kongeriget Danmark Hesteforsikring. The funding sources had no involvement in the study design, collection, analysis and interpretation of data, writing the paper or the decision to submit the paper. Our grateful thanks to Hamish E.G. McWilliam (Monash University, Melbourne, Victoria, Australia), as well as Michelle Yeargan, Sharon Tolliver, Drs. Ablesh Gautam, Macarena G Sanz, and Alan T. Loynachan (all University of Kentucky) for invaluable help with practical challenges, providing helpful pointers and collection of samples. The staff at the Maine Chance Farm is warmly appreciated for their valuable work with maintaining the unique parasitology herds at University of Kentucky.


  • Diagnosis
  • IgG(T)
  • Prepatent
  • SXP
  • Strongylus vulgaris
  • Validation
  • cDNA library

ASJC Scopus subject areas

  • Parasitology
  • Infectious Diseases


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