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Equine veterinary journal2020; 53(1); 38-43; doi: 10.1111/evj.13276

Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers.

Abstract: Serology is commonly used as a means of identifying horses that might be chronic and silent carriers of S. equi but its sensitivity is rarely examined. Objective: The study was designed to investigate the sensitivity of serological testing for antibodies against S. equi antigens A and C to detect guttural pouch carriers of S. equi. Methods: Retrospective clinical study. Methods: As part of routine surveillance and quarantine procedures horses arriving at a welfare charity quarantine unit were subject to both microbiological sampling of guttural pouches and also serological testing for antibodies directed at S. equi antigens A and C. Laboratory results and endoscopic findings were examined to determine associations between serological results and guttural pouch carriage of S. equi. Results: Of 287 included horses, 9 (3.1%) were found to be guttural pouch carriers. There was no significant association between serological status and guttural pouch carriage of S. equi Only one of the nine carriers (11%) was seropositive using a cut-off of OD ≥ 0.5, and only three of nine (33%) using a cut-off of OD ≥ 0.3. Conclusions: Horses examined in this study were new arrivals at a welfare centre rather than from a general, well-managed, equid population. As a retrospective clinical study, the laboratory test results could not be repeated for further confirmation. Conclusions: Caution is advised when relying on seronegativity to antigens A and C in order to discount the possibility of chronic carriage of S. equi in guttural pouches.
© 2020 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2020-05-20 PubMed ID: 32374892DOI: 10.1111/evj.13276Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article investigates the reliability of serological tests for antigens A and C in detecting horses that are chronic carriers of Streptococcus equi (S. equi) in their guttural pouches. The result of the study suggests caution in relying on seronegativity to antigens A and C to dismiss the possibility of chronic carriage of S. equi in horses’ guttural pouches.

Objective

  • The objective of the research was to examine the sensitivity of serological testing, a method that uses blood samples to detect specific antibodies, in detecting the antigens A and C of S. equi. These antigens are proteins of the bacteria that stimulate an immune response in the host body, in this case, horses.

Methods

  • The study method involved a retrospective clinical study that looked back on previously collected data.
  • Microbiological sampling of the guttural pouches and serological testing for antibodies aimed at the S. equi antigens A and C were done on horses as part of standard surveillance and quarantine procedures upon their arrival at a welfare charity quarantine unit.
  • The association between serological results and guttural pouch carriage of S. equi was investigated, i.e., looking for a relationship or correlation between the result of the blood test and the presence of bacteria within the guttural pouch of the horses.

Results

  • Out of 287 horses in the study, nine (3.1%) were identified as guttural pouch carriers of S. equi.
  • No significant correlation was found between the serological status and carriage of S. equi in the guttural pouch.
  • Only one out of nine carriers (11%) was seropositive, i.e., the blood test was positive for the antigens, at a cut-off point of OD ≥ 0.5. And only three out of nine (33%) were seropositive at a lesser cut-off OD ≥ 0.3.

Conclusion

  • The study concluded that the use of seronegativity, i.e., the absence of detectable levels of specific antibodies in the blood, as a method to dismiss guttural pouch carriers of S. equi should be approached with caution.
  • The researchers noted that the results could have been influenced by the fact that the horses were new arrivals at a welfare centre instead of from a general, well-managed, equid population.
  • As the research was a retrospective clinical study based on the investigation of previously collected data, laboratory test results could not be repeated for further confirmation.

Cite This Article

APA
Durham AE, Kemp-Symonds J. (2020). Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers. Equine Vet J, 53(1), 38-43. https://doi.org/10.1111/evj.13276

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 53
Issue: 1
Pages: 38-43

Researcher Affiliations

Durham, Andy E
  • The Liphook Equine Hospital, Liphook, Hampshire, UK.
Kemp-Symonds, Jeremy
  • Bransby Horses, Bransby, Lincoln, UK.

MeSH Terms

  • Animals
  • Carrier State / diagnosis
  • Carrier State / veterinary
  • Horse Diseases / diagnosis
  • Horses
  • Retrospective Studies
  • Streptococcal Infections / diagnosis
  • Streptococcal Infections / veterinary
  • Streptococcus equi

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This article includes 27 references
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Citations

This article has been cited 6 times.
  1. McLinden LA, Kemp-Symonds JG, Daly JM, Blanchard AM, Waller AS, Freeman SL. Effectiveness of a screening protocol employed at a UK rescue centre to prevent introduction of strangles. Equine Vet J 2026 Mar;58(2):466-475.
    doi: 10.1111/evj.70080pubmed: 41031843google scholar: lookup
  2. Abdul-Latif SAK, Yousif AA. Molecular study of Streptococcus equi isolated from horses with strangles in Iraq. Open Vet J 2025 Feb;15(2):731-737.
    doi: 10.5455/OVJ.2025.v15.i2.22pubmed: 40201849google scholar: lookup
  3. Zu H, Sun R, Li J, Guo X, Wang M, Guo W, Wang X. Development of a Real-Time Recombinase-Aided Amplification Method for the Rapid Detection of Streptococcus equi subsp. equi. Microorganisms 2024 Apr 11;12(4).
    doi: 10.3390/microorganisms12040777pubmed: 38674721google scholar: lookup
  4. Pringle J, Aspán A, Riihimäki M. Repeated nasopharyngeal lavage predicts freedom from silent carriage of Streptococcus equi after a strangles outbreak. J Vet Intern Med 2022 Mar;36(2):787-791.
    doi: 10.1111/jvim.16368pubmed: 35072293google scholar: lookup
  5. Morris ERA, Boyle AG, Riihimäki M, Aspán A, Anis E, Hillhouse AE, Ivanov I, Bordin AI, Pringle J, Cohen ND. Differences in the genome, methylome, and transcriptome do not differentiate isolates of Streptococcus equi subsp. equi from horses with acute clinical signs from isolates of inapparent carriers. PLoS One 2021;16(6):e0252804.
    doi: 10.1371/journal.pone.0252804pubmed: 34125848google scholar: lookup
  6. Pringle J, Venner M, Tscheschlok L, Waller AS, Riihimäki M. Markers of long term silent carriers of Streptococcus equi ssp. equi in horses. J Vet Intern Med 2020 Nov;34(6):2751-2757.
    doi: 10.1111/jvim.15939pubmed: 33074578google scholar: lookup
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