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Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers
Author(s) -
Durham Andy E.,
Kemp-Symonds Jeremy
Publication year - 2021
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/evj.13276
Subject(s) - serology , carriage , horse , medicine , population , antibody , immunology , biology , pathology , paleontology , environmental health
Background 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. Objectives 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 . Study design 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. Main limitations 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.