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Longitudinal Observations of Silent Carriers of S treptococcus Equi in A Swedish Yard
Author(s) -
Gröndahl G.,
Båverud V.,
Ljung H.,
Melys V.,
Aspán A.,
Riihimäki M.
Publication year - 2015
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.12486_50
Subject(s) - serology , medicine , horse , penicillin , veterinary medicine , immunology , antibody , antibiotics , biology , microbiology and biotechnology , paleontology
Reasons for performing study When managing strangles in horses, it is crucial to detect chronic infection with S treptococcus equi ( SE ), i.e. silent carriers. Objectives Evaluate diagnostics for SE carriers over time in a farm. Study design Longitudinal observational study. Methods Sixty‐three Icelandic horses isolated on an island were studied 4 to 26 months after remission of acute strangles, including repeated clinical examination and collection of blood, nasopharyngeal lavage ( NPL ), and guttural pouch lavage ( GPL ) samples. Twenty‐two horses were treated with penicillin locally and systemically. Serology for S . equi was examined by iELISA [1]. Nasopharyngeal lavage and GPL samples were investigated for S . equi and S . zooepidemicus by real‐time PCR [2]. Results Thirty‐three per cent were SE carriers after 15 months, despite repeated penicillin treatment. In 16/18 carriers, GPL samples were PCR ‐positive, but not NPL samples, whereas the opposite was true in 2 horses. Several carriers with persistent aerocystitis were not detected by 3 consecutive NPL samples. Five of 18 carriers were seronegative (27.8%) at 15 months. Following conservative treatment, 7 of these 18 carriers were still carriers at 20 months, 8 were negative, and 3 were lost for sampling. Only GPL samples were positive at this point, and only 1/7 carriers were seropositive. Conclusions To detect chronic carriers of strangles, RT‐PCR analysis from both GPL and NPL samples may be necessary. Serological screening at individual level often misses individual carriers in long‐term cases. Ethical animal research: The testing was approved by the Swedish Ethical Committee on Animal Experiments and horse owners gave their informed consent for inclusion of animals in the study. Source of funding: The Swedish‐Norwegian Foundation for Equine Research. Competing interests: None declared.