Changes in Serum Antibody Levels after Vaccination for Strangles and after
Intranasal Challenge with Streptococcus equi subsp. equi
in Horses |
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| Authors: | Seiji HOBO Hidekazu NIWA Toru ANZAI James H JONES |
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| Institution: | 1. Epizootic Research Center, Equine Research Institute, Japan Racing Association, 1400–4 Shiba, Shimotsuke, Tochigi 329-0412, Japan;2. Department of Surgical and Radiological Science, Giannini Equine Athletic Performance Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616, U.S.A. |
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| Abstract: | In this study, to evaluate the influence of strangles vaccination on serological test
results, we investigated the changes in strangles serum antibody levels in horses after
vaccination and subsequent intranasal challenge with S. equi. The horses were vaccinated
for strangles with either a component vaccine (Group C) or a live vaccine (Group L). We
measured changes in strangles serum antibody levels weekly for 20 weeks after vaccinating
horses twice for strangles over a 3-week interval, and for 7 weeks after intranasal
challenge with S. equi in the same horses. Serum antibody responses to the
proline-glutamic acid-proline-lysine (PEPK) antigen with five repetitions (PEPK-5R) were
higher at all times (up to 2.4-fold) following vaccination in Group C than in Group L, and
the value peaked at 2.9-fold above the initial value after the second vaccination in Group
C horses. However, the value was lower than that in horses infected with S. equi, and it
gradually decreased, reaching the initial (week 0) value by the 15th week. Serum antibody
responses to PEPK-5R after challenge with S. equi increased in both groups of horses, but
the value tended to be lower than that reported for unvaccinated horses. In addition, the
average value in Group C was 2.6-fold higher than that of Group L. These results suggest
the serum antibody responses of horses infected with S. equi varies according to the type
of vaccine with which they have been vaccinated. Although the serological diagnostic test
for strangles in which PEPK-5R is used as an antigen is effective for the investigation of
serum antibodies to strangles in vaccinated horses, the present data suggest it is
necessary to consider the vaccination history when interpreting the results. |
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| Keywords: | horse PEPK antigen with five repetitions serological diagnostic test strangles Streptococcus equi |
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