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A case-control study developing a model for predicting risk factors for high SeM-specific antibody titers after natural outbreaks of Streptococcus equi subsp equi infection in horses.
Abstract: OBJECTIVE To develop a risk prediction model for factors associated with an SeM-specific antibody titer ≥ 3,200 in horses after naturally occurring outbreaks of Streptococcus equi subsp equi infection and to validate this model. DESIGN Case-control study. ANIMALS 245 horses: 57 horses involved in strangles outbreaks (case horses) and 188 healthy horses (control horses). PROCEDURES Serum samples were obtained from the 57 cases over a 27.5-month period after the start of outbreaks; serum samples were obtained once from the 188 controls. A Bayesian mixed-effects logistic regression model was used to assess potential risk factors associated with an antibody titer ≥ 3,200 in the case horses. A cutoff probability for an SeM-specific titer ≥ 3,200 was determined, and the model was externally validated in the control horses. Only variables with a 95% credibility interval that did not overlap with a value of 1 were considered significant. RESULTS 9 of 57 (6%) case horses had at least 1 titer ≥ 3,200, and 7 of 188 (3.7%) of control horses had a titer ≥ 3,200. The following variables were found to be significantly associated with a titer ≥ 3,200 in cases: farm size > 20 horses (OR, 0.11), history of clinically evident disease (OR, 7.92), and male sex (OR, 0.11). The model had 100% sensitivity but only 24% specificity when applied to the 188 control horses (area under the receiver operating characteristic curve = 0.62.) CONCLUSIONS AND CLINICAL RELEVANCE Although the Bayesian mixed-effects logistic regression model developed in this study did not perform well, it may prove useful as an initial screening tool prior to vaccination. We suggest that SeM-specific antibody titer be measured prior to vaccination when our model predicts a titer ≥ 3,200.
Publication Date: 2017-06-02 PubMed ID: 28569630DOI: 10.2460/javma.250.12.1432Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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The research article aims at developing and validating a model to predict risk factors for high levels of SeM-specific antibody titers in horses after natural outbreaks of Streptococcus equi subsp equi infection. Despite its low specificity, the model could function as an initial screening tool for horses prior to vaccination.
Design of the Study
- The approach used in this study is that of a case-control study.
- The sample size comprised 245 horses split into 57 horses which were involved in strangles outbreaks, referred to as case horses, and 188 healthy horses, referred to as control horses.
- Serum samples were collected from the case horses over a time period of 27.5 months following the start of the outbreaks, while the control horses were sampled only once during this time frame.
Research Methodology
- By applying a Bayesian mixed-effects logistic regression model, the researchers set out to examine the potential risk factors linked with an antibody titer of at least 3,200 in the case horses.
- The model was tested in the control group of horses after defining a cut-off probability for an SeM-specific titer greater than or equal to 3,200.
- Only variables with a 95% credibility interval that did not overlap with a value of 1 were identified as significant.
Results of the Study
- 9 out of 57 cases and 7 out of 188 controls exhibited a titer greater than or equal to 3,200.
- Farm size greater than 20 horses, the presence of evident clinical disease and male gender were found to be significantly linked with a titer greater than or equal to 3,200 in the case horses.
- When applied to the control group, the model presented a sensitivity of 100% but a low specificity of only 24%.
Conclusions of the Study
- The Bayesian mixed-effects logistic regression model developed in this study did not show high performance.
- However, the model could potentially prove useful as a preliminary screening tool prior to vaccination of horses.
- The researchers recommend that, before vaccination, an SeM-specific antibody titer be measured when their model predicts a titer of 3,200 or above.
Cite This Article
APA
Boyle AG, Smith MA, Boston RC, Stefanovski D.
(2017).
A case-control study developing a model for predicting risk factors for high SeM-specific antibody titers after natural outbreaks of Streptococcus equi subsp equi infection in horses.
J Am Vet Med Assoc, 250(12), 1432-1439.
https://doi.org/10.2460/javma.250.12.1432 Publication
Researcher Affiliations
MeSH Terms
- Animals
- Antibodies, Bacterial / blood
- Antibody Specificity
- Case-Control Studies
- Disease Outbreaks / prevention & control
- Disease Outbreaks / veterinary
- Female
- Horse Diseases / epidemiology
- Horse Diseases / microbiology
- Horse Diseases / prevention & control
- Horses
- Male
- Models, Theoretical
- Pennsylvania / epidemiology
- Risk Factors
- Sensitivity and Specificity
- Streptococcal Infections / epidemiology
- Streptococcal Infections / veterinary
- Streptococcus equi / immunology
Citations
This article has been cited 4 times.- Cummings CO, Krucik DDR, Price E. Clinical predictive models in equine medicine: A systematic review. Equine Vet J 2023 Jul;55(4):573-583.
- Delph KM, Beard LA, Trimble AC, Sutter ME, Timoney JF, Morrow JK. Strangles, convalescent Streptococcus equi subspecies equi M antibody titers, and presence of complications. J Vet Intern Med 2019 Jan;33(1):275-279.
- Boyle AG, Timoney JF, Newton JR, Hines MT, Waller AS, Buchanan BR. Streptococcus equi Infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles-Revised Consensus Statement. J Vet Intern Med 2018 Mar;32(2):633-647.
- Rask E, Righetti F, Ruiz A, Bjerketorp J, Frosth S, Frykberg L, Jacobsson K, Guss B, Flock JI, Henriques-Normark B, Hartman E, Gustafsson A, Paillot R, Waller AS. Closing the Stable Door on Strangles: Serological Responses of Vaccinated Horses on a Farm Following the Arrival of a New Horse. Animals (Basel) 2025 Dec 13;15(24).
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