This research looks at the potential of using serum synergistic hemolysis inhibition (SHI) testing to predict C pseudotuberculosis infection in horses. The findings indicate that while higher antibody titers typically point to an active C pseudotuberculosis infection, the SHI test isn’t useful for predicting internal infections specifically, especially in horses with external abscesses.

Background and Objective

• The study aimed to determine the likelihood ratios (LRs) for accurately predicting internal Corynebacterium pseudotuberculosis (C pseudotuberculosis) infection in horses using the serum synergistic hemolysis inhibition (SHI) test which measures antibody levels.

Methods

• This was a retrospective case-control study involving 170 horses, 92 of which had confirmed C pseudotuberculosis infections and the other 79 were the control group.
• Medical records of the horses were reviewed to group them based on whether they had evidence of internal or external C pseudotuberculosis infections.
• The LRs, with corresponding 95% confidence intervals, for identification of internal C pseudotuberculosis infection using the SHI test results were estimated.

Results

• The study found that as antibody titers increased, the likelihood ratios for detecting the infection also increased.
• However, when only horses with external C pseudotuberculosis infections were considered, the likelihood ratios did not show a significant change from 1, indicating no change in odds of predicting an internal infection from pretest to post-test.
• The study found a LR of 2.98 for detecting internal infection in horses with titers over or equal to 512.

Conclusion

• The research concluded that while higher titers pointed more towards an active external or internal C pseudotuberculosis infection, the SHI test was not an effective predictor of internal infection specifically in horses with external abscesses.
• However, the test was found useful in predicting the absence of external disease.