Pooling of genital swabs for detection by PCR of Taylorella equigenitalis, the cause of contagious equine metritis.
Authors: Mawhinney I, Errington J, Stamper N, Torrens N, Engelsma M Y, Roest H I J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Pooling Genital Swabs for T. equigenitalis Detection Screening breeding stock for *Taylorella equigenitalis* (contagious equine metritis) typically involves culturing or PCR-testing multiple genital swabs per animal—usually two to four sites—which is labour-intensive and costly. Mawhinney and colleagues evaluated whether pooling these swabs into a single PCR test would maintain diagnostic sensitivity using 149 historical positive samples and 24 laboratory-prepared pools combining positive and negative swabs in ratios reflecting naturally-infected cases. Pooling one positive swab with three negative samples produced only minor increases in PCR cycle threshold (Ct) values, with all pools remaining clearly positive and easily distinguishable from negative controls. The findings demonstrate that pooled testing detects infected animals with equivalent reliability to individual swab testing, making it a practical and cost-effective alternative for population screening without compromising diagnostic accuracy. For practitioners involved in pre-purchase or breeding soundness examinations, this approach could streamline testing protocols and reduce laboratory expenses whilst maintaining the sensitivity needed to identify carriers reliably.
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Practical Takeaways
- •Pooling genital swabs for PCR testing reduces laboratory costs and workload while maintaining reliable detection of T. equigenitalis in screening programs
- •Instead of testing 2-4 swabs individually per horse, practitioners can submit pooled samples with confidence in diagnostic accuracy
- •This method is suitable for population screening programs where CEM status needs to be determined at the animal level rather than site-specific detection
Key Findings
- •Pooling one positive swab with three negative swabs produced only small drops in PCR Ct values while maintaining clear positive detection
- •Laboratory-prepared pools of genital swabs demonstrated that pooling is applicable to field cases of T. equigenitalis infection
- •Pooling of swabs confers no appreciable reduction in ability to detect positive animals compared to individual swab testing
- •Pooling swabs represents a cost-effective alternative to individual swab testing without compromising diagnostic sensitivity