Ten years of Taylorella equigenitalis ring trial results comparing culture and polymerase chain reaction.

Taylorella equigenitalis, the cause of contagious equine metritis (CEM), can be detected by culture but in recent years polymerase chain reaction (PCR) has also been used. In 2008, the World Organisation for Animal Health (OIE) Reference Laboratory for CEM in the United Kingdom set up a ring trial for laboratories to assess their ability to identify T. equigenitalis in laboratory-prepared samples because the identification of T. equigenitalis in the laboratory was recognised to be difficult. Freeze-dried culture suspensions in various combinations of any of T. equigenitalis, Taylorella asinigenitalis, other typical equine contaminant organisms, or no organism were used. All laboratories provided culture results and some also gave PCR results. The results reported here cover the ten years since inception and look at the ability to identify T. equigenitalis under ideal laboratory conditions, a necessity to be able to detect its presence in equine genital samples. The detection rate was very high by both methods. The accuracy was not significantly different between the culture and PCR methods for pure T. equigenitalis samples. For T. equigenitalis mixed with contaminants, culture missed about 2% (p = 0.02) compared with PCR, which was over 99% accurate. Difficulty in differentiating T. asinigenitalis from T. equigenitalis was apparent in a number of laboratories for both culture and PCR in 2008 but was less evident in 2016. It was also noted that culture results from laboratories that also tested by PCR had around 4% higher detection rates (p < 0.05) of T. equigenitalis than those that only used culture.