EPIDEMIOLOGIC ASPECTS OF TAYLORELLA-EQUIGENITALIS

Contagious equine metritis (CEM) is a sexually transmissible disease i n mares. Although the disease is commonly diagnosed by culturing the c ausative bacterium Taylorella equigenitalis (T. equigenitalis), false negative results do occur. A recently developed Polymerase Chain React ion (PCR) assay, however, appeared to be much more sensitive, with ini tial results indicating an unexpected high incidence of the agent in s elected horses. In this study, samples from 107 randomly selected mare s with no clinical signs of CEM submitted for conventional culture wer e all negative for T. equigenitalis, but in the PCR-assay 54 (49%) wer e positive for Taylorella-DNA. Positives in the PCR-assay were found i n all breeds tested, even in horses imported from the isolated populat ion in Iceland. These findings suggest that T. equigenitalis was prese nt long before it was first isolated in 1977. The high incidence of Ta ylorella in horse populations without apparent clinical signs of CEM, the occurrence of incidental clinical case and the known variability b etween strains, all indicate that Taylorella is endemic in the horse p opulation. In order to explore whether the organism is present in spec ies other than the horse, we also used the PCR-assay on clinically hea lth donkeys (n=14), zebras (n=15), Przewalski horses (n=2) and cows (n =21). All the animals showed negative results except one of the Przewa lski horses, and one cow that was repeatedly found to give positive re action. We also found that the fertility of 7 stallions with cultures positive for Taylorella (6 used in an AI-program and 1 by natural bree ding) was not affected, as shown by the normal range of foaling rates in mares inseminated or bred by these stallions. The overall results m ay be interpreted to mean that Taylorella is of limited significance i n horse breeding. (C) 1997 by Elsevier Science Inc.