Bacteria detected in the genital tract, semen or pre-ejaculatory fluid of Swedish stallions from 2007 to 2017

Although artificial insemination(AI) was developed as a means of controlling disease transmission, pathogenscan still be transmitted to females in semenused for AI. In addition, bacteria can cause deterioration in sperm quality during storage. Semenbecomes contaminated by the male’s normal bacterial flora as it passes out of the reproductive tract but potential pathogensmay also contaminate the semen. Therefore, semen samplesfrom stallions to be used for AI are tested before the breeding season to minimize transmission of pathogensto inseminatedmares. In Sweden, semen samplesare tested at the National Veterinary Institute, Uppsala (SVA). For the present study, a retrospective analysis was made of potentially pathogenicbacteria isolated from samples submitted to the SVA from 2007 to 2017. In our study, Taylorella equigenitaliswas found infrequently (53 out of 25,512 samples), representing 11 out of 2308 stallions. If T. equigenitalis was detected, the stallions were treated with antibiotics and re-tested later in the same year. Klebsiella pneumoniae and beta haemolytic streptococci were the most commonly found potential pathogens, whereas Pseudomonas aeruginosa was also isolated occasionally. There were considerable differences in the number of species isolated each year. Potential pathogenswere identified in relatively few of the samples submitted to SVA during this period, with T. equigenitalis not being identified since 2015. Of the other potential pathogens, K. pneumoniae and beta haemolytic streptococci were the most common. The information is relevant for determining guidelines on the testing and treatment of stallions before breeding.