Streptococcus equi subsp. zooepidemicus is the most common pathogen associated endometritis in mares. We recently showed that bacterial activation in the uterus, enable diagnosis of subclinical S. zooepidemicus1.
To assess the effect on fertility activation was introduced as a diagnostic aid for problem mares. Activation was conducted by uterine infusion of bActivate during early estrus follow by diagnostic sampling. A total of 19 mares were selected based on poor reproductive performance and a previous history of endometritis. The age of the mares was 12.7±4.1 years. The mares had been barren for 1.4±0.7 years and bred for an average of 6.3±2.3 cycles prior activation. Following bActivate instillation, growth of S. zooepidemicus was identified in 16 (84%) mares. Endometritis were treated for five consecutive days. Eighteen mares were bred and pregnancy was established in 16 (89%) using on average 1.1 cycle per pregnancy. The pregnancy rate per cycle was 70% (16/23). Two of the 16 mares (13%) lost the pregnancy.
Baseline fertility data from 888 problem mares from the same stud farm of showed a pregnancy rate per cycle and the fetal loss rate of 61% and 19.3%, respectively2. In comparison the pregnancy rate, activated vs non-activated, was 70% compared to 61%, and the fetal loss rate was 13% vs 19% in activated vs non-activated problem mares, respectively.
While a randomized trial had been ideal, this was not been possible in a commercial clinical setting. Yet activation induced bacterial clearance in 84% of the included mares. Pregnancy was established in 16/18 (89%) mares using on average 1.1 breeding cycle as opposed to 6.3 cycles per mare in the same mares without establishing pregnancy.
The data suggests that activation and treatment of subclinical bacterial endometritis likely increases the pregnancy rate per cycle and lower the fetal loss in problem mares.