1. Impact of activation and subsequent antimicrobial treatment of dormant endometrial streptococci in the Thoroughbred problem mare – a descriptive field study Aim To determine the impact of activation and subsequent antimicrobial treatment of dormant endometrial streptococci in the Thoroughbred problem mare Introduction The expected fertility of problem mares (non-pregnant for >3 cycles) is reduced despite intensive breeding management compared to the general broodmare population (15 to 50% vs. 80 to 85% foaling rate, Bosh et al., Equine Vet Journal 2009). Streptococcus equi subspecies zooepidemicus (S. zoo) can enter a dormant state with a multifocal distribution deep within the endometrium of a chronically infected mare. Uterine infusion of BACTIVATE induces active growth of dormant streptococci. As most antimicrobial compounds assert their activity against metabolically active bacterial cells, we hypothesized that activation of dormant streptococci and subsequent antimicrobial treatment of the activated bacteria would increase treatment efficacy and indirectly increase fertility of the problem mare. Materials and Methods A low volume lavage sample and endometrial biopsy was obtained in early estrus, and a bacterial activation solution (10 mL; BACTIVATE) was infused into the uterine lumen. A specimen for endometrial culture (low volume lavage or guarded swab) was obtained 24 h after activation (figure 1). Activation was classified as positive if mare that were culture-negative or S. zoo- negative (e.g. positive for E. coli) on day 0 changed to culture-positive for > 5 CFUs S. zoo 24 h after activation. Petersen, M.R. 1, Lu, K. 2, Christoffersen, M. 3, Møller Nielsen, J. 4, Troedsson, M.H. 5, Bojesen, A.M 6. 1 The Fertility Clinic, University Hosp. of Copenhagen, Denmark. 2 Hagyard, Davidson and McGee, Lexington, Kentucky, USA. 3 Veterinary Reproduction and Obstetrics, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. 4 Ansager Large Animal Hospital, Ansager, Denmark. 5 Gluck Equine Research Center, Lexington, KY, USA. 6 Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark F A C U L T Y O F H E A L T H A N D M E D I C A L S C I E N C E S U N I V E R S I T Y O F C O P E N H A G E N 0h 24h Timeline : Figure 1: Timeline illustrating uterine samplings, activation, treatment and breeding. 48 h Next 2 cycles Early estrus (0h): Uterine cultures+cytology, followed by 10 ml Bactivate infusion/activation 24h: Uterine culture 48h: Treatment Next two cycles: Breeding KU LOGO Results A total of 64 problem mares from intensively managed stud farms in Central Kentucky during the 2011 and 2012 breeding seasons satisfied the inclusion criteria (barren > 3 cycles, gynecologic- ally normal). In the 2011 breeding season the “time barren” was recorded (table 1): Mares included in the study had been barren for an average of 1½ years. Table 1: Time barren mares activated and bred in 2011 breeding season Before activation more than half of the mares were culture negative (39/64=60%), and the majority of the remaining mares were culture positive for S. zoo or E. coli, 19 and 8 mares, respectively(Table 2). Following activation 30 mares became culture positive for S. zoo (activation positive), and only 15/64=23% mares remained culture negative Table 2: Uterine culture before and after activation On the day following activation, mares with positive uterine cultures were treated with systemic and intrauterine antimicrobials, ecbolics, uterine lavage with or without mucolytics(clinicians choice), and bred in the following cycle (maximum two cycles). Pregnancy was established in 53 (83%) mares (Table 3). Of the 21 pregnancies established in 2011, 18 (86%) gave birth to a live foal. Foaling data from the 2012 season is pending.Since all mares were infused with the activation solution, the pregnancy rate of non-activated mares cannot be determined. Table 3, Fertility results, mares bred for a maximum of 2 cycles following activation: Conclusion Within this selected group of Tb problem mares, subclinical chronic S. zoo infections is a common finding (30/64=47%), despite intense management including routine uterine sampling for culture and cytology, as well as repeated lavage and antimicrobial treatment. A marked increase in fertility was noted following activation and treatment. Being a field study involving client owned mares, all mares were activated and culture positive mares were treated. Fertility of non-activated mares can therefore not be determined. Potential relevance We demonstrate that chronic subclinical S. zoo is a common finding in the subfertile intensely managed Tb mare and that activation and subsequent antimicrobial treatment of dormant S. zoo in problem mares can restore the expected pregnancy and live foal rates to levels reported for the general mare population. Appreciations Generation of this work would not have been possible without clients and mares participating in the study, as well as the institutions supporting this research.