How bActivate Stands Out: Tackling Dormant Bacteria in Mares
One of the major challenges in equine breeding is dealing with latent bacterial infections that traditional diagnostic methods fail to detect and treat. At Bojesen & Petersen Biotech, we developed bActivate specifically to address this problem — not by treating symptoms, but by exposing the root cause of chronic mare infertility.
The Challenge: Dormant Persister Bacteria
When a mare fails to conceive despite normal cycles and clean swab results, dormant bacteria are often the hidden culprit. Streptococcus equi subsp. zooepidemicus (“Strep zoo”) — the most common pathogen in equine endometritis — can enter a dormant persister state deep within the uterine mucosa. In this state:
- The bacteria are not multiplying, so standard culture swabs return negative results
- They are metabolically inactive, meaning antibiotics have no effect on them
- They can persist for years between breeding seasons, surviving routine treatments
- They reactivate during oestrus, triggering inflammation that prevents embryo implantation
This biological survival mechanism — known as persister cell formation — was characterised in peer-reviewed research by Prof. Anders Miki Bojesen and Dr. Morten Rønn Petersen, published in Veterinary Microbiology (2015). Their work demonstrated that dormant streptococci reside embedded within the endometrial tissue, effectively hidden from both the immune system and standard diagnostics.
Why Standard Treatments Keep Failing
The conventional approach to endometritis — take a swab, culture the bacteria, treat with antibiotics — works well for acute infections. It fails systematically for dormant infections, for a simple reason: antibiotics only kill bacteria that are actively dividing. A metabolically inactive persister cell is not killed by penicillin, gentamicin, or any other standard antibiotic.
The result is a pattern familiar to many breeders and equine veterinarians: the mare responds to treatment, fluid clears, the swab goes negative, she is cleared for breeding — and then fails to conceive again. The dormant bacteria survived the antibiotic course, reactivated at the next oestrus, and the uterine environment remains hostile to embryo survival.
Research suggests that 50–75% of mares that remain open at the end of the breeding season are chronically infected with dormant bacteria. This is not an unusual edge case. It is the most probable explanation for a mare with unexplained infertility.
The bActivate Approach: Activate First, Then Treat
bActivate is a bacterial growth medium formulated to stimulate dormant streptococcal bacteria out of their persister state. When instilled into the uterus during early oestrus, it creates the metabolic conditions that trigger the bacteria to become active and begin multiplying. Within 48 hours:
- Dormant bacteria reactivate and begin to grow
- A post-activation culture swab now detects the true infection
- Targeted antibiotic therapy can be applied based on the culture result
- The bacteria, now metabolically active, are susceptible to treatment
This activate-first protocol solves both diagnostic and therapeutic problems simultaneously. The culture result reflects the actual infection rather than a snapshot of whichever bacteria happened to be active on the day of sampling. And the antibiotic treatment that follows is applied to bacteria that are now in a state where it can work.
Clinical Validation
The effectiveness of this approach has been confirmed in field studies at some of the world’s leading equine facilities. At Hagyard Equine Medical Institute in Lexington, Kentucky — the largest equine hospital in the world — Dr. Kristina Lu treated 64 problem mares using the bActivate protocol. The pregnancy rate was 83%. At Kildangan Stud in Ireland, part of the Godolphin organisation, 89% of 19 barren thoroughbred mares conceived after a single bActivate treatment cycle.
These results stand in sharp contrast to typical outcomes in problem mare populations, where pregnancy rates often fall below 50% using conventional approaches.
Watch: The Science Explained
Dr. Morten R. Petersen and Prof. Anders Miki Bojesen have presented the clinical and microbiological basis for the bActivate protocol in detail. The videos below cover the identification of dormant streptococci, how persister cells behave within the endometrium, and practical guidance on treatment.
Clinical aspects — Dr. Morten R. Petersen (DVM, PhD, Dipl. ACT): best practice, treatment efficiency, and why standard swabs produce false-negative results.
Prof. Anders Miki Bojesen (Department of Veterinary and Animal Sciences, University of Copenhagen): how endometrial cells communicate with streptococci, persister cell biology, and the mechanism behind bActivate.
Is bActivate Right for Your Mare?
bActivate is indicated for mares with reduced uterine defence mechanisms and suspected chronic subclinical infection. It is a prescription veterinary product, administered by a veterinarian during early oestrus. If your mare has unexplained infertility despite normal cycles and negative swabs, dormant bacterial infection is a likely cause. Learn when to use bActivate or review the full clinical evidence.
Written by the Bojesen & Petersen Biotech ApS team. Medical oversight: Prof. Anders Miki Bojesen DVM PhD (University of Copenhagen) and Dr. Morten Rønn Petersen DVM PhD Dipl. ACT.
What our clients say
Real results from veterinarians and breeders who have made bActivate part of their reproductive protocol.
“We incorporated bActivate into our standard reproductive work-up for problem mares at Hagyard. Out of 64 mares that had failed to conceive for at least 3 cycles, 83% became pregnant following bActivate activation and targeted antibiotic treatment. Nearly half had a dormant Streptococcus infection that standard culture had completely missed. It changed the way we approach the problem mare.”
“We used bActivate on 19 of our most persistent problem mares — horses that had been barren for over a year despite every conventional treatment we tried. 89% of them got in foal. What really opened our eyes was how many had a hidden infection that standard swabs had never detected. It is now a routine part of our protocol at Kildangan.”
“We have been using bActivate on several mares — all got pregnant and most of them in first try with frozen semen!”
“bActivate is an excellent tool that allows us as reproductive vets to do our job as effectively as possible. When you compare the cost to the expense of a mare that fails to conceive — or worse, never produces a foal — bActivate is both a smart and cost-effective solution in the long run.”
“I used bActivate and after just one covering got a colt foal — after 3 years of hardship where the mare went in foal but never managed to produce a live foal. I cannot recommend bActivate enough.”