Therapy Offers Hope for Infertile Mares

According to researchers in Denmark, a common cause of infertility in mares is a chronic subclinical Streptococcus equi zooepidemicus uterine infection. Up to 10% of mares have difficulty becoming pregnant, and the researchers think that dormant S. zooepidemicus infection is one of the most common causes of this infertility. They developed a product, Bactivate, that would signal the bacteria to resume an active state in which they could be successfully combated by antibiotics.

Bactivate was used in a study group of 64 broodmares that had trouble conceiving for one or more years. After being dosed with Bactivate, the mares developed uterine infections that were then treated. The mares were bred in their next heat cycle. Most of the mares (83%) became pregnant within 6 weeks, and a majority of those gave birth to live foals.

The researchers explained that dormant bacteria have such low metabolic rates that they are not susceptible to treatment with antibiotics. They can interfere with pregnancy in this inactive state, but will become more vulnerable to antibacterial medications only when they are active enough to cause infection.